THD Yellow Jackets... Serious potential for fun.

joshuaaewallen · 03-02-2009, 11:30 PM

I recently discovered The THD Yellow jackets as an option to open up new tonal possibilities. So, thanks to getting my state tax refund already, I took a leap of faith and ordered a set.

Before I go into my initial impressions of them, I would like to hear what you all have to say about these EL34/6L6 to EL84 adapters. Has anyone else out there used these? If so, what do you think of them? Do you have any suggestions, or advise on how, when, and where to use them, if at all?

That being said...

Well... I got my Yellow Jackets last week. I finally got a chance to play around w/ them on Saturday. I ordered the YJS Triode model. These came from the Tube Store and included two EL84 tubes.

First I tried going w/ only the two Yellow Jackets/EL84 in the middle tube sockets. This did dramatically decrease the amp's power (documentations says down to 20%). Suffice to say, I was unimpressed. This made the amp waaay too trebly... Shrill and unpleasant, even w/ the treble knob backed way off. It made the clean channel very thin to my ears and probably more suited for some country style chicken pickin', but really not dynamic enough even for that. I don't even wanna talk about the crunch and lead channels... Just painful.

But...

When I threw the EL34's back into the two outer tube sockets the amp really came alive. The combination of the two EL34's and the two EL84's is just amazing! It really changed the dynamics of the amp and gave it an amazing depth and texture that I hadn't even realized was missing. The bottom end seems fuller, highs are less brittle and shrill (richer somehow), and the mids are impossible to describe, just very pleasing.

I'm not really sure exactly how to describe it now. The crunch channel nails AC/DC rhythm tones, and the lead channel so far seems rather like if Brian May's Vox and Slash's JCM had a love child. It's really a cool sound.

Anyhoo... These are just first impressions made only after playing for a couple hours. I'm sure that w/ more time I will be able to expound more fully on the subject. In the meantime feel free to let me know if you have any questions.

Mase947 · 03-03-2009, 12:32 AM

interesting stuff

MartyStrat54 · 03-07-2009, 05:16 PM

I own a DSL401 and I love the overdrive sound that an EL84 makes. I wished that Marshall would have gone farther and made a DSL 60 watt model with six, EL84's. (You can actually get 15 watts out of one EL84, but it will only last about 4 or 5 months with moderate playing time.) Yeah, that would be my dream Marshall amp...a 60 watt EL84 amp with at least two channels.

I've known about Yellow Jackets, but never thought about trying them since I have a variety of amps. I would be curious to know what the total power output would be on your 122 with four of them in use? It would probably knock her down more than 20 per cent. 12 watts per EL84 is about the safe max and since you are using the EL34 power transformer, I'm sure you have plate voltage (B+) in the 400 volt range. The YJ's must have a large resistor built in as EL84's do not like B+ over 330 volts. (Do the YJ bases get hot? I mean hotter than what the tubes will make them?)

Enjoy your new equipment. Marty

MUSICIAN'S AUDIO EQUIPMENT-MAKERS OF VERSACAB

joshuaaewallen · 03-08-2009, 12:38 PM

I had a chance on Friday (that'd be the 6th) to put in a few hours playing my PRS through the amp again. I didn't change anything w/ the tube set up, but since my wife was home...

... I had to keep the volume down. That being the case, this time I opted to try it w/ the VPR button engaged (Virtual Power Reduction, which as you likely know is supposed to simulate the volume reduction and saturation you would get if it were a 25 watt amp).

With the VPR on, and my final settings when finished looking something like:

Clean - Gain 3, Volume 4.5, Treble 3, Middle 3, Bass 5, Presence 5.5
Crunch - Gain 5, Volume 2, Treble 4, Middle 5, Bass 8, Presence 6.5
Lead - Gain 8.75, Volume 2, Treble 7, Middle 4, Bass 6.75, Presence 6.5

This too was a different experience from what I had been used to. The lead channel was definately more saturated than when not on the VPR mode. But for low volume playing this was pretty fun. Once again I was very happy w/ the tones I was getting. I used various tone settings and depending on what I was looking for would switch the "Tone Shift", and the "Deep" in or out.

With these settings it made for what I would term as a pretty nice bedroom amp volume level, but my wife still thought it was too loud to try to nap through... Either way it was a ton of fun to play.

Quote:

Originally Posted by MartyStrat54

... I own a DSL401 and I love the overdrive sound that an EL84 makes. I wished that Marshall would have gone farther and made a DSL 60 watt model with six, EL84's. (You can actually get 15 watts out of one EL84... that would be my dream Marshall amp...a 60 watt EL84 amp with at least two channels.

I've known about Yellow Jackets, but never thought about trying them since I have a variety of amps. I would be curious to know what the total power output would be on your 122 with four of them in use? It would probably knock her down more than 20 per cent. 12 watts per EL84 is about the safe max and since you are using the EL34 power transformer... The YJ's must have a large resistor built in... Do the YJ bases get hot? I mean hotter than what the tubes will make them?...

A DSL 60 watt model based on EL84's could be very interesting.

I love the DSL401 sound. I wish I had the $$$ for a DSL 401 for my second/travel sized amp. But sinse I sold off just about everything I had for guitar gear other than my PRS and two other guitars just to get my Marshall... I decided to go w/ the overall versatility of the TSL122. So when I ound this one and it had been proven reliable, I pounced on it.

The documentation for the yellow jackets says that w/ all other power amp tubes removed the output is 20% of what it normally is. Not knowing the actuall math on this, I would assume then, that w/ four Yellow Jackets running the amp should be between 40 and 60 watts? One day I will try this out to see how it sounds, I just didn't have the extra $$$ to buy another set of Yellow jackets. I will say definatively that w/ only two and no EL34's, this amp sounded terrible. But with the split power section I am very happy with the tones I am getting. It really is pretty sweet.

joshuaaewallen · 03-09-2009, 04:44 PM

Quote:

Originally Posted by MartyStrat54

... Do the YJ bases get hot? I mean hotter than what the tubes will make them?...

Enjoy your new equipment. Marty

MUSICIAN'S AUDIO EQUIPMENT-MAKERS OF VERSACAB

It doesn't seem like the bases of Yellow Jackets get that hot. They are definitely waaay cooler than the temp of the actual tube.

MartyStrat54 · 03-09-2009, 09:45 PM

Man, those tubes come close to the speakers don't they? I wonder if the magnetic field of the speakers are putting some kind of mojo on those EL84's? If you did put all four in with the YJ's would they all clear the back of the speakers? It looks really close.

Marty

joshuaaewallen · 03-10-2009, 05:47 PM

MARSHALL MOJO...

MartyStrat54 · 03-10-2009, 06:00 PM

Ahh ha! I knew it. A whole bunch of little Marshall electrons bouncing back and forth between the tubes and the magnet producing, "MARSHALL MOJO!"

Puffer Fish · 03-12-2009, 03:38 PM

I do not want to come across as a killjoy or act like a know-it-all, because I have a lot to learn, but the experience I had with the Yellow Jackets was quite a disappointment. My brother and I loaded them into a head and they worked and sounded great for a short time. Then things went bad. One of the two Yellow Jacket units burnt out and the other would have followed close behind. Our amp doctor tells us that they will not work--that what THD is saying is not the entire picture. Whatever, right? All I REALLY know is one of the units got charred by high voltage. I really, really hope that for any of you who bought them that they work well long into the future and that you have great success with the Yellow Jackets. It is one of those products I really wanted to work. I LOVE the idea, EL84s--I love them. For me it did not work out. Fortunately no harm was done to the amp.

If anyone has other good news to share regrading the Yellow Jackets, I would love to hear about it. Especially someone who has owned and used them for a year or longer. I think that would be good information.

joshuaaewallen · 03-12-2009, 10:38 PM

Quote:

Originally Posted by Puffer Fish

I do not want to come across as a killjoy or act like a know-it-all, because I have a lot to learn, but the experience I had with the Yellow Jackets was quite a disappointment. My brother and I loaded them into a head and they worked and sounded great for a short time. Then things went bad. One of the two Yellow Jacket units burnt out and the other would have followed close behind. Our amp doctor tells us that they will not work--that what THD is saying is not the entire picture. Whatever, right? All I REALLY know is one of the units got charred by high voltage. I really, really hope that for any of you who bought them that they work well long into the future and that you have great success with the Yellow Jackets. It is one of those products I really wanted to work. I LOVE the idea, EL84s--I love them. For me it did not work out. Fortunately no harm was done to the amp.

If anyone has other good news to share regrading the Yellow Jackets, I would love to hear about it. Especially someone who has owned and used them for a year or longer. I think that would be good information.

I wouldn't say you are a killjoy for stating your experience with this product. That's kinda the point of the whole forum thing. I started this thread specifically to find out what other forum members have found with regard to Yellow Jackets. Good or Bad. That being said... Thanks for posting!

Now... My experience with Yellow Jackets is limited. As I've stated, so far I've only had them in my amp for almost two weeks, and have only been able to play the amp for 5-10 hours during that time. My experience thus far has yielded somewhat mixed results. The original set up with only the yellow jackets was depressing, while the "mixed power section" set up has been a thrill to play through. It probably goes w/out saying that as far as the reliability of this product goes... only time will tell.

Quote:

Our amp doctor tells us that they will not work--that what THD is saying is not the entire picture. Whatever, right? All I REALLY know is one of the units got charred by high voltage.

Can you give more details as to exactly what your amp doctor said? I guess that statement leaves things just vague enough to leave a bad taste in one's mouth, without really explaining why. What is, "the rest of the picture" that THD is not giving us?

MartyStrat54 · 03-13-2009, 12:49 AM

I still would like someone with the knowledge to explain how THD gets the voltage drop with their circuitry. As I said before, the hottest you can run an EL84 is about 330 volts (B+). Most amps run them very conservatively, say 285 B+. The DSL401 is not pushing the tubes hard, as they are only getting 10 watts per tube. Again, as I have said before, you can get 15 watts out of an 84, but the tube life suffers. The TSL122 has around 450 volts of B+. The circuit built inside of the YJ base has to have a power resistor (large and capable of getting very hot) as it is performing a 150 volt drop. If they are not using a resistor, then I would really like to hear how they do it. I know that there are other ways.

I'm a tech/player. If there are any tech's out there who know how these work, drop a line on this thread. I guess I could contact one of the big online tube stores and ask them how they work. They ought to know, they sell them.

Marty

joshuaaewallen · 03-13-2009, 06:09 AM

Quote:

Originally Posted by MartyStrat54

I still would like someone with the knowledge to explain how THD gets the voltage drop with their circuitry...

Marty

Diddo. I don't pretend to be a tech. And while there are variables that I don't understand that I'm willing to jokingly pass off as MoJo, I do, whenever possible, like to get the real understanding on what makes something tick (in this case something would be the THD Yellow Jackets).

Unfortunately after many hours of scouring the web (I've been sick in bed all day yesterday) about all I can find regarding the THD's is more of what led me to them in the first place... That being various mostly positive reviews, and a bunch of sites that also sell them. Thus... to reiterate Marty's question, if there is anyone out there reading this who knows, "I still would like someone with the knowledge to explain how THD gets the voltage drop with their circuitry..."

In the meantime... Rock On!

Puffer Fish · 03-13-2009, 10:53 AM

Okay, I JUST got off the phone with my amp tech/ amp doctor guy and I will try to paraphrase what he told me regarding the Yellow Jackets and why he thinks they are not a good idea and why in my situation they failed....

Quite simply the plate voltage on any octal based power tube amplifier has a plate voltage that exceeds 450 volts and the EL84s can only handle around 300 volts. The Yellow Jackets have a couple resistors and capacitor to attempt to absorb and deal with this excess voltage. The capacitors block the bias voltage and thus limits frequency response and as a result you get cuts to low frequency--which explains the mentioned thin sound someone experienced with their Yellow Jackets. The power transformers on the octal based amps produce too much voltage and the Yellow Jackets have no way to dissipate the heat--so they run very hot and operate in a somewhat dangerous situation.

Okay, that is the paraphrase from my phone conversation with a very knowledgeable and experienced guy who makes his living repairing and building amplifiers of many makes and eras. I trust his judgement and opinion on the matter, for what it is worth.

I really do not have anything against THD. I really liked the amps I heard and tried out from them. And as I mentioned in my original post, I REALLY wanted the Yellow Jackets to work, but in my experience they failed due to excess heat in the electronic components of the unit. Believe me, I was bummed. I thought I was going to have myself some more EL84 amplifiers!

The good news is I do not think they will hurt anyone's gear. But I am really not qualified to say that with certainty--just based upon my experience and my rudimentary understanding of what the Yellow Jackets are doing.

All of this said, I hope that folks who already own them are able to get good life out of the things and find a tone they are into. This is about everything I can offer on the Yellow Jackets. I hope it was at least a little helpful.

joshuaaewallen · 03-13-2009, 01:20 PM

Thanks Puffer Fish. Now I have something to work with. How long did you and your brother have the YJ's before they became crispy critters?

So far I have not had any problems with my YJ installation, which is not to say that I won't at some later point. Unfortunately there has been very little feedback info online regarding YJ's, so I sorta feel like someone needs to give 'em a good go and report back to the rest of civilization on what happens.

I really appreciate you and Marty actually taking an interest in this thread and providing some feedback. I think that the info you got from your amp tech may come in useful in the future. I'm not a tech-guy (more like a wanna-be tech guy) and it usually takes a lot for me to wrap my head around technical data, but from my point of view, if we can get enough info out there, collectively we can "build a better mousetrap".

I sent an email to THD inquiring as to what they may be willing to tell me on how these work. They may or may not tell me anything, but hopefully they will tell me something...

Anyhoo...

Since I really love the tones I'm getting from my amp with the EL84's & EL34's, I reckon' I'll leave it that way for a while. More than likely (from what I can tell), if I run into trouble it'll more than likely be with the EL84's or with the YJ's themselves... Should be a good trial run, and I will try to keep ya'll up to date with how they are working. Let the journey begin...

MartyStrat54 · 03-13-2009, 03:56 PM

With what Puffer said, I'm wondering if the reason you haven't had any problems is because you are running a split pair. How this is affecting bias, I can't answer that. I wonder if the bases would get hot if you were running all four sockets with YJ's?

I knew they had to do something to get that big voltage drop and when you get rid of voltage, you create heat. From an original idea standpoint, the YJ's are a great idea. But its sort of like taking a motor out of a car and replacing it with a motorcycle engine. It may fit and hook up to the drivetrain, but how does it run? That's the question here...how do these YJ's run?

Just curious. What is the manufacturer's warranty on these? A year?

Marty

joshuaaewallen · 03-13-2009, 06:51 PM

The sheet that came with the Yellow Jackets says they come with a "1-year limited warranty on converters"... This to my mind reads that if something is wrong w/ the converters and they fry, THD will replace them. Anything outside of that... I am probably on my own. Either way, since I am in Minneapolis, Minnesota, and they are in Seattle, Washington... Problems could be difficult to resolve. I am however optimistic regarding their customer service as I have emailed them in the past and gotten fairly fast response (trying to determine if these adapters would be suitable for my Marshall).

MartyStrat54 · 03-13-2009, 07:50 PM

Guitar World and Guitar Player seem to think they are hot stuff (no pun intended).

I wouldn't want to change a 6V6 amp over to EL84's, even with the special adapter. They both put out around the same output wattage.

They are running the EL84's as triodes and not as pentodes. No wonder the power drops to around 90 per cent. These two tubes might be making 5 watts. In pentode mode, you can get 16 to 20 watts out of two tubes, hence the DSL 201.

I do not understand how they are blending Class A with Class AB without a chop in part of the signal. Class A is on all of the time and AB is on most of the time. That's why Class A amps are the best for fast shredders.

I don't know, but the more I learn about these, the more I am inclined to say, "Thanks, but no thanks." As a tech, I have too many questions about why they take a pentode tube (EL34) and replace it with a pentode tube (EL84), but run it in triode mode? It really makes me wonder why they went this route. If you take four EL34's and you have an amp with a power switch, it usually converts the EL34's from pentode to triode operation which gives you 30 to 50 watts of Class A power and almost as loud. (Some amps cut the plate power in half on the tubes and they remain in pentode mode with self biasing [like my Traynor YCS100] and this gives 30 watts of Class A.)

There are several other threads on this subject, but I am only placing comments on this one.

Conclusion: Taking an EL34 100 watt amp and putting four of the YJ's in it will yield around 10 watts of power (90 per cent off of 100 equals 10). This is because it operates in triode mode. If it was in pentode mode, then you would have close to a DSL 401 in power. But what about sound? Good question, because you have choked the hell out of the B+ voltage and are doing it with resistors that override the bias voltage. So even if the EL84's did run in pentode mode, I doubt if it would sound like a DSL 401. The DSL runs pentode with around 285 volts B+ on the plate. All the associated circuitry is all designed around this. Yellow Jackets are like a giant erasure on the schematic. They erase the power tube circuit and replace it with what can be contained in the base of the converters. I'm sorry, but all of this is a big negative to me as a tech.

Marty

joshuaaewallen · 03-13-2009, 08:21 PM

I can see what you mean from a tech/purist point of view. Personally what I hope to achieve here is:

A) Tone that make me dream about playing my guitar.
B) Enough technical knowledge to know what goes into getting tone that I like.
C) Hopefully get some communication and info out there on the forum to help others achieve their own personal tonal nirvana.

In that order.

I know that my TSL122 is not a bedroom amp, so either way I have a challenge ahead of me in my quest for tone. Thanks again Marty & Puffer Fish for your input, and anyone else out there reading this, please feel free to weigh in on the subject. I'm lovin' it!

Puffer Fish · 03-13-2009, 11:31 PM

wow, this thread really took off! What was mentioned a little earlier about two Yellow Jackets and two EL34s in the TSL 122 might be something. I see what the person was thinking: the plate voltage may be dispersed enough amongst the tubes to allow the YJs to do their thing without getting too hot.

The coolest new amp I have heard is the new JVM model line. My brother picked one up (50 watt head, two channels) and it sounds fantastic to my ears. It seems to actually achieve bedroom volumes because the preamp section is doing a lot of the work I guess. Anyway, it might be something worth looking into if you would consider making a trade in or a trade up or whatever you want to call it.

Of course there are always DSL 201 amps out there as well as the DSL 401s like I have. But I use my DSL 401 on stage and at practice--everywhere in fact--so I suspect it would be way too loud for bedroom volume. Hmmm... that term bedroom volume is pretty loose. For me, bedroom volume is the guitar is sometimes too loud even unplugged! That is why I have a practice space and I always appreciate being able to go there and crank it up.

MartyStrat54 · 03-14-2009, 01:15 AM

Puffer: It kind of makes you wonder when someone spends $1500 on a boutique "half watt" amplifier. I mean it blows my mind. Maybe in a studio application it works well, but come on, a 1/2 watt for a grand and a half? To me, the smallest practice amp I would want would be ten to twenty watts with at least a 10-inch speaker. I know with these one half and one watt boutique amps, you can crank them up and get the saturated power tube sound. Just don't fart or you'll drown out the saturation!

You give the world a bunch of choices and this is what you get...ridiculous mayhem. "Hey Puffer, come on over to my house and we can shred our 1/2 watt amps!" "Look out AC/DC, there's a new sheriff in town." "Wow! Listen to those power tubes saturate..."dyno-mite!"

I know people with 1/2 watt hearing aids. Maybe I can make a boutique amp out of one of those. Sheesh!

Marty

Puffer Fish · 03-14-2009, 01:42 AM

Ha! I so agree! In fact I was having a similar conversation JUST the other day about botique amps in general and how I mostly just don't get it. But the 1/2 watters seem pretty seriously absurd. What is the point? Well, okay, I get the point regarding tube saturation, okay, I get it. But what ever happened to isolation cabinets or the old trick of wrapping the speaker cab with blankets so you can crank it up, work the speakers but not melt everyone's ears. Really, there have ALWAYS been ways to deal with getting the tubes saturated on a normal amp, but still dealing with the shear volume/ dBs of the amp. After all, borrowing some quilts from your mother will always be way cheaper than the $2000.00 special amplifier, even though it may not be all that sexy.

On another related subject, I have cranked the volume on the master while in the clean channel on my DSL 401 and I did the same thing on my Peavey Classic 30 (backup amp : 0 ) and the levels were indeed quite loud, but I did manage to achieve pure power tube over drive and I could handle being in the same room while playing. Verdict: 1/2 watt amp is a serious waste of money in my little world. If I had that kind of extra cash to throw about, it would go toward a Focusrite Liquid Mix or maybe a FMR Audio preamp or something like that to really expand my world for real.

Cheers!

joshuaaewallen · 03-16-2009, 06:49 PM

Quote:

Originally Posted by MartyStrat54

Puffer: It kind of makes you wonder when someone spends $1500 on a boutique "half watt" amplifier. I mean it blows my mind. Maybe in a studio application it works well, but come on, a 1/2 watt for a grand and a half? To me, the smallest practice amp I would want would be ten to twenty watts with at least a 10-inch speaker...
...Sheesh!

Marty

Quote:

Originally Posted by Puffer Fish

... I was having a similar conversation JUST the other day about botique amps in general and how I mostly just don't get it. But the 1/2 watters seem pretty seriously absurd. What is the point? Well, okay, I get the point regarding tube saturation, okay, I get it... But...

... 1/2 watt amp is a serious waste of money in my little world.

Some "botique" features on a modern production amp is a cool thing, but the cash some folks drop on a tiny amp is, in my opinion, obscene. I've been down the 5 watt amp path before (no I didn't drop a grand on it...) and yeah, you get tube distortion when you crank it up, but it ain't loud enough to gig with, and if your a home player you either have it too loud for the house if you want that distortion, or you have absolutely no clean head room. There's no in-between. Personally I think this is why we have pre-amp distortion, master volume knobs, attenuators, yellow jackets, distortion pedals, etc...

That's also why I love my TSL122, it has plenty of versatility, it can be tamed down to low volumes, but if I need power I've got more on tap than I'll ever really need. And if I don't like something about it, I'll mod, sell it, or live with it. Bottom line, whether played loud or soft, a Marshall is still the best amp out there. Done.

tim warner · 03-18-2009, 04:56 PM

well here is where all you guys are, I've had mine in my superlead 100 for a couple of weeks and I love em! very Rich robinson, which is exactly what I was looking for.
I also did what you did at first , just install 2 and it was very treblly like a vox with the treble switch on , not my thing but it is for others so.... but the 2 mixed with the el's
I had a TONEGASM! I hope we are not going to have the same luck as pufferfish's friend though. I wonder if the THD people would be honest if I just called them and got there take on this thread and would they put there money where there mouth is.

joshuaaewallen · 03-18-2009, 05:48 PM

Quote:

Originally Posted by tim warner

... I also did what you did at first , just install 2 and it was very treblly like a vox with the treble switch on , not my thing but it is for others so.... but the 2 mixed with the el's I had a TONEGASM.

Indeed. I found the pairing to add a lot of complexity to the tone that I really love!

Quote:

Originally Posted by tim warner

... I hope we are not going to have the same luck as pufferfish's friend though. I wonder if the THD people would be honest if I just called them and got there take on this thread and would they put there money where there mouth is?

I agree with you on both points. So far they seem pretty stable, so I'm willing to ride it out and see how they go over a period of time.

As far as THD... It'd be interesting to see if they'd actually even read, much less offer any feedback on this thread. If you do call them let us know what happens. I tried emailing them, summing up my initial impressions, and asking for info, but so far they have not responded.

joshuaaewallen · 03-20-2009, 09:09 AM

Quote:

Originally Posted by tim warner

... I had a TONEGASM! ...

That's funny. Now I know how to describe what I experienced! So... Was it good for you?

tim warner · 03-22-2009, 09:41 AM

Quote:

Originally Posted by joshuaaewallen

That's funny. Now I know how to describe what I experienced! So... Was it good for you?

LIKE THE KIND THAT LEAVES YOU DRAINED,,,,,,,,,,,COMPLETELY!
were talkin jessica alba looks with jenna jameson enthusiasm!

I only wish that I hadn't quit smoking , a marb. would've been nice after a few chords!

joshuaaewallen · 03-24-2009, 07:27 PM

joshuaaewallen · 03-24-2009, 08:15 PM

Quote:

Originally Posted by MartyStrat54

... (Do the YJ bases get hot? I mean hotter than what the tubes will make them?)...

Just double checked this...

They do get warm, but not as hot as the tubes. I'd never want to touch a hot tube while the amp is on (OWIE!!!) but the bases of the YJ's are not too hot to touch.

Ok... Here's a question for you guys... Obviously I want to keep the the split power section going for a while... So far I like it. However... If I were to want to get new power tubes (in my case just two since I'm running the Yellow Jacket pair) do I need to actually replace all four power tubes and re-bias, then pull the two middle power tubes replacing them with the YJ's again, or could I get away with just replacing the two EL34's and not rebiasing? Does that make sense?

Another question... Should an EL34 rattle at all when shaken? May seem like a dumb question, but this is slightly different than a light bulb...

Dejoblue · 04-01-2009, 04:04 PM

I have been looking at these and my web research has brought me here. I am looking to convert a JTM 45 with KT66 over with these.

Some things I would like to note and get clarification on with reference to failures and other phenomena is:

Those having a failure, what is your plate voltage and did you use the warranty to replace the converters and if so what was the costumer service like?

Those using two, as I intend to, did you try the outer two sockets to see if it changed the tone and have you biased the amp with 4 EL34s or post conversion with 2 EL34s?

I also saw some disapproving posts on the triode conversion and would like clarification of which type the posters are using.

If you go to THD you can see that they offer 3 types of converters.

Standard conversion, Triode conversion and 6V6 conversion.

A good read on them is:

http://www.thdelectronics.com/pdf/yj.pdf

Plate voltage must be under 520 volts DC.

A recommendation, while I am not qualified, is when using 2 converters in a 4 tube amp with the other 2 tubes in place and non converted, I.E., 2 YJ 2 EL34, bias the amp in that configuration. The YJ's are self biasing and when biasing tubes that are not self biasing, the EL34's, you have to get all of the tubes within the proper bias range. So, bias as normal you only have 2 tubes, the EL34's, to consider when adjusting the bias trim pot.

As to the questions about why low power amps are all the rage lately, I would like to offer my point of view.

We live in a world of pre amp distortion and solid state rectifiers where the power tubes are never fully engaged with typical, to club venues I have visited, Master Volumes set to 2 or 3.

I doubt very seriously that many club gigging musicians are able to blast their 50 or 100 watt Marshall heads at full volume to experience or take advantage of their power tubes saturation and character without a contrived slave, attenuation, iso cab or other stage volume control setup. As a matter of fact, most professional tours use in ear monitors and/or very low stage volumes with very low monitor volumes.

With this in mind we have all sorts of attenuation devices for large power amplifiers, and even the small ones. From THD's Hotplate and other power soaks to triode/pentode switches and low power/wattage switches on amplifier power sections, there are a multitude of options out there. A logical extension of this is high quality, multi feature low power amplifiers.

The benefit of a low power amplifier can be two fold. Benefit being subjective, if you dont like power tube saturation, power amp "sag" and its effects on the pre amp tubes and are happy with an MP1, Triaxis, running a 100 watt head with only pre amp distortion, then your opinion is just as valid, but this wont apply to you. The two fold being that Class A operation is inherently low power and at low power, power tubes can be more easily driven to saturate and develop their signature character. Class A is also always running with the full waveform, anecdotally giving a richer creamier distortion, just as preamp tubes are class A.

The lower power has the drawback of lower clean headroom, this may or may not be good depending on style and intent.

The expense of many boutique low power amps is the addition of features such as additional attenuation, for example, Mesas Lonestar Special with its 5 Watt Class A mode and THDs UniValve and BiValve with its built in attenuator, and others are just name/quality or unique topology like Alessandro amps.

Perhaps the greatest draw to these type of amps is the lessened need for attenuation. It is simply easier to lower 20 watts down to club volumes than 50 or 100. There are also different classes or subsets, for instance the mentioned 1/2 watt or 1 watt or 3 watt amplifiers, which are directly aimed at recording and slaving.

On top of this, a mere 5 watts is usually too loud for bedroom/home practicing while 15 - 20 watts is the most volume that most gigging club musicians will ever need. If you need more volume, simply mic it up and that brings me to my last point.

The great sounds we hear and try to emulate from our favorite recordings always have a mic and a mic pre amp involved. Many comparisons are apples and oranges, comparing recordings or professional touring rigs that are micd and mixed with a single amplifier that is not micd. A great combination used by iso cab enthusiasts and low power amp enthusiasts is finding a really nice sounding mic and preamp combination and then using that through the PA or a separate super clean cabinet with effects or even a dedicated amp PA, much like Eric Johnsons delay monitor setup(http://www.ericjohnson.com/pictures/newtrick.jpg). I am personally getting my main sound with a JTM 45 attenuated and using Guitar Rig for all other genres with Mackie studio monitors HR624s and Logic for various effects and plugins , etc.

The JTM 45 is too loud at around 30 watts and I was looking to these since I love EL84s but also love the trite, tried and true Marshall preamp designs sound. Yes, I said preamp, the predominant sound character but we are talking aesthetics and detail in sound here.

So I am looking at YJs with the JTM 45, an 18 Watt Marshall reissue with EL84s or a THD Uni or BiValve.

Oh, and the feeling is mutual, we low power amp users look at you high power amp users and say, "What is the point of having all of that power you will never use". IMHO use a MP1 and a Solid State power amp and get he same result. Been there, done that, even with tube power amps but when you cant crank it, it is pointless.

So that is my POV and I hope I didn't offend anyone. There is a multitude of sounds out there and I hope these YJs provide me with my dream sound, JTM 45 with EL84s.

rockinr0ll · 04-01-2009, 05:38 PM

This is a long read! :0

Could you tell me if you liked them?

03-02-2009, 11:30 PM	#1 (permalink)
joshuaaewallen Senior Member Join Date: Jan 2009 Location: Minnesota Posts: 372	THD Yellow Jackets... Serious potential for fun. I recently discovered The THD Yellow jackets as an option to open up new tonal possibilities. So, thanks to getting my state tax refund already, I took a leap of faith and ordered a set. Before I go into my initial impressions of them, I would like to hear what you all have to say about these EL34/6L6 to EL84 adapters. Has anyone else out there used these? If so, what do you think of them? Do you have any suggestions, or advise on how, when, and where to use them, if at all? That being said... Well... I got my Yellow Jackets last week. I finally got a chance to play around w/ them on Saturday. I ordered the YJS Triode model. These came from the Tube Store and included two EL84 tubes. First I tried going w/ only the two Yellow Jackets/EL84 in the middle tube sockets. This did dramatically decrease the amp's power (documentations says down to 20%). Suffice to say, I was unimpressed. This made the amp waaay too trebly... Shrill and unpleasant, even w/ the treble knob backed way off. It made the clean channel very thin to my ears and probably more suited for some country style chicken pickin', but really not dynamic enough even for that. I don't even wanna talk about the crunch and lead channels... Just painful. But... When I threw the EL34's back into the two outer tube sockets the amp really came alive. The combination of the two EL34's and the two EL84's is just amazing! It really changed the dynamics of the amp and gave it an amazing depth and texture that I hadn't even realized was missing. The bottom end seems fuller, highs are less brittle and shrill (richer somehow), and the mids are impossible to describe, just very pleasing. I'm not really sure exactly how to describe it now. The crunch channel nails AC/DC rhythm tones, and the lead channel so far seems rather like if Brian May's Vox and Slash's JCM had a love child. It's really a cool sound. Anyhoo... These are just first impressions made only after playing for a couple hours. I'm sure that w/ more time I will be able to expound more fully on the subject. In the meantime feel free to let me know if you have any questions. __________________ Josh 2004 PRS Custom 24 10 Top Dean Caddy w/ Bare Knuckles Nail Bombs (This One's For Sale, Just Let Me Know If You Are Interested) 1999 Marshall JCM 2000 TSL 122 - Power Tubes: JJ EL34L's - Assorted New & Vintage pre-amp tubes... I like to roll... HardWire DL-8 Delay/Looper http://irkinempire.spaces.live.com/ "... When you do things right, people won't be sure you've done anything at all." - Futurama Last edited by joshuaaewallen; 03-05-2009 at 08:25 PM.

03-03-2009, 12:32 AM	#2 (permalink)
Mase947 Member Join Date: Oct 2008 Posts: 91	Re: THD Yellow Jackets... Serious potential for fun. interesting stuff __________________ I dont know these guys but they are my new favorite. http://www.mixposure.com/THUNDERHEAD/music.php

03-07-2009, 05:16 PM	#3 (permalink)
MartyStrat54 Senior Member Join Date: Feb 2009 Location: Formerly Phoenix, now north of KC Posts: 2,580	Re: THD Yellow Jackets... Serious potential for fun. I own a DSL401 and I love the overdrive sound that an EL84 makes. I wished that Marshall would have gone farther and made a DSL 60 watt model with six, EL84's. (You can actually get 15 watts out of one EL84, but it will only last about 4 or 5 months with moderate playing time.) Yeah, that would be my dream Marshall amp...a 60 watt EL84 amp with at least two channels. I've known about Yellow Jackets, but never thought about trying them since I have a variety of amps. I would be curious to know what the total power output would be on your 122 with four of them in use? It would probably knock her down more than 20 per cent. 12 watts per EL84 is about the safe max and since you are using the EL34 power transformer, I'm sure you have plate voltage (B+) in the 400 volt range. The YJ's must have a large resistor built in as EL84's do not like B+ over 330 volts. (Do the YJ bases get hot? I mean hotter than what the tubes will make them?) Enjoy your new equipment. Marty MUSICIAN'S AUDIO EQUIPMENT-MAKERS OF VERSACAB

03-09-2009, 09:45 PM	#6 (permalink)
MartyStrat54 Senior Member Join Date: Feb 2009 Location: Formerly Phoenix, now north of KC Posts: 2,580	Re: THD Yellow Jackets... Serious potential for fun. Man, those tubes come close to the speakers don't they? I wonder if the magnetic field of the speakers are putting some kind of mojo on those EL84's? If you did put all four in with the YJ's would they all clear the back of the speakers? It looks really close. Marty

03-10-2009, 05:47 PM	#7 (permalink)
joshuaaewallen Senior Member Join Date: Jan 2009 Location: Minnesota Posts: 372	Re: THD Yellow Jackets... Serious potential for fun. MARSHALL MOJO... __________________ Josh 2004 PRS Custom 24 10 Top Dean Caddy w/ Bare Knuckles Nail Bombs (This One's For Sale, Just Let Me Know If You Are Interested) 1999 Marshall JCM 2000 TSL 122 - Power Tubes: JJ EL34L's - Assorted New & Vintage pre-amp tubes... I like to roll... HardWire DL-8 Delay/Looper http://irkinempire.spaces.live.com/ "... When you do things right, people won't be sure you've done anything at all." - Futurama

03-10-2009, 06:00 PM	#8 (permalink)
MartyStrat54 Senior Member Join Date: Feb 2009 Location: Formerly Phoenix, now north of KC Posts: 2,580	Re: THD Yellow Jackets... Serious potential for fun. Ahh ha! I knew it. A whole bunch of little Marshall electrons bouncing back and forth between the tubes and the magnet producing, "MARSHALL MOJO!"

03-12-2009, 03:38 PM	#9 (permalink)
Puffer Fish Member Join Date: Jan 2009 Posts: 69	Re: THD Yellow Jackets... Serious potential for fun. I do not want to come across as a killjoy or act like a know-it-all, because I have a lot to learn, but the experience I had with the Yellow Jackets was quite a disappointment. My brother and I loaded them into a head and they worked and sounded great for a short time. Then things went bad. One of the two Yellow Jacket units burnt out and the other would have followed close behind. Our amp doctor tells us that they will not work--that what THD is saying is not the entire picture. Whatever, right? All I REALLY know is one of the units got charred by high voltage. I really, really hope that for any of you who bought them that they work well long into the future and that you have great success with the Yellow Jackets. It is one of those products I really wanted to work. I LOVE the idea, EL84s--I love them. For me it did not work out. Fortunately no harm was done to the amp. If anyone has other good news to share regrading the Yellow Jackets, I would love to hear about it. Especially someone who has owned and used them for a year or longer. I think that would be good information.

03-13-2009, 12:49 AM	#11 (permalink)
MartyStrat54 Senior Member Join Date: Feb 2009 Location: Formerly Phoenix, now north of KC Posts: 2,580	Re: THD Yellow Jackets... Serious potential for fun. I still would like someone with the knowledge to explain how THD gets the voltage drop with their circuitry. As I said before, the hottest you can run an EL84 is about 330 volts (B+). Most amps run them very conservatively, say 285 B+. The DSL401 is not pushing the tubes hard, as they are only getting 10 watts per tube. Again, as I have said before, you can get 15 watts out of an 84, but the tube life suffers. The TSL122 has around 450 volts of B+. The circuit built inside of the YJ base has to have a power resistor (large and capable of getting very hot) as it is performing a 150 volt drop. If they are not using a resistor, then I would really like to hear how they do it. I know that there are other ways. I'm a tech/player. If there are any tech's out there who know how these work, drop a line on this thread. I guess I could contact one of the big online tube stores and ask them how they work. They ought to know, they sell them. Marty

03-13-2009, 10:53 AM	#13 (permalink)
Puffer Fish Member Join Date: Jan 2009 Posts: 69	Re: THD Yellow Jackets... Serious potential for fun. Okay, I JUST got off the phone with my amp tech/ amp doctor guy and I will try to paraphrase what he told me regarding the Yellow Jackets and why he thinks they are not a good idea and why in my situation they failed.... Quite simply the plate voltage on any octal based power tube amplifier has a plate voltage that exceeds 450 volts and the EL84s can only handle around 300 volts. The Yellow Jackets have a couple resistors and capacitor to attempt to absorb and deal with this excess voltage. The capacitors block the bias voltage and thus limits frequency response and as a result you get cuts to low frequency--which explains the mentioned thin sound someone experienced with their Yellow Jackets. The power transformers on the octal based amps produce too much voltage and the Yellow Jackets have no way to dissipate the heat--so they run very hot and operate in a somewhat dangerous situation. Okay, that is the paraphrase from my phone conversation with a very knowledgeable and experienced guy who makes his living repairing and building amplifiers of many makes and eras. I trust his judgement and opinion on the matter, for what it is worth. I really do not have anything against THD. I really liked the amps I heard and tried out from them. And as I mentioned in my original post, I REALLY wanted the Yellow Jackets to work, but in my experience they failed due to excess heat in the electronic components of the unit. Believe me, I was bummed. I thought I was going to have myself some more EL84 amplifiers! The good news is I do not think they will hurt anyone's gear. But I am really not qualified to say that with certainty--just based upon my experience and my rudimentary understanding of what the Yellow Jackets are doing. All of this said, I hope that folks who already own them are able to get good life out of the things and find a tone they are into. This is about everything I can offer on the Yellow Jackets. I hope it was at least a little helpful.

03-13-2009, 01:20 PM	#14 (permalink)
joshuaaewallen Senior Member Join Date: Jan 2009 Location: Minnesota Posts: 372	Re: THD Yellow Jackets... Serious potential for fun. Thanks Puffer Fish. Now I have something to work with. How long did you and your brother have the YJ's before they became crispy critters? So far I have not had any problems with my YJ installation, which is not to say that I won't at some later point. Unfortunately there has been very little feedback info online regarding YJ's, so I sorta feel like someone needs to give 'em a good go and report back to the rest of civilization on what happens. I really appreciate you and Marty actually taking an interest in this thread and providing some feedback. I think that the info you got from your amp tech may come in useful in the future. I'm not a tech-guy (more like a wanna-be tech guy) and it usually takes a lot for me to wrap my head around technical data, but from my point of view, if we can get enough info out there, collectively we can "build a better mousetrap". I sent an email to THD inquiring as to what they may be willing to tell me on how these work. They may or may not tell me anything, but hopefully they will tell me something... Anyhoo... Since I really love the tones I'm getting from my amp with the EL84's & EL34's, I reckon' I'll leave it that way for a while. More than likely (from what I can tell), if I run into trouble it'll more than likely be with the EL84's or with the YJ's themselves... Should be a good trial run, and I will try to keep ya'll up to date with how they are working. Let the journey begin... __________________ Josh 2004 PRS Custom 24 10 Top Dean Caddy w/ Bare Knuckles Nail Bombs (This One's For Sale, Just Let Me Know If You Are Interested) 1999 Marshall JCM 2000 TSL 122 - Power Tubes: JJ EL34L's - Assorted New & Vintage pre-amp tubes... I like to roll... HardWire DL-8 Delay/Looper http://irkinempire.spaces.live.com/ "... When you do things right, people won't be sure you've done anything at all." - Futurama

03-13-2009, 03:56 PM	#15 (permalink)
MartyStrat54 Senior Member Join Date: Feb 2009 Location: Formerly Phoenix, now north of KC Posts: 2,580	Re: THD Yellow Jackets... Serious potential for fun. With what Puffer said, I'm wondering if the reason you haven't had any problems is because you are running a split pair. How this is affecting bias, I can't answer that. I wonder if the bases would get hot if you were running all four sockets with YJ's? I knew they had to do something to get that big voltage drop and when you get rid of voltage, you create heat. From an original idea standpoint, the YJ's are a great idea. But its sort of like taking a motor out of a car and replacing it with a motorcycle engine. It may fit and hook up to the drivetrain, but how does it run? That's the question here...how do these YJ's run? Just curious. What is the manufacturer's warranty on these? A year? Marty

03-13-2009, 06:51 PM	#16 (permalink)
joshuaaewallen Senior Member Join Date: Jan 2009 Location: Minnesota Posts: 372	Re: THD Yellow Jackets... Serious potential for fun. The sheet that came with the Yellow Jackets says they come with a "1-year limited warranty on converters"... This to my mind reads that if something is wrong w/ the converters and they fry, THD will replace them. Anything outside of that... I am probably on my own. Either way, since I am in Minneapolis, Minnesota, and they are in Seattle, Washington... Problems could be difficult to resolve. I am however optimistic regarding their customer service as I have emailed them in the past and gotten fairly fast response (trying to determine if these adapters would be suitable for my Marshall). __________________ Josh 2004 PRS Custom 24 10 Top Dean Caddy w/ Bare Knuckles Nail Bombs (This One's For Sale, Just Let Me Know If You Are Interested) 1999 Marshall JCM 2000 TSL 122 - Power Tubes: JJ EL34L's - Assorted New & Vintage pre-amp tubes... I like to roll... HardWire DL-8 Delay/Looper http://irkinempire.spaces.live.com/ "... When you do things right, people won't be sure you've done anything at all." - Futurama

03-13-2009, 07:50 PM	#17 (permalink)
MartyStrat54 Senior Member Join Date: Feb 2009 Location: Formerly Phoenix, now north of KC Posts: 2,580	Re: THD Yellow Jackets... Serious potential for fun. Guitar World and Guitar Player seem to think they are hot stuff (no pun intended). I wouldn't want to change a 6V6 amp over to EL84's, even with the special adapter. They both put out around the same output wattage. They are running the EL84's as triodes and not as pentodes. No wonder the power drops to around 90 per cent. These two tubes might be making 5 watts. In pentode mode, you can get 16 to 20 watts out of two tubes, hence the DSL 201. I do not understand how they are blending Class A with Class AB without a chop in part of the signal. Class A is on all of the time and AB is on most of the time. That's why Class A amps are the best for fast shredders. I don't know, but the more I learn about these, the more I am inclined to say, "Thanks, but no thanks." As a tech, I have too many questions about why they take a pentode tube (EL34) and replace it with a pentode tube (EL84), but run it in triode mode? It really makes me wonder why they went this route. If you take four EL34's and you have an amp with a power switch, it usually converts the EL34's from pentode to triode operation which gives you 30 to 50 watts of Class A power and almost as loud. (Some amps cut the plate power in half on the tubes and they remain in pentode mode with self biasing [like my Traynor YCS100] and this gives 30 watts of Class A.) There are several other threads on this subject, but I am only placing comments on this one. Conclusion: Taking an EL34 100 watt amp and putting four of the YJ's in it will yield around 10 watts of power (90 per cent off of 100 equals 10). This is because it operates in triode mode. If it was in pentode mode, then you would have close to a DSL 401 in power. But what about sound? Good question, because you have choked the hell out of the B+ voltage and are doing it with resistors that override the bias voltage. So even if the EL84's did run in pentode mode, I doubt if it would sound like a DSL 401. The DSL runs pentode with around 285 volts B+ on the plate. All the associated circuitry is all designed around this. Yellow Jackets are like a giant erasure on the schematic. They erase the power tube circuit and replace it with what can be contained in the base of the converters. I'm sorry, but all of this is a big negative to me as a tech. Marty

03-13-2009, 08:21 PM	#18 (permalink)
joshuaaewallen Senior Member Join Date: Jan 2009 Location: Minnesota Posts: 372	Re: THD Yellow Jackets... Serious potential for fun. I can see what you mean from a tech/purist point of view. Personally what I hope to achieve here is: A) Tone that make me dream about playing my guitar. B) Enough technical knowledge to know what goes into getting tone that I like. C) Hopefully get some communication and info out there on the forum to help others achieve their own personal tonal nirvana. In that order. I know that my TSL122 is not a bedroom amp, so either way I have a challenge ahead of me in my quest for tone. Thanks again Marty & Puffer Fish for your input, and anyone else out there reading this, please feel free to weigh in on the subject. I'm lovin' it! __________________ Josh 2004 PRS Custom 24 10 Top Dean Caddy w/ Bare Knuckles Nail Bombs (This One's For Sale, Just Let Me Know If You Are Interested) 1999 Marshall JCM 2000 TSL 122 - Power Tubes: JJ EL34L's - Assorted New & Vintage pre-amp tubes... I like to roll... HardWire DL-8 Delay/Looper http://irkinempire.spaces.live.com/ "... When you do things right, people won't be sure you've done anything at all." - Futurama

03-13-2009, 11:31 PM	#19 (permalink)
Puffer Fish Member Join Date: Jan 2009 Posts: 69	Re: THD Yellow Jackets... Serious potential for fun. wow, this thread really took off! What was mentioned a little earlier about two Yellow Jackets and two EL34s in the TSL 122 might be something. I see what the person was thinking: the plate voltage may be dispersed enough amongst the tubes to allow the YJs to do their thing without getting too hot. The coolest new amp I have heard is the new JVM model line. My brother picked one up (50 watt head, two channels) and it sounds fantastic to my ears. It seems to actually achieve bedroom volumes because the preamp section is doing a lot of the work I guess. Anyway, it might be something worth looking into if you would consider making a trade in or a trade up or whatever you want to call it. Of course there are always DSL 201 amps out there as well as the DSL 401s like I have. But I use my DSL 401 on stage and at practice--everywhere in fact--so I suspect it would be way too loud for bedroom volume. Hmmm... that term bedroom volume is pretty loose. For me, bedroom volume is the guitar is sometimes too loud even unplugged! That is why I have a practice space and I always appreciate being able to go there and crank it up.

03-14-2009, 01:15 AM	#20 (permalink)
MartyStrat54 Senior Member Join Date: Feb 2009 Location: Formerly Phoenix, now north of KC Posts: 2,580	Re: THD Yellow Jackets... Serious potential for fun. Puffer: It kind of makes you wonder when someone spends $1500 on a boutique "half watt" amplifier. I mean it blows my mind. Maybe in a studio application it works well, but come on, a 1/2 watt for a grand and a half? To me, the smallest practice amp I would want would be ten to twenty watts with at least a 10-inch speaker. I know with these one half and one watt boutique amps, you can crank them up and get the saturated power tube sound. Just don't fart or you'll drown out the saturation! You give the world a bunch of choices and this is what you get...ridiculous mayhem. "Hey Puffer, come on over to my house and we can shred our 1/2 watt amps!" "Look out AC/DC, there's a new sheriff in town." "Wow! Listen to those power tubes saturate..."dyno-mite!" I know people with 1/2 watt hearing aids. Maybe I can make a boutique amp out of one of those. Sheesh! Marty

03-14-2009, 01:42 AM	#21 (permalink)
Puffer Fish Member Join Date: Jan 2009 Posts: 69	Re: THD Yellow Jackets... Serious potential for fun. Ha! I so agree! In fact I was having a similar conversation JUST the other day about botique amps in general and how I mostly just don't get it. But the 1/2 watters seem pretty seriously absurd. What is the point? Well, okay, I get the point regarding tube saturation, okay, I get it. But what ever happened to isolation cabinets or the old trick of wrapping the speaker cab with blankets so you can crank it up, work the speakers but not melt everyone's ears. Really, there have ALWAYS been ways to deal with getting the tubes saturated on a normal amp, but still dealing with the shear volume/ dBs of the amp. After all, borrowing some quilts from your mother will always be way cheaper than the $2000.00 special amplifier, even though it may not be all that sexy. On another related subject, I have cranked the volume on the master while in the clean channel on my DSL 401 and I did the same thing on my Peavey Classic 30 (backup amp : 0 ) and the levels were indeed quite loud, but I did manage to achieve pure power tube over drive and I could handle being in the same room while playing. Verdict: 1/2 watt amp is a serious waste of money in my little world. If I had that kind of extra cash to throw about, it would go toward a Focusrite Liquid Mix or maybe a FMR Audio preamp or something like that to really expand my world for real. Cheers!

03-18-2009, 04:56 PM	#23 (permalink)
tim warner Member Join Date: Feb 2009 Location: upstate ny Posts: 75	Re: THD Yellow Jackets... Serious potential for fun. well here is where all you guys are, I've had mine in my superlead 100 for a couple of weeks and I love em! very Rich robinson, which is exactly what I was looking for. I also did what you did at first , just install 2 and it was very treblly like a vox with the treble switch on , not my thing but it is for others so.... but the 2 mixed with the el's I had a TONEGASM! I hope we are not going to have the same luck as pufferfish's friend though. I wonder if the THD people would be honest if I just called them and got there take on this thread and would they put there money where there mouth is.

03-24-2009, 07:27 PM	#27 (permalink)
joshuaaewallen Senior Member Join Date: Jan 2009 Location: Minnesota Posts: 372	Re: THD Yellow Jackets... Serious potential for fun. Last edited by joshuaaewallen; 03-25-2009 at 04:16 PM. Reason: eh...

04-01-2009, 04:04 PM	#29 (permalink)
Dejoblue Junior Member Join Date: Apr 2009 Posts: 1	Re: THD Yellow Jackets... Serious potential for fun. I have been looking at these and my web research has brought me here. I am looking to convert a JTM 45 with KT66 over with these. Some things I would like to note and get clarification on with reference to failures and other phenomena is: Those having a failure, what is your plate voltage and did you use the warranty to replace the converters and if so what was the costumer service like? Those using two, as I intend to, did you try the outer two sockets to see if it changed the tone and have you biased the amp with 4 EL34s or post conversion with 2 EL34s? I also saw some disapproving posts on the triode conversion and would like clarification of which type the posters are using. If you go to THD you can see that they offer 3 types of converters. Standard conversion, Triode conversion and 6V6 conversion. A good read on them is: http://www.thdelectronics.com/pdf/yj.pdf Plate voltage must be under 520 volts DC. A recommendation, while I am not qualified, is when using 2 converters in a 4 tube amp with the other 2 tubes in place and non converted, I.E., 2 YJ 2 EL34, bias the amp in that configuration. The YJ's are self biasing and when biasing tubes that are not self biasing, the EL34's, you have to get all of the tubes within the proper bias range. So, bias as normal you only have 2 tubes, the EL34's, to consider when adjusting the bias trim pot. As to the questions about why low power amps are all the rage lately, I would like to offer my point of view. We live in a world of pre amp distortion and solid state rectifiers where the power tubes are never fully engaged with typical, to club venues I have visited, Master Volumes set to 2 or 3. I doubt very seriously that many club gigging musicians are able to blast their 50 or 100 watt Marshall heads at full volume to experience or take advantage of their power tubes saturation and character without a contrived slave, attenuation, iso cab or other stage volume control setup. As a matter of fact, most professional tours use in ear monitors and/or very low stage volumes with very low monitor volumes. With this in mind we have all sorts of attenuation devices for large power amplifiers, and even the small ones. From THD's Hotplate and other power soaks to triode/pentode switches and low power/wattage switches on amplifier power sections, there are a multitude of options out there. A logical extension of this is high quality, multi feature low power amplifiers. The benefit of a low power amplifier can be two fold. Benefit being subjective, if you dont like power tube saturation, power amp "sag" and its effects on the pre amp tubes and are happy with an MP1, Triaxis, running a 100 watt head with only pre amp distortion, then your opinion is just as valid, but this wont apply to you. The two fold being that Class A operation is inherently low power and at low power, power tubes can be more easily driven to saturate and develop their signature character. Class A is also always running with the full waveform, anecdotally giving a richer creamier distortion, just as preamp tubes are class A. The lower power has the drawback of lower clean headroom, this may or may not be good depending on style and intent. The expense of many boutique low power amps is the addition of features such as additional attenuation, for example, Mesas Lonestar Special with its 5 Watt Class A mode and THDs UniValve and BiValve with its built in attenuator, and others are just name/quality or unique topology like Alessandro amps. Perhaps the greatest draw to these type of amps is the lessened need for attenuation. It is simply easier to lower 20 watts down to club volumes than 50 or 100. There are also different classes or subsets, for instance the mentioned 1/2 watt or 1 watt or 3 watt amplifiers, which are directly aimed at recording and slaving. On top of this, a mere 5 watts is usually too loud for bedroom/home practicing while 15 - 20 watts is the most volume that most gigging club musicians will ever need. If you need more volume, simply mic it up and that brings me to my last point. The great sounds we hear and try to emulate from our favorite recordings always have a mic and a mic pre amp involved. Many comparisons are apples and oranges, comparing recordings or professional touring rigs that are micd and mixed with a single amplifier that is not micd. A great combination used by iso cab enthusiasts and low power amp enthusiasts is finding a really nice sounding mic and preamp combination and then using that through the PA or a separate super clean cabinet with effects or even a dedicated amp PA, much like Eric Johnsons delay monitor setup(http://www.ericjohnson.com/pictures/newtrick.jpg). I am personally getting my main sound with a JTM 45 attenuated and using Guitar Rig for all other genres with Mackie studio monitors HR624s and Logic for various effects and plugins , etc. The JTM 45 is too loud at around 30 watts and I was looking to these since I love EL84s but also love the trite, tried and true Marshall preamp designs sound. Yes, I said preamp, the predominant sound character but we are talking aesthetics and detail in sound here. So I am looking at YJs with the JTM 45, an 18 Watt Marshall reissue with EL84s or a THD Uni or BiValve. Oh, and the feeling is mutual, we low power amp users look at you high power amp users and say, "What is the point of having all of that power you will never use". IMHO use a MP1 and a Solid State power amp and get he same result. Been there, done that, even with tube power amps but when you cant crank it, it is pointless. So that is my POV and I hope I didn't offend anyone. There is a multitude of sounds out there and I hope these YJs provide me with my dream sound, JTM 45 with EL84s.

04-01-2009, 05:38 PM	#30 (permalink)
rockinr0ll Senior Member Join Date: Feb 2009 Posts: 1,340	Re: THD Yellow Jackets... Serious potential for fun. This is a long read! :0 Could you tell me if you liked them?

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