The JCM 900 and modification... Thoughts?

V-man · 09-17-2009, 08:38 AM

Sorry about my "thoroughness". The gist of passages are underlined for the helpful members who lack the time or attention span to wade through my prose.

These past months I have been rediscovering guitar and reacquainting myself with my gear. Lately I have been looking more into the sound dynamics of the amp and seeing what I can do to shape the tone. I have read all 100+ comments on the Harmony Central review board, along with people's impressions here, and what I have found is about 50% inconsistent opinion, and 50% unified criticism with respect to the 4100's capabilities.

What I have come to experience is the 3 knob EQ (+ presence) is a liability because it is a master EQ for both channels and there is minimal shaping with the manipulation of the knobs (particularly with treble and mid). The FX loop may also change the dynamics in sound for the worse, (or so it seemed in my experience, but this requires further experimentation). Finally, the amp has good cleans and a "working" ability to get some mud at sub-bedroom volumes, but it has been a difficult to dial in the tone that complements my style of music.

The consensus (with a dissenting minority) seems to be that the amp's crunch channel hits the nail on the head for "AC/DC" but that's as far as it goes, and between the lacking low end and the lack of high gain (despite the misleading moniker) leaves one rather disappointed for "the brootalz". I KNOW, I KNOW... I CAN HEAR IT NOW BEFORE THE FINGERS TAP THE KEYS: "sell the amp and get the amp you 'really' want."

Before the fingers DO tap that out, let me cut those of you off at the pass with the following:

1. This is my first halfstack, first tube amp, and the only Marshall I have known, and I have no intention of selling, let alone taking a bath due to the bad rap these have gotten. 2. I don't have the funds to swing another amp now so the option is deal with what I have stock and wait, or mod. 3. Who the hell knows what I need, or that the 4100 with/without mods isn't truly "the amp I really want"? Hey, I have even come across a front contending that you need to get out of Marshalls alltogether for post-80s metal. Sidestepping that arguably nonsensical statement, I don't see the point in playing russian roulette or merry-go-round with 2203KKs, Mesas, Framus Cobras, etc, etc that are impossible to demo in my area. What makes sense today is making the most of what I have and looking at other possibilities on the horizon (if necessary).

Other facts to consider:

- This is an early 90s EL-34 driven model.

- I have 2 MXR 108s and a Soundtank TS5 to shape tone

- I like the clean tone, and see potential in the crunch, but it is "thin," lacking low-end punch

- The TS5 adds some decent grain. MXR#1 gives a subtle improvement, but not enough to raise low end. MXR #2 (in conjunction) gives it thunder, but now it's got a muddy sound. This may be rectified with further experimentation.

- Master volumes rarely exceed 3.5 on the crunch and 5 on the clean, so some of what I am missing might be on the "loud" side of the amp that's hard to reach for long in the neighborhood.

- I would prefer reversible modifications, but having no plans to sell my first marshall means that the amp I love playing takes a higher priority than the amp I like collecting.

The three mods I know of thus far are:

Liam's Mod: seems "quasi-reversible" and simple, but may be the least effective for achieving a dramatic result.

TriodeAmplification mod: sold as instruction + pics. I am wary of sold instructions as this may be $30 for something marginally better/worse than Liam's mod + pics and have no idea about the extent of the mods.

VoodooAmps mod: Seems to have the most potential for improvement, reasonably well-reviewed, and the advertisement is suggestive that the mods are reversible, but this also is the most expensive and requires the cost and risk of shipping to/from Voodoo.

Based on my situation, what do you think? Also are there other mods you can add or recommend? Also, bear in mind I will be spending some time tone shaping while I research these alternatives before doing anything, and of course, I am receptive to any tone-shaping input you may have as well
TIA

LesPaulopolis · 09-17-2009, 02:43 PM

V-Man, I have experienced the same dilemma. The most valuable tool (besides the EQ pedal) I found was a volume pedal in the loop.

The vol. pedal lets you crank the master more and then bring it down a bit. Def. a balancing act but I find that when you get a clean setting you like, the dirty channel is too 'woofy'. This trick brings the channels into a close balance I think (and also tames the treble).

Also, keep everything on 5 and use your 'always on' EQ to shape you main tone and the other one as your solo boost.

Option 2: Get a OD pedal you really like using w/the clean channel. Use that for dirty chords and set channel B as your creamy solo/boost channel in conjunction w/the already in-use OD pedal.

Hope this helps.

Ken · 09-17-2009, 03:47 PM

JCM 900's fetch a good price; if you sell it you'll get a fair dollar which is about $700. For that you can get a DSL! I say that's your best bet.

Ken

V-man · 09-17-2009, 07:23 PM

LP, Thanks for the tips. The volume pedal trick is one avenue I haven't gone down yet and I'll be sure to add that into my experiments before committing.

Ken, I appreciate that but this is my first Marshall. I don't want to sell it, much less sell it for an amp with no guarantee that it will rectify my problem. As I see it today, my two options are tweaking the 4100 (with/without alteration) until the problem is solved and if necessary, getting an additional amp in the future as funds permit.

ironlung40 · 09-17-2009, 08:11 PM

Quote:

Originally Posted by Ken

JCM 900's fetch a good price; if you sell it you'll get a fair dollar which is about $700. For that you can get a DSL! I say that's your best bet.

Ken

Hey, It's Ken the JCM 900 hater again, saying get rid of it and get a DSL!! After all, it's only a 900, right Ken?

Seriously, though, you should try the 6L6GC output tubes in the amp, and also do the eq and volume pedal trick. For more info on the 6l6GC's I'd check out Eurotubes.com. Another thing, that I think gets neglected with these 900's is the speakers used. They are kinda treble heavy amps, and the typically configuration of a marshall 4x12 with 75's really makes them more harsh. I run vintage 30's with mine and it tames the shrillness some.

I see you have v30s and a 1960 cab. Which sounds best with it in your opinion?

I've got an early model 900 4100, and I've got an 800 2203. Yeah the 2203 sounds better, and I record with it. But when I play out, I take the 4100 for the versatility and in my opinion with it set up properly, it sounds really good.
I wouldn't sell mine for a 2000 series amp ever. I just don't like the voicing of the 2000 series, but they're good amps, just not my thing. If I wanted to have a better live tone with versatility, I would run my 2203 for dirt and run my fender twin reverb for cleans.

One last note on mods. I personally don't believe in them. You're just hurting resell on an amp by doing them, and there are enough tube, pedals, speaker options to use that will alter your tone enough. I think any of the amps marshall has put out are great stock and need little or no tweaks on the circuit. It is just a matter of finding the one or two amps that work for you. The only mod I've ever done on an amp was to clip one leg of the bright cap on a friend's 2204, but a little solder will put it back like new.

Good Luck

(war)thrash5150 · 09-17-2009, 09:38 PM

I have a 4500 that I picked up for $300 and it just needed a quick soldering job on the tranny for 120V instead of 220. I always had a love of marshalls and couldn't pass up this deal. I've had a DSL100, JMP 2203, JCM 2210, avt's, valvestates, mg100rcd and a lead 12 combo way back in 1987. They all had their qualities that I liked (jmp with a rat up front was unreal

) but the 900 delivers what I like most...quality distortion with clarity. The very best thing you can do with the 900 is this: like others have suggested, get you some new powertubes, high gain preamp tubes and have the amp biased. Run an eq in the loop, and a bad monkey boost on the B channel with the low all the way up.
I've thought about flipping the amp several times but I only have 300 into it and even if I sold it for 6-ish, there isn't an amp in that price range that sounds better than this for what I do. I also have a 5150 blockletter that smokes it in the low end, but the distortion to me isnt anywhere as near as musical. Sorry so wordy...but if you get anything out of this post...keep the amp!

V-man · 09-17-2009, 10:02 PM

Great input guys... by all means, keep it coming.

Quote:

Originally Posted by ironlung40

Seriously, though, you should try the 6L6GC output tubes in the amp, and also do the eq and volume pedal trick. For more info on the 6l6GC's I'd check out Eurotubes.com.

Is this advice based on the assumption this is a 5881 model or based on the knowledge mine is an EL-34 model and you think those 6L6s are an improvement over 34s? Right now I am running Winged-Cs 34s with fresh caps and they have a lot of life left on them. If I were going for retube, I think I'd try KT-88s first.

Quote:

I see you have v30s and a 1960 cab. Which sounds best with it in your opinion?

I really like the V30s and I am glad I picked up the cab.

Quote:

Yeah the 2203 sounds better, and I record with it. But when I play out, I take the 4100 for the versatility and in my opinion with it set up properly, it sounds really good.

This underscores the point about the dynamic shift of an amp's capabilities with the master past noon and within the mix of the band... both of which I haven't had suffient experimentation with before making the call.

Quote:

Originally Posted by (war)Thrash5150

I see this the 900 delivers what I like most...quality distortion with clarity. The very best thing you can do with the 900 is this: like others have suggested, get you some new powertubes, high gain preamp tubes and have the amp biased. Run an eq in the loop, and a bad monkey boost on the B channel with the low all the way up.

I definitely agree with the 900 distortion potential. EQ is definitely in the loop (2 right now) as is an OD, though I may experiment with others. I may have to look into your preamp tube suggestion too. Thanks!

Adrian R · 09-17-2009, 10:09 PM

V-man..

Been using 900s for years and I love em' , but they do need a bit of help to get them to roar properly...First of all dump the 34s...install a matched quad of good 6L6GCs..bias it properly.. (like 35-40mA)..drive the front end with a good quality overdrive pedal..and then use the 108 in the loop or better yet...run a BBE 362 in the loop.

With this configuration you will get a tone that is comparable to a strong 800...but MUCH cleaner and quieter.

Of yea, don't sell it for one of them mushy, unreliable DSLs! The 900 series..although not as strong as the DSLs are out of the box...are much more reliable, quieter..with good, clear distortion character.

Jesstaa · 09-18-2009, 03:17 AM

Alright, what's with everyone saying the 4100 has no low end, am I missing something here, because all I have is low end, too bloody much of it. My treble is on like 9, my presence on like 7 and my bass on about 4 or 5, and at low volumes it still shakes everything in my house... Through a fucking 4x10 cab.

And Ken, why must you always seek out every JCM 900 thread, and pretty much troll it, somebody asks for a good opinion or suggestion, and you say "Sell it, it wont give you what you want, buy a DSL". You sound like a broken record.

V-man · 09-18-2009, 05:40 AM

Quote:

Originally Posted by Jesstaa

Alright, what's with everyone saying the 4100 has no low end, am I missing something here, because all I have is low end, too bloody much of it. My treble is on like 9, my presence on like 7 and my bass on about 4 or 5, and at low volumes it still shakes everything in my house... Through a fucking 4x10 cab.

I don't know if we're talking about the same thing in terms of "low end". If I put the preamp vols past 2 o' clock and the masters past 3 on either channel I've had no problem rattling windowpanes, etc bone stock either. The low end I am talking about is best described with the slow chug of a palm-muted power chord.

When I do that my power chords go: BUNG! BUNG! BUNG! They have a "middy" and springy texture played bone-stock.

Run an EQ for bass-boost and it has more of a DUM! DUM! DUM! There is more of a thunder to the muted notes.

Run a second EQ to bass-boost that and it sounds like "IAMGOINGTOEARFUCKYOUTODEATH!!!"

RobS · 09-18-2009, 06:31 AM

V-man,
I have a 4100 and recently put in JJ6l6gc's. All I can say is it sounds ^&*(great!
Not sure if someone else has posted yet but these amps 'wake' up at vol levels over 4-5, but then they wake the dead as well. They sound much much tighter,fuller, crunchier and better.
That's why I use the Powerbrake at home.
I do not recall seeing what tubes you have in there but I run the jj6l6gc OP + EH12ax7's up front and cannot fault it. The sound with a good guitar is great in my opinion. Cleans are excellent, crunch is very crunchy and then with gain2 over 15 it really is a heavy sounding amp. But I only run about gain at12-13 and with more master vol it's very much 800 like.

Rob

ironlung40 · 09-18-2009, 05:41 PM

Quote:

Originally Posted by Jesstaa

And Ken, why must you always seek out every JCM 900 thread, and pretty much troll it, somebody asks for a good opinion or suggestion, and you say "Sell it, it wont give you what you want, buy a DSL". You sound like a broken record.

That's my thought exactly. I got into a little pissing match with Ken not too long ago about his negative comments ALL the time in virtually every 900 thread I find. I was bashed a little as if I didn't know what I was talking about. Nice to see someone else noticed "Ken the 900 Hater". Why even post, if you're not going to try and contribute to the actual questions the OP asks? I'm sure he knows there are other amps out there that he could buy if he wanted to.

ironlung40 · 09-18-2009, 05:47 PM

Quote:

Originally Posted by V-man

Is this advice based on the assumption this is a 5881 model or based on the knowledge mine is an EL-34 model and you think those 6L6s are an improvement over 34s? Right now I am running Winged-Cs 34s with fresh caps and they have a lot of life left on them. If I were going for retube, I think I'd try KT-88s first.

Not based on 5881's only. These tubes can be put into EL34 amps as well, and they really sound good. I've currently got the EL34's in a JCM 900 4100 I just bought. It actually has had very, very, little play time on it, and the tubes are still the factory tubes. It's practically a brand new amp except for a small patch on the tolex. Anyway, I've also got a 900 4100, that had EL34's in it,but based on Adrian's advice and Bob at Eurotubes, I decided to go with the 6L6GC's. They sound awesome, and I think much better than the EL34's. Winged C's are good tubes though, but I think with the type of amp the 900 is the 6L6GC's just compliment it better. they make it a fuller more tonally rounded machine.

Anyway, you can get a set from Bob that will bias right up with no mods necessary. Just make sure to tell him that it currently runs EL34's.

Webslinger · 09-18-2009, 06:12 PM

Quote:

Originally Posted by V-man

Based on my situation, what do you think? Also are there other mods you can add or recommend? I am receptive to any tone-shaping input you may have as well

Your research is about what I had come up with.
I bought a JCM900 2x12 combo. It's a 1998 model, supposedly that came with 5881s as stock, but the previous owner had EL34s in it. It had a decent tone, and roared with a LesPaul, but I couldnt get it clean enough for my taste when I occasionally played my Strat or acoustic through it. Granted I fully understood Marshal tone is not Fender clean, but my amp tech said he could do something. He replaced the El34s with 6L6s and biased it cooler?. He also installed a master volume kit. When I got it back, it was cleaner, at the cost of a little midrange (and volume on the clean channel, but I might be able to correct this). And it still has enough gain for me. If I need more I'll use a pedal.
I was able to regain a good amount midrange, and them some, by replacing one of the Celestion G12T-75 speakers with an Eminence Governor. It never had alot of low end, even before, but using an EQ pedal does help. I also have Boss OD20 muti-sound distortion pedal that has a "bottom" knob* that really helps too.
(*the Bottom is no so much a bass control, but more like a parametic lower end boost...Like pyramiding the 3 next-to-last left-side slides on a 10 band EQ, it's cool, I dont know why more FX pedals dont have it)

V-man · 09-18-2009, 06:59 PM

Quote:

Originally Posted by ironlung40

Nice to see someone else noticed "Ken the 900 Hater". Why even post, if you're not going to try and contribute to the actual questions the OP asks? I'm sure he knows there are other amps out there that he could buy if he wanted to.

For the record, I tried the DSL on the floor back when and for what little time I spent with it, I was completely underwhelmed. Even if I had more time to dial in a DSL, I am very doubtful that it would be worth the trouble replacing given the other better (for my style) alternatives out there. If I were to buy a new Marshall it would be a 2203KK or 1959RR. If I was going to buy used, it would be a 2203, 255X, or maybe an SLX.

I appreciate the 6l6GC comment (again). Apparently it comes well-recommended between you, RobS and Adrian R. Maybe I will try those instead of KT88s when and if I ever burn the 34s out (most of the time I'm crunch running the preamp section).

Webslinger and those before (and after): I appreciate every spec of input regarding how you harnessed the tone of your 900. It's great to see each person's approach as it gives me more alternatives to pick and chose from. Clearly my decision today is to continue playing with the tools I have to see what I can get out of the amp, and perhaps implement a few suggestions you guys contributed that I haven't performed myself. A mod may/may not be the best idea in the end, but it seems there are many avenues I could and probably should try before going down that road. Thanks for the input, and don't be shy with further suggestions!

ironlung40 · 09-19-2009, 12:29 AM

Quote:

Originally Posted by V-man

For the record, I tried the DSL on the floor back when and for what little time I spent with it, I was completely underwhelmed. Even if I had more time to dial in a DSL, I am very doubtful that it would be worth the trouble replacing given the other better (for my style) alternatives out there. If I were to buy a new Marshall it would be a 2203KK or 1959RR. If I was going to buy used, it would be a 2203, 255X, or maybe an SLX.

I with you on the DSL comment. I never could make myself like the tone from one. I kept hearing all of this great hype about it, but never got what I wanted from one.

Jesstaa · 09-19-2009, 02:08 AM

Quote:

Originally Posted by ironlung40

Not based on 5881's only. These tubes can be put into EL34 amps as well, and they really sound good. I've currently got the EL34's in a JCM 900 4100 I just bought. It actually has had very, very, little play time on it, and the tubes are still the factory tubes. It's practically a brand new amp except for a small patch on the tolex. Anyway, I've also got a 900 4100, that had EL34's in it,but based on Adrian's advice and Bob at Eurotubes, I decided to go with the 6L6GC's. They sound awesome, and I think much better than the EL34's. Winged C's are good tubes though, but I think with the type of amp the 900 is the 6L6GC's just compliment it better. they make it a fuller more tonally rounded machine.

Anyway, you can get a set from Bob that will bias right up with no mods necessary. Just make sure to tell him that it currently runs EL34's.

Just watch out with Eurotubes, I got a quad of KT77's for my JCM 900 and they mustn't have been matched properly, because they drifted and red plated.

Also, yeah, if you mean the low end for chugging palm mutes, I got plenty of that too.

RobS · 09-19-2009, 06:57 AM

Jessta,
Did you burn in the KT77's? When I put new tubes in I run them with the probe inline for at least 4 hours with music playing through the amp (ipod or similar). Then adjust bias if need be. Then check periodically.

Rob

Ken · 09-19-2009, 09:22 AM

Quote:

Originally Posted by ironlung40

Hey, It's Ken the JCM 900 hater again, saying get rid of it and get a DSL!! After all, it's only a 900, right Ken?

Pretty much! LOL Look, anyone who has a JCM 900 and loves it should keep it and rock on!! But this guy ISN'T happy with it, so the suggestion to get a warmer and more versatile amp isn't a bad one.

People who hate the DSL's should probably try a VM, JCM 800 etc. as opposed to spending too much money trying to change a design that Marshall spent a lot of money developing with no guarantee they'll like the results. The same applies to anyone with an amp they don't like. I might try changing the tube types as the mods to do that are minor, but that's about it.

Ken

ironlung40 · 09-19-2009, 09:56 AM

Quote:

Originally Posted by Ken

Pretty much! LOL Look, anyone who has a JCM 900 and loves it should keep it and rock on!! But this guy ISN'T happy with it, so the suggestion to get a warmer and more versatile amp isn't a bad one.

People who hate the DSL's should probably try a VM, JCM 800 etc. as opposed to spending too much money trying to change a design that Marshall spent a lot of money developing with no guarantee they'll like the results. The same applies to anyone with an amp they don't like. I might try changing the tube types as the mods to do that are minor, but that's about it.

Ken

Hey Ken, What's up? I completely agree with not changing a design. I personally don't like to mod amps, unless it's a bias mod, too. One, can however change their tone with different tubes, and experiment with different pedals too, so that's always my suggestion with any amp. If you do that, and still can't find mojo with it, it's probably not the right amp for you.

It really sucks though when trying to find the right amp as most if not all dealers only carry what's hot at the moment. It's nearly impossible to sit down with an amp of your choosing and experiment before buying, especially with the older marshalls that aren't in production.

If it wasn't for ebay, I would never have had the opportunity to experiment with a lot of the amps I've tried. I've spent a lot of money buying several amps, though, but I have been re-selling the ones I didn't want to keep, and I often find that if you're patient you can get decent deals that you can get your money back out of or turn a profit when you re-sell.

I do know first-hand, what most of these amps that we talk about in here sound like to me, because I've either owned one for a short while, kept it, or played one in store. Playing them in person is really the only way to know, and it's better if that can be done at home were you can crank it and use your own gear with it.

00jett · 09-19-2009, 10:07 AM

i had the 900 combo for quite a while and had the same dilema. i actually did mod my amp. i did some of the mods found on the net and forum sites cause i could not afford to send it away to voodoo or something like that. let me point out that in my opinion the mods i found (Liam's mod) gave less than desirable result. i could definately hear a change in tone but it was actually for the worse instead of better. this puzzled me but than i downloaded a program called Tone Stack Calculator and looked at the eq curve for the amp both pre and post mod. i saw that i made those harsh frequencies even worse and made the gain buzzier. using this program i formulated my own mod that smoothed out the high end of the amp and added some low end. This and vintage 30 speakers with and eq in the loop made that amp incredable. the only reason i got rid of it was to buy a head format.

Jesstaa · 09-19-2009, 10:20 AM

Quote:

Originally Posted by RobS

Jessta,
Did you burn in the KT77's? When I put new tubes in I run them with the probe inline for at least 4 hours with music playing through the amp (ipod or similar). Then adjust bias if need be. Then check periodically.

Rob

I left it for about an hour with nothing running through it, and the volume on about 3, but the bias kept drifting so much that I pretty much gave up once I got it to stay around 37 for more than 5 minutes.

And also, it was a good example of the fact something screwed up in my amp, because I had the volume on 3 with nothing running through the amp, and there was no noise AT ALL (It was dead quiet) but now, if I have my amps volume on 2 with nothing plugged in, it's loud as fuck.

And Ken, here's where our opinions differ greatly, I believe if somebody has an amp they're almost fully content with, but they just need a little extra, they should go all out and mod it, a stock DSL wont give a modded JCM 900 sound, and a stock JCM 900 sound wont be everybodys cup of tea. Alot of artists out there use modified/funky ass rigs, so if somebody needs a slightly different flavour over the top of their amp, that's the way to go.

Hey, isn't the JCM 2000 supposidly an all tube amp? IF so, why does it have transistors and those IC things in it, it has more transistors than my 900, and by the looks of it, about the same amount of IC's. (Dunno if they're IC's or whatever, but those little chip like things)

Adrian R · 09-19-2009, 12:02 PM

Quote:

Originally Posted by V-man

For the record, I tried the DSL on the floor back when and for what little time I spent with it, I was completely underwhelmed. Even if I had more time to dial in a DSL, I am very doubtful that it would be worth the trouble replacing given the other better (for my style) alternatives out there. If I were to buy a new Marshall it would be a 2203KK or 1959RR. If I was going to buy used, it would be a 2203, 255X, or maybe an SLX.

I appreciate the 6l6GC comment (again). Apparently it comes well-recommended between you, RobS and Adrian R. Maybe I will try those instead of KT88s when and if I ever burn the 34s out (most of the time I'm crunch running the preamp section).

Webslinger and those before (and after): I appreciate every spec of input regarding how you harnessed the tone of your 900. It's great to see each person's approach as it gives me more alternatives to pick and chose from. Clearly my decision today is to continue playing with the tools I have to see what I can get out of the amp, and perhaps implement a few suggestions you guys contributed that I haven't performed myself. A mod may/may not be the best idea in the end, but it seems there are many avenues I could and probably should try before going down that road. Thanks for the input, and don't be shy with further suggestions!

**Hey V-Man..

Its physically impossible to run either KT88s/66s in a 900..reason being is that there is not enough room between the tube sockets in order for them to fit! I think this totally sucks! 900s would sound AWESOME with 88s or 66s...

IMO, so far the best sounding current production tube in a 900 4100 is either the JJ 6s, or the SED 6s...I've tried just about all of them...

One day I hope to get my hands on some NOS tubes and really see if there is a big difference...but they are just SO expensive!

Ken · 09-19-2009, 07:08 PM

Quote:

Originally Posted by Jesstaa

Hey, isn't the JCM 2000 supposidly an all tube amp? IF so, why does it have transistors and those IC things in it, it has more transistors than my 900, and by the looks of it, about the same amount of IC's. (Dunno if they're IC's or whatever, but those little chip like things)

That's for things like channel switching. The tone path is all tube, unlike the 900. But that's not really that important; it's the sound you like that counts. There's not a single amp ever made that everyone likes, so forget what people say and find an amp you personally like. Hell, the Jubilee has diode clipping too.

As for mods, rich rock stars can mod the crap out of their amps and if they still suck they sell them and buy something else. Seems to me any meaningful mod to a 900 will put it in an 800 price range which is probably what the OP should have bought in the first place.

As for the DSL..well 95% of people who've played one like it but that's not to say the other 5% are stupid. They just want something else...OR they plated a crappy DSL which is what I think. Maybe a VM is better to someone's ear than a DSL but that doesn't make a DSL a bad amp. And yes, there are nice 900's out there too. Or so I'm told.

Ken

V-man · 09-19-2009, 07:43 PM

Quote:

Originally Posted by Ken

Pretty much! LOL Look, anyone who has a JCM 900 and loves it should keep it and rock on!! But this guy ISN'T happy with it, so the suggestion to get a warmer and more versatile amp isn't a bad one...

...As for mods, rich rock stars can mod the crap out of their amps and if they still suck they sell them and buy something else. Seems to me any meaningful mod to a 900 will put it in an 800 price range which is probably what the OP should have bought in the first place.

As for the DSL..well 95% of people who've played one like it but that's not to say the other 5% are stupid. They just want something else...OR they plated a crappy DSL which is what I think. Maybe a VM is better to someone's ear than a DSL but that doesn't make a DSL a bad amp. And yes, there are nice 900's out there too. Or so I'm told.

Calling it like I see it and I am REALLY hoping this isn't going to turn yet another of those hijacks:

An otherwise constructive amp change suggestion is in pretty poor taste and smacks of trolling when it is explicitly stated in the OP that people withhold all "Sell the amp and buy XXXX" comments for 3 distinct and practical reasons. It seems a little more suspect when later I have explicitly stated that I do not want a DSL, I didn't like one, and If I got good sound on it with patience, I am sure I could get a better sound (for my tastes) with another amp altogether and there is still talk about how the DSL can be a great amp for reasons ABC. The same behavior from other threads combined with the dismissal of my input suggests to me that you are promoting a personal agenda instead of offering constructive advice.

Trying to be constructive myself, I think you have a solid argument about modified amps and with all the suggestions listed here now and (hopefully) the future, there seems to be plenty of alternatives to try before taking such measures.

tbellisario · 10-26-2009, 12:38 PM

I think this is a graet discussion on the JCM 900.
When I picked this amp up it was given a fresh coat of white wall paint by some chick in a grunge band.
After recovering it I comitted myself to bring out the best in this amp. My other amp is a 69' Super Reverb.
I now have EL-34 power tubes and will try swapping out with 6L6's I also run into a 4x12.
Keep up the discussion on mods as they are interesting to consider.

LesBalls · 10-26-2009, 03:34 PM

I am an admitted JCM900 fan. However, I do understand that the amp is not for everyone.

With that in mind, I would first decide if you like the tone of it. It has been my experience that modding will only help to improve your existing tone. It's not going to give you a brand new 100% new tone like buying a new amp will.

You seem to like the amp, or at least don't want to sell it.

So, I would change the power tubes and preamp tubes. I prefer Winged C EL34's in the power section and some sort of chinese 12ax7 in the preamp. Opinions differ on this so, do some tube research.

I would also change the filter caps. Filter caps get old, dry out, and take tone with them as they die.

Put in new tubes, new filter caps, and having the amp properly biased.

Second, invest in an attenuator. I prefer the THD Hotplate, but again, opinions vary.

The most important part of the "Tone of The Gods" equation is volume. You need to turn the amp up to hear the power tubes. This is where the attenuator comes in handy. I don't really like the sound of Master Volume amps with the master on 10...but it needs to be on 5 at least...7 sounds the best to me...Paul Gilbert likes 8...again, opions and results vary but the bottom line is turn the amp up loud.

Third, invest in an EQ or the BBE Sonic Maximizer to run in the effects loop. I would recommend trying the EQ first (MXR 10 Band). The BBE has more of an 80's sound inherent to it which may not be your cup of tea. I use the BBE and it works great.

Fourth, goose the front end with an OD pedal. I usually run my Master at 7 and preamp at noon...I then replace the gain that I lost when I turned the preamp down with an OD pedal...not a distortion pedal.

Turning the amp up is your main problem right now.

Hope this helps you!

LesPaulopolis · 10-27-2009, 02:02 PM

^^^ Another reason why a volume pedal is a good investment. Crank that amp and bring it down a bit with the pedal. I have compared the tones at similar volumes and I'm telling ya, it works. Finally, when you're just a bit too loud or quiet you don't need to monkey with the really touchy volume and gain controls on-board the head...just use the pedal and 'set and forget' the head controls.

(war)thrash5150 · 10-29-2009, 07:29 AM

Les, would a volume pedal work equal to or as well as an attenuator? It's def cheaper!

TPR · 10-29-2009, 09:39 AM

I'll jump in here, although I'm curious about Les' thoughts. The volume pedal can only work in front of the power amp, either between gtr and amp or in the loop. In front, it's basically acting like a pickup output control and in the loop, it's acting like another master volume. Either way, my understanding is (and someone correct me if this is wrong), the power tubes are not really being pushed by the preamp.

The attenuator goes between the power output (speaker out jack on the amp) and the speaker, so the power tubes get pushed and then the volume is controlled to the speaker.

As you may already know, NEVER put a volume pedal or anything other than a properly rated attenuator between the amp speaker jack and the speaker.

I find that putting the volume pedal in the loop does give me a better sound at a lower volume than just using the master volume. I'm sure it's because of the particular components in the pedal plus the slightly different location in the signal chain, but I don't know the specifics. However, it still isn't the same as the attenuator since the sound is better overall with harder driven power tubes. If you have a way to check out these options, that would be the best way to see what works for you. And best to test in your real environment if you can, rather than the store.

09-17-2009, 08:38 AM	#1 (permalink)
V-man Senior Member Join Date: Jan 2009 Posts: 189	The JCM 900 and modification... Thoughts? Sorry about my "thoroughness". The gist of passages are underlined for the helpful members who lack the time or attention span to wade through my prose. These past months I have been rediscovering guitar and reacquainting myself with my gear. Lately I have been looking more into the sound dynamics of the amp and seeing what I can do to shape the tone. I have read all 100+ comments on the Harmony Central review board, along with people's impressions here, and what I have found is about 50% inconsistent opinion, and 50% unified criticism with respect to the 4100's capabilities. What I have come to experience is the 3 knob EQ (+ presence) is a liability because it is a master EQ for both channels and there is minimal shaping with the manipulation of the knobs (particularly with treble and mid). The FX loop may also change the dynamics in sound for the worse, (or so it seemed in my experience, but this requires further experimentation). Finally, the amp has good cleans and a "working" ability to get some mud at sub-bedroom volumes, but it has been a difficult to dial in the tone that complements my style of music. The consensus (with a dissenting minority) seems to be that the amp's crunch channel hits the nail on the head for "AC/DC" but that's as far as it goes, and between the lacking low end and the lack of high gain (despite the misleading moniker) leaves one rather disappointed for "the brootalz". I KNOW, I KNOW... I CAN HEAR IT NOW BEFORE THE FINGERS TAP THE KEYS: "sell the amp and get the amp you 'really' want." Before the fingers DO tap that out, let me cut those of you off at the pass with the following: 1. This is my first halfstack, first tube amp, and the only Marshall I have known, and I have no intention of selling, let alone taking a bath due to the bad rap these have gotten. 2. I don't have the funds to swing another amp now so the option is deal with what I have stock and wait, or mod. 3. Who the hell knows what I need, or that the 4100 with/without mods isn't truly "the amp I really want"? Hey, I have even come across a front contending that you need to get out of Marshalls alltogether for post-80s metal. Sidestepping that arguably nonsensical statement, I don't see the point in playing russian roulette or merry-go-round with 2203KKs, Mesas, Framus Cobras, etc, etc that are impossible to demo in my area. What makes sense today is making the most of what I have and looking at other possibilities on the horizon (if necessary). Other facts to consider: - This is an early 90s EL-34 driven model. - I have 2 MXR 108s and a Soundtank TS5 to shape tone - I like the clean tone, and see potential in the crunch, but it is "thin," lacking low-end punch - The TS5 adds some decent grain. MXR#1 gives a subtle improvement, but not enough to raise low end. MXR #2 (in conjunction) gives it thunder, but now it's got a muddy sound. This may be rectified with further experimentation. - Master volumes rarely exceed 3.5 on the crunch and 5 on the clean, so some of what I am missing might be on the "loud" side of the amp that's hard to reach for long in the neighborhood. - I would prefer reversible modifications, but having no plans to sell my first marshall means that the amp I love playing takes a higher priority than the amp I like collecting. The three mods I know of thus far are: Liam's Mod: seems "quasi-reversible" and simple, but may be the least effective for achieving a dramatic result. TriodeAmplification mod: sold as instruction + pics. I am wary of sold instructions as this may be $30 for something marginally better/worse than Liam's mod + pics and have no idea about the extent of the mods. VoodooAmps mod: Seems to have the most potential for improvement, reasonably well-reviewed, and the advertisement is suggestive that the mods are reversible, but this also is the most expensive and requires the cost and risk of shipping to/from Voodoo. Based on my situation, what do you think? Also are there other mods you can add or recommend? Also, bear in mind I will be spending some time tone shaping while I research these alternatives before doing anything, and of course, I am receptive to any tone-shaping input you may have as well TIA __________________ Gibson: '88' Explorer 90, Flying Vs - '02' V-Factor, '06' RI, '07' RI Jackson: '92' Rhoads Tribute, '92' Rhoads PCS, '02' KV2 '92' ESP/Hill King V '04' Epiphone Goth V '81' Marshall 1992 '92' Marshall 4100 '97' Crate Blue Voodoo BV-60 Combo

09-17-2009, 02:43 PM	#2 (permalink)
LesPaulopolis Senior Member Join Date: Jan 2009 Location: Minneapolis Posts: 250	Re: The JCM 900 and modification... Thoughts? V-Man, I have experienced the same dilemma. The most valuable tool (besides the EQ pedal) I found was a volume pedal in the loop. The vol. pedal lets you crank the master more and then bring it down a bit. Def. a balancing act but I find that when you get a clean setting you like, the dirty channel is too 'woofy'. This trick brings the channels into a close balance I think (and also tames the treble). Also, keep everything on 5 and use your 'always on' EQ to shape you main tone and the other one as your solo boost. Option 2: Get a OD pedal you really like using w/the clean channel. Use that for dirty chords and set channel B as your creamy solo/boost channel in conjunction w/the already in-use OD pedal. Hope this helps. __________________ '68 RI LP Custom JCM900 + EQ & Boost

09-17-2009, 03:47 PM	#3 (permalink)
Ken Senior Member Join Date: Feb 2009 Location: Arlington Heights, IL Posts: 607	Re: The JCM 900 and modification... Thoughts? JCM 900's fetch a good price; if you sell it you'll get a fair dollar which is about $700. For that you can get a DSL! I say that's your best bet. Ken

09-17-2009, 07:23 PM	#4 (permalink)
V-man Senior Member Join Date: Jan 2009 Posts: 189	Re: The JCM 900 and modification... Thoughts? LP, Thanks for the tips. The volume pedal trick is one avenue I haven't gone down yet and I'll be sure to add that into my experiments before committing. Ken, I appreciate that but this is my first Marshall. I don't want to sell it, much less sell it for an amp with no guarantee that it will rectify my problem. As I see it today, my two options are tweaking the 4100 (with/without alteration) until the problem is solved and if necessary, getting an additional amp in the future as funds permit. __________________ Gibson: '88' Explorer 90, Flying Vs - '02' V-Factor, '06' RI, '07' RI Jackson: '92' Rhoads Tribute, '92' Rhoads PCS, '02' KV2 '92' ESP/Hill King V '04' Epiphone Goth V '81' Marshall 1992 '92' Marshall 4100 '97' Crate Blue Voodoo BV-60 Combo

09-17-2009, 09:38 PM	#6 (permalink)
(war)thrash5150 Member Join Date: Apr 2009 Location: Crestview, FL Posts: 33	Re: The JCM 900 and modification... Thoughts? I have a 4500 that I picked up for $300 and it just needed a quick soldering job on the tranny for 120V instead of 220. I always had a love of marshalls and couldn't pass up this deal. I've had a DSL100, JMP 2203, JCM 2210, avt's, valvestates, mg100rcd and a lead 12 combo way back in 1987. They all had their qualities that I liked (jmp with a rat up front was unreal ) but the 900 delivers what I like most...quality distortion with clarity. The very best thing you can do with the 900 is this: like others have suggested, get you some new powertubes, high gain preamp tubes and have the amp biased. Run an eq in the loop, and a bad monkey boost on the B channel with the low all the way up. I've thought about flipping the amp several times but I only have 300 into it and even if I sold it for 6-ish, there isn't an amp in that price range that sounds better than this for what I do. I also have a 5150 blockletter that smokes it in the low end, but the distortion to me isnt anywhere as near as musical. Sorry so wordy...but if you get anything out of this post...keep the amp!

09-17-2009, 10:09 PM	#8 (permalink)
Adrian R Senior Member Join Date: Jan 2009 Location: Far North Chicago Burbs' Posts: 170	Re: The JCM 900 and modification... Thoughts? V-man.. Been using 900s for years and I love em' , but they do need a bit of help to get them to roar properly...First of all dump the 34s...install a matched quad of good 6L6GCs..bias it properly.. (like 35-40mA)..drive the front end with a good quality overdrive pedal..and then use the 108 in the loop or better yet...run a BBE 362 in the loop. With this configuration you will get a tone that is comparable to a strong 800...but MUCH cleaner and quieter. Of yea, don't sell it for one of them mushy, unreliable DSLs! The 900 series..although not as strong as the DSLs are out of the box...are much more reliable, quieter..with good, clear distortion character. __________________ Adrian R. Amplification: Marshall JCM800 2205 Marshall JCM900 MKIII 2100 Marshall JCM900 Dual Reverb 4500 Marshall MG15 Micro Stack Marshall 1960A 4x12 Cab. w/75w Celestions Sonic 2x12 Cab. MXR Fx. Guitars: Gibson LP Standard Gibson Explorer Gibson Flying V Guild DV 6 Acoustic "Only two tones apply: loud and LOUDER"

09-18-2009, 03:17 AM	#9 (permalink)
Jesstaa Senior Member Join Date: Apr 2009 Location: Gippsland, Vic, Australia. Posts: 801	Re: The JCM 900 and modification... Thoughts? Alright, what's with everyone saying the 4100 has no low end, am I missing something here, because all I have is low end, too bloody much of it. My treble is on like 9, my presence on like 7 and my bass on about 4 or 5, and at low volumes it still shakes everything in my house... Through a fucking 4x10 cab. And Ken, why must you always seek out every JCM 900 thread, and pretty much troll it, somebody asks for a good opinion or suggestion, and you say "Sell it, it wont give you what you want, buy a DSL". You sound like a broken record. __________________ GEAR LIST Marshall JCM900 4100 (6L6) (1995) Marshall Valvestate 1965A cab (????) Cort VX-2V (2008) TUBES/SPEAKERS Power: Groove Tube 6L6GCB Phase Inverter: Sovtek 7025 Pre: V1 - N.O.S Mullard ECC83. V2 National 12AX7A Speakers: Celestion G10L-35 Marshall forever My tube amp & Real Music appreciation forum

09-18-2009, 06:31 AM	#11 (permalink)
RobS Senior Member Join Date: Apr 2009 Location: Melbourne - Australia Posts: 144	Re: The JCM 900 and modification... Thoughts? V-man, I have a 4100 and recently put in JJ6l6gc's. All I can say is it sounds ^&*(great! Not sure if someone else has posted yet but these amps 'wake' up at vol levels over 4-5, but then they wake the dead as well. They sound much much tighter,fuller, crunchier and better. That's why I use the Powerbrake at home. I do not recall seeing what tubes you have in there but I run the jj6l6gc OP + EH12ax7's up front and cannot fault it. The sound with a good guitar is great in my opinion. Cleans are excellent, crunch is very crunchy and then with gain2 over 15 it really is a heavy sounding amp. But I only run about gain at12-13 and with more master vol it's very much 800 like. Rob __________________ JCM900 4100 DR + 1960 A + B + Powerbrake Ibanez PS10CL Paul Stanley Custom Gibson LP Traditional Epiphone LP Custom No pedals.........

09-19-2009, 06:57 AM	#18 (permalink)
RobS Senior Member Join Date: Apr 2009 Location: Melbourne - Australia Posts: 144	Re: The JCM 900 and modification... Thoughts? Jessta, Did you burn in the KT77's? When I put new tubes in I run them with the probe inline for at least 4 hours with music playing through the amp (ipod or similar). Then adjust bias if need be. Then check periodically. Rob __________________ JCM900 4100 DR + 1960 A + B + Powerbrake Ibanez PS10CL Paul Stanley Custom Gibson LP Traditional Epiphone LP Custom No pedals.........

09-19-2009, 10:07 AM	#21 (permalink)
00jett Senior Member Join Date: Jan 2009 Posts: 134	Re: The JCM 900 and modification... Thoughts? i had the 900 combo for quite a while and had the same dilema. i actually did mod my amp. i did some of the mods found on the net and forum sites cause i could not afford to send it away to voodoo or something like that. let me point out that in my opinion the mods i found (Liam's mod) gave less than desirable result. i could definately hear a change in tone but it was actually for the worse instead of better. this puzzled me but than i downloaded a program called Tone Stack Calculator and looked at the eq curve for the amp both pre and post mod. i saw that i made those harsh frequencies even worse and made the gain buzzier. using this program i formulated my own mod that smoothed out the high end of the amp and added some low end. This and vintage 30 speakers with and eq in the loop made that amp incredable. the only reason i got rid of it was to buy a head format.

10-26-2009, 12:38 PM	#26 (permalink)
tbellisario Junior Member Join Date: Feb 2009 Posts: 2	Re: The JCM 900 and modification... Thoughts? I think this is a graet discussion on the JCM 900. When I picked this amp up it was given a fresh coat of white wall paint by some chick in a grunge band. After recovering it I comitted myself to bring out the best in this amp. My other amp is a 69' Super Reverb. I now have EL-34 power tubes and will try swapping out with 6L6's I also run into a 4x12. Keep up the discussion on mods as they are interesting to consider.

10-26-2009, 03:34 PM	#27 (permalink)
LesBalls Member Join Date: Dec 2008 Location: USA Posts: 63	Re: The JCM 900 and modification... Thoughts? I am an admitted JCM900 fan. However, I do understand that the amp is not for everyone. With that in mind, I would first decide if you like the tone of it. It has been my experience that modding will only help to improve your existing tone. It's not going to give you a brand new 100% new tone like buying a new amp will. You seem to like the amp, or at least don't want to sell it. So, I would change the power tubes and preamp tubes. I prefer Winged C EL34's in the power section and some sort of chinese 12ax7 in the preamp. Opinions differ on this so, do some tube research. I would also change the filter caps. Filter caps get old, dry out, and take tone with them as they die. Put in new tubes, new filter caps, and having the amp properly biased. Second, invest in an attenuator. I prefer the THD Hotplate, but again, opinions vary. The most important part of the "Tone of The Gods" equation is volume. You need to turn the amp up to hear the power tubes. This is where the attenuator comes in handy. I don't really like the sound of Master Volume amps with the master on 10...but it needs to be on 5 at least...7 sounds the best to me...Paul Gilbert likes 8...again, opions and results vary but the bottom line is turn the amp up loud. Third, invest in an EQ or the BBE Sonic Maximizer to run in the effects loop. I would recommend trying the EQ first (MXR 10 Band). The BBE has more of an 80's sound inherent to it which may not be your cup of tea. I use the BBE and it works great. Fourth, goose the front end with an OD pedal. I usually run my Master at 7 and preamp at noon...I then replace the gain that I lost when I turned the preamp down with an OD pedal...not a distortion pedal. Turning the amp up is your main problem right now. Hope this helps you!

10-27-2009, 02:02 PM	#28 (permalink)
LesPaulopolis Senior Member Join Date: Jan 2009 Location: Minneapolis Posts: 250	Re: The JCM 900 and modification... Thoughts? ^^^ Another reason why a volume pedal is a good investment. Crank that amp and bring it down a bit with the pedal. I have compared the tones at similar volumes and I'm telling ya, it works. Finally, when you're just a bit too loud or quiet you don't need to monkey with the really touchy volume and gain controls on-board the head...just use the pedal and 'set and forget' the head controls. __________________ '68 RI LP Custom JCM900 + EQ & Boost

10-29-2009, 07:29 AM	#29 (permalink)
(war)thrash5150 Member Join Date: Apr 2009 Location: Crestview, FL Posts: 33	Re: The JCM 900 and modification... Thoughts? Les, would a volume pedal work equal to or as well as an attenuator? It's def cheaper!

10-29-2009, 09:39 AM	#30 (permalink)
TPR Senior Member Join Date: Sep 2009 Posts: 109	Re: The JCM 900 and modification... Thoughts? I'll jump in here, although I'm curious about Les' thoughts. The volume pedal can only work in front of the power amp, either between gtr and amp or in the loop. In front, it's basically acting like a pickup output control and in the loop, it's acting like another master volume. Either way, my understanding is (and someone correct me if this is wrong), the power tubes are not really being pushed by the preamp. The attenuator goes between the power output (speaker out jack on the amp) and the speaker, so the power tubes get pushed and then the volume is controlled to the speaker. As you may already know, NEVER put a volume pedal or anything other than a properly rated attenuator between the amp speaker jack and the speaker. I find that putting the volume pedal in the loop does give me a better sound at a lower volume than just using the master volume. I'm sure it's because of the particular components in the pedal plus the slightly different location in the signal chain, but I don't know the specifics. However, it still isn't the same as the attenuator since the sound is better overall with harder driven power tubes. If you have a way to check out these options, that would be the best way to see what works for you. And best to test in your real environment if you can, rather than the store. __________________ The awesome tone coming out of my amp almost makes up for my inability to play. '91 JCM 900 Head w/ EL34s '68 Bassman Head- Blackfaced Hand Built 2x12 Classic 30 Gibson LP Studio w/ PAFs Epi LP Standard w/ G 57s The usual assortment of pedals and stuff

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