thekilligans

Hey guys...

Ive read and heard a lot about power tube pulling to get a little less volume and more tube saturation. Heres what I know...pull the two outside tubes like so XOOX

Need to have the amp set to half the impedance of the speaker cab. Heres where Im confused. I dont want to fry my amp.

I run a DSL 100. Would like to turn it up past 3 for shows. It has the 3 speaker outputs on back. 16ohm, and then 2- 4/8ohm jacks. It also has an impedance selector of 4 and 8 ohms.

I run a 1960A cab. It has 2 inputs and a stereo/mono switch. One input says 16ohm, one says 4 ohm. Underneath, they read, 8 ohm stereo left and right.

If I run 2 out of the 4 power tubes, do I leave my speaker plugged into the 16ohm jack on the speaker cab, and then run out the 4/8ohm output from the amp? And leave the impedance selector on 8? very confused...thanks in advance dudes..

c

Marshall Amps

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LoKi

I've yanked 2 power tubes on my 800, left the head on 8ohm output and used a single 8ohm cab with no problems though. Dunno for sure if this is 'recommended' or not.

Adwex

It's not. thekilligans is correct, the impedance on the amp should be set for 1/2 the speaker impedance. You've been lucky.

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Adwex

You're not confused at all, you're correct.

With only 2 tubes...
16 ohm cab input...
switch set to mono...
amp set for 8.

But....

I betcha it would sound alot better with all 4 tubes, with an attenuator between the amp and cab. You could turn the amp up a little to get the tone you want, but the attenuator will bring the volume down. A more expensive option, but it'll probably sound better.

Adam

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thekilligans

yeah, I know the attenuator would sound better, but right now, I dont want to drop the money. Ill look into them though. I might want to splurge...

so If I use the amp switch on 8, and use the 16ohm input on the cab, what output do I want to use on the amp?? the 16 still, or one of the 4/8s?? thanks tons for all your guys help.

LoKi

Lucky how? Minimum ohms are just that... the minimum required. An 8 ohm JCM 800 with 2 tubes yanked going into an 8 ohm cab is fine... just like running a 8 ohm head into an 16 ohm cab won't blow it up.

You guys worry too much.

Adwex

Lucky that he didn't blow his output transformer....an expensive item to replace. I know this from experience, because it happened to me. Impedance should always be matched, but some output transformers are built well enough to handle the mismatch, some are not. If your tranny doesn't blow from a mismatch, you're lucky. I wasn't.

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LoKi

A mismatch in the opposite direction is fatal, (lets say an 16 ohm head into a 4 ohm cab... that will pop your OT within a minute or 2) but as long as you have more resistance than is needed for normal operation it'll work, but you'll lose some output power, and gain a tiny bit of heat. Not too much to worry about. Lets say if you put a 4 ohm head into a 16 ohm cab, you'll also work the transformer too hard and possibly heat damage it, especially if running at full output power.

An already weak transformer won't like the added resistance, but any decent tranny used in a Marshall tube head shouldn't even react.

Adwex

You'd use one of the 4/8's .....with the switch on 8.

You seem to understand, but you're confusing yourself. The idea is this...with a pair of tubes removed, the amp impedance should be set for 1/2 the impedance of the cab. Your amp has separate speaker jacks for 16 and 4/8. The 4/8 switch will determine what the 4/8 jack is set for, where the 16 jack is always 16 (the 4/8 switch doesn't matter when your plugged into the 16 jack).

Basically, with 2 tubes removed and the amp set for 8 into a 16 cab, is the same as all 4 tubes and the amp set for 8 into an 8 ohm cab. Hmmm, now it's sounding more confusing than it really is.

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LoKi

The rule of thumb, as a pretty famous amp builder in Canada once told me, is that you can safely go 1 step down... but not 2.

So an 8 ohm head wont be damaged by an 16 ohm cabinet, an 4ohm head wont be damaged by a 8ohm cabinet, but a 4 ohm head will be damaged by a 16 ohm cabinet.

Any of that in the reverse will cause serious damage though.

LoKi

There used to be a great article about this on Marshall's website back in the day. I'm sure its still on there in the archives...

strangeroutside

ThEKilligans: Did that work out for you, pulling the tubes? I also run a DSL 100 and was thinking of doing the same just as a few people have told me I'd get a better sound when the tubes are more saturated. What were your results?

RachelMorgan

Even though they unofficially say you can pull two of the tubes and half the impedance of teh speaker outputs, I noticed in a few different places on the Marshall FAQ that they don't advise this because it can damage the amp. So... if you've got one still under warranty, I wouldn't do it simply because it would be an excuse to void the warranty if something did go wrong.

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Ultimeter

Not to really drag this out but what about this example: DSL100 with the two outside power valves removed. 1960A & 1960B cabinets. What would be the correct hook-up for this combo using both cabinets? Both cabs set to 16ohms Mono and the parallel output jacks set to 4 ohms? Both cabs run in parallel set to 16 ohms should be 8 ohms actual load but with the tubes removed do you want to set the selector switch at 4 ohms (1/2 the actual load)? Still paying for the amp, the attenuator will have to wait. Thanks for any reply.

lerxst88

ummm doesnt he have to rebias the amp for only two tubes???

Sir Punk

bump for this. I'd like to run my 50w JMP with only one tube. I know I will have to check the filament voltage so that stays within range and half the impedance. Also I will have to rebias.

Has anybody ever tried this on a 50w?

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steelhorse

I never understood the reasoning behind tube pulling? No offense but why not get some yellow jackets and go that route instead of creating all kinds of potential problems and issues.

No bias required to add yellow jackets and they sound great.

So many players get these big ass amps and then want to pull tubes? Why not get something that either offers you power reduction or a smaller amp with the delicious tones already happening?

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RachelMorgan

Hmmm... I think a Hot Plate is less than Yellow Jackets, and won't change the character of the amp, and still allow one to turn the amp up way past 3.

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steelhorse

A hot plate isn't necessarily less than yellow jackets and in order to get that great saturation a hot plate really has to be attenuated which will change the character of the tone.

My presumption is that the players who are interested in pulling tubes are after that really sweet saturation that removing tubes allegedly accomplishes, my impression is that if you really want to achieve this yes, either get a hotplate or get yellow jackets.

A hotplate for most Marshall's can be had for 329.00 at MF

A QUAD of Yellow Jackets is 236.00, and a duet is around half that.

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Adwex

Marshalls (and most other tube amps) employ a "push-pull" design, the tubes work in pairs. It won't work with 1 tube.

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Sir Punk

you are asking me why I don't get a lower wattage tube amp. There is nothing that gets a JMP tone, which is a 10 watt head. 20w is still too loud. If there is such thing please tell me who makes it.

The nano amp is a joke, it has great sounds but not like a 800, the epi valve jr.? it's just a different beast. The 2061x, maybe, but I haven't tried it personally so I can't say.

If I get an attenuator I will get the ultimate or the Richter one. The hotplate works only for one ohm setting, and it's a mass market thing.

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steelhorse

Not sure of what your definition of 'too loud' is so not sure if I can help you.

What you're asking for may not exist as well, at least in Marshall land.

As I also already suggested you may be the candidate for Yellow Jackets. I've used them before when I was traveling and lived in apartments. They are amazingly good.

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RachelMorgan

Actually a Hot Plate handles two ohm ratings:

* its rated
* or you can run ONE cabinet at the next higher rating (eg. an 8 ohm hot plate can run ONE 16 ohm speaker cab but still connects in the 8 ohm speaker output). Your amp still sees the Hot Plate's load.

This is acc'd to THD. It doesn't void the warranty on the unit. And you can use your EQ to compensate for any tonal coloration -- and all attenuation will color the tone simply due to the fact that at lower volumes you're moving less air and your ears are more sensitive to mid range. I think the ones that are reputed not to color tone have built in tonal adjustments that make the compensations as you apply more attenuation.

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Sir Punk

This is totally your opinion. Can you prove that?

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Adwex

The HotPlate has low and high boost switches.

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steelhorse

No offense here folks, I like the hotplate fwiw and I don't really think it's my imagination or a marketing thing, sucka does work, but in order to get that really kick ass saturation the amp and the hotplate have to be driven hard and therein lies my issue, it does affect the tone and the deep and high switches do help but they affect the tone also.

imo.....

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Adwex

I share your opinion.
I have a Hotplate...I've only used it a few times, now it's sitting in the box.

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RachelMorgan

I can't PROVE it because I haven't taken one of the other ones apart, but the technology has been available since the 1950s.

Sound is about moving air. Some say that when you put a hot plate on high attenuation that it colors tone. This is putting the sound level at "bedroom" levels. You're moving less air....

* it is known that the human ear is much more sensitive to midrange than to lows and highs.
* some say when you reduce the volume over the entire sound spectrum the lows and highs will seem to be lowered far more than midrange. some call this "coloring the sound."
* so to compensate on some hi-fi systems they use a bass and treble boost that gradually comes in as you lower volume -- Harmon Kardon did this in the 1970s. I had one.
* so by extrapolating the unscientific testamonial data that some attenuators do not "color" the sound may be indicative of more of a midrange selective sound reduction with less of a reduction in lows and highs so as to seem like they don't color the sound -- because you're moving less air and your speakers aren't punching out the bass or screaming out the highs.

Why else would gear like the Ultimate Attenuator cost so much more if they're not putting anything more into them? It's because they are.

Prove that they're not.

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steelhorse

Not to jump into your guys' kool aid and all but for me it's really simple, scientific data notwithstanding, if I hear a difference, and I don't like it I try my best to work with it and maybe for awhile it seems ok or maybe not just depends, but eventually, I realized this isn't why I have this great tube amp(s).

If I want real tube sound I need to be able to hear the unadluterated true tones.

Once I became enlightened to that realization I just decided I no longer needed my hotplate and sold it and I've been fine around here without it ever since.

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