#1
Hi all,
I recently got my first tube amp ( Marshall half stack jcm 2000 dsl 100 watts). Obviously , this is a rather loud amp. I was wondering however, if there is a mod you can do (or has ever been done) on tube amps to make them run at lower wattage settings (ex: going from 100watts to 30 watts or something). I saw this feature on a bogner combo amp in guitar center (the alchemist i think) and it seemed to be a great feature that would allow you to sound better at lower volumes.

I am new to tube amps, but i do know that they sound best when the master volume is somewhere around 4 or 5, but this is simply to loud for an apartment (i bought it so i could start gigging soon). While their is little difference in max volume for amps based on wattage, it seems to make sense that a lower wattage tube amp would be able to sound better at a lower volume (relative to the listener) than a large 100 watt one would (since the master volume would have to be lower, and thus tone would be no bueno).

now i am aware of attenuators, but this seems like a better idea (for getting a better tone at least) . So does anyone know anything about this? feel free to correct me if this idea is wrong. also, any attenuator suggestions are welcome.
#2
A lot of tube amplifiers incorporate a 1/2 power switch to drop the power, so modifying a tube amplifier to do this is possible. I don't know how much it would cost.
#4
I do believe on some amps you can pull the two inner power tubes to run the amp at half power (50 watts). Do some research because I'm not quite sure if it would work with yor Marshall.

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#6
outer. on most amps it's the outer two powertubes. consult your owner's manual for specifics, but I believe this to be true for the JCM2000.

attenuators, the hot plate series in particular, will begin to destroy your tone beyond about 8db (not a ton, but some) of attenuation. before that it's largely unnoticeable, the tone change that is. 8db is enough to take the edge off, but it'll still be hella' loud, much too loud for an appartment.

if you want it to truely run on lower wattages, side effects are going to have to happen: you get it professionally modded (talk to Trace at Voodoo Amps), but in lowering the power required, expect to also require different output tubes and a different feel/tone. these could, theoretically, be built in alongside your standard powertubes in a switchable configuration, though I can't say I've even seen this. otherwise, you will be relegated to only the less powerful powertubes, or, more commonly, the switch will only act as though the outer pair of tubes were pulled, effectively removing them from the chain. still not a bad move, turn your 100w into 50w, slap a modest attenuator on it, run it through a floating 2x12 cab with a quilt thrown over the speakers, and you're getting close to bedroom levels with a silouette of your gigging tone.
#7
Quote by GrisKy
outer. on most amps it's the outer two powertubes. consult your owner's manual for specifics, but I believe this to be true for the JCM2000.

attenuators, the hot plate series in particular, will begin to destroy your tone beyond about 8db (not a ton, but some) of attenuation. before that it's largely unnoticeable, the tone change that is. 8db is enough to take the edge off, but it'll still be hella' loud, much too loud for an appartment.

if you want it to truely run on lower wattages, side effects are going to have to happen: you get it professionally modded (talk to Trace at Voodoo Amps), but in lowering the power required, expect to also require different output tubes and a different feel/tone. these could, theoretically, be built in alongside your standard powertubes in a switchable configuration, though I can't say I've even seen this. otherwise, you will be relegated to only the less powerful powertubes, or, more commonly, the switch will only act as though the outer pair of tubes were pulled, effectively removing them from the chain. still not a bad move, turn your 100w into 50w, slap a modest attenuator on it, run it through a floating 2x12 cab with a quilt thrown over the speakers, and you're getting close to bedroom levels with a silouette of your gigging tone.



I checked the manual and it really doesn't say anything that would be useful.

I'm mainly curious about this though since i had actually seen it built into a few amps and its really a great idea. I did a bit of research on line and found a patent for a device like this, I'm not an electrical engineer (only industrial engineer :shrug but i know some EE's who could fully understand it. here is a link to the read

http://www.freepatentsonline.com/5550509.html

I can understand portions of this, but it seems to be the right conceptual idea. I'm really curious if anyone in ug has done this since the patent was filed nearly 15 years ago. It seems that with an invention like this, you could more than likely even go below cutting wattage in half without installing extra tubes that would produce a different tone so much as a lower volume.

I think i'm going to make another thread just asking about this patent and see if anyone knows anything about it because if this patent is what i'm thinking it is, it could be a great value to tube amp owners since its seems like a do able mod (with a qualified worker of course). If this mod weren't too expensive, it could almost replace the need for practice amps (assuming you don't mind paying to change your tubes).

I'll try to keep this thread alive if i find out anymore information on the subject, but i'm not going to meaninglessly bump it.
#8
i took a look at the patent, and it's a pretty interresting concept.

...i believe the roadking mkII's have a similar, asignable function. then again, now that i think about it, i'm pretty sure the rk simply uses a form of optional gain-staging...?

i would be a bit worried that the process described would cause "starving tubes," but i couldn't tell you that for certain. find yourself a true-blue EE and let him take a look at your amp and the schematic... see if he thinks it's a safe/worthwhile move.