You mean a variac on the power from the wall? Chris661 The EVH lore about using a variac is just not true. It also lowers the filament voltage and it all stops working. But, you can indeed vary the B+ with a regulator or dropping resistors, switch off extra pairs of push/pull tubes or some of the paralleled single-ended tubes if that's what you're running. But a resistive dummy load doesn't work as well as you'd expect, because a lot of a guitar amp's frequency-related distortion characteristics have to do with how the resonant and inductive speaker load affects the amplifier's outputs. Read up on the Aiken Reactive Load over on thegearpage.com as I was advised to do. Lots of good stuff in that thread if you really want to run your amp balls-out and want the same sound but quieter.
No, a variac on the output.
With the dummy load in place, the power stage is still working hard, but the variac will let you dial in any volume you like. A step-down transformer would give the same result, but isn't adjustable.
Regarding reactive speaker loads, I don't think it'd be that difficult to replicate - a notch filter for Fs and then, say, 0.5-1mH to get the HF impedance up a bit will be somewhere near.
Chris
reducing guitar amp master volume
hi guys,
This is my first post!!!
Interesting topic and one that has troubled guitarists for ages! I have been playing guitar for 42 years and can attest to the problems with parents and neighbours due to this phenomenon. Most new amps have master volumes that restict drive to the output stage. Unfortunately the distortion of the output stage and beakup is a desired requirement to achieve the "tone". A renowned amp design called the Trainwreck amplifiers, is the king of tone. Apparently the output section is overdriven before the input stage. If one googles or searches on you tube, you can hear and read about these great sounding (simple) designs.
I have decided to attempt a build of the Trainwreck express.
hi guys,
This is my first post!!!
Interesting topic and one that has troubled guitarists for ages! I have been playing guitar for 42 years and can attest to the problems with parents and neighbours due to this phenomenon. Most new amps have master volumes that restict drive to the output stage. Unfortunately the distortion of the output stage and beakup is a desired requirement to achieve the "tone". A renowned amp design called the Trainwreck amplifiers, is the king of tone. Apparently the output section is overdriven before the input stage. If one googles or searches on you tube, you can hear and read about these great sounding (simple) designs.
I have decided to attempt a build of the Trainwreck express.
This will also kill the amp
Those 70V matching transformers will make your amp, say, 8 ohms output try to drive , say, 80/160/320/etc. ohms, because the same voltage lowering action becomes an impedasnce raising one.
Even worse, it follows an exponential law, so 1/2 the voltage means 4X reflected impedance, and so on.
Instant OT nuke.
It might work on an SS amp ... but who would overdrive an SS power amp to get killer smooth sound?
Me. It kept blowing its output stage, but I got a lovely "trashy" distortion sound. Think early days Nirvana. The amp had 4 controls: volume, bass, mid, and treble. Wind up volume , bass and mid and use the treble control to change the brightness of the distortion.
I think its awaiting yet another set of output transistors atm. Its on the list of things to get around to.
Chris
As Lead guitar player and DIYer, i tried so many ways of reducing power since I use mostly 100W tube heads.
The problem came with home praticing (bedroom volume) , recording and small pubs.
Attenuators always sounds fake, not only because they load output stage in a different manner than a speaker would do, this is half the problem, i believe the "tone" of a cranked amp came from the cranked speaker it self , try a 100W head into 4 cabs 4x12, it will sound worse than a single cab (you will gain some lows BTW)...
I've found that the only way for home recording, praticing or small events is to use a speaker simulator with a dummy load, still not perfect but sounds better than some recordings. I built one my self with the V30 freq. response in mind. I've sold a units to a recording engineer 2 years ago.
For Live events i go with a 4x12 for big stages, 2x12 and a dummy load for medium gigs so half power to speaker half to the dummy, small pubs i've tried 1x12 with a resisitive dummy attenuator but i still prefer the 2x12 solution.
The problem came with home praticing (bedroom volume) , recording and small pubs.
Attenuators always sounds fake, not only because they load output stage in a different manner than a speaker would do, this is half the problem, i believe the "tone" of a cranked amp came from the cranked speaker it self , try a 100W head into 4 cabs 4x12, it will sound worse than a single cab (you will gain some lows BTW)...
I've found that the only way for home recording, praticing or small events is to use a speaker simulator with a dummy load, still not perfect but sounds better than some recordings. I built one my self with the V30 freq. response in mind. I've sold a units to a recording engineer 2 years ago.
For Live events i go with a 4x12 for big stages, 2x12 and a dummy load for medium gigs so half power to speaker half to the dummy, small pubs i've tried 1x12 with a resisitive dummy attenuator but i still prefer the 2x12 solution.
Has someone mentioned lowering b+ voltage to the power tubes w/ a regulator? (actually, looks like cyclecamper did)
I asked a similar question about how to get distortion at low volumes, and someone suggested a VVR.
It works.. Lowers the headroom on the output stage, so it distorts earlier. In fact, it's more of a clean/dirty knob in my case, until you get to the last 3rd of travel, where the volume starts lowering.
I think at certain levels it sounds the same as having the amp fully cranked.. But I am new to guitar, so maybe not as critical as others...
I asked a similar question about how to get distortion at low volumes, and someone suggested a VVR.
It works.. Lowers the headroom on the output stage, so it distorts earlier. In fact, it's more of a clean/dirty knob in my case, until you get to the last 3rd of travel, where the volume starts lowering.
I think at certain levels it sounds the same as having the amp fully cranked.. But I am new to guitar, so maybe not as critical as others...
^^^^ lowering +V is the most transparent way of lowering power, because everything else stays the same: reactive load, speaker interaction, low damping, grid rectifying, bias shifting, etc.
The only problem is that controlled +V supplies used by most are "too good" and are stiff, you miss the voltage sag at high power, but that can be added to the circuit.
At least I do
The only problem is that controlled +V supplies used by most are "too good" and are stiff, you miss the voltage sag at high power, but that can be added to the circuit.
At least I do
Again, if you really want to understand why a dummy load or resistive element doesn't sound the same, investigate the threads on the Aiken Reactive Load.
Achieving your goals may involve several of the above techniquues, switching off pairs of tubes, adjustable B+ and adjustable series sag, an Aiken Reactive Load, and a mic in an absorptive isolation box possibly with subsequent re-amping.
Chris661 has a completely different objective, and is not relevant to the common case; the SS sound he wants should be easier to achieve earlier in the signal chain.
Achieving your goals may involve several of the above techniquues, switching off pairs of tubes, adjustable B+ and adjustable series sag, an Aiken Reactive Load, and a mic in an absorptive isolation box possibly with subsequent re-amping.
Chris661 has a completely different objective, and is not relevant to the common case; the SS sound he wants should be easier to achieve earlier in the signal chain.
Eeka Chu, I am not exactly sure what it is you are trying to achieve. You speak of output tube distortion, but then you want to swap out the speakers for Greenbacks. You are using a 100 watt amp with 2 power tubes pulled. That is correct in saying you will operating the amp at 50 watts. However the impedance of the output transformer is chosen to have 4 output tubes, and not 2 tubes. A change in the load. Not such a big deal, but you may want to rethink the plan.
May I suggest you use a lower powered amp. Here is where I am coming from. If you have a 10 watt amp with a suggested speaker configuration, then in order to achieve twice (2x) the loudness it is required an amp ten times (10x) the power into that same speaker configuration. This also works in reverse. Half the volume requires 10% of the power. I think that is a good starting point.
Next, I would look at speaker efficiency. A 20 watt amp can keep up with a 100 watt amp just using the correct speaker to achieve this. Using less efficient speakers will also simmer down the volume. This may also allow you to push the amp into distortion without the intense volume.
This is all a " trial and error " exercise. I would suspect you are likely using a 4x12 speaker cab since you are using a Marshall. Have you tried just a single 12? You won't be pushing as much air!
Just my take on it. Good luck.
May I suggest you use a lower powered amp. Here is where I am coming from. If you have a 10 watt amp with a suggested speaker configuration, then in order to achieve twice (2x) the loudness it is required an amp ten times (10x) the power into that same speaker configuration. This also works in reverse. Half the volume requires 10% of the power. I think that is a good starting point.
Next, I would look at speaker efficiency. A 20 watt amp can keep up with a 100 watt amp just using the correct speaker to achieve this. Using less efficient speakers will also simmer down the volume. This may also allow you to push the amp into distortion without the intense volume.
This is all a " trial and error " exercise. I would suspect you are likely using a 4x12 speaker cab since you are using a Marshall. Have you tried just a single 12? You won't be pushing as much air!
Just my take on it. Good luck.
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