I haven't owned a guitar amp with a master volume since 1983. I get yelled at a lot for playing too loud. I had a Marshall with a master volume, but to me it didn't sound like a Marshall. You know... Thin Lizzy, Hendrix, Trower, Alex Lifeson? The thing I eventually found out was that the distortion you get with a master volume is that which is generated by an overdriven preamp, usually a 12AX7. It can sound good, but it's not the same as a power tube pushed into distortion. Plus, you don't have much dynamic range. With my setup, I dime the amps. If I want to clean it up, I back off on the guitar volume. If I want distortion, I max the guitar. If I want to send it into warp drive for a lead solo, I hit my SD-1 or other overdrive pedal. You can't get this with a master volume. With an MV it's all dirt, or all clean.
Now, having said all that, sometimes I do want to dial it down a bit, but keep the sound of the cranked amp. The Sholtz Power Soaks allow me to do this. The PS was the second (The Altair PW-5 was the first, back in the 70's) commercial device made to attenuate the volume of a guitar amp running full tilt. These days, there are many devices on the market that will do that. You can dial your amp down to virtual bedroom level volume if you want to. I use my Soaks to practice and learn songs, or just to play along with CD's. I have also done some recording using the PS that didn't sound too bad. When playing with a band, it's pretty much only good for the first couple of clicks, about 6 DB down, before you start losing tone.
A word about that: You will lose tone with ANY ATTENUATOR!!! Reasons:
About the myth that power attenuators will damage your amp: I call bullshit. I own numerous Fenders, A Traynor YBA-1A, and other tube amps as well. I have run all of them through my Power Soaks (The Silverface Bassmans for 20 years!) at one time or another, as well as my DIY attenuators. I have never had any problem with any of them. In My Opinion, the stories abounding about amp damage due to Power Soaks can be attributed to poor or worn out tubes, or amps that were on the verge of failing anyway or had other issues and were close to failure. You have to remember that an amp is usually running flat out when using an attenuator, and that places big demands on all portions of the circuit! Also, Tom Sholtz of the band Boston designed these things to work with his Marshalls before he switched to that dumbass solid state Rockman setup, and he cranked the shit out of them.
- Yer not moving air. Running something like a Plexi Marshall through a 4x12 moves low frequencies. Low frequencies take a lot of energy to generate. When you remove the energy with a PS, you lose the low end.
- You lose the high end crunch. Adding it back in with equalizers or capacitors ain't the same thing.
- The speaker is as important as the amp. Pushing a speaker cab with a dimed amp makes it do things it won't/can't do at attenuated volumes. At low volumes the speaker is merely reproducing/transmitting the sound, at full blast it is PART of the sound.
- You lose dynamic range. When you dial an amp down with a PS, the volume difference between quiet and loud is reduced. Using the technique I use (Described above), by the time you get the distorted sound to a manageable level, your clean sound is fucked because you have to turn the guitar down to practically zero to get it.
I have three Sholtz Power Soaks; I have modified two of them and added in and out jacks in the back. Dunno why they put them on the front in the first place, it doesn't make any sense. Amp and speaker jacks are usually in the rear 99% of the time.
I also have built several DIY guitar amp attenuators, check them out: