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Master Volumes

majorminor

Gold Supporting Member
Messages
1,590
There seems to be a school of thought here that a master volume on an amp is bad, or a compromise at best. True?

If a master is cranked is it the same as having no master or are there still compromises to the circuit? I'm playing more recently on a master volume amp and am not hearing the limitations. Seems like it's just another option which is a good thing right?
 

bgh

Silver Supporting Member
Messages
6,974
The (oversimplified) idea behind a master volume is to allow you to crank the preamp to get whatever tone you want and then use the MV to determine how much of that signal goes to the power amp section. Some MV amps get a bad rap because the preamp sections don't sound good. Others get good vibes because their preamp section sounds good.

At bedroom level with an MV amp, and not counting the use of pedals, the distortion you hear is almost always coming from the preamp (the position of the MV itself may allow the PI to distort). This is why some good MV amps can double as good practice amps. However, you are almost surely not getting any power tube breakup at this point.

Power tube breakup occurs when you drive the power tubes past what they can cleanly handle. The only way to do that is to feed them a strong signal. On most MV amps, you do that by turning up the MV. However, if you turn up the MV all the way, but turn the preamp down (to keep the volume at a fairly low level), you are not going to get a whole lot of power tube breakup. The only way to do that is to (1) turn both preamp and MV up and deal with the volume, or (2) use an attenuator of some sort.

This is where some of the newer power scaling features come in. They turn down the power going to the tubes and allow you to turn up the gain to the tubes - allowing them to distort, but at a lower volume.

Hope I didn't muddy the water too much.

Thanks for reading.
 

trailrun100s

Member
Messages
3,569
There seems to be a school of thought here that a master volume on an amp is bad, or a compromise at best. True?

If a master is cranked is it the same as having no master or are there still compromises to the circuit? I'm playing more recently on a master volume amp and am not hearing the limitations. Seems like it's just another option which is a good thing right?
Don't let the "net" get the best of you...If it sounds good to you, then that is all that matters...

Now PPIMV's, I don't think sound too good a low volumes, plus it interferes with the presence and tone controls if the master is set too low...Turned full up, it is out of the circuit if done correctly...
 

stratovarius

Silver Supporting Member
Messages
9,141
A well designed master volume is as you say "just another option". I do think certain amp designs, such as the typical cathode-biased EL84 type of amp, don't perform well without pushing the output tubes hard.
 

Heady Jam Fan

Member
Messages
9,009
Some amps designed for a MV, such as my MKIII, sound great whether the MV is wide open or pretty quiet. Other amps like old Fenders almost never sound better with a MV - I've owned many with and without and the only one I kinda liked with a PPIMV was a BF Bassman.
 

big mike

Cathode biased
Platinum Supporting Member
Messages
13,517
Don't let the "net" get the best of you...If it sounds good to you, then that is all that matters...

Now PPIMV's, I don't think sound too good a low volumes, plus it interferes with the presence and tone controls if the master is set too low...Turned full up, it is out of the circuit if done correctly...
True, but can be a reasonable compromise IMO. 1/3rd or so up and it sounds pretty transparent to me.
Lower than that, I reamp.
 

bobcs71

Member
Messages
5,379
It's just not a straight good/bad answer. As stated, it can depend where the master is set. It depends where the master is in the circuit. One idea behind NMV amps is that you get the power amp section to clip giving extra overdrive/compression. In some amp designs, the power amp never clips. Often you hear the phase inverter tube clipping. You can see this if you scope the amp. I've seen a couple SF Fenders scoped with that result. Plenty of pro's use amps with master volumes.
 

Chicago Slim

Member
Messages
4,430
I've Master Volume amps that I liked, and those that I didn't. Some like the Kustom's, will control the gain at several points, within the amp. I like having a master volume on a large amp. If I were to pick my favorite design, I would say a simple Volume, Tone and Gain, would be my favorite.
 

Cado

Member
Messages
615
I've stopped using them, but only because it's best for me at this time. Ultimately, if your ears says it's right than it's right.
 

kingink

Member
Messages
769
There seems to be a school of thought here that a master volume on an amp is bad, or a compromise at best. True?

If a master is cranked is it the same as having no master or are there still compromises to the circuit? I'm playing more recently on a master volume amp and am not hearing the limitations. Seems like it's just another option which is a good thing right?
Master volumes can be a great option. Worry not! :)

Not sure about nowadays, but IIRC some of the early anti-MV thinking (back in the late 90s) had at least something to do with those of us who are old enough to remember when Fender put masters on the late 70s silverface twins.

Well designed MVs shouldn't compromise tone. Soldano, Carol Ann, Suhr/CAA, etc., are usually regarded as tone machines. I'm not an electrical engineer but my understanding is that the designers of these amps put a lot of attention into getting much of the tone out of the preamp so that you can get good tone at low volumes.

If you're interested:

Check out Soldano's YouTube video of the Hot Rod 25. Mike Soldano says something about how he always thought of the output stage of an amp as a hi-fi way to make the preamp louder, or something like that. I can't remember exactly what he says but the implication is that the tonal heart of an SLO is its preamp stage; you get awesome high gain tones without having to crank the power amp.

Also, in that looooong thread about the forthcoming Suhr mid-powered channel switcher, John Suhr says something about the advantages of amp circuits with master volumes that get most of the drive in the preamp--allows for more versatility and control or some such.

I maintain that my Soldano Hot Rod 50 sounds killer at low volumes. I like it way better than pedals.

So MVs can be both useful and toneful.
 

rotlung

Member
Messages
956
A good MV is a requirement for me. I like overdrive, rarely play clean, and can't be cranked all the time.
 

MSLBend

Senior Member
Messages
2,225
A number of people I know who use non master volume amps often use them as a pedal platform setting the amp clean at a usable volume. In essence isn't that the same thing as turning the NMV knob into a MV knob because with the overdrive pedals you get control of the volume before it gets to the amp? Obviously some differences, but it's the same principle, right? The other thing about NMV amps that typically don't have effects loops is it's practically impossible to control the delay and reverb level because as the amp gets louder and the tubes start to distort and compress, the delay volume gets higher and higher.
 

Fulldrive-1

Senior Member
Messages
5,926
Depends on the amp.

I've put PPIMV on black and silver faced Fenders; I don't think it's an improvement and recommend against it.

I've put PPIMV on JMP Marshalls and they sound very good.
 

GasMask

Member
Messages
3,419
I will never buy another "gain" amp without a master volume.

If I'm going to run an amp 100% clean, then it is not needed.
 






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