Master volume, Non Master volume, can anyone explain?

Discussion in 'Amps and Cabs' started by Tone, May 30, 2005.


  1. Tone

    Tone Member

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    Hey guys.
    Can anyone explain to me what the pros/cons are of amps with a Master volume, or non master volume amps? When did the master volume start showing up in amps, and what is it's purpose?

    On amps like Mesas, where you have individual volumes for each channel, and then a main output volume that controls the level of the whole amp, what is the best way to get power tube distortion? Cranking the main volume, or the channel volume?

    Thanks!:dude
     
  2. John Phillips

    John Phillips Member

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    Simple - with a MV amp, you can get distortion at any volume; with a non-MV one you have to have the amp up loud, unless you run an attenuator between the amp and speaker.

    You will often hear it said that MV amps inherently don't sound as good as non-MV ones - that is untrue, if you're just talking about the MV itself. You can have an MV amp that behaves exactly like a non-MV amp when the MV is turned up full, if the circuit is designed like that. The difference is that the distortion you get with the MV set lower is purely preamp distortion, whereas that with the MV up full (like a non-MV amp) is usually a mixture of preamp and poweramp distortion - it's rare that it's only from the power stage, also contrary to popular belief.

    But most MV amps are not simply non-MV amps with an additonal MV (although some are) - usually they have different preamp circuits with more gain, in order to create more distortion at lower volume - partly to compensate for the lack of any power-stage distortion, and partly because that's simply what most MV-amp users want. It's definitely true that these don't sound the same as non-MV amps, even with the MV dimed. Some MV circuits also work better than others at preserving the tone at lower settings.

    In order to get power amp distortion on something like a Mesa, you will need both the channel volume and the overall level control up a fair way, and the amp will be LOUD - there's no way around that unless you use an attenuator too (which you can, they're not only for non-MV amps).

    The question is, does it matter? Don't assume "power amp distortion is the only good kind" - it isn't. Most of the classic amps get their tone from a mixture of both. There's a certain sound you generally only get when the power amp is working fairly hard (though not necessarily distorting), but you can get great tones by blending preamp distortion and poweramp characteristics, far more flexibly than you can by just giving yourself one control (which is actually a gain) on a non-MV amp.

    I really don't understand why anyone would purposely rob themselves of the extra control of having a MV on an amp - you don't have to use it if you don't need to, but it gives more options when you do...

    Just my opinion.


    The first amps with MV (for controllable distortion, as opposed to simple overall loudness on a multi-channel PA amp) that I know of were the first Boogies in about 1971.
     
  3. riffmeister

    riffmeister Gold Supporting Member

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    weren't the first MV amps in the early 70's?
     
  4. Tone

    Tone Member

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    Thanks John, great post! Very enlightening.:dude

    "The question is, does it matter? Don't assume "power amp distortion is the only good kind" - it isn't. Most of the classic amps get their tone from a mixture of both. There's a certain sound you generally only get when the power amp is working fairly hard (though not necessarily distorting), but you can get great tones by blending preamp distortion and poweramp characteristics, far more flexibly than you can by just giving yourself one control (which is actually a gain) on a non-MV amp."

    Nope, I don't assume power amp distortion is the only kind, or best kind at all. Just wanted to see how it all works. I had my Mesa cranked pretty good yesterday and noticed it was a lot more touch sensitive. (clean channel with a little breakup with guitar volume on full.) Which got me to thinking about the whole master/non master design. Channel volumes were in the middle region (11-2:00) and main output at 3:00.


    On Mesa's, the channel volumes are labelled "master". But it's actually the main output volume that is the master right?

    Thanks!

    :dude :dude
     
  5. John Phillips

    John Phillips Member

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    Yes... they're confusing. A lot of amp companies do that though.

    It's hard to tell whether you were into power-stage distortion at those settings... maybe not, although it was definitely working pretty hard. Even though you were hearing clipping on the clean channel, it still could have been later on in the preamp. The sound of a tube amp does change - and improve, I've never heard anyone disagree with that! - as the power stage is worked harder, but sometimes becomes too mushy when the power stage actually distorts.

    If you do want to see what it sounds like, dime the output level and the channel master - and get the channel EQs fairly high too, they also limit the signal level - and wind the gain up until the amp distorts. Even then, you're not guaranteeing that it's power-stage distortion only, but it will be closer than any other method. And it will be REALLY loud.

    The great thing about a MV amp is that you can do that, or alternatively when you want completely saturated buzzy mush you can dime the gain and keep the volumes low ;).

    Or to be serious, you can balance the two to get the best combination... that's why I like attenuators too, even on MV amps - more control. I am a control freak :).
     
  6. TaronKeim

    TaronKeim Member

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    John... for some reason this doesn't shock me... at all:D :dude

    -TJK
     
  7. flatfinger

    flatfinger Member

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    OK....................... So if it's all about making the power tubes sweat, why don't class A amps distort at a lower volume???

    I read that there allready conducting at half throttle when there's no signal from the guitar!!

    there already reved up!!!!!!!!!!!



    And on the same note, why do all the speaker mfg'rs continue to increas the spl efficiency???? Old celestions were something like 93 or 95DB and now there all around 100DB??


    If someone is seriously looking to work those tubes, why not look at the blue tick hound????
    I've heard detractors say it's a one trick pony because of the early breakup, but now were introducing cone coloration in addition to the amps distortion.



    The Ideal would be a speaker thats not at all efficient, but has a very slow , if non-existant breakup!!!!



    I basically have read so many people say that attenuators effect the tone adversly, so I cant't see wearing out tubes sooner by running one!
     
  8. John Phillips

    John Phillips Member

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    They do, relative to the type and number of tubes used, simply because the maximum power output is less. Class A is less efficient than Class AB, which is why it's so rarely used. I'm guessing that you're thinking of "marketing Class A" anyway ;).

    Because the higher efficiency speakers sound different (better, IMO... bigger and clearer) - it's not just about the point the amp overdrives. They also allow you to do more (filling a space) with less (size and weight of amp), which appeals to me too. "Old" Celestions - if you mean Alnicos - are 100dB+as well - it's the G12M-25 types that are lower, at around 97dB... not enough to significantly reduce the volume of an amp, anyway.

    That's why I like them in combination with MV amps - I never use the amp fully cranked for that reason, as well as that I don't think it sounds as good. I like to balance a lower MV setting with slightly less attenuation, I find that gives the best tone at low volumes - much better than using either alone.
     
  9. reaiken

    reaiken Member

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    One of the biggest differences between MV and non-MV amps is that the tone controls actually work on (most) MV amps. The tone controls on non-MV amps are much more subtle in their effect. Amps that use a post-phase-inverter (PPI) master volumes also suffer from this "problem".

    This is because MV amps get their distortion from preamp stages, and the tone controls come after these distortion stages. When you crank up a non-master amp to the point where the output tubes are distorting, the tone controls don't do anywhere near as much, because the signal is already clipped by the output stage, and the tone controls are ahead of this clipping, so they can't do as much to affect the signal level in the frequency bands of interest (once a signal is clipped, it can't get any bigger, and if you make it small enough to affect the output level, it is no longer clipping, so the distortion character is changed).

    The upside to this effect is that non-master amps typically are more "touch-sensitive", because they can be set up to go into and out of output stage clipping by adjusting the guitar volume control, or by picking harder or softer.

    Speaker choice becomes extremely critical in non-master amps, because, for all practical purposes, the speaker *is* the tone control when the amp is heavily distorted. If you use a speaker that has too much high end, it will reproduce too many of the high frequencies that sound "buzzy".

    Randall Aiken
     
  10. Tag

    Tag Gold Supporting Member

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    VERY well said John!!

    Also, using a distortion box with gain and level controls in front of a non MV amp, instatly converts that amp to a MV amp, with a SS pre amp. (If the box is not 100% tube derived)

    :dude
     
  11. Tag

    Tag Gold Supporting Member

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    Randall is the man, but I have to dispute this. A MV amp can be set so it is working just like a Non MV amp. Also, in side by side tests with a Komet, Trainwreck and Bruno Non MV amps, against, TwoRocks, Brunos and Dumbles with MVs, I specifically checked for this, and could find no difference whatsoever. I am a touch sensitive freak, and they all reacted extremely similar. Surprisingly, my Bassman RI and HR DeVille hung right there with all of the above amps.
     
  12. Jackie Treehorn

    Jackie Treehorn Member

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    So true!
     
  13. Tone

    Tone Member

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    Are there any basic guidelines that you follow to make a MV amp more touch sensitive than people will usually think it is?:dude
     
  14. riffmeister

    riffmeister Gold Supporting Member

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    turn it up.
     
  15. Tag

    Tag Gold Supporting Member

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    Yea. Put on a blindfold and A\B it with a non MV amp. :AOK

    The "magical" Trainwrecks which are supposedly so "touch sensitive", are no more so than a Bogner Shiva or Bassman RI. Neither are the mighty 25K Dumbles. :eek:
     
  16. Tag

    Tag Gold Supporting Member

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    This is true as well. Guys CRANK the preamp, turn down the MV, and then say it is not as dynamic as a NMV amp that they have at ear drum ripping volumes! LOL!! :rolleyes:
     
  17. riverastoasters

    riverastoasters Member

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    The typical case of seeing if you like speaker X vs. speaker Y with your amp is to simply try the amp into X and then Y without changing any settings. In this situation, the more efficient speaker has an advantage just because it's louder. This is that old psychoacoustic effect "a slightly amplified sound always sounds better". Even if the amount of amplification is not enough that you can tell which sound is louder.

    I expect a lot of the reasons people who are involved in music think that in order to sound good things have to be loud is because they don't keep this effect in mind. But whether it's clubs or radio stations, amps or speakers, there have been decades of loudness wars.

    In this case, a speaker manufacturer who makes a less efficient speaker is betting that the buyers will swim against the tide of psychoacoustics and figure it out. I would guess that they already know how that bet turns out.
     
  18. Tone

    Tone Member

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    Very cool results. I'm learning a lot.

    Thanks guys!:dude
     
  19. daddyo

    daddyo Guest

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    So, crank the pre, lower the master volume, and then I can use the guitar volume for touch sensitivity?
     
  20. Tag

    Tag Gold Supporting Member

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    Totally depends on what you mean by touch sensitivity. If you want a MV amp to react like a non MV amp, simply turn up the MV, and down the preamp. It will then respond exactly like a non MV amp. (Essentially, it IS at that point.) On the other hand, you can turn down the MV, and turn UP the preamp and get lots of gain at lower volumes. You also have all points in between! TOTAL flexibility! Something no Non MV amp can give you. (The Maven Peal I believe is the exception, with the power control)
     

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