Basic amp Qs Volume/ gain/ MV.

[Sea Chief]

I am reluctantly resigned to the fact that I really dont understand tube amps, altho Ive built two and been playing for 30 years! for eg I recently asked a Q here re speaker break up/ wattage relationship basics but got answers totally confusingly that didnt adhere at all to info I read countless times for eg "I think I'll try a lower wattage speaker to get some earlier break-up"). I was told there is no such basic rule of thumb at all.

The other basic parameter I dont understand is vol/ gain/ master volume which I want to ask here. I -do- understand that simply if say a fender Tweed amp is turned up it will distort (that being the amp will break-up/ the tubes will overdrive): that (although the physics I dont understand even reading countless times about it) I basically understand, & its simplified by the fact that there is only ONE volume knob. I also understand this tube saturation is most desired. It sounds the best as we all know and want.

But what are folks asking (about a decent tube amp as Ive read countless times) when they say 'it sounds great but I wish it had a master volume'-? I thought the only distortion desired for us Tube-Nuts was the natural tube satration by way of ONE volume knob, and that any 'added' volume/gain/MV knobs are 'Mickey-Mouse' approximations of the real thing.

Take for eg the Mesa Boogie Mark* combo. It has volume, gain, master volume. Why? what are these if they are not the -real McCoy- tube distortions? I'd understand if they were cheap practise amps (like my peavey bandit) but this is a pro quality high cost amplifier.

I have a rough idea any -extra- volume/gain/mv knob is something to do with increasing the input signal? (or pre-amp is it?) and not increasing the power amp side of things.. and so can this be termed an -approximation- of the real power-amp od.. but so why all the boogie knobs?

Thanks Sea Chief.

[Alex R]

There is no particular inherent goodness or badness in distortion, just differences and functions that add up to things people prefer or don't prefer. Volume controls can be placed at various points in the preamp, and do the same thing - cut gain, and in a guitar amp, control distortion. They can be before or after the EQ section, or if a master volume, controlling the output of the preamp to the power amp.

[Sea Chief]

But surely there is goodness and badness. Surely that is fundamental to good tone. For eg a fender tube amp's "gain/ distortion channel" if it has one uniformly sounds pretty shoddy compared to a tweed amp with no gain control at all and just the vol turned up to achieve distortion (or an AC30 turned up full). One is goodness, and one is badness. Night and day.

Ok let me ask a Q relative to this area. Why would fender on one Twin Reverb model decide to add a "Master Volume" knob? What would this be for? what does an added MV knob do?

[Alex R]

With a MV fully open there is no audible difference from a non-MV amp. I used to fit MV pots with a pull switch to take the MV out of the circuit, but the difference in a preamp output signal between 1 meg to ground and nothing to ground is inaudible, so I stopped offering it.

The MV is there to dial down the overall volume level so you can crank up the gain and get some preamp distortion at lower volumes. A different kind of distortion from power amp distortion but it's a useful sound. Mesa distortion is largely preamp distortion, that's not an inherently bad sound, it is what it is. I would say a MV adds versatility to most amps with no downside but some guys think they are evil. I think only people are evil (and wasps), I was never deliberately harmed by a potentiometer.

Good and bad sound are in the ear of the listener not in the amp.

There are some current fashions. Some prefer power amp distortion and use attenuators to cut volume; some like preamp distortion (though they rarely admit it and often don't really know they like it!). There is a current fashion for putting the EQ section late in the preamp so you can use EQ on the distortion sound, I think most would agree that's a good idea. One day we may realise that most distortion sounds quite unpleasant to most people, so the opportunity to tune it into sweetness with the EQ section is useful. There is a trend for post-phase-inverter MVs, these allow you to push the PI into distortion, rarely a good sound to my ears, I prefer the mesa distortion sound. Chaq'un a son gout.

[potatofarmer]

There's no one ideal tone; what sort of distortion sounds "good" or "the best" is very subjective. Get 5 guitarists in a room and they'll give you 10 opinions.

You might as well ask why people buy channel-switching amps. There is a conventional wisdom around that the only REAL, TRUE, BEST distortion comes from running a 100W amp into a pair of 412 cabinets (even a 50W model of the same amplifier can be seen as woefully inadequate and clearly only for those who aren't in the know). You know, because most weekend warriors practice in giant abandoned stadiums without modern PA systems.

"Good tone" is a myth, and an astoundingly expensive one at that. Figure out what YOU like and take any other advice with a grain of salt. If you like power amp breakup but want it at reasonable levels, there are many ways people try to accomplish that. Post-phase inverter master volumes, voltage scaling, attenuators, isolation cabinets... all have pros, cons, and different costs.

The master volume was added to the Twin, I presume, for a little distortion at sane volume levels. They generally aren't very popular because Fender preamps aren't tailored specifically for pleasing distortion. They're also useful for finer volume control of clean signals - I have a friend with a Blackface Bassman who hardly ever plays it because by the time the gain pot gets to 2 it's way too loud for the living room.

[Enzo]

when you turn up an old fender, it distorts in a pleasing way, pleasing to many of us anyway. You are overdriving it. But what part are you overdriving? ANY portion of the amp can be overdriven. Most of what you hear is preamp tube distortion, but at full power you can also add in some distortion from the power tubes.

Now imagine on that Fender you turn it up and get preamp tube distortion, and you really like it. But it is just way too loud. A master volume control allows you to still overdrive the preamp for that tone you like, but it lets you turn down how LOUD it is by reducing what is fed to the power tubes. Turning the master down won't un-distort the preamp.

Many amps today have more than one control. Typically the first stage volume control will be called GAIN. Sometimes called Pregain. Later in the preamp, we might find the post gain control. Pre and post mean before and after the bulk of the circuit. I can turn the pre way up for lots of overdrive distortion, but turn the post down to keep the volume lower. Or I can keep the pre low for clean, and turn the post up to make that clean sound louder.

Think of your auto engine. It can drive along with high revolutions in a low gear or low revolutions in a higher gear, but be driving at the same speed either way. You can play your amp with a pre control up and the post down or pre down and post up to get to the same volume. But the tones will be diferent. That Mesa amp has more controls to make it more versatile. The distortions are legitimate, but they do come from all through the amp. The controls help us to adjust how much distortion we have from any one part of the circuit.

Or try this. Imagine a microphone plugged into an amp, and the amp plugged into a speaker. A reasonable sound at the microphone is cleanly amplified by the amp and comes out the speaker clean. Now what if the sound was so loud that the microphone overloaded. That would distort, and the amp would cleanly amplify that distorted mic, and the speaker would reproduce it. Mic distortion. Now we get us a mic that can handle really loud sounds, no more mic distortion, but we turn up the sound even more and now the clean signal from the heavier mic overdrivs the amp. The speaker then cleanly reproduces the distorted sound of the amp. That was amp distortion. But what if both the amp and microphone could handle all this sound, but the speaker can't? The mic and amp might send out a clean signal, but the speaker itself is overdriven and breaks up. Speaker distortion. You might find any one or more of those desirable, but they are separate things. BY having volume controls at several points in a guitar amp, we have something similar - we can adjust just which part of the system is overdriving.

Or ever run a mixer? Each channel has a volume control, and then there is a master volume control. On some mixers there are also sub-group volume controls. You can run the channels high and the master low or for the same output volume you could run the channels low and the master high. What might the difference be? In some cases, it is a way to control headroom in the mixer. Also we might find that the master section was less noisy than the channels, and so running the master high and channels low was less noisy than the other way around. But it is just an example of a system with more than one volume control.

I think you are looking for some sort of universal truth answers, and they don;t exist. If there was an ideal amp, then all amps would be like it. Guitar tone is totally subjective. That is why one guy likes Fender and another likes Marshall.

[Sea Chief]

Thanks Alex, PaulP and Enzo for your explanations- Im much more understanding things now. It seems terribly complicated with all these "volumes in different places in the amp" and then I guess there is another vol on the guitar! crikey Im still pretty flumoxed tbh.

I didnt even know folks actually -wanted/ even prefer- preamp distortion (now I undertand adding the MV means you can control overll volume so you can then OD the preamp, and that causes distortion like in my Peavey bandit 65) to well whatever it is when you turn up a fender one-knob amp full [I shall call it simply 'AMP OD']. Really? to me thats like saying there are cheapo rubbish 'budget' sausages (all pink and anaemic- like yeeuww?) and ones from Prince Charles's estate (seriously- theyre called Dutchy Originals, and yummy scrummy they are too) and you say some folks will prefer the crap ones and some will like the posh ones. Thats insane. No ones going to prefer the pinko crappy ones unless they are retarded, or have only gums-and-no-teeth or something like that.

Both my amps have preamp/MV (now I think thats correct? one has GAIN and next to it VOL, the other has PRE and next to it POST) one is a ss and one is a fender (all) valve. Both are absolutely terrible. Theres just no way -anyone- would prefer this to what I deem is 'proper distortion'.

Another thing I dont understand on this subject. Why if as I beleive eveyone in their right mind wants (if they can control the volume of course) and that being 'AMP OD' and not preamp OD.. is it not simply done by turning ypur amp up to 11, and then turning your guitar down to 0. Dial in GTR 2 for clean, GTR 4 for rich OD, and GTR 11 for your OD guitargasm ? I have seen 'our' Brian (that May to you) do exactly this demo'ing his voxac30 he loves so much. Its a great YTube clip too.

[Jazz P Bass]

Another thing I dont understand on this subject. Why if as I beleive eveyone in their right mind wants (if they can control the volume of course) and that being 'AMP OD' and not preamp OD.. is it not simply done by turning ypur amp up to 11, and then turning your guitar down to 0. Dial in GTR 2 for clean, GTR 4 for rich OD, and GTR 11 for your OD guitargasm ? I have seen 'our' Brian (that May to you) do exactly this demo'ing his voxac30 he loves so much. Its a great YTube clip too.

It's all about amplifying the signal.
If your guitar puts out a 100 millivolt signal, then that is what gets amplified.
The preamp can now be overdriven & distort the signal & so can the power amp.
If you turn your guitar down & it is now outputting 10 millivolts, the amplifier circuits will respond to that signal in a very wimpy way.
You probably will not get any distortion at all.
Simply a clean signal.

[Sea Chief]

Sorry I didn't put my point very well there JazzP Bass. I understand the varying signal strength= varying distortion.

What I was wondering is -why- after all the myriad of ways, amp volume A/B/C nonsense, folks trying attenuators, pedals etc, ie this that and all the other methods to get to --that sweet spot amp OD tone area-- (all very expensive and all an absolute bore IMO).. then why dont folks just use simply the "GTR volume method" that I mention?? ie why isnt this simple method not used uniformly, by us all?

[Justin Thomas]

Chief,

It still depends on the amp. It sounds like you prefer traditional Fenders. When they are cranked up loud, ther's probably distortion happening at EVERY stage past the input. The second preamp stage will clip a little bit, the phase inverter maybe, the power tubes, the speaker... all of it.

As an extreme example, let's take the metal channel of a 5150. If you've got the gain set so high to get the metal distortion, and then turn down the guitar volume to clean up, the preamp is so distorted that it can't clean up but so far. That's why there are separate channels - the clean channel can easily bypass that super-distorted preamp stage.

It sounds like you and I have similar taste in what constitutes a guitargasmic tone - a nice vintage tube amp on ten that we control with guitar volume & picking. But if I hand oh, James Hetfield ca. 1985 my Bassman & 2x15 w. a Tele, it will sound like him, sure, but it probably ain't gonna happen. It's just not the right tools. But he might like the clean sound. So he'd probably want a pedal. Dave Gilmour could probably make it happen with my rig.

It sounds as though you've found your solution and the answers you need for YOUR tone. Just understand that YOUR tools won't work for everyone else. You can probably cut a board with a sledgehammer, but the circular saw might be a little more efficient and less frustrating.

Now the secret to me is to find a kickass clean sound and dirty it up with pedals if I need it. I can always filth it up later, but I can't clean up a dirty clean sound...

Justin

[defaced]

^Exactly. At some point in time you step off the cliff, per se. With some amps, regardless how far you turn down the volume knob the signal clips or otherwise sounds bad. So with those setups, all you can really do is get a sound with less distortion, but not a sound that's really "clean". Further, what EQ (both the knobs and the fixed EQ filters in the circuit) sounds good with heavy distortion might sound really bad for clean signals, and visa versa. Generally, the more distortion one gets from the circuit, the more low frequency content that needs to be filtered out to avoid "muddy" or "farty" distortion sounds. When the guitar volume is rolled back, you get a very articulate and thin clean sound - it sounds nothing like a Twin, but it's clean. Now if I start tweaking knobs to get a thicker clean sound, my distortion sound is going to go to crap. And as Justin rightfully points out, a good solution to this problem is to make the amp switch channels. Effectively rerouting the signal to a circuit that's tailored for a given type of sound.

Also, not everyone is looking for that "sweet spot" distortion sound. Every approach to distorting the signal makes a different kind of sound. Some ways of distorting the signal are really great for some applications but terrible for others. It's all about finding the right tool for the job. Amps are like guitars, some just work better for certain kinds of music.

[Sea Chief]

The thing is I altho Ive had a few valve amps: one at the mo is a fendersuper112 which apparanty is clean all the way up to its bone-shattering 60w at 10.. for some reason (but I wont try & understand that one) & its 'gain/ volume' channel (I assume this volume is a MV?) sounds absolutely terrible I cannot get even one place on either dial that sounds anything but awful!!

Hence my trying to understand all this gtr vol/ vol/another vol, then master.. it still confuses me tbh. For eg if the Brian May (no Im far from a Queeno) example I mentioned ie he seems to simplify things so much that he simply gets his clean sound with GTR on 1, OD on with GTR on 4, and May-tastic distortion with GTR on 10.. then why oh why oh why don't we all have a volume 'box' ????????? or for arguments sake lets take the GTR volume knob and the wire in and the wire out, and put in in a box. A box with a vol knob simply that. I then put this box on my amp. Then -surely- I have every stage of my amp sound like 'our Brian' eg, ie amp sounding its best, controllable for the price of a few beers.

Why is it that this is not used???????????????? I just dont understand: all these other vols, vol, gain, preamp vol, post vol, master vol, distortion pedals, attenuator boxes....... I want to throw the whole damn lot in the sea. Why? beacause A) I dont undertand why my cheapo GTR vol box idea isnt just used instead of all this line of confusion B) cos it costs an arm and a leg like 'superOD pedal' or 'weber attenuator' £££sillyness C) cos all these things sound -rubbish- compared to simple amp distortion.

One vol. Thats it. (and one GTRVOL in my $5 box on top of the amp). There ---has--- to be a reason why this is not universally used by all of us (ie maybe say having the amp on max for the duration of a play, say 1 hr each day, is inherrantly bad for the amp regardless of the position of the GTRVOL knob on my $5 box). That is the thing that confuses me most.

Maybe I need to ask 'our' Brian.

[Justin Thomas]

That Vox Brian is using is not your Fender. Go plug into his rig and see if you can do what he can do. If it works for you, sell your Fender & get an AC30... I've also found that the "Distortion Channels" on Fenders need to have the Master Volume cranked up. I used to play my Prosonic's dirty channel with Gain 1 & 2 around 7, Master on 2. Then I figured out I liked it better with the Master on 5 and the Gains low. If I needed the metal sound, I still had to tur the Master above 3 to get it to sound good. There/s just a certain amount of air you have to move, I guess.

Try it with your Super. Crank the Master & start the gain on zero. It might work. That said, I don't know anyone who uses the dirty channel of a Fender for a lead sound without an extra pedal... In an attempt to make amps that try to do everything, they're going to fall short somewhere...

There's a guy I play with at church who uses every piece of technology available -digital everything, tubes, modelers, etc - and sounds GREAT. I plug my Tele into a Boss PD2 then into my humble Fender and sound GREAT. We both respect what the other can do with our tools. There are just some things he can't do with his, and things I can't do with mine. But if one of us is missing, it's noticed. There's room for everything. And besides, tone is subjective! If having 10 miles of signal path makes you happy and helps you play better, fine. Just don't ask me to fix it!

Justin

[Enzo]

I love the clean sound of a Fender. I think a Hot Rod DeVille sounds good. But I also think Fender can't design an overdrive channel to save their souls. The drive channel on that same DeVille sounds like crap to me.

WHy doesn't everyone do anything? because everyone does not agree on what sounds good.

Really? to me thats like saying there are cheapo rubbish 'budget' sausages (all pink and anaemic- like yeeuww?) and ones from Prince Charles's estate (seriously- theyre called Dutchy Originals, and yummy scrummy they are too) and you say some folks will prefer the crap ones and some will like the posh ones. Thats insane. No ones going to prefer the pinko crappy ones unless they are retarded, or have only gums-and-no-teeth or something like that.

Really? Is Beef Wellington better than a hamburger? Is prime rib roast better than a hamburger? I think the majority of us think so. And yet how many of us still enjoy a hamburger? I bet an equally large percentage. There are guys who have poked a bunch of pencil holes in their speaker cones to get a real ratty distorted tone. Van Halen experimented with using a device to dial his mains voltage WAY low to get a different distortion from the amp. he called it his "brown sound."

When you have one volume knob on a simple amp, you can turn the amp up until you get distortion. SOMETHING in the amp is distorting. You really don;t know what. COuld be one stage, could be several. Unless you go in and electrically analyze it, you won;t know. By putting a level control between each stage, you get the ability to determine which parts of the amp distort and which do not.

Listen to Eddie Van Halen's sound. Does he sound the same as Brian May? Does Jimi Hendrix? Mark Knofler? A little gritty overdrive is one thing, and serious distortion is another. There is no universal guitar tone that everyone adores. An amplifier like the PV 5150 doesn;t even have a clean channel. The "clean" on it is simple less distorted than the other channels. And yet many players still add a distortion pedal out front of it , just to add a different distorted character to the sound.

[Sea Chief]

That Vox Brian is using is not your Fender. Go plug into his rig and see if you can do what he can do. If it works for you, sell your Fender & get an AC30... I've also found that the "Distortion Channels" on Fenders need to have the Master Volume cranked up. I used to play my Prosonic's dirty channel with Gain 1 & 2 around 7, Master on 2. Then I figured out I liked it better with the Master on 5 and the Gains low. If I needed the metal sound, I still had to tur the Master above 3 to get it to sound good. There/s just a certain amount of air you have to move, I guess.

Try it with your Super. Crank the Master & start the gain on zero. It might work. That said, I don't know anyone who uses the dirty channel of a Fender for a lead sound without an extra pedal... In an attempt to make amps that try to do everything, they're going to fall short somewhere...

There's a guy I play with at church who uses every piece of technology available -digital everything, tubes, modelers, etc - and sounds GREAT. I plug my Tele into a Boss PD2 then into my humble Fender and sound GREAT. We both respect what the other can do with our tools. There are just some things he can't do with his, and things I can't do with mine. But if one of us is missing, it's noticed. There's room for everything. And besides, tone is subjective! If having 10 miles of signal path makes you happy and helps you play better, fine. Just don't ask me to fix it!

Justin

Justin- I know the amp is not a fender, but the principle is exactly the same (its the principle- not the excat sound he gets there I want to replicate, not at all really esp the v high distortion '10' sound). Its an eg to simply show an amp at max, and the 3 basic sounds a GTR can get (approximate to his/ not exact at all) simply by using the GTR vol.

I have tried doing the MV pot at max and then GAIN next lhs to it from 0 up. It doesnt work- there is so much volume still with gain at 0, hugely loud. Its channel 2 is so useless Im getting fed-up finally you see/ want some 'proper' amp od hence trying to fathom how: so far its proven 30 years and countless amps and Ive never got it (well a Musicman i did with the gain up to 8/9/10, but it sounded buzzy & poor: so much so a flamin od pedal -which I just find nasty and wrong really- was far preferable.

I just cant see why in principle (& therefore why its not common practise in principle instead of all this vol/vol/gain/MV/boost/arse/tit and bollocks:-) if say I had a Deluxe Reverb (which I cant afford) I ripped out the plastic vol pot in my Squier (no2- I do have a gibbo SG but Id rather rip my balls off than play with her knobs!) put it in a $5 box & put it on the amp. Turn amp to 10 and Squier knob from 0 up etc etc.