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What's the deal with Vomume knobs on guitar amps

Discussion in 'Guitars' started by redbort, Jan 6, 2006.

  1. redbort

    redbort Active Member

    are they liniar?
    are they logarithmic?
    inverse logarithmic? <this is my guess
    why does it always seem like 10 is just a notch higher then 5
    yet their should be many more steps between 0-2?

    follow what i'm saying?
    it's time to start a union
  2. moonbaby

    moonbaby Mmmmmm Well-Known Member

    Those damned Volume controls are the original sales hype, aren't they? Even Leo Fender used their crappy scale in the 50s to sell an amp..."Look, Pa, it's only on 3!!! Just think what it'd be like on 10!!!" When in actuality it's really running flat-out by the time you get to '5'! Yeah, Spinal Tap said it all when they had Marshalls that "go to 11"...!
  3. Hardtailed

    Hardtailed Guest

    Don't forget though that tube guitar amps are designed to run out of headroom on purpose. Past a certain point (seems to be 5 on my Marshall), they don't get much louder but start distorting more and more.

    It would be nice though to have more control under 2, but since I only use it live, it's never under 3 anyway (which is not loud enough actually :)
  4. audiowkstation

    audiowkstation Active Member

    The numbers don't mean anything. The value of the potentiometer selected by the manufacturer makes any of these numbers meaningless. Just put the volume where you like it and note the number value and that is all they are good for. "Ten" simply means the potentiometer is out of the circuit.
  5. GregP

    GregP Guest

    Exactly what was said above. Which is why at least half (if not more) of the popular guitar knob styles don't even feature numbers. ;)

    They're "audio taper" (appropriately enough!) A linear taper would actually sound stranger to your ears than an audio taper's logarithmic ratio.

    As the resistor is introduced (by turning the pot down), high frequencies are bled off first, which is why a lot of guitarists 'warm up' their sound by backing off on the vol knob a bit. Not only are they reducing the levels by which the amp's input is hit, but are changing the frequency content.

    A nice little trick is to put a tiny capacitor (.001 uf will do!) between the high end and the wiper lug, which acts as a high-pass filter and allows you to maintain treble frequencies as you turn the knob down. I put this onto my Tele-style guitar, and while it wasn't strictly necessary to begin with (my guitar was never particularly muddy) it was a nice little $0.50 mod.

  6. moonbaby

    moonbaby Mmmmmm Well-Known Member

    Yep, "real" telecasters have the cap already wired into the circuit for this pupose. And the "bright" switch on a Fender blackface and silverface amps is actually a cap to counteract the effects of treble-loss when the volume control is less than full-throttle.
  7. greyskull

    greyskull Guest

    Hey how is it, im geetarist/ producer.

    Yeppers after 5 the amps never get louder, which with valve amp is great, as you get more poweramp drive and sag and more 'warmth' hahahah nah that word is over used.
  8. GregP

    GregP Guest

    Er, just noticed that the topic says, "volume knobs on guitar amps" and I was talking about knobs on guitars. Sorry about that. Hopefully still useful for someone reading the thread. ;)

  9. Tommy P.

    Tommy P. Well-Known Member

    Hey, this has turned into a cool thread about how guitarists get thier tone. People rarely talk about the knobs, and the expressive control that in no small part, helps balance thier tones.
    Definitly cool to really know when your your amp is set to respond best, without regard to the number value. And to have a right hand technique that utilizes the knobs on the guitar for best tone.
  10. moonbaby

    moonbaby Mmmmmm Well-Known Member

    I don't like to talk about "my knobs". They're nobody's business! Seriously, I wish there was a way to get the tone to darken when I turn up the Volume control on my guitar, instead of getting brighter. I have modded my guitars' volume controls to NOT lose the highs when I turn the Volume DOWN, so that I can maintain some clarity. That's pretty easy, thanks to Dan Torres. P90s, PAFs, SCs, whatever. The problem lies in when I want the "pump from the pup" without the top end "rasp". Anybody got a suggestion for that?
  11. Tommy P.

    Tommy P. Well-Known Member

    A Seymour Duncan pickup booster is a great tool for those of us that like to keep our knobs rolled back a bit. It has a resonance switch to help fatten Sc's too. There's a booteek pedal named "TIM" that is really great sounding. Both are very dynamic and musically wide ranging.

    My Duncan Booster is turned on most of the time, I love it. There is an internal version of the electronics that can be installed into the axe.
  12. moonbaby

    moonbaby Mmmmmm Well-Known Member

    Thanks, Tommy. I had a Duncan Pick-Up Booster that I used with a '69 Fender Pro Reverb so that I could play in the control room with my amp in the studio. It worked great for a l-o-n-g guitar cord. But I sold the amp and the pedal went with it. I haven't seen the "in-guitar" version that you mentioned, but I'll look for it. So that "resonance" switch should help 'round off" the tone when the guitar's volume knob gets jacked....hmmm....I'll have to try that one on for size. I never really played with it much when I had the pedal, but it sure kept the signal quiet when I used a couple of 25-foot cords strung together.
  13. Tommy P.

    Tommy P. Well-Known Member

    moonbaby if you can try a TIM booster pedal, or if you know someone or a studio that has one, its a great booster. Its also got an effects loop. Its custom made by a guy who works at Heritage amps, a side business him and his wife runs. There may be a waiting list. I can PM you his number if you're interested.

    If you'd like a Duncan booster internal, its available here : http://guitarelectronics.zoovy.com/product/PASFX This circuit gives one the versitality of having on-board active electronics for any passive pickup. You can balance two pickups on the same guitar that have differing output voltages, or change the resonant peak of a single coil pup to match a humbucker on the same guitar. But what I like about the Duncan booster is how my signal chain is improved, and my guitar knobs work real nice. :cool: And its soooo easy to slam the front end of an amp with this pedal.
  14. Tommy P.

    Tommy P. Well-Known Member

    lol, knobs to boosters? wtf, Tommy P.?

    I think I jumped the gun a little going from pots to booster pedals. Its because 250k, 300k, 500k, and 1meg volume pots change tone, due to the tuning of the resonance of the complete signal path of which everything that comes after the guitar is also part of. A high quality buffer circuit after the output jack, makes all those pot choices and wiring schemes take on a less reactive role. In short, 500k or 1 meg pots will have resonant peaks noticeably shifted when cable capacitance increases, due to the cables design, multiplied by its length.
    Yes, anyone will hear a pronounced difference in guitar cables in a demonstration like this. Not as easily heard with 250k pots, though.

    The resonance tuning effect would be even more noticable in single coils, with higher amplitude resonant peaks in the 2-5k range....but the use of 250k pots with these types of pups reduces the resonance tuning of the circuit by the volume pot. I doubt most will hear a difference in cable quality or length with 250k pots, the resonance of the signal path is not much affected.

    This may also explain why some guitarists hear a difference in cables and some do not. Different setups will give different results, simple as that.

    I happen to like the PAFish sound of a guitar with humbuckers and 500k pots. I also like Tele bridge tones, which is probably why I like Barden pickups- theres a little of everything in thier tones.

    A quality buffer in the chain takes the capacitance of the cable out of play, and the way it reacts to the KNOBS. Not an option for the purists, eh?
  15. moonbaby

    moonbaby Mmmmmm Well-Known Member

    Thanks for the input, Tommy. I will check out the TIM pedal. I have no problem with modding my guitars....have done so for too many years now. The technology and information behind guitar electronics has really taken off the last few years. Pick-ups and controls/switches were "stone-age" for soooo long. I love being able to use the knobs to accurately and repeatedly dial-in the tone I "feel" at that moment.

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