When is 18v better then 9v

Started by modsquad, March 05, 2010, 11:58:55 AM

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modsquad

Stupid me posted this in the member section by accident so reposting it here:

I guess what I was getting at is that I see a lot of posts about using charge pumps and running pedals at 18v as opposed to 9v.   What I was wondering is if there is a theory or "rule of thumb" that certain effects/circuits gain some sort of improvement by running them at the higher voltage. 
"Chuck Norris sleeps with a night light, not because he is afraid of the dark but because the dark is afraid of him"

anchovie

18v for an amplification stage will give you more clean headroom, so if that's what you need then 18v is an improvement.
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Mark Hammer

Certainly whenever preservation of dynamics is critical, or immunity to dynamics-related clipping is critical, is a circumstance that could benefit from the higher headroom afforded by a higher supply voltage.  Will it necessarily do so?  No.  EQs tend to "like" the luxury of more headroom.  If I feed my guitar to a compressor that I always leave on, and feed that to a graphic EQ, the odds of that EQ pedal being hit with an excessive transient that taxes its headroom are very small.

R.G.

As I posted in members-only:
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Interesting question. I don't know the real answer. I do know that for tube amps, a 12AX7 front end is biased at about -1 to -1.5V on the grid. Signals bigger than that will definitely clip the front end of the amp. A 9V powered pedal can put out maybe +/-3.5V peaks, so these are already bigger than the amp front end can handle. Presumably there may be some situations where you're not liking even getting close to the 9V rails, or where  you want to over drive an amp's input even more. I guess. If you drive a 9V powered pedal after an 18V powered pedal, it's for sure going to be outside what the second pedal can handle without an input pad.

I guess like everything musical, if you like the resulting sound, it's good.
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R.G.

In response to the questions in the forum - PCB Layout for Musical Effects is available from The Book Patch. Search "PCB Layout" and it ought to appear.

petemoore

What I was wondering is if there is a theory or "rule of thumb" that certain effects/circuits gain some sort of improvement by running them at the higher voltage. 
  If it's CMOs and you're looking for the near-rail waveshaping effect of 'tube', try 5v instead of 9v.
  When stretching the booster to fit in the spot where the preamp isn't, I tried the MAX1044, it's working but I still don't have a pre...er...boost circuit working with it.
  7v for FF, some other GE effects, starve some Jfets @3v supply...hit with say a 9vLPB output for distortion. The JFet @ 3v, then12v, for those types of sounds may require re-biasing if it's not a Mu amp, careful pre-setting of the boost that forces the Jfet to expend all of it's supply.
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