When you guys design pedals what do you assume the input voltage to be?

[JasonG]

Hi
I would like to try my hand at designing an OD pedal. There is quite a range of pickup out put voltages out there. What input voltage do you use when designing a pedal?

[Phorhas]

I messured my US strat (2006) at about 0.1 volts AC. My humbuckers messured 0.190 v. some active PU go to about a volt

[Gus]

I am not going to give a fixed answer because it can depend.  Maybe the following will help.

If you have access to a scope?
connect a 1 meg as a load for the pickup
play the guitar or bass
Look at the peak and decaying output voltage vs time
Load the pickup with 470K
220K
100K
do the scope test again
This should help let you calculate the gain a bit

If you don't have a scope build a buffer with a changeable input R 100K to 1meg to simulate effect to tube amp input Rs to plug into your sound card and maybe use one of the PC scopes that use a sound card(I have not used a PC soundcard software scope so I am not sure how it will work out)

Do you care if you clip the attack? if you don't, you can set it up for more gain

Now does the overdrive clip hard and harsh sounding or does it clip softer

Some gain stages clip ugly some clip, compress nice

What power supply voltage?

[JasonG]

Thanks guys!
It seems that 1 kHz is the standard frequency for testing / designing (?)audio circuits. I thought that in a similar manner there might be a standard voltage for guitar pedals. A voltage that would be about right for 90% of the guitars out there. There are a lot of very usefull tutrials full of formulas to calculate this gain and that frequency responce but I have yet to find a standard for the input voltage.

[R.G.]

You can't. Whatever you assume, there are guitars that are different.

As a designer you have to know how they all may act, and know how your stuff works with all the different guitars. There isn't just one.

[JasonG]

Ok, so there is no industry standard.  Thanks again.

[gez]

I once plugged my Jazzmaster into the scope, selected the neck pickup, thwacked an open E chord as hard as possible and measured around 800mV peak-to-peak. 

Humbucker would be more.  Active pickups even more (possibly).  As stated, there's no real way of telling.  Plus, what if there's another effect in the chain beforehand adding some gain?

[JasonG]

I am surprised those pickups put out that much. I got about the same voltage with humbuckers.

[gez]

I am surprised those pickups put out that much. I got about the same voltage with humbuckers.

Jazzmaster PUs are hotter than skinny, strat single-coils etc, but definitely lower output than humbuckers (though probably about the same output as mini-humbuckers); when I said I thwacked the strings as hard as I could, I meant hard!  Plus, it was with an open chord.  You'd see/hear a difference with A/B testing.

[PerroGrande]

I have a set of humbuckers on one of my guitars that can, when thwacked aggressively, put out over 1 volt.  No fooling. 

Yes, I really have to dig into that low E-string way down by the bridge, but I can get the output to be in the ballpark of some active pickups.  I have another guitar that has trouble reaching 100mV when set to single coil mode.  Just depends.

I know that at some point, an assumption has to be made or a circuit will never get started.  I usually start with a 100mV input as a guidepost and then try to see how a given design will behave with stronger or weaker inputs.   But, as you can see from the responses, the actual output is all over the board. 

[DDD]

Hi men!
Pls take a look at the AMZ Lab Notebook and you'll get the most average guitar pickup I've seen before.

[Paul Perry (Frostwave)]

I've seen more than 2v peak to peak, from a bass.
Makes it pretty difficult when designing a front end.. bad enough in the analog domain, but if the signal is going to be digitised, you have real problems with clipping.

It's a real problem if part of the circuit has a low peak signal to noise floor ratio (eg. an OTA filter stage, or a BBD delay stage).