Maximum recomended pedal output voltage?

[slotbot]

Hi,

I have recently designed my own tremolo pedal. This is the first pedal that i have designed myself and i was wondering what the maximum allowable  voltage should be at the output so i dont damage my amp.

thanks.

[Peter Snowberg]

Welcome slotbot,

That's a loaded question because it depends on the output impedance, the input impedance, and the type of amp.

I would keep things under a few volts to be safe. The most you should ever need to hit a guitar amp with is a few volts. Keep in mind that they're made for signals that are generally much less than a volt at maximum. A 15 volt swing is going to be pretty useless for most applications, but if you have a device with that kind of headroom there will no doubt be somebody who will take advantage of it.  

With a solid state amps, at some point your amp will start clipping and conducting any excess voltage off to the power or ground rails via protection diodes. If you have a small resistance (say 1K) after the output stage of your effect or in the input stage of your amp, any excess voltage will be safely limited by the resistor. Without current limiting it will be up to the particular circuits as to what they can bear without letting the blue smoke out.

A tube amp can handle much more voltage and again it becomes a value which is specific to the amp in question. Tube amps are MUCH harder to damage with big inputs because tubes take overload very gracefully and tube amps typically have a big (10K-68K) input resistor in front of the first grid anyway.

To give a specific voltage…. I’ll say 4 volts is more swing than you’re going to need in 99% of 9V effect situations. There are 18 volt powered boosters that could probably take advantage of more, but they’re not too common.

Sorry for the lack of a clear answer.

Take care,
-Peter

[smoguzbenjamin]

To give a clearer but less elaborate answer:

I generally try to keep maximum voltages in the 3.5vAC region, basically because this is when my SS amp goes muddy

[downweverything]

yeah if you go a little over 3Vac you will actually be hitting your power rails (of a nine volt battery).  if you are measuring in Vac RMS (which is usually what a meter would normally measure).  ben that may be what you are noticing, good ear.  3.2V*sqrt(2)*2 is approximately 9V peak to peak.

[smoguzbenjamin]

Hmmm I was guessing at  why it went muddy, you just confirmed my suspicions Cool! I'm amazed why ibanez didn't opt for 12v instead of 9 in the preamp stage for more headroom.... Oh well I don't really care

[zachary vex]

a million billion volts!  i never worry much about generating a voltage with a 9 volt battery that will harm a healthy guitar amp.  you can always turn the amp down if it's a little too loud.

[Ansil]

3watts maximum is what i aim for..  

[anyuser00]

3watts maximum is what i aim for..  

3 Watts ?!?!

Thanks everyone, I also was looking for this information, but got some unhelpful smart remarks on another board.

[puretube]

I try to keep it under 50Vpk/pk, so as not to ruin lo-volt input caps in succeeding pedals (assuming they`re no electrolytics...).

[smoguzbenjamin]

3 w = 3v x 1A hehe
or 9v x 0.333A

lol