Maximum input voltage ????

[Stevo]

Bought an amp to check my pedals in the garage and I was wondering what does maximum input voltage mean? Most pedals are nine volts what kind of output do most give, even the supasustain is 18 volts should I worry about the amp..It says maximum input voltage 2.2 volts.. I thought that there is millavolts on the output which would be plug into the input... This brings up an interesting point where is the breaking point of how much stuff you can plug into an amplifier... I hope this isnt stupid but I am interested? Thanks

[niftydog]

unity gain pedals (gain equals 1x) will attempt to reproduce the input voltage, which for most guitars is WELL below 2.2V. However, anything with gain has the potential for causing destruction, although it would have to be set at "pretty damn extreme" to get there.

I would suggest building up a cheap op amp buffer to put in front of the amp. Most op amps can handle significantly more input voltage that 2.2V and if it blows you haven't ruined the amp and can fix it easily.

[Stevo]

What would a Fuzz Face put out in terms of voltage.. I know the collector at the second trans can be as high as 5 volts but then you have the cap that reduces to an AC signal?  I checked one on my multimeter and could never get 1 volt coming from the output around 115 millivolts and moving  and it is a three transistor Fuzz... Than checked another overdrive pedal and never got over 100 millivolts.... it is digital though :? The meter :oops:

[niftydog]

you really need an oscilloscope to get the full picture, a multimeter just won't do it. But, sadly, I cannot tell you. Maybe someone else has looked into this on their fuzz face?

[DDD]

Solder a parallel couple of green LEDs from input jack to ground - something like diode clipper. They will limit input voltage at 2 Volts approx.
Please note the LEDs may cause signal distortion beginning from 1.5-1.8 Volts (amplitude).

[Stevo]

What does an effect send to input in voltage? :? ...Does anybody know..... wouldnt this be a concern to someone with an expensive amp....that they dont send to much signal...

[Stevo]

What would say a chorus like the TC with a wire to the wall socket.. What if something happened internally what would it do to your amp?

[sean k]

Well I built the AMZ booster the other day and put a coupla diodes ,1N914 then 1N60's,to ground after the output caps and they had absolutely no effect on the signal so that tells you I wasn't even getting 600mV peak to peak as I wasn't able to get the diodes conducting.If you just opened up a lead and put two diodes in parallel but in opposite orientation from hot to cold you'd have the protection you need...as the DDD suggests.

[Stevo]

I guess no digs on this one? thought this woukd be a good topic :cry:

[brett]

Hi.
Max guitar output from kneck pickup is about 100mV peak-to-peak.
Output from high-gain, signal-clipping pedals is up to 2V ptp.
Output from other pedals could be up to the full power supply (9V), but why anybody would want to do that is a mystery.
A fuzz face puts out a couple of volts at full volume.

I'm no expert on this, but a typical pre-amp tube (12AX7) has a -2V bias on the grid, so I'd guess anything more than 4V ptp will be seriously overdriving it (but will not destroy it unless the amp designer was over-optimistic about heat dissipation, etc).  To outright destroy a pre-amp tube I think would require something more like 50V ptp.  So the safety margin is HUGE.

With regular transistor input stages, you can expect them to blow at something like 10 to 50V input.  I've found that small signal FETs make great input stages, but are more sensitive than BJTs to transients.  I've blown a few while using them as buffers for an audio probe (386) amplifier.  Touching a 30 or 40V DC line can send enough signal through a cap to blow them.  In any case, there's still a LARGE safety zone above what a 9V pedal puts out.

cheers

PS That 2.2V maximum input on your amp is almost certainly an RMS value.  It is also going to be conservative.  So you might be able to throw up to 10V peak-to-peak at it.

[Stevo]

I noticed it did say at 400rms 2.2volts..I am assuming it is normal but it is interesesting what you say about normal operations. Thanks