Can i destroy an amp with a FX pedal?

[kwijibo]

Yes, but once the speakers are blown the amp is left running with no load, which can cause damage.

[object88]

I did some repairwork for a Crate solid-state amp that a friend broke.  He took a drum machine (figure, 1-2V peak-to-peak max output), ran it straight into the amp, and dimed all the distortion / drive circuits.  After a few minutes of blissful industrial rock action, the amp let out a wisp of smoke, and lost a good bit of power.  When he tried using it again a few days later (under less-stressful circumstances), it refused to play a single note.

I opened it up and discovered that a single resister had blown.  Crate had selected 1/4W resisters, and I think they figured that no-one was going to run such a strong signal into their amp.  I replaced the resister, and everything seemed just fine.  I kept the amp for some time, then lent it out to a neighbor so that he could practice his punk rock musings at home.  It came back to me a few days later, again dead.  I didn't ask what he was doing, but I opened it up, and if I remember correctly, the same resister had gone.  I'm going to guess that what the first friend did caused more than a single resister failure-- perhaps weakened some other part of the circuit.  As I recall, I fixed it again, and sold it off for some pittance, with due warning to the buyer.

Another story, not quite so relevant.  I was in a noise performance band, and was eager to try out my MOTM synth modules at stage-volumes, through a recently acquired QSC power amp (~280W total?  140W/channel) and single PA speaker.  The QSC output wasn't bridged, so in theory the PA should have only seem 140W at peak.  The MOTM puts out something like 10V peak-to-peak.  I had the QSC turned up to something like... 4?  Blew the PA speaker in 5 seconds.  I took the PA cab apart when I got home, and by manually excersizing the cone, found that the voice coil was toast-- there was a distinct scraping sound as it flexed.  I think the markings on the speaker cone was rated around 100W?  I replaced the speaker with something rated around 200W, and had no further problems.

So, uh... watch that gain-staging, kids!

[the_random_hero]

I did some repairwork for a Crate solid-state amp that a friend broke.  He took a drum machine (figure, 1-2V peak-to-peak max output), ran it straight into the amp, and dimed all the distortion / drive circuits.  After a few minutes of blissful industrial rock action, the amp let out a wisp of smoke, and lost a good bit of power.  When he tried using it again a few days later (under less-stressful circumstances), it refused to play a single note.

I opened it up and discovered that a single resister had blown.  Crate had selected 1/4W resisters, and I think they figured that no-one was going to run such a strong signal into their amp.  I replaced the resister, and everything seemed just fine.  I kept the amp for some time, then lent it out to a neighbor so that he could practice his punk rock musings at home.  It came back to me a few days later, again dead.  I didn't ask what he was doing, but I opened it up, and if I remember correctly, the same resister had gone.  I'm going to guess that what the first friend did caused more than a single resister failure-- perhaps weakened some other part of the circuit.  As I recall, I fixed it again, and sold it off for some pittance, with due warning to the buyer.

Was that from the input signal being too large, or the amp working too hard? I'd put my money on the latter. Sure, running something like 30V peak-to-peak isn't going to be good for an amp, but most pedals have nowhere near the output power to fry your amp. I wouldn't be too concerned if I was you.

[darron]

i'm going to go against the flow and say the chances of you frying ANYTHING with ANY stompbox that is properly wired are slim to none, short of mark's wise warnings about blowing speakers. there is a finite voltage you are going to see on the output of a pedal, and no amp circuit i've ever seen would come close to frying at it's top end. speakers, on the other hand, you can blow quite easily.

interesting topic that i dug up searching for a review of analog man's book. not too old i hope.

i've been recently thinking of making an opamp boost of about 20 gain that uses the geofex charge pump idea. having read above i started second guessing, especially since i make a lot of use of 'budget' practice amps. i fried the speakers in a fender fm212r by running the amp with a 250v source instead of 240v.... TOUCHY huh? it came back from fender with the new speakers soldered in instead of having the spade connections perhaps they assumed i plugged them into something else.

after reading Barcode's comment I thought "yeah, hold on, we're just talking 9v stompboxes here... a coupling capacitor at the end and hopefully one on the amp's input" is 17v getting to be a bit too much to assume safety though? if a gave a pedal to a bass player with 20x clean gain potential, would that start leading to problems and blame in my direction?

i once brought a circuit to show a friend which had not been housed yet. as in, it was a board with everything offboard on short wires. he refused to let me plug it in because "everything's all dangling everywhere". i gave it a moments thought and in the same moment told him it was very safe.

[soulsonic]

If a battery-powered pedal destroys an amp, then the amp was junk and DESERVED to die! I've used an abused guitar gear for almost 20 years making all kinds of horrible noise and I've never blown up anything, except the occasional junk speaker. The only thing that ever blows up for me is these junk PAs that no one seems to be able to set up properly...

[runmikeyrun]

When I was a kid I destroyed the phono in on my stereo buy feeding it an active bass.
We were kids! We wanted to jam but no amps.

I did something like that too- plugged my bass into the rec input on my tape deck (hey it was 1991) and then ran i through my stereo.  I was sitting on the edge of my bed playing, not even too loud if i remember right, and something caught my attention out of the corner of my eye- the speaker behind me was on fire!  This was a 12" eminence rated at 120w coming from a 100w head unit.  The cone itself had caught fire somehow.  Never figured out how that happened, the speaker must have gotten really really hot. 

I would say as long as the volume coming out of the amp is the same with the effect on and bypassed you should be ok, other things being equal like no DC or other strange ultrasonic frequencies.