Can i destroy an amp with a FX pedal?

[Albot]

#1 Well. I've got a quite crappy amplifier and when i send boosted or overdriving (strong) signals into it i get it to be alot louder then it normally is.
This got me thinking if the amp has to "work" harder and might burn out if i send too strong a signal into it.
I realize this might break the speaker or speaker elements but what im interested in is the "amp section".

#2 What makes a effect pedal "safe" to use. Any routines you guys have to test a pedal before connecting it to an amp?

[GibsonGM]

The first thing I do when a circuit is done is to test it before adding the stomp switch, so I know it works and later problems are in that wiring.  I check between output and ground for any DC present (output caps block it, solder bridges can defeat that!).   DC ain't so good for your amp! 
After that, I hook up to an old marshall ss 10W practice amp I have.  If I kill it, I won't feel bad.  When it passes that test, it can go before my tube amp.

Theoretically, you could pump so much juice into your amp input that you could toast something.  I don't know what that level is, though.  I've heard it said that up to 5-7 volts on the input won't cause problems, but don't quote me!!  Depends on whether it's tube or SS, too.  The most I really have run into my input is around 3 to 5V (ac), with no bad results. 

[Shepherd]

http://www.monstereffects.net/GuitarWorld.jpg

[Paul Perry (Frostwave)]

I would say, no.
Or at least, if you do, it's not the fault of the pedal as such, it's the fault of having the amp turned up too high for the input.
In which case, you might say that some pedal makes it POSSIBLE to damage the amp, but the damage is done by the idiot using the amp.

[slacker]

you'd like to think the amp would have enough protection on its input, so that you couldn't kill it just by overloading the input. Don't know if all of them do though.

[Mark Hammer]

 "Loud" = more current passing somewhere.  If the component is equipped to handle that heat, groovy.  If not, poof!  Even though your focus is on feeding an amp a hot, hot, hot signal as a result of a booster/distortion of some kind, the input stage is not the only part to be affected.  One has to distinguish between:

a) The speakers and how much current/wattage they can handle, both continuously and in terms of instantaneous peaks.  Managing those peaks successfully is one of the reasons for the existence of limiters, since a cone moving too far too fast for its voice coil is not a problem restricted to guitar amps, but P.A. systems too.  Note that some amps have a small margin of "safety" as regards speakers (e.g., one or more speakers rated to handle maybe 20% more power than the amp itself is rated to deliver) while others may have a much wider margin of safety (e.g., 2 speakers rated at 100W capacity@ on an amp rated at 45W output capability).

b) The output transformer (if a tube amp, though some older transistor amps will have interstage transformers).  Transformers are also rated in terms of current-handling capability, and you will sometimes see comments in passing about "upgrading" the output transformer on amplifier X to handle more wattage, or about the output transformer in amplifier Y being insufficient.  Whatever current is not effectively handled gets turned into heat, and at that point the transformer changes into just another piece of wire that go "Poof!" just like another well-known piece of wire - the fuse.

c) Individual semiconductors or tubes.  Again, repeated heat build-up can, over time, reduce the lifespan of a component that is expected to handle large current.  That's why some tube amps have fans near the power tubes, and it is also why power transistors and chips are mounted on heat sinks.

d) The circuit structure itself.  Admittedly, this one is the rarest.  The first personal computer I bought almost 25 years ago, to the day, was one of those all on one board affairs, including the on-board voltage regulation.  Unfortunately, the regulator was not properly heat-sinked, and within a relatively short period (<year), a crack or two had occurred in the traces on the board and the thing would not boot unless I pointed a hair-dryer at it, caused the metal traces to expand slightly and eventually make contact so that the ROM could be read.  Thankfully, the traces on an amp's PCB are generally thicker and wider than those found on a computer PCB, so the risk of heat-caused fracture is much lower, but the same principle applies: if the amp is forced to run hotter, then anything which is susceptible to heat-related stresses is vulnerable.

Of these 4, speaker damage (and ear damage ) is probably the only one that could occur as a result of a single power chord at juiced-up volumes.  Maybe not quite the same way it occurred in "Back to the Future", but with the same negative consequences for the speakers.

I suppose one of the ways to assure that none of this ever happens is to use under-rated fast-blow fuses so that power is removed before the point of no return.  So, if the amp wants a 6A slow-blow, use a 4A fast-blow.  That will keep you tame enough.

[MikeH]

My bass player cooked the preamp on his rig by pushing a bunch of extra signal into it with an EQ.  But I've heard bass amps arent designed to have all kinds of effects and crap coming at them.  I could be wrong.

[Mark Hammer]

It can happen, just not often.  My stereo amp at home has separate fuses for the preamp and the power amp, so I'm assuming this is in anticipation of something that is a realistic possibility.

[Toney]

 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. It was usually fine with a regular guitar but that extra bit of push from the active pickups killed it.
I also got pretty weird results using a Red llama into an 80s solid state amp.
Waaaaay to much boost for that puppy. Went a bit awol tone wise for a some time.
Took a while to settle back down. I've never cracked it open to see whats going on in there, but in my experience, yes, too much input boost with a SS can stuff things up nicely.

I think GibsonGM's comments above are good advice.

[Mark Hammer]

Not to be a doubting Thomas (apologies to all the Thomases, it's just an expression), but we keep hearing all these stories that begin "I destroyed/broke/fried my...", and we never ever hear exactly what it was that was put out of action.  Naturally, these are exactly the sorts of folk legends and nonspecific testimonies that prompted the original question in this thread.  Doesn't mean it didn't happen.  It simply means that without details, the naive listener is free to confabulate whatever %^&*amamie explanation and mythology they want, like "Fuzz boxes will destroy your amplifier".

There are LOTS of reasons why an amplifier malfunction could co-occur with a hot input signal.  In the absence of followup diagnostic info (was it a speaker? a transformer? a diode in the PS?  an input resistor? an under-rated cap in the signal path?), it is difficult to know what sort of advice to provide.

Keep in mind there is one sort of "explanation" for budget amps that cut corners in production costs and use components at the margins of their ratings, and another set of explanations for professional products that apply best industry practices and use components rated high enough for a more than sufficient margin of error.  I'm sure a person could fry a Hi-Watt if they did all the "right" things.  Everything has its Achilles heel.

[Gila_Crisis]

that mastortion is making me reaaaaaaallllly curious!!!
and it sounds really fine as well!

[Bernardduur]

I once put my Colorsound Overdriver in the FX loop of my old practise amp

It worked for a while; live it started to turn the volume up on the Overdriver. Then the amp started smoking (and sounding really good)

Now it is a passive monitor

[Albot]

I just bought a nice solid state bass amp from 1979 and i would hate to kill it, however i would like to have maybe a boost and some other effects.

So is overloading imput something i should worry about unless i do some realy silly things?
Both the amp and cabs have some fuses i will replace with some weaker ones (thanks for the tip) but will this make it foolproof?
Anything special to take into concideration with old solid state amps?

I'm asking cause i don't wanna know from experience what not to do with an amp.

[Mark Hammer]

Boost is one thing.  Distortion at the transformer and speaker level quite another.  Unless you are certain the speakers are rated well above what the amp could ever possibly hope to deliver, they will almost always be your weakest link as far as abuse-related malfunctions go (obviously you can always bugger up a pot or switch, but that was not the nature of your question).

For bass, try to keep a few things in mind:

• A little bit of limiting goes a long way.  Note that I say limiting and not compression.  Limiting prevents sudden peaks from exceeding some preset value, while leaving everything below that ceiling unaffected and at its original level.  Compression attempts to maintain a constant level by bpopsting weaker portions of the signal.  At low volumes, compression is a wonderful thing, but at higher volumes it is everything an amplifier and speaker were designed to avoid.
• Speaker voice coils are generally suspended in the gap without touching anything.  At higher amplitudes, their movement is not purely piston-like and there will often be some friction as the coil touches the sides of the magnet structure.  A little bit of sluggish rubbing is tolerable and does not result in significant heat build-up.  Lots and lots of fast rubbing (and you should interpret this to mean tons of treble and harmonics from, oh I dunno, distortion pedals) at high amplitudes results in heat build-up which the speaker coil can not dump as fast as it occurs.  At higher heat the voice coil is simply a fuse, waiting to burn.  So, if you are going to have a distorted sound, either keep the volume restrained, or if it needs to be louder make a point of taming the treble.

[Ben N]

I had the input stage of a small SS practice amp go smokey while I was feeding it a boosted fuzz signal. But I doubt it died from overloading, because the opamp input stage was running on +/-15v--it probably didn't even overload.

[Albot]

Cool, thanks alot for the quick and ediucating replies guys  .
Seems to be a subject that atracts quite alot of myths.

I got quite supprised to find that my cabs had fuses acctualy, as i understaind it they will only blow if i pass enough current through them and are not  helping against the distortion demage problem .

The fuses in the amp will almost always save the amp if i would do something silly or stupid (right?) 

[jonathan perez]

Can i destroy an amp with a FX pedal?

depends on the size, weight, and force by which you will be throwing at the amplifier...or shooting....

[notchboy]

There's a story in "Analog Man's Guide to Vintage Effects" where a guy who helped design the Moog Stage Phaser mentions making a custom rack version of it for Keith Emerson, and trying it out with a live PA.  They had it operating in inverse mode (peaks instead of notches), with the sweep frequency under CV control.  When the lowest peak swept down into subsonic frequencies, it blew up a 400 watt amp.

Likewise, I can imagine that a bass through an auto-wah pedal with a high resonance setting and low cutoff might be capable of blowing an amp.  Think "Bill Laswell through a DOD FX-25" taken a little too far...

[Mark Hammer]

Cool, thanks alot for the quick and ediucating replies guys  .
Seems to be a subject that atracts quite alot of myths.

I got quite supprised to find that my cabs had fuses acctualy, as i understaind it they will only blow if i pass enough current through them and are not  helping against the distortion demage problem .

The fuses in the amp will almost always save the amp if i would do something silly or stupid (right?) 

I'm not sure the subject attracts myths as much as it generates them, since not as many people spend the time to learn about  how speakers work when they need to devote their time towards mastering software or complex controls.  As a result, stuff that makes you smack your forehead and go "Well, of COURSE!" after you grasp it, tends to bypass a great many users.

That's good that the cabs have fuses.  I hope that is a sign that other precautions have been taken as well, rather than a sign they threw in a fuse because they knew they were taking too many risks elsewhere!  I'm leaning towards the former rather than the latter, so you can exhale.

Will the fuses "save" the the amp?  If they are rated appropriately, and are fast blow, probably.  I can't imagine, however, that I am the first and last guy in history to blow a 2A fuse, find he doesn't have a spare in the parts bin, replace it with a 5A slow-blow under the assumption that he won't be cranking the amp past the critical point, and then forgets that he put a 5A slow-blow where a 2A fast-blow was supposed to be.  So, make sure the fuses are rated appropriately....for real....not just on the chassis label.

And, I will still put in a vote for a touch of limiting so that you never have to rely on the fuses alone.

[Barcode80]

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.