Can you overload/damage an amp with too much distortion?

[garrettendi]

So me and the bassist were mucking about in the studio last night.

We plugged my guitar through a fuzz (a clone of the Dallas-Arbiter Fuzz Face) which was maxed out on volume and fuzz, into an overdrive set to about 12 o'clock (a clone of the Fulltone OCD), and then into a Line 6 Pocket Pod with a touch of gain (just to get a good clean tone without the pedals on... Probably about 2/10 level).

We were listening on our headphones from the Pod and it sounded FANTASTIC.

But we were wondering... If we plugged both of the fuzz/od pedals into my Lead 12 micro stack (15 watts, solid state, 2x 10" speaker, made in 1986) would it damage the amp? Come to think of it, did we risk damaging my Pocket Pod or our headphones?

Both pedals are powered by a 9v battery btw, along with a tuner (battery) and a a Boss DD-20 delay (9v adapter).

[Sam Spoons]

Highly unlikely.

[garrettendi]

Is that true regardless of the volume coming out the pedals?

Surely there must be a point where the volume is so loud it'll blow something?

How far would I be able to take it? 3 distortion pedals on max? 4? 20? I'm reminded of a world record attempt someone did in Brighton for the most pedals in one chain...

[grab]

You're exceptionally unlikely to damage the guitar amp. Clipping/distortion is an issue for tweeters in a PA, but most guitar amps won't do anything above maybe 4-5kHz. You'll effectively get a higher impedance from the speaker as the frequency goes up, and that higher impedance will stop the amp having to deliver as much power, so it all stays OK.

The Pocket Pod will be OK too. It doesn't care whether the signal is a clean sine-wave or a full-on square wave. It does care about levels, but its inputs are designed to cope with anything you'd get out of a standard FX pedal. Unless you do something truly stupid like putting an amp's speaker-out into it, you'll be fine.

You could be at risk of losing your headphones though. Decent earmuff-type headphones (especially those aimed at audio professionals) should be able to withstand the kind of spot frequencies and distortion that comes from a guitar. Your standard little ear-bud ones definitely won't though, and nor would most "consumer" headphones.

[garrettendi]

Is that because of the size of the speakers inside the earbuds, or is to do with the internals?

[resistorman]

Is that because of the size of the speakers inside the earbuds, or is to do with the internals?

In general, square waves look like DC to coils...

[Wonks]

The second pedal can't amplify the output of the first pedal beyond it's voltage rail limit, so it can't actually produce any more signal voltage level than the second pedal on its own. The first pedal might increase the overall energy level by adding more distortion, but it's not going to increase the voltage. And it's either much too great a voltage or trying to force a sizeable current through the input that will do any damage in input circuits. Pedals might amplify signal voltages but they do it at very low currents - they are driving into a typical input resistance of 500k ohms to 1meg ohms and the pre-amp is just amplifying voltage levels, so doesn't need to see a lot of current at all.

But stick the unattenuated output from a power amp into the pre-amp and it will cause damage, possibly a fire. Don't ever do that!

[garrettendi]

So the general consensus is, a couple/few distortion pedals on max won't damage the speaker, but don't do anything stupid like plug a power amp into a pre-amp. So basically, don't plug the speaker output of my Lead 12 into the Pocket Pod!!!

Just out of curiosity, what about the situation where a pedal has a simulated amp setting? My Biyang Metal End King distortion has such a setting, but is still powered by a single 9v battery. The way I interpret your statement Wonks, is that even in such a setting, the pedal does not qualify as a power amp so could feed into an pedal train/amplifier just fine.

EDIT: Also the Pocket Pod is designed to feed into an amplifier of course, but also has a Direct Mode designed to feed into a mixing desk/recorder. Again, I assume this would not qualify as a power amp.

Forgive the stupid questions, but even after playing guitar for over a decade, the technical stuff is still difficult for me.

[Wonks]

No, it's nothing like a power amp. It's just applying some gain stages, EQ and low-pass filtering to simulate the sound of a miked-up amp so it can be played through a full range speaker without sounding very harsh and fizzy. If you switch any speaker emulation off, then you normally get just the amp emulation, but then it really needs to be put through a clean amp with a very flat response to sound anything like the amp it's supposed to be emulating (if a specific model). Amp + speaker emulations are really designed for recording or going straight into a full range PA.

But anything form an FX pedal is all done at guitar signal level voltages and power. You are only talking of one or two milliwatts of signal power here, as opposed to the obvious 12W of power available from the Lead 12. That's around 10 000 times more power from the amp!

[garrettendi]

I think I understand it now. If a pedal was rated at something like 10 W, sure it'd be an issue, but it's working at such low power same as the guitar signal.

Obviously the Pocket Pod could be regarded as a somewhat fancy effects pedal in this regard.

Thanks for all the help, I think I know now how safe it is to put in multiple distortion pedals into an amp, or use the Pocket Pod with headphones.

I'll keep in mind the earlier post about earbuds though.

[garrettendi]

One last question: How far do I take the whole "square wave" warning with headphones? Surely two distortion pedals wouldn't be even approaching enough a square wave to represent a DC signal?

[ef37a]

One last question: How far do I take the whole "square wave" warning with headphones? Surely two distortion pedals wouldn't be even approaching enough a square wave to represent a DC signal?

Yes, they can. Any device if driven hard enough will clip* and in the limit will "flat top" to the supply rail(s) voltage. A square wave "fills" all the waveform space through a whole cycle and that is equivalent to DC (if you have a wet weekend to kill look up "rms, "peak" and "average" AC values). This will do not harm to the device because the design should take this possibility into consideration.

The situation is however much more complicated with power amplifiers and loudspeakers. A high quality and expensive "studio" power amp should not be damaged by any level of drive nor any value of load, the exception to the latter being you should never connect very low resistance transformers to solid state amps and even "hi fi" valve amps can be damaged by an open circuit load.

When we come to the less than ideal world of guitar amplifiers the situation is very tricky. A well designed valve output stage guitar amp SHOULD cope with any degree of drive (assuming the correct load) This can be as distorted an input waveform as you like including square waves and noise, pink or white. The input can also be clean but drive the amplifier into distortion and again, a GOOD amp will stand that abuse indefinitely. It is after all why they are there! ...But! Not ALL amps ARE that well designed and a few (admittedly old designs in most cases) will be damaged by serious abuse. Often this is the result of a valve failing from an arc over and then "collateral" damage is caused to surrounding circuitry. This is poor design and inadequate (sometimes no!) fusing.

Solid state guitar amp stages should be treated with a bit more care. Once again, a good one SHOULD stand abuse but the problem is transistor OP stages tend to suffer "chain reaction" failures and many transistors and resistors are cooked to buggery, often making repair uneconomic. Just DRIVING a sstate amp with a distorted signal should do no harm but driving the OP stage into distortion is not a good idea and in any case rarely sound good! Never load a sstate amp LOWER than the book says, usually 4 Ohms min' but 8 Ohms for some older designs. Always ensure heatsinks are clear and well ventilated.

Loudspeakers are a complex case. Tweeter burn out was touched on but those are rarely found in git'cabs. The main thing to remember is that the speaker should have a rating AT LEAST 50% above the maximum amplifier power but since that latter figure is very hard to determine with valves, 100% over rating is a safer bet, especially for amps of 50W nominal and up. The common idea that speakers only sound good when driven to within an gnat's undercarriage of their rating is generally regarded as bllx in "the trade". N.B. Celestion rate their speaker's power on the conservative side, other makers are not so cautious!

*The old TL072 series of op amps can "latch up" if driven hard. This does not sound good and can damage following devices such as the rather feeble coils in a reverb tank, especially if the mnfctr is daft enough to DC couple it to the chip...Many are!

Dave.

[garrettendi]

Wow, that's a lot to take in. So do you recommend not using two distortion pedals into each other then?

[ef37a]

Wow, that's a lot to take in. So do you recommend not using two distortion pedals into each other then?

Well sorry! It is not a black and white subject and we have to live with less than stellar designs and crap valve quality!

I can confidently say that you can daisy chain as many of the pedals "I " was associated with and drive them as hard as you like.
I would also say this is true of any other pedal maker's products that I am aware of.

See, it is the POWER that does the damage. Lots of volts and lots of amps (current that is) A pedal might put out close to 8 volts peak to peak but there is next to no current capability and therefore no damage potential (some of "our" pedals can deliver over 25 volts pk-pk but again, next to no power there) .

Dave.

[garrettendi]

Thanks for giving me the bottom line!

I appreciate it's a very diverse topic, as you say, there are so many different designs of amps and pedals, it's impossible to pin it down to a "all of the amps do this and that".

I'll continue using two distortion pedals as it sounds like you say it's fine bottom line. It also sounds like your case with the earbuds is kind of a "worst case" scenario, so I won't worry about those. I actually use a device that transmits to my cochlear implant wirelessly, so there are no coils or anything to worry about, just bluetooth style radio waves.

[Wonks]

I often use two drive pedals in series and will often than add a clean boost pedal after that if I need a bit more volume when playing live.