Testing New Designs?

BrownPanick · January 21, 2011, 02:05:26 PM

I had what is probably a stupid question, but still...

Is it possible to damage an amplifier while testing with an effect that's been breadboarded and hooked up? I'd hate to cause irreparable damage to my amp to test something I threw together to see how it sounded.

What is the best way to determine if the effect would damage an amplifier if it's possible?

Thanks!

PRR · January 22, 2011, 12:19:55 AM

> probably a stupid question

Questions aren't stupid. Nobody is born knowing this stuff. Everybody had to figure stuff out, usually with the help of others.

> Is it possible to damage an amplifier while testing with an effect

Anything is possible. Murphy's Law never sleeps.

However, the world is full of crazy guitarists. Sometimes drunk, angry, or careless too. Most stage-amps will take just-about ANYTHING and survive. Commercial amps which can be blown-up by absurd connections and inputs soon go bankrupt from warranty-returns.

If you know your circuit can generate supersonic garbage (notably digital systems), it would be wise to add a 5KHz-10KHz high-cut on the output. You probably want that anyway, otherwise the supersonics beat against the sonics which is non-musical. The other reason is that some transistor amp outputs can be blown by sustained supersonic signal. I'm sure that 99% of transistor stage amps have some filtering to make such trouble unlikely, but best to not deliver large inaudible crap in the first place.

Ronsonic · January 22, 2011, 01:50:42 AM

In general, your amp is safe.

Mostly it's you that makes sure of it. Be sure you don't have a bunch of DC coming off the pedal output, bring levels up carefully and stay alert when you first try something out.

BrownPanick · January 22, 2011, 11:17:01 AM

Thanks for the advice. I was just so worried about blowing out hundreds of dollars of good equipment just to test a design I laid out that may or may not even sound good.

Maybe I should also just invest in a beater amp; one that wouldn't matter to me if I aslopded it. Sounds like maybe yet another project... hmmm....

Ronsonic · January 23, 2011, 01:57:12 PM

It isn't a bad idea to have some amp-like thing on the bench for basic testing anyway. Doesn't even need to be a real guitar amp, a computer or other powered speaker will do fine. Won't tell you how your latest project sounds, but it'll let you know if it works.

runmikeyrun · January 23, 2011, 09:28:37 PM

Sometimes probing around or soldering while stuff is plugged in can send really loud hums to your amp, which could damage the speakers if the amp's turned up loud enough. Keep the amp turned down to a reasonable level! If you're really concerned, get a cheap limiter (like a behringer) and put that right before the amp.

cpm · January 24, 2011, 05:10:21 AM

Quote from: runmikeyrun on January 23, 2011, 09:28:37 PM
Sometimes probing around or soldering while stuff is plugged in can send really loud hums to your amp, which could damage the speakers if the amp's turned up loud enough. Keep the amp turned down to a reasonable level! If you're really concerned, get a cheap limiter (like a behringer) and put that right before the amp.

wow, you solder with the circuit powered, and connected to an amp, !!

ItZaLLgOOd · January 24, 2011, 09:28:29 AM

Make a simple Ruby or Little Gem amp and test with it. With about $5-10 worth of parts, it will save your stage amp from any unnecessary abuse.

cpm · January 24, 2011, 09:40:06 AM

better yet, get a cheap 2nd hand scope
you can visualize the sound and whats going on in the circuit. Provides a quick view of volume, shape, DC levels, clipping,
Also, is the best tool for biasing transistors and tuning LFO and clock circuits...

jefe · January 24, 2011, 11:08:16 AM

Quote from: ItZaLLgOOd on January 24, 2011, 09:28:29 AM
Make a simple Ruby or Little Gem amp and test with it. With about $5-10 worth of parts, it will save your stage amp from any unnecessary abuse.

+1 - I built a Ruby in an old bookshelf speaker, works great as a bench amp.

Ronsonic · January 24, 2011, 12:22:34 PM

Quote
wow, you solder with the circuit powered, and connected to an amp, !! Cheesy

Bro' I'll solder with the circuit powered, plugged into an amp with the guitar on my lap.

Of course it depends on what I'm doing, some things are noisier and more dangerous than others. Working with live circuits I only power with a battery, more current limited than a DC supply. And I am a bit selective in how I go about some of that stuff. But sometimes if you gotta know what value widget you need in circuit for best tone you gotta keep the time in your A/B tests short and a palate cleansing BBBBRBRBRRRBRRRRRTTTTTT between tests won't hurt.

familyortiz · January 24, 2011, 12:52:08 PM

Having things sitting out open while running or testing is one thing but to connect/disconnect, solder or anything like that, while powered is taking chances that you need not take.
Aside from getting electrocuted or causing a noticable failure, you may cause damage that won't show up til later.

Ronsonic · January 25, 2011, 11:57:19 AM

Maybe that deserves a "Don't try this at home - professional driver on closed roads - serving suggestion only, product color and taste may vary" sort of warning.

Or just a "this is for battery powered gadgets when you know just what you're doing and know you can put that soldering iron only where it belongs" sort of warning.

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Testing New Designs?