The twilight zone

[anonymous02282011]

What does gain staging mean?

[Chris Fitzgerald]

Originally Posted by adbass

What does gain staging mean?

I'm no techie, but gain staging is a term used to describe a signal path that has multiple preamp sources; each preamp is called a "stage" of the overall gain structure. Since there is a limit to the amount of clean signal that a poweramp can amplify, it is easy to overdrive the input of the a poweramp and create all manner of sonic havoc by having two preamps in the same line that don't interact well. A real techie-type dude could (and likely will) give a much better explanation, but there's the caveman version.

[norbusser]

Originally Posted by fingers

Last night I had a wedding gig in a 100+ year old ballroom here in Chicago. Beautiful old room.

The strangest thing happened with my amp though. AI Clarus and EA cab. The speaker was pulsating even when I wasn't playing. I use a Fishman Platinum Pro and a Realist. I freaked. When I disconnected the Fishman the pulsating stopped. I have used this setup many times in other rooms with no pulsating. The stranger thing was that when I had the Fishman connected and I engaged the HPF on the AI the pulsating stopped.

What the heck was going on?

60hz electricity thing?

Ghosts of disgruntled wedding guests of days of yore?

Who ya gonna call? Ghostbusters.

[anonymous02282011]

Originally Posted by Chris Fitzgerald

I'm no techie, but gain staging is a term used to describe a signal path that has multiple preamp sources; each preamp is called a "stage" of the overall gain structure. Since there is a limit to the amount of clean signal that a poweramp can amplify, it is easy to overdrive the input of the a poweramp and create all manner of sonic havoc by having two preamps in the same line that don't interact well. A real techie-type dude could (and likely will) give a much better explanation, but there's the caveman version.

cool. thanks. So having two preamps, one external and the one built into the Clarus, is too much for the power amp. I'd be interested to hear more about this.

[robgrow]

The speaker cone moving slowly (pulsating) by itself when you aren't playing is caused by a low-frequency oscillation (at a very low frequency of just a few Hertz, too low to actually hear). The source could be many things but is most likely at the front of the gain structure (ie... it's probably the external preamp). The low-frequency instability (oscillation) is usually caused by a poor path to ground at very low frequencies in a gain stage. This oscillation is then amplified by the following stages.

[Ric Vice]

Originally Posted by robgrow

The speaker cone moving slowly (pulsating) by itself when you aren't playing is caused by a low-frequency oscillation (at a very low frequency of just a few Hertz, too low to actually hear). The source could be many things but is most likely at the front of the gain structure (ie... it's probably the preamp). The low-frequency instability (oscillation) is usually caused by a poor path to ground at very low frequencies in a gain stage. This oscillation is then amplified by the following stages.

+ Lots of us, myself included have this kind of signal chain where we Doubled the Bass. I used to use a Fishman Pre A II or a Bass Blender into the amp and I remember having trouble with just this thing. You could see the 8" woofer moving in and out. Ultimately I got rid of the boxes because they were a nuisance to lug around. It's probably a good thing that I'm such a gear whimp.

Ric

[Marc Piane]

So the question is...

Does this damage the speaker?

[robgrow]

Originally Posted by fingers

So the question is...

Does this damage the speaker?

No. But it does waste some power.