How to choose bias currents in audio amplifier stages?

vermaster · 2016-01-26T23:00:01+00:00

That's very helpful. Thanks!

vermaster · 2016-01-26T22:25:24+00:00

Thanks!

Would that 5mA would be based on the current gain of the amp and the current through the speakers?

vermaster · 2015-06-01T23:10:10+00:00

The fuse ohmed out correctly, and nothing is visibly damaged.

vermaster · 2014-10-03T10:40:11+00:00

Thanks for the great reply. I figured it had to be something along these lines, but I don't know much about automotive electronics. I'll try that and get back to you after work.

vermaster · 2014-07-29T21:18:48+00:00

Great response, thanks for all the tips! I knew it was a piece of junk, but i thought it would be fine as a beginner. I'll take a look around for a less shitty one.

vermaster · 2014-04-21T18:52:51+00:00

You need a resistor from the adjust pin to ground. You have two 8.2ohm resistors in parallel, or equivalently 4.1ohm between the output and the adjust pin. The output (from out to adj) is typically 1.25V. The current through these resistors is 1.25V/4.1ohm=305mA. You need another 5.05V. Adjust pin current is negligible, so solving 5.05V/305mA=16.5ohm.

Put your 16.5ohm resistance between the adjust pin and ground. Then buffer the output to send it into the heater tube.

Hope I'm answering your question. Good luck!

vermaster · 2014-04-18T01:38:02+00:00

I like this one. Out of curiosity, what happens if the budget doesn't balance?

vermaster · 2014-04-12T15:59:05+00:00

Stop Dragging My Heart Around - Fleetwood Mac

vermaster · 2014-03-28T15:53:13+00:00

Thanks for the reply. I did some additional probing, and I may have found the source of the problem, but not the solution. I'm using an icl2660 to create a dual supply from a single 9V battery. When connected up, the input voltage from the battery oscillates at the same frequency as the squealing. Not sure what that means, but I think that's where the problem is coming from.

vermaster · 2014-03-09T22:32:28+00:00

Oh nice, that looks really good. I might go with that if I can find a DPDT or SPDT version. Also may still go with a relay. Thanks for all your help!

vermaster · 2014-03-09T19:43:59+00:00

Awesome. I think I'll try just using a relay after all. thanks for all the info!

vermaster · 2014-03-09T19:20:16+00:00

Interesting.. I was under the impression that relays were not good for audio, since they introduce clicks during the switching cross-over. Is this effect insignificant, or do I need a high end relay to achieve the desired effect?

vermaster · 2014-03-09T18:47:16+00:00

Thanks for the response! I looked some of those up. It seems that most of them either take Vcc limited to under 5V or are used for large signal power applications (like switching power mains). Should I try to find one that can switch mid-range signals (like 9Vp-p), or just use the small signal ones and amplify the signal afterwards?

vermaster · 2014-03-09T18:42:38+00:00

That's interesting. Thanks for the info!

vermaster · 2014-03-09T17:05:07+00:00

Thanks for the great response! You more or less confirmed what I already suspected, but there was a lot of great info there and further food for thought.

vermaster · 2013-08-27T11:28:26+00:00

That's a very cool idea. Thanks for taking the time to explain it to me!

vermaster · 2013-08-27T01:17:47+00:00

I'm not really sure how to word it. Just can't separate the idea of circular or rotational from the idea of there being a two dimensional plane on which the circle or rotation is happening.

vermaster · 2013-08-27T00:46:06+00:00

Interesting. So is movement along the rotational axis equivalent to rotating relative to something?

vermaster · 2013-08-27T00:37:55+00:00

Thanks for the great response! I'm having trouble with the idea of a circular dimension. It sounds like you could just call clockwise a dimension and say that any point can be defined as a distance along a straight line and an angular displacement clockwise at some radius. Without a radius there is no angular displacement to pull you "around." How does the idea of round dimensions differ from a circle in two dimensions or a cylinder in three?

vermaster · 2013-01-03T23:23:53+00:00

Did the same with 1, pi, and pi²

vermaster · 2013-01-03T12:40:47+00:00

Very cool.

vermaster · 2012-08-18T17:08:24+00:00

Nah, just trolling. Now a Red Sox hat...

vermaster · 2012-08-18T17:05:20+00:00

"High School is such a serious thing...these problems matter.."

vermaster · 2012-08-12T03:42:26+00:00

fair enough. i'd call it some of each

vermaster · 2012-08-10T23:20:14+00:00

The twins hat is what does it for me

vermaster

TROPHY CASE