Pro Audio Design Forum

The low gain offset trim corrects only the output diff amp offset. Though you might be able to offset a single OP07, adjustment would be problematic since the servo would have to have its loop closed. The adjustment would require a lot of trial and error. I tried this and didn't like it. As shown, t...

Du.uh! I see the problem. The 22k attenuates the correction signal which has to be much bigger to have an effect so much bigger common mode. :? Correct. Most of the correction that you want to be differential becomes common mode due to the 22K in the middle. By driving both ends of the "T"...

I wanted to bump this thread since we're discussing THAT1510/1512 mic preamp servos once again. http://www.proaudiodesignforum.com/forum/php/viewtopic.php?f=6&t=256 To make along story short, if you want to use the servo shown in the link above with T-bias, you have to provide a differential ser...

Interesting to revisit this old thread... I've got at least one new question... Do they still make chopper stabilized opamps? IIRC they were slow as dirt, but very low offset voltage. Probably too noisy for a mic preamp. JR I think they do. However, the OP07 is probably good enough when the servo i...

I tried that first. Unfortunately, there's too much temperature drift. Dielectric isolation makes great transistors but the insulating "tubs" they sit in insulate thermally as well as electrically. Thus the Vos, tends to have more drift than a monolithic matched pair would typically have. ...

Roger - I think the buffered class-A might have some merit in non-transformer coupled applications where long cable lengths and lots of capacitance are anticipated. I agree though that it's hard to improve on the 1646 connected directly to a transformer. To get the output impedance really low for th...

There's alot to be said for galvanic isolation.

My Toro has a Briggs and Stratton. It's just a push mower with the self-paced self-propelled feature. We have about 1/3rd of an acre where we live now and it's not a difficult mow. At the new place, which is about 1-1/4 acres, most of it is wooded. The mowable yard is about the same. I don't think I...

I wonder if the ethanol in gas is trashing stuff Yes, it eats up rubber in chainsaws. My mowers don't get enough of a rest for it to happen but I've had stored gas in a chainsaw eat up rubber in less than a year. They say stabilizers help and I do use them now but on the chainsaws I just drain them...

David Birt (ex BBC) had the speaker & amp in a DC bridge to compensate for this on the fly. I've followed David's work on audio interfaces and did a fair amount of work adapting his line reciver to the 1570 mic preamp. Small world. http://www.proaudiodesignforum.com/forum/php/viewtopic.php?f=6&...