Pro Audio Design Forum

That looks like some of the old national app notes material. I recall using that in the early days with their LM381 and LM387 bipolar phono preamp chips. OK technology for the '70s and my first preamp design (I used two LM387 inside a DJ mixer kit in 1978). This was written before very low noise JFE...

Another benefit of fixing stuff yourself (when you can) is that you actually care about the outcome.

JR

I might call that 1.5 out of 3 on a bad day, 2 out of 3 if you're feeling great. : ) My local small engine guy has gone silent on a few problems mine has from time to time. He either has no idea, or does and has some reason not to mention it.....since I bought it from him several years ago. I'll pr...

A few new anecdotes.. one fail and two successes. #1 fail... my next door neighbor gave me his old weed whacker that he said worked perfectly when he parked it several years ago... Probably a 20 odd year old Stihl with an oddball unobtanoum carb. I got a rebuild kit and did all the obvious tricks bu...

mediatechnology wrote:I think the essence of analog op-amp based servos are that they make little capacitors act like big ones.

exactly... op amp gain is used to make small (linear) caps look like big linear caps...

JR

Servo is more complex than AC coupling for sure, but I would say maybe equally or less complex than a hybrid design that is DC stable without the need for a servo. yup Putting a monolithic matched pair front end on an op-amp (curse the thought of degrading the monolithic pair by marrying it with an...

Nobody uses servos because they like the complexity, but they are a lesser evil than not using one. Servos are pretty mature but there are often trade-offs (well discussed).

JR

mediatechnology wrote:Very cool. I remember that one.

What Popular Electronics issue?
I'm pretty sure I have it in storage.

June 1976

JR

I recently got a request to publish this old schematic because the PM suggested this circuit had "historical" significance (his words not mine). In fact this early flanger was used on Heart recording "Barracuda". One of the Fisher boys who played in the band back then bought my k...

The patent was US4922535 by Ray M. Dolby. https://docs.google.com/viewer?url=patentimages.storage.googleapis.com/pdfs/US4922535.pdf I wasn't sure if the OTA was inverting or not so it could be additive or subtractive. I think the review was HH. Thanks, that pat was 40 pages of mumbo jumbo to descri...