Pro Audio Design Forum

+1 that is a classic.

IIRC there was also a National application/tutorial on heat sinks and thermal resistance, junction to case, junction to ambient, etc. That was good for covering the basics.

JR

It may be a GBW or loop gain issue, not slew rate per se. The bode plot of opamps is usually in terms of "voltage" gain so what we really need to see is a plot of input voltage to output current. If the output of that opamp has an input voltage term riding on top of it (since servo output ...

I would be surprised (if I was right :lol: ) this way... I suspect that servo path will be dominated by the 100nF integrator cap across the opamp. The 1/4dB may be a measurement artifact, or something too subtle for me to easily see... There might be some odd input capacitance interaction with an el...

This is arguably over design on my part (or not) to use servos with real poles but IMO that adequately finesses this issue and is cheaper that doubling up opamps.

If you think about it, that two opamp approach is like adding a servo to a servo.

JR

PS: Are there two R1s in that schematic?

Apple had a long running conflict with the Beatle's record label (Apple records) over the name usage, and IIRC Apple always swore that they had no interest in the music business... :oops: Apple eventually made peace with the record label from their later, significantly stronger, relative position, a...

The polarity inversion inside the feedback loop, means the NF needs to be returned to what was the + input for it to be negative feedback overall, and drive the two opamp inputs to follow each other. They have added + /- signs just to the left of the input Rs signifying the polarity at that point an...

I need to sketch up the circuit in the Sony patent. It's an interesting single op-amp approach with many of the limitations of single op amp varible gain inputs but it does seem to work reasonably well. It seems to have a nicer taper in its' favor. If you are talking about that sony circuit posted ...

The Eico was a stereo receiver IIRC , i remember 35W, but that was in late 60s so my memory was so-so.. You know what they say about Boston in the 60's. If you remember it you weren't there. :lol: The Lafayette SW radio kit was branded lafayette and sold by Lafayette , they were a major electronics ...

I recall them messing with educational programs and IIRC they bought or were somehow involved with a PC brand too on their way out of business... The economics of kit building for the mainstream consumer was terminally flawed. I sold lots of kits to college students who needed to build something for...

Thanks John. In your gain stage the only interaction i could imagine is if a DC blocking cap was used in series between the input stage and the gain stage (like to prevent clicks from the polarity switch). Fortunately the DC gain of stage two remains unity regardless of the pot setting so the click...