Pro Audio Design Forum

Thanks for posting the schematic John.

The VCA scale is 6.1 mV/dB typically vs. the 3 mV/dB of the junction so the output buffer would need a gain of about 2.

I agree that you could do the same thing with a transistor.
On a one-off project or test fixture the VCA linearizer makes it easier.

In this case it is required over a large number of channels so a transistor logger seems almost as simple and definitely lower cost.

An article in Ugly Things magazine details a fascinating chapter in Ann Arbor music history: the story of the Fifth Dimension, a downtown teen club that hosted an amazing roster of musical performances from 1966-1968. They included local and national legends like Bob Seger, the Rationals, and the S...

Glad it worked! I also simulated a variation with 'differential drive' and it works as well; I buffered the output of IC1 using G=1 and G=-1 opamp sections; the non-inverting one feeding the Ec- ports of both VCA's and the inverting one feeding the Ec+ ports. Glad you tried that. I've done that befo...

Hi Igor. Its been awhile since we've heard from you. Welcome back. I've seen that circuit before and its very clever. I haven't done exactly the same thing with 2180/2181s but I have done log converters using them in the feedback loop which is the IC1 portion of the linearizer. I've also made them e...

Sorry about the hard drive failure.
While you were dealing with all that we had a dbf server crash and rolled back the forum a few days before we found a backup that worked.
After running it for a few days I upgraded the board.

Sounds like the project is moving along nicely.

Putting the RFI protection on the I/O board makes sense. The cap multiplier would serve to isolate crosstalk if that is a concern. The 48V rail output impedance should be low enough without phantom currents causing crosstalk. Since you only have a SPST switch the 100K arrangement makes sense for pha...

I defrosted the second deep freezer today.

Not sure why you need 2 inductors in gain leg, is the gain pot mounted at some distance in a noisy environment? In the past I have driven the gain pot cable shield to reduce capacitance effects. To provide gain rolloff at AM RF frequencies is why I've tried them. The THAT chip probably has clamp di...

Thank you for joining us and posting NOON. Your schematic looks good. I would do the following. 1) Add a differentially-connected capacitor across the input network for RFI. 200 pF-1nF? 2) The peak current at turn-on in R9 and the phantom switch is 480 mA or limited by the short-circuit current of t...