Pro Audio Design Forum

rp3703 wrote:
Obviously that part of the schematic is incorrect.

Well then, check the connections to C5... (and which value to use)
Also, if you want a real matched pair for Q1-2, look at the SSM2212 (SMT-Only though...)
MAT12 (thru-hole) prob too expensive. MAT02 still available as NOS

JP

JR Wrote:
yup base of q8 probably goes to collector q5

Yes, and base of Q7 goes to collector of Q9 (not emitter)

JP

We used them at Crest and APB for the EQ circuits in our Consoles. We used the Panasonic ECHU Series, but Cornell Dubilier also offers similar parts with their FCP Series. Bought them mostly from DigiKey, used the 5% & 2% parts, depending on what was available. Values we used ranged from 1N0 to ...

JR has been advising you about "grounding", but before you etch any boards, your schemo for the 2520 is incorrect.
The bases of the output transistors (Q7-8) are not connected properly.

JP

[quote="JR." I am partial to limiters that are out of the path unless limiting, and I even experimented with using VCA's that way to make their already good nominal performance even better (downside is subtractive VCAs are cut only, but below limiting as clean as a simple op amp.) JR[/quot...

Thought I'd chime in here, since (like JR) I've used Optocouplers in a number of products over the (many) years. Addressing the RoHS situation first. These parts contain cadmium (in the photocell); cadmium is one of the hazardous materials listed for RoHS. AFAIK, Silonex (now Advanced Photonix) rece...