Shure m62v level-loc

I have been messing around with the level-loc circuit and trying to do research on possible mods, but it seems like every link to valid information is dead and everyone who has built clones for diy use or mass production have stopped their efforts.  I am mostly curious about adding a variable release control, but I'm sure there are other interesting things that can be done with this circuit.  I made a direct copy of the m62v schematic in eagle cad, which I would be happy to share with anyone interested.  My board layout is rather sloppy, but it works.  I really like what my clone does, but I feel like it could be a lot better without too much effort...  Does anyone have any info or incite?

Let's assume this is your schematic: http://www.freeinfosociety.com/electronics/schematics/audio/shurem62v.pdf

That being the case, a release control would simply be changing the resistor across the charging cap driven by Q6 and Q7.
The attack time is determined by the impedance into the cap (i.e. the two 39R resistors) and the decay/release time by the impedance across the discharge cap (the 1M across the cap).

So longer release time, increase the 1M, lower release time, decrease it.
Same goes for the 39R resistors driving the cap, you could simply change them to modify the attack time.

That's the basics.

maxkracht said:

I have been messing around with the level-loc circuit and trying to do research on possible mods, but it seems like every link to valid information is dead and everyone who has built clones for diy use or mass production have stopped their efforts.

Click to expand...

This one is quite alive and well!  http://groupdiy.com/index.php?topic=54964.0

> attack time is determined by the impedance into the cap (i.e. the two 39R resistors)

Also the reflected impedance driving Q6 Q7. I don't think you can make it faster. I also don't think it could ever need to be faster. Slower might be useful. Bring Q6 Q6 collectors together, to a ~~~1K resistor, then to point C and the R-C release network.

If *both* attack and release want to go the same way, best to change the 2u cap, smaller for faster.

Thank you all for the responses.  Oddly, I marked that 1M resistor wrong on my PCB and swapped it out for the "correct" value a couple hours before posting.  If I had been recording while testing I could have answered my own question.  Will desolder that part again and put a pot or rotary switch in its place.  I don't know how I missed that 500 series project...