[quote author="PRR"]> it matters a LOT how much voltage you need. The Fairchild had to swing 8 grids 60V without a DC amplifier. The grid leakage set an upper limit on the release resistor value. The longish decay time sets the capacitor value. And the very short attack time and high control voltage requires a large peak drive power. Many folks would think the 660 is way too large. With modern parts we could do something like it much smaller, but still not a teeny job.
And if this is a limiter (sounds like it; but not certain), are you
sure you really want a hyper-fast attack time? Clipping less than 1 millSecond (1,000 uSec) is pretty darn inaudible. [/quote]
Well now. this slipped between the cushions didn't it?!! :grin:
Yep it certainly is a limiter I'm thinking of.
Basically I have a VCA comp and I want to graft a limiter onto it so that and big spikes get hacked off at the knees. I have no idea what it sounds like to have an attack time in the order of 10s of milliseconds so I am tempted to try and build it just to see what it's like, good or bad. I shouldn't think i'll ever hear a 660 so although it's a totally different beast I'm still intrigued.
check out
http://www.symetrixaudio.com/tech_support/schematics/501_1F05.pdf
and the limiter section that is on page 2 i think. someone beat me to it but the diode gate thing looks simple and I almost understand the i/p circuitry :?
[quote author="PRR"]> But, just for discussion, you want 10uSec in 1uFd, you can probably use a fast op-amp driving a power transistor and rectifier, with feedback to negate the rectifier drop. 1A peaks would be trivial for TL071 and 2N3055. [/quote]
Ok it's worth a punt. Will get on it next week.
[quote author="PRR"]>You better bypass the heck out of the supply rails, and be very sure where the capacitor return current is dumping to. That's one advantage of the 660's transformer coupled rectifier: cap current is local to the time filter and never gets back into the supply rails to click and thump. [/quote]
Ok heavy bypassing but if this thing isn't isolated like the gr amp on the 660 how to get around those pesky clicks and thumps?
Sorry just thinking out loud so don't worry about me to much :green:
Will get my head back own soon...
Chuf[/quote]