Diamante Compressor

I'll add a Diamond Compressor layout at some point, but this one was a must for me and I'm surprised it's taken me this long to do the layout.  This is Fred Brigg's stripped down version of the Diamond, which is essentially the same but without the Tilt EQ section of the circuit or the (admittedly funky) colour changing LED depth indication part.  As someone who tends to leave EQ around the middle default setting anyway this made perfect sense for me, and as the omitted sections added a lot to the circuit size, and now with only two pots, it means it will be an easy one for a 1590B.  My rack tray thanks you Fred :o)

The other thing Fred changed was the input buffer which is now opamp instead of BJT, but the main compression part and envelope detector is as per the original and so should be comparable.

The circuit uses a VTL5C3 Vactrol which is 10M off resistance.  I'm not sure whether you will get a low enough on resistance with a 10M LDR and LED combo, but by all means give it a shot and let us know how you get on.  If you do want to try an LED/LDR instead, just use the points shown where the Vactrol is connecting.  Right hand side is LED with cathode at the lower connection, left side LDR.

Read more about it on Fred's page here.  I can't find a video of the Diamante, so here's the Diamond to give you an idea what to expect

[15th July 2014 addition]

And this is a modified version to include the tilt eq.  I have kept it true to Fred's Diamante philosophy and swapped the BJT buffer used in the original for an opamp buffer, using the second channel of the opamp added for the eq.  Because the tilt eq is inverting I made the buffer inverting too so that the output will be back in phase.  This won't matter to most people but thought that if maybe a bass player wanted to use this with a blend circuit, then having the output out of phase could cause cancellation issues.  I noticed before that the original tilt scheme from the 70s preamp also has an inverting buffer, so this is also in keeping with that.

So this one is basically an all opamp Diamond Compressor, just omitting the funky LED

[updated 11th Nov 2014]