How does the Turbo board do it? Keith?

I must be dense today, I have been looking at the Turbo board installation PDF, trying to understand how it integrates into the Gyraf PCB. I do not understand how it provides separate control of the 2 audio VCA's. If the CV input of both the GSSL audio VCA's share a single CV input via 2 x 120 Ohm resistors into the two NE5534's, I cannot see how the turbo board takes over one of the VCA's. Can anyone explain to me where the CV's of the 2 main audio VCA's are separated in the Turbo install process to provide independent operation of the two main VCA's by the two sidechain VCA's? From looking at Jakob's schematic and the Turbo installation manual, it looks like the 2 sidechain VCA'a are in series, not parallel? What am I missing?

S/C signal goes in where the resistor lifts.

S/C signals sum (after parallel/identical paths) at point 'C'... where they reunite and go on to have happy children.

Joy ensues.

That's about it really... It really does sound great, though!

there is no seperate control of the signal path VCA's, just the sidechain vcas. The signal path VCAs MUST at all times and under all circumstances have the same control voltage, otherwise the L/R signal path gain is "tilted".

The Gyraf cannot tilt, nor can the SSL, nor can the turbo; which is basically a recreation of the SSL. The switchable turbo allows for BOTH options, with attendant deep joy.

Keith

Thanks Keith, I get it now. I could see that the Turbo board separates the two channel's sidechains, I hadn't realized that the two audio VCA's needed to stay tied together. The turbo does sound great, and having both options is even better. The reason that I was looking into it so deeply is that I have a case here with the sidechain option on the front panel, but only 1 sidechain board, so I was busy working out a switching system to leave the single SC board in circuit in GSSL mode, and to leave it out altogether in Turbo mode. I think that I will use the relay on the SSC board to do this rather than as a hardwire bypass.

Thanks for straightening me out Keith :

Hi,

S/C signals sum (after parallel/identical paths) at point 'C'... where they reunite and go on to have happy children.

Click to expand...

So it's not the "highest S/C signal" that's sent to the main VCAs but the sumof both, right ? Is there a way to implement a circuit that "chooses" the "highest S/C signal" ?
Best regards.
Eric
PS : sorry for diging out that old thread...