How to true-bypass an old Ibanez SC-10 and a CP-10

[gigimarga]

Hello all,

I've just bought an Ibanez SC-10 chorus at a very low price and I immediately fell in love with him. The only problem seems to be that it sucks the tone too much for my taste, so I decided to rehouse it and to true-bypass it, too. After I've looked at its schematic (http://www.aronnelson.com/DIYFiles/up/ibanezsc10.pdf) I realized that I had no ideea how to true bypass it.
The method that they used seems strange to me (if I understood right...): they disconnect the wet signal in the bypass mode!

I have the same question for the compressor of that serie, Ibanez CP-10 (http://www.aronnelson.com/DIYFiles/up/ibanez_cp10_compressor.pdf).

Thank you very much for your help!

[gigimarga]

 

[R.G.]

The two pedals use different methods of disabling. The SC10 does disable the wet signal. To permanently enable it, put a shorting wire from drain to source of Q9.

For the CP10, short across C17 (disables Q10) and short across drain and source of Q9.

Then do the external bypass wiring.

[gigimarga]

Thank you very much R.G.!

Regarding SC10, isn't better to eliminate D6 from the gate of Q9, before shorting it?
And Q8 what is for? Doesn't affect the sound? It seems to me that this effect sucks the tone a lot...

Best regards!

[R.G.]

Regarding SC10, isn't better to eliminate D6 from the gate of Q9, before shorting it?

I think it makes no difference at all. The JFET drive signal that comes through that diode makes the JFET go between a few hundred ohms and open circuit. A shorting wire will not notice what the JFET is doing. The diode is driven from the footswitch by a 1M resistor, so it can't be affected much by the antics of the footswitch circuit.

And Q8 what is for? Doesn't affect the sound?

Q8 is probably some kind of a muting device to kill the hiss from the delay between notes. Think of it as a primitive noise gate. It should not affect treble much, which is what I think you're worried about.

It seems to me that this effect sucks the tone a lot...

If you mean that it loses treble, maybe. The dry signal is treble cut in the input section, IC1 and IC2. That's likely to avoid aliasing in the delay section on long delays. The way it's set up would cut dry treble too. I have not calculated the response of that section, so this is speculation.

In any case, if you're true bypassing the whole thing, the bypass sound will not suffer. If you're worried about losing treble during effect operation, that's going to be the nature of the beast. The other tricks they play with inverted outs and such probably rely on the IC1/IC2 input section for proper signal inversion, and changing the inner workings is a whole new step in complexity beyond just true bypassing.

[gigimarga]

Thank you very much again, R.G.!

Of course, you was right about the lost of the treble...but I don't want to modify too much it...and I think that I'm not enough skilled to do that

Best regards,
Radu