Hello,

The VTL5C1 used in the SLO channel swithching are used in series with the signal path in the SLO. When off, the resistace is a few 100 ohms, so from a multimeter point of weiw it is out of the circuit. However, did anyone try if/how it affects the sound of the amp? There should be some coloration, no? If so, it is a part of the SLO sound and that's it... Otherwise the switching would nowadays be by relays if optoswitching would affect the sound in a bad way.

Thank you for keeping this great forum! I'm sorry to post in English, I have only reading skills in German. 

Best regards
--
Anders   

Hello,

the optocoupler has 2 major states: on and off

On means, the resistance is very low.
The value depends on the type of optocoupler, in case of the used one in the Slo (VTL5C1) it is around 300 Ohms

Off means, the resistance is very high, typically around several Megohms.

I have built several SLO clones, with Vactrols, with Relais and with other optocouplers.

The soundeffect of the different types is in the area of 3% so very very low.

A different Power Transformer or different capacitor types will have more effect.

Conclusion:

Do not worry about the couplers, take care of a good wiring harness :-)

Hi!

Thank you for your reply. I see my mistake on the on/off state.

Anyway, the effect should be subtle, that is for sure. As an experiment one could short the signal over the vactrols with a switch and listen... But I think it makes sense what you say that any effect of the switching circutry is very low down on a list of things that can be optimised in a DIY build...

Cheers

Hab auch ne Frage dazu. Habe gerade ein Projekt mit VTL5C1. Habe im "OFF" 2,4V anstatt der geforderten 2,7 (oder 2,9). Gibt das Probleme oder muss ich noch ein wenig mit der Widerlingen spielen?