Noisy guitar switcher

[evilcat]

Hi there,

A friend of mine complain of his midi switcher for guitar effects. It seems to have a lot of hiss whatever loop is engaged. Where should I start to look at ? Recapp or what ?
I'm good at soldering, but I have very limited knowledge in electronic so any help is very welcomed !
Attached is the manual with the schematic.

Tanks,

Ben

 

[JohnRoberts]

From a quick look it appears all the audio is passing through relays which should introduce no electronic noise.

What is nature of the hiss? Is it perhaps digital noise leakage from a bad ground or something like that?

JR

 

[AMZ-FX]

I would suggest that you take some short patch cables and connect the pedals in series without the looper and see if the hiss is noticeable.  There should be no hiss from simple relays.

It is interesting that some of the transistor switches on the relays have 0.047uF caps from base to collector, while others don't.  (See Q7,Q8,Q9 and Q10, for example) Why not consistent?

regards, Jack

 

[evilcat]

Thanks for those suggestions. I'll look at more deeply to find where the problem come from (I don't have the unit yet so I have just reported what my friend told me).