Valve Itch phono

Jump to Latest
Salas

Salas

diyAudio Chief Moderator
Joined 2002
Paid Member
webby said:
On further listening I have introduced hum, and a LR channel swap.
So lid off and time for photos!
I have checked the diagram Salas provided, and the circuit switched between channels. The output from the Itch is swapped?

The hum issue.
I grounded the input RCA shell via shielded cable to Itch input, at the copper circuit ground that goes to SSHV ground. I used the shield of the black input cable, Hot L to V1 Pin 2, Hot R to V1 Pin 7.

The pink wire is non shielded, only used for the short run from RCA to relay, could this be the cause?
Maybe a ground loop?

Thanks for any help.
Ian
Click to expand...

I went back to #2260 and read the diagram again for possible channel routing errors but it seems correct for keeping L or R inputs on the same sides of the relays. Its showing the relays from bottom view. Check the pins order with that in mind. If its something I don't see or a mix up happened in the wiring its very easy to follow the diagram with a DMM's continuity buzzer. Disconnect the TTs and buzz away the signal routes from input RCAs to the Itch channels when test switching. A swap between relays outputs and their Itch input channels connections fixes that anyway.

Better use coax for each input and output run, not single wires. Connect the shields to a common place on the little board. Maybe the swap has something to do with the hum also.
 
C

chat72

Member
Joined 2012
PCB from my spare time. :D
Any suggestion? Should I use a ground plane on the top side of PCB?

salas_zpseocd2lzt.png
 
Salas

Salas

diyAudio Chief Moderator
Joined 2002
Paid Member
chat72 said:
PCB from my spare time. :D
Any suggestion? Should I use a ground plane on the top side of PCB?

salas_zpseocd2lzt.png
Click to expand...

Solid ground plane is very good when used as the only ground. Because the ground return paths try follow the send power and send signal traces on the other side as the frequency gets higher, there should be a proper visualization of those paths so they won't mix. I.e. if not a complete study better not do it.
 
Salas

Salas

diyAudio Chief Moderator
Joined 2002
Paid Member
Not very productive just to check two good E283s. I am not sure they will be as quiet for microphonic noises either. On the other hand its just a rewiring if you are too curious about that Siemens pair you got. There is just little difference to 6N2PEV like the pin count for sides is swapped or something like that? Maybe no rewiring? Check closely.
 
You must log in or register to reply here.
Top Bottom