EAR 834 PCB question

[stenak]

I bought a pcb on E-bay couple of months ago. Found out that there are two capacitors on the pcb that I do not find og the 834 curcuit diagram.
What is the purpose for these two capacitors? I use insulated standoff spacers.

 

[Boydk]

They are used to isolate the gound holes on the PCB from chassis. Typically 100nF-470nF. Using isolated stand off´s, you might still want to connect these, and then have a couple of wires with "lugs" connected to chassis. Left side of capacitors presumably goes to "ground" on PCB,

 

[avtech]

Probably just a low value polypropylene (WIMA etc) for hum/noise suppression.

Assembled versions just have a wire link, see:

ZEROZONE Assembled 12AX7 E834 RIAA MM Tube phono stage amp board base on EAR834 L5 35-in Amplifier from Consumer Electronics on AliExpress - 11.11_Double 11_Singles' Day

Try with just a wire link to begin with, although with insulated standoffs it probably isn't even required.

 

[Steve Morley]

I'd ground it this way

This is what Broskie does (see link). Take all of the circuit grounds back to the power supply and connect to the chassis at one point through the Broskie circuit in the link. Connect all of the chassis panels (assuming they are metal) at this point too. Connect the ground from the AC inlet to this point as well.
I've found that this circuit can be a bit sensitive to RFI. Try the "Hash Filter", courtesy of Jeff Yourison. See attached. I've also taken the hot lead from the input jack, just as it exits the shield, and run it through a small ferrite core just before it attaches to the board. That killed the final bit of RFI.
The other tip with this circuit is to change V3 (output tube) to a 12AT7. The only mod is change its cathode resistor to about 33K ohm.

Steve

https://sep.yimg.com/ay/glass-ware/house-gnd-7.gif