Where is your chassis ground? I fail to see it. It needs to be one point and 1 point only. It should be on a piece of a large metal panel that preferably holds your main SP14 pcb, and your toroids. Can you show a close up photo of your chassis ground (i.e. star in your drawing?). Why the 2 wires from the top plate to the star? There is only ONE purple ground wire in the original SP14 diagram, not 2. And there is a wire from IEC mounting bolt to the star?
A failing rectifier in this circuit would cause hum in both channels not one. Both channels get their B+ from it. We’ve already gone through the HV B+ supply and filament supply I think.
Best,
Anand.
A failing rectifier in this circuit would cause hum in both channels not one. Both channels get their B+ from it. We’ve already gone through the HV B+ supply and filament supply I think.
Best,
Anand.
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Ok. So, if I have this right, you are saying that the star ground - which is connected to the earth ground - should only be connected to the chassis at one point? And seeing as how I have three separate pieces of metal in the chassis, that all three pieces of metal should be connected together and then only connect to star from one of the three plates?
Looking at the first picture, post 3, I see a wooden case, no metal sheet below the pcb.
Maybe you changed this later. Although sometimes preamps can be made without metal
shielding, as reported here also, this is not the usual case. Try to put a grounded magnetic
or even aluminium plate below the pcb as easy first step. Wrote this before seeing your
post 165.
Maybe you changed this later. Although sometimes preamps can be made without metal
shielding, as reported here also, this is not the usual case. Try to put a grounded magnetic
or even aluminium plate below the pcb as easy first step. Wrote this before seeing your
post 165.
Let’s start with only working on this diagram below and getting it right:
Notice there is only ONE purple wire from the PCB. And only one direct connection from the IEC ground terminal to a point on the chassis metal.
Does your green metal plate have the chassis ground connection or is it somewhere else?
Best,
Anand.
Notice there is only ONE purple wire from the PCB. And only one direct connection from the IEC ground terminal to a point on the chassis metal.
Does your green metal plate have the chassis ground connection or is it somewhere else?
Best,
Anand.
What does this mean ? I suggested moving and rotating the transformers for a try.I’ve already rote fed the transformers so I could move the primary cables away from the PCB
The general assumption that toroidals have no stray field is not true. The field is strong.
You might also try this, though it'd be a pain: Isolate one pair of input jacks, detach them from the chained ground, and run twisted pairs from left and right to the master pot. Then twisted pairs from the pot to the input of the board. Finally twisted pairs from the boardoutput to a pair of isolated output jacks. In my p-to-p build I use all twisted pairs for the signal wiring and I have no hum.
Thanks
Yes, I meant rotated
I don’t mind trying that at all.
(Making sure auto correct doesn’t change what I’m typing into something that will be difficult to extrapolate from - changed mind to mint - I changed it back)
Not sure I have any decent cables here for that? (Most of the wire I have on hand is heavier gauge for internal speaker runs) I can easily try running a shielded cable from a single set of RCA’s to the volume pot?
Yes, I meant rotated
I don’t mind trying that at all.
(Making sure auto correct doesn’t change what I’m typing into something that will be difficult to extrapolate from - changed mind to mint - I changed it back)
Not sure I have any decent cables here for that? (Most of the wire I have on hand is heavier gauge for internal speaker runs) I can easily try running a shielded cable from a single set of RCA’s to the volume pot?