Pars Posted January 15, 2012 Report Share Posted January 15, 2012 I'm modding an Adcom CD player for a member here, installing a pair of Colin's I/V boards (player is balanced), and am debating on how and where to connect ground on these to the main board and power. These boards have on-board shunt regulators, so I am tapping power from the main filter caps right after the rectifiers for the 2 +/-15V power supplies for the analog section on the main board. AFAIK, it is usually not a good idea to connect more than 1 ground per board. The options I see are: Ground the boards through the power connectorGround the input of the boardsGround the output of the boards Currently, I am leaning towards #1, thinking that noise from the shunt regs, etc. should feed back to the ground plane near the PSU instead of being dumped into the ground plane near the DACs. Ground plane seems to be common between the sections. The one that Colin did (same player) used #2. The stock analog stage is completely depopulated, other than the muting relays. From the schematics, it does not appear that anything else uses the +/-15V supplies. Thanks for any thoughts. Quote Link to comment Share on other sites More sharing options...
luvdunhill Posted January 15, 2012 Report Share Posted January 15, 2012 #1 is my vote Quote Link to comment Share on other sites More sharing options...
dsavitsk Posted January 15, 2012 Report Share Posted January 15, 2012 1 as well, but it surely doesn't matter here. Since it is balanced, any induced ground noise will be cancelled. And, the preamp this is feeding has input transformers, and the circuit is truly differential and has no ground reference. What matters more is keeping the offset between the + and - pins to absolutely 0. Even a mV will interfere with the amorphous cores. Quote Link to comment Share on other sites More sharing options...
Pars Posted January 15, 2012 Author Report Share Posted January 15, 2012 The player has both single ended and balanced outputs, so both need to work. Output jacks will remain wired to the main board. So with his preamp (I presume you know who this is for), the two halves of the I/V stage boards (+ and - signals per) need to be within a mV of each other? Hmmm, didn't know what I was signing up for here May not be a problem as they seem rather close just checking individual offsets to ground, but that is on the bench and just each individual board. Quote Link to comment Share on other sites More sharing options...
dsavitsk Posted January 15, 2012 Report Share Posted January 15, 2012 So with his preamp (I presume you know who this is for), Indeed. the two halves of the I/V stage boards (+ and - signals per) need to be within a mV of each other? As close as you can. Each board has a servo that should keep the output very close to ground. In a pinch, the servo opamps can have their offset trimmed, so you can solder in a trimmer across two of the pins (I think Colin left them unused) to zero this out. It probably won't be necessary. But, the transformers really do not like any offset. Quote Link to comment Share on other sites More sharing options...
luvdunhill Posted April 30, 2012 Report Share Posted April 30, 2012 interesting article: http://www.diyaudio.com/forums/diyaudio-com-articles/163575-audio-component-grounding-interconnection.html Quote Link to comment Share on other sites More sharing options...
recstar24 Posted April 30, 2012 Report Share Posted April 30, 2012 So basically you are saying singlepower amps aren't safe - cool. Quote Link to comment Share on other sites More sharing options...
luvdunhill Posted May 1, 2012 Report Share Posted May 1, 2012 So basically you are saying singlepower amps aren't safe - cool. fair assumption, yes. Quote Link to comment Share on other sites More sharing options...
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