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-   -   Salas DCG3 preamp (line & headphone) (https://www.diyaudio.com/forums/analog-line-level/296406-salas-dcg3-preamp-line-headphone.html)

dewdrop 1st May 2020 01:41 PM

Hi Salas,
My setup is a dual mono TF with 4 UBiB PSU instead of the standard offering. I am getting a pretty audible hum. What is the best way to ground the setup? TIA

Salas 1st May 2020 03:44 PM

Is there any signal zero or PSU zero wire to your chassis? Is your chassis wired to the mains ground? Upload a bird's eye view photo of the build.

dewdrop 2nd May 2020 04:59 AM

1 Attachment(s)
I have ground (green yellow) for the DCG3 board which is connected to a CL60 (top left) before terminating at the PE point.

The transformers do not have any ground lines.

As for the UBiB, there isn't any ground apart from through the stand offs.


Attachment 839882

killie99 2nd May 2020 08:39 AM

Did you scrape away the paint on the chassis at the grounding point so that you have a good connection and is the body of the pot grounded?

dewdrop 2nd May 2020 08:54 AM

Oh yes, that has been done as I drilled and tapped the chassis for the grounding point.

Salas 2nd May 2020 02:47 PM

Try something. Disconnect the CL60 from the PE but keep the green/yellow wire connected on its other end. Do the input signal wiring conventionally through the volume pot. Attach the CL60's free end on the volume pot's mounting hardware somewhere conductive. Does something change for hum?

By the way, the UBiB mounting points are isolated islands from its PCB's ground plane. No continuity there.

nashbap 2nd May 2020 03:07 PM

Dewdrop how have you connected the four UBib G's to the DCG3 board?

Is this a new DCG3 board or an old one? I remember Salas mentioning that the new DCG3 board has a split G for each side while the old one had a common G.
nash

dewdrop 2nd May 2020 03:11 PM

Hey Nash,
I wasn't aware of that difference. What version marking?

Thanks for the tip.

Ed

Salas 2nd May 2020 03:12 PM

Current board should have V1.03 printed with tiny letters at the right bottom corner. I looked in the photo for that and it does not.

dewdrop 2nd May 2020 03:21 PM

Sorry, I didnt answer the other question.

The each ground zero of +/- UBiB pair is connected to the PWR GND of the DCG3 channel.

I connected the left channel HP GND to the pot GND and then the right channel HP GND to a CL60 (yellow green cable) and terminating at the chassis GND.


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