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

manniraj 19th February 2019 03:16 PM

Thanks Salas

Salas 19th February 2019 04:06 PM

Will they possibly be Indian made CMI or Shilchar R-Core tranformers?

transcendent 25th February 2019 08:57 PM

1 Attachment(s)
Few steps away from running the test finally !

Dual-mono ultra-bib measured fine @ +/- 17V - checked.
Aimed gain for DCG3 slightly above 100mA with R10 12R - checked.
DN2540 bias matched well ~100mA in 5% range
J3 tested - got ~4.3mA with 221R - checked.
Bc560 came pretty well matched, was easy to pick ones in 5% Hfe range - checked.

I'll be running DCG3 with 2x matched pairs of 2SK170.

Anything else I might have missed? :cool:

Salas 25th February 2019 09:06 PM

Nothing for now.

Salas 25th February 2019 09:09 PM

Sinking looks little for the UBiBs though. Better use the perforated plate for the sinking of their Mosfets. But they will need insulation. Both silpads and nylon grommets.

transcendent 25th February 2019 09:24 PM

Couldn't find proper plate to fit so I cut the sink in smaller pieces. Looks ugly but these pieces are not that small as they look. What dissipation should I expect? Should I at least give it a try and monitor temperature first?

Salas 25th February 2019 09:57 PM

Monitor temperature not to go over 90C on those wings when just for testing. Also watch not to allow accidental contact between any of them or to a grounded surface. Because they seem live to me as I think I see direct mounted Mosfets on them. But maybe not now that I look closer. Make sure the insulation is good for each one by using the DMM's continuity buzzer anyway.

transcendent 26th February 2019 04:17 AM

Mosfets are insulated properly with mica pads and sinks definatelly touch the ground plane :) I used platic grommets to avoid screw touching it as well. Some goop as well for better heat transfer.
Will double check with DMM in any case, though I got steady 17V on each board during the test..

Thanks the tips !

nashbap 26th February 2019 04:36 AM

Quote:

Originally Posted by transcendent (https://www.diyaudio.com/forums/analog-line-level/296406-salas-dcg3-preamp-line-headphone-post5710497.html#post5710497)
Few steps away from running the test finally !

Dual-mono ultra-bib measured fine @ +/- 17V - checked.
Aimed gain for DCG3 slightly above 100mA with R10 12R - checked.
DN2540 bias matched well ~100mA in 5% range
J3 tested - got ~4.3mA with 221R - checked.
Bc560 came pretty well matched, was easy to pick ones in 5% Hfe range - checked.

I'll be running DCG3 with 2x matched pairs of 2SK170.

Anything else I might have missed? :cool:


Wire AWG? You may wish to read the wire size discussion on the Ubib thread.
nash

transcendent 26th February 2019 04:58 AM

AC side I use thick 1.5mm, ~15 AWG wire. DC side 1mm or 18 AWG. Can't find the discussion on that thread - do you have the link? What AWG did you use for signal wires?


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