Salas DCG3 preamp (line & headphone)

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alexkosha

alexkosha

Member
Joined 2013
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Salas

Salas

diyAudio Chief Moderator
Joined 2002
Paid Member
alexkosha said:
Thank you, Salas. That chunky R-Core is 120VA 4x18V made in India and I got it by luck from Selectronic. It was a replacement unit for the damaged during shipment one that I ordered about a year ago . Was not easy to figure out its wiring, but I use Mark Jonhson's trany polarity tester and the whole process was simplified. If someone interested, it is here: http://www.diyaudio.com/forums/powe...rmer-phasedots-no-scope-signal-generator.html
In did, my second trany (toroid) is intend to feed i-Select and I plan to go for the same GND elevation as I used for DCSTB channels with two of these units: House GND Kit
I did not use 1R resistors to separate 2 mono channels and just used two units. Not cheap, but better aesthetically looking than SS rectifier bock. It is question of taste…
I got Rev2 of Monolith headphones and Monoprice fixed the most of things that people complied about. Please see attached images. Cable is 6FT now and 2,5mm connectors instead of MMCX. I assume they use some type of electropolish with anisotropy etch to fix sharpness of girls. More material removed from edges and less at the thick portion of these bars. It is very smooth now. Some guy already made a video about Rev2: https://www.youtube.com/watch?v=YE3Zu6vjZzU

My tube preamp is Triode TRV-4SE Special Edition. It is upgraded with new output CAPs (Vcap) and Step Attenuator volume control.Probably, will sale it soon.
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Alex thanks for the detailed info. We will be happy to see your finished build soon. BTW that's an already costly Japanese made tube preamp you have there even before you added those expensive modifications. I wish you will retrieve a fair portion of that investment on a sale.
 
pinnocchio

pinnocchio

Member
Joined 2010
quebecdiy.forumactif.com/
My DCG3 build is coming along nicely..!

All tests have passed and my DC offset with input shorted is very close to 0mV on both channels. It actually hovers +/- 0.4mV which is really good.

See thread below. It is a French thread but there's nothing Google translate cannot do! Hehe

Salas DCG3

Can't wait to test it!

What the best pot impedance we can install on this preamplifier?

Thanks
Do
 
A

ammel68

Member
Joined 2009
pinnocchio said:
To your knowledge, what the best Opamp/most adapted I can put in there. I know this is DC servo so the best opamp for this task?
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Obviously, Salas had good results with the AD823 or he wouldn't have recommended it.

Plenty of other dual FET op-amps to try like the AD712, OPA2134, OPA2604, etc..

Just plug your favorite(s) in the socket and see if you can hear any difference or measure even lower offset with it.

Op-amp rolling at its finest!:D
 
Salas

Salas

diyAudio Chief Moderator
Joined 2002
Paid Member
pinnocchio said:
What the best pot impedance we can install on this preamplifier?

Thanks
Do
Click to expand...

pinnocchio said:
Hi Salas,

To your knowledge, what the best Opamp/most adapted I can put in there. I know this is DC servo so the best opamp for this task?

Thanks
Do
Click to expand...

As the other members said.

In the context of a standard DCG3 + DCSTB configuration I recommend 20K high quality attenuator (preferably a switcher or micro controller LDR, 25K is also good) and the AD823 as servo chip. With those choices I find the system's tonal result is neutral. You may also roll some other chips if curious but make sure they can stand +/- 18V rails too. FET input types usually tend to tighter offset control in this design.
 
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