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

MagicBus 18th January 2017 04:41 PM

At last, I found some time to do the first electrical test! It came to life easy! I remind you that I' m using two DCG3 stereo modules, each one powered by one half DCSTB.
First DCG3: power rails @ 17,22V/-17,22V bias @ 111mA/113mA
Second DCG3: power rails @ 17,34V/-17,35V bias @ 113mA/113mA
Should I trim anything?
I haven't insert the opamps yet but DC offset was easily adjusted around 1mV although it fluctuates, of course.
My DMM has lost the ability to measure temperature but I can say DCG3 was just warm after 15 min and DCSTB even less with its 2,5" heatsinks.

Salas 18th January 2017 04:45 PM

Looks like a perfect start, nothing to trim.

MagicBus 18th January 2017 04:53 PM

Quote:

Originally Posted by Salas (https://www.diyaudio.com/forums/analog-line-level/296406-salas-dcg3-preamp-line-headphone-post4956146.html#post4956146)
Looks like a perfect start, nothing to trim.

OK! I need to put some work into the chassis before any listening. I hope to have news by the weekend:)

Morde 18th January 2017 05:20 PM

Quote:

Originally Posted by Salas (https://www.diyaudio.com/forums/analog-line-level/296406-salas-dcg3-preamp-line-headphone-post4956125.html#post4956125)
Yes no problem with R7 470R instead of 499R, it will just make 3.12x which is peanuts practical difference to 3.0x

For 2x spot on put both R6 and R7 470R

Thanks for your quick answer. Pardon my ignorance, but it says in your instructions: "R6 sets the gain. 1k for 3x, 499R for 2x, 1.5k for 4x." There must be something that I don't quite understand. What gain do I get if I change just the R6 from 1k to 470R? :scratch: Or is it a no go and I must change the R7 as well?

Salas 18th January 2017 05:28 PM

1.94x

lykkedk 18th January 2017 05:35 PM

:up: Salas :up:

AlephJ Mimi! second channel up (Failure was faulty cable from source)!

Offtopic sry... :)

Jesper.

Ryssen 18th January 2017 06:19 PM

Unsure how the upa68HA should be turned..is it text side on upa68 towards text on pcb?

JimT 18th January 2017 06:44 PM

Quote:

Originally Posted by Salas (https://www.diyaudio.com/forums/analog-line-level/296406-salas-dcg3-preamp-line-headphone-post4956026.html#post4956026)
Did you also notice those large gunshot earmuff like phones the drummer wore in the Pidgeon clip? Those have Sony 7506 drivers inside. They are specials for high isolation called UltraPhones. Drummers must protect their hearing the most as the kit is loud and if it leaks in enough they pump up the volume of their foldback mix in the cans too. So they end up with ringing ears after longish sessions or when performing loud live events. In Ear monitors do that job well too.

Thats very interesting. You have good eyes to spot them!!

Jim

nashbap 18th January 2017 06:46 PM

Quote:

Originally Posted by Ryssen (https://www.diyaudio.com/forums/analog-line-level/296406-salas-dcg3-preamp-line-headphone-post4956271.html#post4956271)
Unsure how the upa68HA should be turned..is it text side on upa68 towards text on pcb?

Refer to my post #908

nash

Salas 18th January 2017 06:48 PM

1 Attachment(s)
Slim uPA has the N logo indicating pin1 which goes to the white stripe side on PCB

Fat uPA has its upper left corner slant. Again indicating pin1

The board has pin identification printed on every uPA pad also

Ultimately as you watch from the connectors PCB edge towards correctly installed uPAs the left one shows its face the right one shows its rear


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