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

Tea-Bag 10th January 2017 08:56 PM

Quote:

Originally Posted by RCruz (https://www.diyaudio.com/forums/analog-line-level/296406-salas-dcg3-preamp-line-headphone-post4947245.html#post4947245)
Why was the AD823 chosen in the first place ?

We used OPA2604 in early tests, but the AD823 was changed by Salas, better operating values or sound. He would have to fill that out.

vgeorge 10th January 2017 09:17 PM

I think Salas listened to many ICs and decided based on sound. But it is also very subjective. You could try more types and dcide what you like more.

Salas 10th January 2017 09:23 PM

Quote:

Originally Posted by RCruz (https://www.diyaudio.com/forums/analog-line-level/296406-salas-dcg3-preamp-line-headphone-post4947245.html#post4947245)
Why was the AD823 chosen in the first place ?

Among many I tested which could do the servo job alright this one I thought I could prefer a little more subjectively

RCruz 10th January 2017 09:42 PM

Thank you gentlemen

Will find the AD823

Dimdim 10th January 2017 10:09 PM

1 Attachment(s)
Quote:

Originally Posted by Salas (https://www.diyaudio.com/forums/analog-line-level/296406-salas-dcg3-preamp-line-headphone-post4946715.html#post4946715)
The right one must be fake. Mine have the same lettering and orientation edge dent like the one on the left.

So does mine. I got it from Mouser.

https://www.diyaudio.com/forums/atta...1&d=1484089729

nashbap 11th January 2017 12:30 AM

Salas, does the harmonic picture change as the gain/feedback is changed? I think the pics of FFT you posted on the first page are with the standard gain of 10. Will there be any change to the sound if I changed the gain to 6?

Thanks. nash

marcus1 11th January 2017 01:37 AM

1 Attachment(s)
Probably being overly cautious but for mounting the uPA68HA (J1-J2) on the DCG3 board - does the thick white line on the board correspond to the letter N on the left side of the uPA68HA as shown in the photo?

thanks

nashbap 11th January 2017 02:03 AM

1 Attachment(s)
Quote:

Originally Posted by marcus1 (https://www.diyaudio.com/forums/analog-line-level/296406-salas-dcg3-preamp-line-headphone-post4947433.html#post4947433)
Probably being overly cautious but for mounting the uPA68HA (J1-J2) on the DCG3 board - does the thick white line on the board correspond to the letter N on the left side of the uPA68HA as shown in the photo?

thanks

Here's a pic from Tea- Bag's blog that will help.

Hikari1 11th January 2017 04:37 AM

Quote:

Originally Posted by Hikari1 (https://www.diyaudio.com/forums/analog-line-level/296406-salas-dcg3-preamp-line-headphone-post4944426.html#post4944426)
Just some info for builders sourcing parts:

From mouser dn2540 came very well matched. All were between .01v of each other when measured across 6.8r resistor. Measured 1.08v for 160ma ish bias. Out of 5 devices they measured between 1.07 and 1.08v with 6.8r resistor. Nice.

Bc560 required about a dozen devices to get 4 with a hfe match within 5%.

I have not tested the bf256b. Will probably do that when it's in the circuit and adjust resistor values accordingly.

Here is some in progress pics. The case is too small, I know. Psu is lm317/337 followed by a cap multiplier that will sit on the sink opposite of the amp board.

Iam getting +17.6v and -17.8v out of my lm317/337 and cap multiplier when unloaded. Too high or just about perfect?

ammel68 11th January 2017 05:43 AM

Quote:

Originally Posted by Hikari1 (https://www.diyaudio.com/forums/analog-line-level/296406-salas-dcg3-preamp-line-headphone-post4947523.html#post4947523)
Iam getting +17.6v and -17.8v out of my lm317/337 and cap multiplier when unloaded. Too high or just about perfect?

Just about perfect.:D
I say go for it dude!

If you're concerned about it being too high, why not adjust it down? You do have trimmers to adjust the voltages of the 317/337 don't you?


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