Salas DCG3 preamp (line & headphone) - Page 344

Salas · 15th January 2019, 04:17 PM

Quote:

Originally Posted by PKI

Thank you for such a detailed review! I am debating which one to get. ATH-50 are in my list as well as I am listening music at work and really afraid SH will be too loud for other people even nobody seats next to me.

I don't like the ATH-50 that much I must confess

jimk04 · 18th January 2019, 09:12 AM

I managed to get a pair of dual secondary trafos for this project. They measure 25.8v unloaded. They were billed as 19v. Will the drop under load make them suitable?

Salas · 18th January 2019, 09:54 AM

They should come down around nominal when loaded. You could pre-test that if you would load each secondary with a 100 Ohm 10W power resistor and measure their AC output again.

PKI · 21st January 2019, 12:27 AM

Building my third preamp, thank you Salas for such a great design :-). This time I will be using UBIB in dual mono configuration in PSU. What would be the best value for the limiter R1 if I am planing to bias DCG3 @ around 150mA? Thanks!

vgeorge · 21st January 2019, 05:22 AM

You could use 1.8R to 2.0R for 270 to 300 mA consumption on the UBIB (depending on the mosfets)

jimk04 · 23rd January 2019, 08:10 PM

Any benefit to Cb Cc under the board on dcg3?

Salas · 23rd January 2019, 08:20 PM

They don't obstruct your reach to swap the dc servo op-amp chip that way

jimk04 · 23rd January 2019, 09:38 PM

Thanks. My build is underway. I shall report back!

Is J3 BG256B fet for Q5 position?

Salas · 23rd January 2019, 10:20 PM

Yes (BF256B)

jimk04 · 25th January 2019, 09:48 AM

Everything is nearly all populated now. DCSTB are working with 17.54/-17.55 and 17.44/-17.41

Is it ok to leave DCSTB powered up with no load to bring the caps up.?

21st January 2019, 05:22 AM	#3435
vgeorge diyAudio Member Join Date: Mar 2004 Location: poros island	You could use 1.8R to 2.0R for 270 to 300 mA consumption on the UBIB (depending on the mosfets) __________________ "Without deviations from the norm, progress is not possible" - Frank Zappa

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18th January 2019, 09:12 AM	#3432
jimk04 diyAudio Member Join Date: Jul 2018 Location: North Notts	I managed to get a pair of dual secondary trafos for this project. They measure 25.8v unloaded. They were billed as 19v. Will the drop under load make them suitable?

18th January 2019, 09:54 AM	#3433
Salas diyAudio Chief Moderator Join Date: Oct 2002 Location: Athens-Greece	They should come down around nominal when loaded. You could pre-test that if you would load each secondary with a 100 Ohm 10W power resistor and measure their AC output again.

21st January 2019, 12:27 AM	#3434
PKI diyAudio Member Join Date: Aug 2011	Building my third preamp, thank you Salas for such a great design :-). This time I will be using UBIB in dual mono configuration in PSU. What would be the best value for the limiter R1 if I am planing to bias DCG3 @ around 150mA? Thanks!

23rd January 2019, 08:10 PM	#3436
jimk04 diyAudio Member Join Date: Jul 2018 Location: North Notts	Any benefit to Cb Cc under the board on dcg3?

23rd January 2019, 08:20 PM	#3437
Salas diyAudio Chief Moderator Join Date: Oct 2002 Location: Athens-Greece	They don't obstruct your reach to swap the dc servo op-amp chip that way

23rd January 2019, 09:38 PM	#3438
jimk04 diyAudio Member Join Date: Jul 2018 Location: North Notts	Thanks. My build is underway. I shall report back! Is J3 BG256B fet for Q5 position?

23rd January 2019, 10:20 PM	#3439
Salas diyAudio Chief Moderator Join Date: Oct 2002 Location: Athens-Greece	Yes (BF256B)

25th January 2019, 09:48 AM	#3440
jimk04 diyAudio Member Join Date: Jul 2018 Location: North Notts	Everything is nearly all populated now. DCSTB are working with 17.54/-17.55 and 17.44/-17.41 Is it ok to leave DCSTB powered up with no load to bring the caps up.?