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

Salas 28th February 2017 10:44 PM

Looks good. Time to put the servo op-amp in now.

PKI 28th February 2017 10:47 PM

Salas I am still struggling with finding a perfect case for my needs. If for example I decide to separate psu, should I move transformers into other box, make smal CRC there just so I don't run AC and connect it right after rectifiers in the psu boards? Or there are some cons i don't see in doing so?

Salas 28th February 2017 10:54 PM

No cons, only benefits. You will just carefully implement the rectification & a first reservoir stage in the first box near the trafos. You can put an R in-between that and the DCG3's box DCSTB reservoir. Use Duncan's PSUD software to analyze as a whole.

nashbap 1st March 2017 12:09 AM

Salas, I am having a hum/mostly buzz problem in my balanced build.

With pin1's of the input and output XLR of each channel and one end of a CL60 connected at the same point on the chassis, I connected the other end of the CL60 to the G point on the DCG3 next to Line out. I got a buzz. Then I removed this end from the DCG3 and connected it to the G point of the DCSTB. Still buzz but a bit less. Finally I removed the end from the DCSTB G and let it float, so essentially no CL60 connection and its very quiet. Must mention that R7's are lifted from ground and linked together.

What do you advice?

Thanks. nash

ernesternest 1st March 2017 05:19 AM

Quote:

Originally Posted by Salas (https://www.diyaudio.com/forums/analog-line-level/296406-salas-dcg3-preamp-line-headphone-post5004100.html#post5004100)
Looks good. Time to put the servo op-amp in now.

Salas, yes, I do think so as well. Servo in, a few connectors and give it a fist listen :-) Looking forward to connecting it to my dac and headphone.

Later then think about a proper housing. For me, this is always the most challanging part.

Cheers Ernst

zman01 1st March 2017 06:29 AM

Quote:

Originally Posted by ernesternest (https://www.diyaudio.com/forums/analog-line-level/296406-salas-dcg3-preamp-line-headphone-post5004375.html#post5004375)
Later then think about a proper housing. For me, this is always the most challanging part.

Cheers Ernst

I hear you! :)

Salas 1st March 2017 07:28 AM

Quote:

Originally Posted by nashbap (https://www.diyaudio.com/forums/analog-line-level/296406-salas-dcg3-preamp-line-headphone-post5004166.html#post5004166)
Salas, I am having a hum/mostly buzz problem in my balanced build.

With pin1's of the input and output XLR of each channel and one end of a CL60 connected at the same point on the chassis, I connected the other end of the CL60 to the G point on the DCG3 next to Line out. I got a buzz. Then I removed this end from the DCG3 and connected it to the G point of the DCSTB. Still buzz but a bit less. Finally I removed the end from the DCSTB G and let it float, so essentially no CL60 connection and its very quiet. Must mention that R7's are lifted from ground and linked together.

What do you advice?

Thanks. nash

Unfortunately I don't have a balanced build to experiment along with you and give you solid practical advice. There is only Kostas's (MagicBus) build example that isn't using linked R7s or CL60. I could attempt to theoretically analyze your config but in real builds there are loop area and rest of system grounding factors at play also. I would just say use the most quiet config you can practically achieve and don't forget to check the outputs DC offset also on the bench for all possible signal modes.

MagicBus 1st March 2017 07:42 AM

Quote:

Originally Posted by nashbap (https://www.diyaudio.com/forums/analog-line-level/296406-salas-dcg3-preamp-line-headphone-post5004166.html#post5004166)
Salas, I am having a hum/mostly buzz problem in my balanced build.

With pin1's of the input and output XLR of each channel and one end of a CL60 connected at the same point on the chassis, I connected the other end of the CL60 to the G point on the DCG3 next to Line out. I got a buzz. Then I removed this end from the DCG3 and connected it to the G point of the DCSTB. Still buzz but a bit less. Finally I removed the end from the DCSTB G and let it float, so essentially no CL60 connection and its very quiet. Must mention that R7's are lifted from ground and linked together.

What do you advice?

Thanks. nash

My SLBs measure 10 ohm DCR. What does CL60? Also, did you test to connect circuit GND directly to chassis?

Salas 1st March 2017 08:15 AM

Maybe just a capacitor instead of Thermistor will work for him. Also pin1 "philosophy" can be opinionated:
http://www.diyaudio.com/forums/pass-...it-ground.html

MagicBus 1st March 2017 11:34 AM

If one designs from scratch a complete audio system, then AES standard is the way to go. But when we have to connect devices that do not confirm with AES then only way is to follow the grounding scheme of each device. Also, AES standard, i.e. pin 1 to chassis, does not allow parallel XLRs and RCAs. The pin 1 problem occurs when the shield connected to it forms a returning path for signal current. Possible solutions to this could be the following;
1) Pin 1 of both devices to each chassis.
2) Pin 1 of first device to circuit GND and pin 1 of the second to chassis.
3)#2 reversed

What I do;
Dac chip pin 1 connected to circuit GND and chassis - I can't do anything about that.
DCG3 pin 1 is at the moment connected to chassis and RCA for SE function to circuit GND but I think pin 1 should also go to circuit GND and that's what I'm going to do.* Amps pin 1 to chassis

* I see DCG3 as a replacement for the sound card analogue section; balanced signal from the DAC chip amplified by what it took the place of the opamps > balanced line out.


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