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

arnd13 10th February 2018 07:30 PM

OK, I will set the gain to 4x

Thanks a lot

bambadoo 10th February 2018 07:35 PM

I use 3x gain with soekris dac. No problem. Quite sensitive speakers though...

Salas 10th February 2018 07:52 PM

Quote:

Originally Posted by fred sonnen (https://www.diyaudio.com/forums/analog-line-level/296406-salas-dcg3-preamp-line-headphone-post5337059.html#post5337059)
Salsa

In Tea-Bag GB page is written that the DCG3 needs 17,5V. Whats about the current?
What happens if just 16V or 18V available? What is the bandwidth that DCG3 can handle?

You are probably using auto correction software that made me a Latin music genre :D

The current is either 100mA or 150mA bias plus a little more for the driver stage, the relay, and the servo chip. It draws 20W from the wall at 100mA bias stereo with its usual DCSTB supplies. If +/-18V is available you are at the servo chip's max spec so better use a +/-24V rails capable chip like the OPA2604. 16V won't do any harm, it might just sound a bit sweeter than neutral. But the tonal details can be also affected by other build choices like volume pot type etc. In general remember to roughly have +/- 0.5A capability when trying various other discrete supplies or chip supplies. Bandwidth is near 1MHz with 20K log pot at its midpoint worst case output impedance.

Salas 10th February 2018 08:24 PM

Quote:

Originally Posted by bambadoo (https://www.diyaudio.com/forums/analog-line-level/296406-salas-dcg3-preamp-line-headphone-post5337067.html#post5337067)
I use 3x gain with soekris dac. No problem. Quite sensitive speakers though...

Me too. DCG3 is primarily meant to be a line level preamp. But some use it exclusively as an HPA.

arnd13 10th February 2018 08:28 PM

Changed R6 to 1.5k. Now it's perfect, there's enough headroom upwards now.

Salas 10th February 2018 08:31 PM

Our simple math about setting it for the specific Beyer cans did not fail us :up:

Russellc 11th February 2018 08:20 PM

2 Attachment(s)
Layout copied off of bambadoo's project as seen here:

http://www.diyaudio.com/forums/analo...ml#post5037088

Here's mine so far, still need extender sets and heat sink.

Salas 11th February 2018 08:39 PM

Looking good so far. Good luck!

Keremito 13th February 2018 02:37 AM

DCG3 not enough bass
 
3 Attachment(s)
Hello, after successfully building a mesmerized B1 buffer and enjoying great sound through my F5 turbo amp I decided to build a DCG3. I got a full kit with dual mono power supplies from Tea Bag. I set it up as a single input preamp in an old velodyne chassis. I am using a ladder type 20 KOhms pot as volume control.
Lately I noticed a lack of bass, there is bass but my full range NHT 2.9's with 10" woofers sound like a mini monitor, you can hear some bass clean and well defined but lacking strength. I wired the input to the pot and from the pot to the amp board using CAT 6 wires, a pair of twisted conductors from the RCA's to the pot and then to the preamp board. I've check polarity of inputs, outputs all seem good. Any ideas where the culprit could be? Thanks

alexkosha 13th February 2018 03:33 AM

I have almost the same setup as yours, beside speakers brand. Same F5T set to about 57W monoblocks, DCG3 x3 gain and 6R nominal impedance on Acoustic Zen Adagios. Speakers are known for weak low bass, but with these components I achieved perfect synergy and bass is very natural. I couldn’t get close to that low frequency and general clarity presentation with my Tube gear. It it very well sounds for my taste.
It sounds like you made some mistake somewhere and need to find it. It should be plenty of bass, particularly with 10” dedicated driver. I also used B1 with great success and this is how I decided to go with x3 gain calculated without F5T clipping. Make drawing and let’s see how you connected your pot and outputs. I just guessing at that point and Salas might get to the the root-cause immediately.


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