Salas DCG3 preamp (line & headphone)

Those are very good DC results but you will also need mid point AC secondary wire(s) for each PSU unit's AC in
Thanks Salas.
Properly wired (!) results shown in the attached photo - embarrassing rats nest of wire but I just used what was close to the top of my wire box.
The final build will use 2 transformers for dual mono as others have done.
-Keith-
 

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Salas,

As far as pots go, I usa a dact type with smds. It's very neutral and transparent. I only have 2 values on hand: 10 and 20k. I switched to 10k and it is almost perfect. I know this is isn't in the proper range for your design, but it really works well for me. Now, I can do what you said and change R1 and go back to 20k. In fact, its the same pot I used with my DCB1 for many years, with no harshness or glare; very smooth sounding.

My 2 channel room has never been bright. What i'm hearing is definitely a component change. With the 10k, I can now enjoy and listen. It really is a truly phenomenal preamp. But, I need to address the slight sibilance I'm hearing. So, I'm all ears for suggestions.

Unfortunately, my tube dac has a very high output impedance of 20k. So, would 50k not be way too bright if 20k was so? I'm open to any suggestions because I love this thing otherwise. There has to be a fix with either a pot and or R1. Maybe a trimmer on R1 to adjust tone? Or would that be stable?

Cheers,

Greg

Greg,

Hope you are enjoying the music (big time)!

Are you still using the 10K pot or tried out other values (20K and 50K) and liked them more?

I am planning to order the same type DACT 21 step attenuators from eBay.
 
Zman,

I'm using a 20k. Made a slight speaker adjustment, no more brightness. In my setup it now sounds just about perfect, basically is slightly on the brighter side neutral. I was getting slap reflections which really made the DCG3 sounds very bright.

I haven't listened to the HP OPS, but that would be the smartest way to evaluate this design.

Anytime I hear something I don't like in my listening room I pull a studio monitor out and listen to the same track with a good source. What you realise in those moments is that your room is trashing all of your efforts.

It's funny how the "digital glare" moniker is used. In my case "digital glare" is simply my crappy room or improper speaker placement.

Amazingly, my phone (LG V20) with a Sabre dac built in has zero digital glare with headphones. Nothing bright at all, just enjoyable with both detail and warmth.

I use really simple house curves for my listening rooms, via Roon and it's built in PEQ and its convolution engine.

Having said all of that, and knowing all of that, I still made the mistake of trying to adjust the DCG3 over the room.

Hope this helps.

Cheers,

Greg
 
Greg,

Thank you for your detailed answer. I agree with your observations - lot of the time it's the room at play. I am using a 50K pot (DACT copy) with my DCG3 now and it sounds "neutral" to me - I have to say I am very happy with the sounds as is, but DIYers love to tweak and was thinking of trying out the 20K.

Also was thinking should I try the BC327-40... but don't want to touch the PCB... maybe I should build another DCG3? :D

You still have the discrete opamp installed?

Cheers,
Zia
 
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Greg,

Thank you for your detailed answer. I agree with your observations - lot of the time it's the room at play. I am using a 50K pot (DACT copy) with my DCG3 now and it sounds "neutral" to me - I have to say I am very happy with the sounds as is, but DIYers love to tweak and was thinking of trying out the 20K.

That is why I left the hi-Z input stage non-buffered so its both minimal circuitry and the pot value choice can have a range of impact on the tonality to can offset other things. Rest of system factors being equal a 20k-25k log pot should be the sweet spot.
 
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You can try further 2.2k or 3.3k or 4.7k in series to the Line in PCB terminals as to evaluate possibly more suitable tonality to your system but its still stable as it is, showing its intrinsically max rise time as well. Your setup right now behaves like having a series type pot but at its minimum output resistance when set very nearly to top volume. Any 20k nominal series type pot would show 5k max output resistance at half its nominal value travel point. But near full clockwise turn their output resistance dies out and becomes a pass through contact to the input signal.