Salas DCG3 preamp (line & headphone)

[Salas]

Just what i like to know Salas

i do not know if it the same thing with this resistor ..as some use to lower output from
a cd player to a amp

it can be heard..sometimes with good result,,but some will say that the sound get smooths ..and lost dynamik

if it not destroy the preamp ,,it will be worth trying

It does not lower output even to 600 Ohm line loading it only adds resistance damping. Try different approaches, I would start by keeping it but with best quality part there is, and let us know your findings in your own system and subjective preferences frame then.

 

[beardman]

Will be great to hear this pre...i use now a 4P1L tube pre it sound so great,,,but i have

some problem with noise,,,so it is time to try something special..like your pre

 

[Salas]

I believe that you will enjoy it. I am familiar with tubes also. It won't give you odd solid state results. Good luck building it and let us know.

 

[nashbap]

Just what i like to know Salas
it can be heard..sometimes with good result,,but some will say that the sound get smooths ..and lost dynamik

This is a very good sounding pre. Use the best you can.
I am using CMF5549R900BEEB which is 25ppm 0.1% in that position.

nash

 

[beardman]

nashbap

No doubt that the vishay is a good resistor

i like the Shinkoh resistor,,use them as I-V in my Dac
Best Bjarne

 

[Salas]

Nice resistor in tube builds was the Rikken also. Anyway, you could try any of your favorites at 47R vs 27R vs Zero I guess.

 

[Syl20m]

Hi All,

for the mosfets IRF and DN..., what type of thermal interface do you recommand?
mica pads + thermal paste?
silicon pads?
thanks in advance

 

[Salas]

Silicon Pads are simpler/cleaner to install and usually there is not much temperature in those Mosfets to worry about minimum thermal resistance pads. I got 38C at 100mA bias on them when using 1cm thick Alu bar mounting interface to the chassis floor.

 

[beardman]

Hi Salas

Is there a max value for C6 and C7

i have some Nichicon gold cap 2200uf

will it be ok to use
Best Bjarne

 

[Salas]

Better don't use too high value because they are on the rails as local decouplers/reservoirs and the DCSTB's pass transistors will have to charge them up instantly, so why push them, on the other hand they will not fit the allowed space on the DCG3 small PCB anyway.

 

[beardman]

i will not be using the DCSTB supply...i have a supply from Newclassd

i will just use some smaller value,,,have other in same serie

 

[Salas]

Its a good audio capacitors series and their 85C rating isn't a problem where they are located.

 

[Salas]

Newclassd recommends 100uF also by the way

http://www.newclassd.com/tpi.pdf

 

[beardman]

yes ,i have forgot this from his paper

my supply is his UWB regulator,,because i like the sound from them..and the can deliver all the power i need
for now i must just wait to get the board,,will take some weeks

 

[lykkedk]

Salas ...

Thank's for the preamp i build ~1 year ago

Still the best, and still playing everyday!

Nothing more, nothing less to say, thanks man

Rgds; Jesper.

 

[Salas]

Nice

 

[bambadoo]

Yes - it truly is a great piece of design and audio equipment.

 

[Salas]

Hi Salas. So here the latest results for the noise floor. As suggested I took my measurement with volume at mid-course, net effect was to see a higher 60Hz component, but reduced higher harmonics. Input is grounded.

Red trace is with case fully enclosed, Green trace is with volume pot ground pins connected to frame through a 10R resistor, it is slightly lower, but still is the better result ever I had. Now the noise floor is at -97dBV, instead of -95dB when I started.

Compare to your own measurement, I can see your using a laptop, probably running on battery. My own CLIO card is inside a PC, its power supply running off an insulated power transformer, so it is probably collecting nasty RF noise that reflects into my measurements. It is still one of the best results I had so far with my test setup.

Thanks for the tip.

Another possibly good tip is try BC327-40 matched transistors in the mirror instead of the matched BC560Cs as they are lower noise pin compatible types with still high enough hfe. They can improve the preamp's input referred noise by 4nVrtHz theoretically. As much effect as adding substantial degeneration to the mirror but intrinsically so. They are bit slower on the other hand but not so much so as to risk stability I would think. Can they even offer more subjective detail because they are quieter? I don't know, I haven't done that replacement, I just simulated it.

 

[fredlock]

What kind of head phone 1/4 jack terminal you guys using? Is this good enough? NYS230 REAN / Neutrik | Mouser

 

[Salas]

I used that one. Its reliable. Another popular kind is the red button pro one with the size and mounting of an XLR but its a bit of hard push to unlock.