Salas DCG3 preamp (line & headphone)

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#2,261
beardman said:
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
Click to expand...

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.
 
#2,268
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.
 
#2,270
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.
 
#2,278
Algar_emi said:
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.
Click to expand...

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.
 
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