cdp/dac output stage gain

[Zuluf]

Bog daj,

Na netu sem našel tole in me zanima koliko je resnice na tem, da z znižanjem gaina na izhodu s pomoèjo upora, lahko zvišaš razmerje S/N in razširiš frekvenèni odziv?

It's very simple to adjust the gain of any CD, DAC, Preamp or Amplifier : they all (except some few open-loop designs) are made around an amplifying stage topology with a non-inverting input, an inverting input and an output. The gain is adjusted by the negative feedback amount determined by Rf (feedback) and Rg (gain) resistors. Generally, Rf remains fixed and the gain is adjusted by varying the Rg value : by increasing it, you'll decrease the gain and vice versa.
Rf starts from the amplifier's output and ends to its inverting (-) input.
In your case, you'll just have to locate both left and right output stages' Op-Amps and increase their Rg value : this resistor is connected to the Op-Amp's inverting (-) input at one side and to the signal ground at the other side.
You should note the original value first, then replace it with a bigger trimpot adjusted at the same value : for example, if Rg=100 Ohms, chose a 500 Ohms trimpot adjusted at 100 Ohms. Then just increase the trimpot's value to say 200 Ohms and the overall gain will be divided approximately by 2 which is -6dB. Gain(dB)=20xlog(1+Rf/Rg)
When the correct Rg is found, then replace the trimpot by a quality resistor with its equivalent resistive value.
Note that by decreasing the gain, you'll also increase the bandwidth and lower the voltage noise of your CD's output stage resulting in a higher global S/N ratio for your system.
If you can't find Rg, just send your CD's analog output stage's schematics and I'll help you to locate it.
Have fun!

[urosst]

manši gain pomeni veèjo pasovno širino,
manše obraèanje faze,sistem je bolj stabilen in stem posledièno
manši šum.
vse to drĹľi za cd preampe buferje.

za ojaèevalec pa ni tako.

[Zuluf]

Standard na cdp-jih in dacih je cca 2V. Bistveno znižanje napetosti ima verjetno prav tako kakšne slabosti, sicer ne vem zakaj bi imeli izhodno napetost vsi tako podobno. Se motim?