flickering noise at silent passages (CS8412+TDA1541)

[weissi]

Hi!

I build the normal TDA1541 Setup feeded by CS8412 with Koax and optical receiver.....
Sounds very good, but when music comes to silent passages (I think I mean passages with low dynamic resolution, only midtones and highs) I can hear some flickering noise, if music gets its full dynamic (bass and high´s) the noise goes?

so any guess what that could be? its with both, coax and optical... Transmitter is my Envy24Soundcard...

if there is no signal there is no noise too.....

thanks for any answers!

[BenY]

It very well could be noise from your power rails,Check to see if your power lines are properly bypassed,You could test it with an oscilloscope.

Yuval.

[Jocko Homo]

Try heating the chip up, and then hitting it with freeze spray. Sounds like a faiure mode that the '1541 has.

Hopefully, it is something else.

Jocko

[weissi]

further listening brings me to the end that it might be aliasing.....
I´ll try it with a 3rd order filter, I´ll let you know if it was that matter......
the problem is that, currently, with 1k installed at the I/V conversion(with AD797 samples ;-)), the level is to high for my headphone amp.... so i have to attenuate the spdif output on my soundcard to very low levels... I know DAC´s don´t work best at low levels......
I´ll try both tomorrow.

question: would it be better to decrease the I/V resistor value, or attenuate the output of the I/V conversion? how low could I go with the I/V resistor without increasing distortion of the opamp?
And no, I have no plans to make a passive I/V conversion ;-)

I also work on a paralleled TDA1541 (since they are easy to get here.... 3€ in germany..) design... I´ll try to summarize both channel signals with an adjustable opamp summarizer to be able to regulate differences of both chips...
I´ll see...

but one can I say: wow, either I have done anything wrong with the TDA1543, to my ears it sound much to rough..... TDA1541A is a dream.... never heard Tori Amos so gently and powerful together...

[weissi]

Hi!

So I finished my parallel design... can´t tell you if it sounds better than single, but it sounds very good....
Also the flickering noise is gone with the new design.... It may really was the "TDA error" , or something with the ground connections.....
But: now there are 4 opamps in the signal path.... "normal" noise is now significantly louder.....