He made it like this in an attempt to synchronize both DEM oscillators.
I am pretty sure it cannot work like this. The solution Joris suggested might work but reliable operation cannot be guaranteed (oscillator drift / component tolerances).
My advice, cut the interlink between the chips and use two separate 470pF caps. I am quite sure the noise problem will be solved then.
How can I do this? I think I found the traces on the upside of the board. How do I cut them without making too much damage to the surroundings ?
The traces on the PCB can be interrupted using a 1mm PCB drill. Drill in the center of the PCB trace. This causes minimum damage to the PCB. You have to interrupt the trace as close to each IC as possible so the remaining piece of PCB trace won't pick up interference.
If you don't mind soldering at the TDA1541A pins you could try to carefully bend pins 16 and 17 so they are outside the IC socket. Then solder a small 470pF cap (1206 NPO SMD cap for example) directly between pins 16 and 17 of each DAC chip. This way you don't have to damage the PCB.
That could be, but there are still lines attached to the cap, so remove those connections to the other TDA first. When those lines are gone it should be OK.
I received two 470 pF caps today, and bent the 1541 legs outside the socket (on both 1541's) and soldered them to leg 16 and 17.
No difference!
Still the dac is very noisy at low volume. Also when comparing to the cheap cs4398 dac, the highs are almost none excisting. The bass seems good, but the sound is clearly not good.
This dac should‘t be noisy even at not full digital volume should it? In quiet music I can hear the noise even at full volume, but at 10% volume the noise is very loud. At 60% volume it is annoying.
No difference!
Still the dac is very noisy at low volume. Also when comparing to the cheap cs4398 dac, the highs are almost none excisting. The bass seems good, but the sound is clearly not good.
This dac should‘t be noisy even at not full digital volume should it? In quiet music I can hear the noise even at full volume, but at 10% volume the noise is very loud. At 60% volume it is annoying.
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Hi Nick,
I had problems with noise(artifacts like) on my 4XTda1541A (similar schematic to yours). After many hours of testing I've found out that one of the voltage regulator was not working properly , even though when voltages were checked the readings were in order. (when I slightly move the regulator, the voltage dropped suddenly). You should try to check the power supply.
Good Luck,
Sorin
Ps. I've got better results using tubes for I/V stage.
OK, I have a noise problem too with my unit (same kind, same supplier). The noise is obviously digital in nature and is omnipresent. Not loud, but annoying anyway. The unit sounds absolutely wonderful, but I cannot make it work in non-OS mode. In non-OS it has distorsion, definately digital in nature. I tried making a I2S filter, result is better but nowhere near clean.
I'm going to look at the filter cap thing and hook up an oscilloscope to the power supplies and see how it looks for starters.
I'm going to look at the filter cap thing and hook up an oscilloscope to the power supplies and see how it looks for starters.
Hello Perfrej
I send a message to him and send the link to this thread,
"....it seems there a few noise issues on the DAC but I have not received any question about such problem before, I will study the links and try to demo the issue, hope to have the answer and come back to you soon. Besides,would you please send me the connection of your DAC unit and my suggest is to disconnect all the grounding from the DAC if made it already..."
I will take some pictures and post them here
I hope will find the problem.
I send a message to him and send the link to this thread,
"....it seems there a few noise issues on the DAC but I have not received any question about such problem before, I will study the links and try to demo the issue, hope to have the answer and come back to you soon. Besides,would you please send me the connection of your DAC unit and my suggest is to disconnect all the grounding from the DAC if made it already..."
I will take some pictures and post them here
I hope will find the problem.
well thats just one of a number of customers, so I dont know that i would call it a happy ending. good he addressed julcat's problem, but what happened to the other guys? I hope there were not warranty issues due to them trying to fix a faulty product themselves. this cop out annoys me when I see it. when selling a component that is DIY by nature, to not provide warranty support for those who have to try to fix bad workmanship or faulty components is not great. of course these other guys might not have pursued the problem with the seller and he cannot be blamed for that.
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