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Problem with HifimediyT1 DC offset, faulty chip?

Problem with HifimediyT1 DC offset, faulty chip?

I recently bought a T1 amp and now have it all set up and working with a SMPS300R. Out of curiosity I checked the DC offset and found that the right channel was within the specified 0 - 10mV but the left channel was way out, over 200mV. I attempted to adjust it but found that the voltage was steadily dropping off by itself. After a few minutes it had dropped to 100mV. If I set it close to 0mV with the pot, after a while it's dropped to a minus value :confused:



There's also audible hiss on the left channel whereas the right channel is silent.



I wonder if the chip is faulty or if there's another explanation for the noise and the weird behaviour of the left channel DC offset.



Any comments most welcome.



Cheers,

Steve



P.S. The amp works OK and sounds fine (apart from left channel hiss).
I recently bought a T1 amp and now have it all set up and working with a SMPS300R. Out of curiosity I checked the DC offset and found that the right channel was within the specified 0 - 10mV but the left channel was way out, over 200mV. I attempted to adjust it but found that the voltage was steadily dropping off by itself. After a few minutes it had dropped to 100mV. If I set it close to 0mV with the pot, after a while it's dropped to a minus value :confused:



There's also audible hiss on the left channel whereas the right channel is silent.



I wonder if the chip is faulty or if there's another explanation for the noise and the weird behaviour of the left channel DC offset.



Any comments most welcome.



Cheers,

Steve



P.S. The amp works OK and sounds fine (apart from left channel hiss).



Hi, I don't think it's the problem of chip. My suggestion is checking the output filter, L1, L4, C24 and C25.

But there is also possibility that the chip is not soldered well, so, re-solder the TC2000 and sta5xx chip may work...



Best wishes.
I've visually inspected L1, L4, C24 and C25 and can't see any problem, all soldered connections are good. Likewise with the 2 chips although the connections are so small I needed a magnifying glass to see them!



The relays don't operate simultaneously, one switches before the other and there is some switch-off pop. Is this normal?



Regards,

Steve
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