Audio amp DC output

Thread Starter

agnaR

Joined Sep 25, 2022
3
Hello all,

I have a Sansui AU-a907 audio amp. It sounds really really good!! A little problem is that there's about 250mv DC output at speaker terminals. I adjust it close to 0mv few times but when I turn it on the next day, it's out of wack. Both sides
This amp has Integrated and Power amp direct option. When I adjust the DC offset at Integrated mode and move the dial to Power amp direct, then the DC offset goes to around 200mv. Both sides
Anyone has any suggestions on where I should look at?
You can look at the diagram here
https://elektrotanya.com/sansui_au-alpha907_au-707_au-607mr_mrx_sm.pdf/download.html
 

Thread Starter

agnaR

Joined Sep 25, 2022
3
250mV is only 31mA into an 8Ω speaker, which should not be a problem.
thanks crutschew,
250mV may not be a problem but when I turn on the amp, speaker gives out a big thud. Plus, why is it vary from integrated to Power amp direct??? :(
 

crutschow

Joined Mar 14, 2008
30,791
when I turn on the amp, speaker gives out a big thud
That's a separate and unrelated issue.
The thud is because the output generates a momentary voltage when power is applied until the circuits stabilize.
The speakers should be disconnected during power up to prevent that (and there is a relay in the output that should do that but apparently doesn't)
why is it vary from integrated to Power amp direct?
Hard to know exactly.
There appears to be a difference in DC offsets between the two paths, but again that should not be a problem.
 

LowQCab

Joined Nov 6, 2012
2,506
You can just ignore it, it's not likely to cause any problems.

Or, You can replace all the Capacitors,

Or, You can just get a new Receiver.
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Thread Starter

agnaR

Joined Sep 25, 2022
3
I will replace the capacitors. But from previous experience I know that if it's a bad cap (or three!!) DC doesn't vary on both sides at same rate.
 
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