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Old 2nd December 2007, 10:31 AM   #1
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Join Date: Mar 2005
Location: Portugal
Default DC bias (AMP6,41hz)


At 6moons review of Trends Audio TA-10 they mention the importance of DC biasing the output.

So I measured the Dc offset of my AMP6 and the result is about +26mV and -28mv.The measurements are made without load and there is few millivolts of fluctuation.
Is this acceptable?
From my understanding this small amount of DC will not hurt the speakers,but how about the +/- difference between the channels.Is this "normal"?

There was a small line written by Jan at 41hz forum, about the possibility of adding a bias adjustment to AMP6 with couple of resistors and trimpots.Has anyone bothered to due such a mod? In that 6moons review they kind of make a big deal of the need of bias adjustment in class-d amps.

xxx I should correct my spelling xxx
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Old 3rd December 2007, 09:18 PM   #2
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Join Date: Aug 2004
Location: Uppsala,Sweden
I don´t think there is a need for adjusting the bias if it doesn´t drift beyond the values you have given.

Here is a quote from Tripath´s technical information about the
TA0105A, please go to this information that I hope is still available if you want some more information, but the circuit there is only due to the TA 105A I think.

"Output offset voltages can be nulled by adjusting the 10KĦ potentiometer shown in Figure 5. Once set, and
the TA0105A reaches equilibrium, the offset does not typically drift. Offsets can typically be set to +/- 25mV.
R103 is used to adjust the offset of CH1, and R203 is used to adjust the offset of CH2. If a different TA0105A
is placed in the RB-TA0105A reference board, the offset of each channel will need to be re-trimmed."
Without wonderment,no life.
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Old 6th December 2007, 05:27 PM   #3
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Join Date: Mar 2005
Location: Portugal
thanks for your reply

If this amount of offset is acceptable and no improvements in sound to expect,I will not bother to try the adjustment.
xxx I should correct my spelling xxx
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