simple question: is midpoint voltage setting for adjusting the DC Offset?

[Arnie75]

Hello,

I am no expert at all in electronics and just bought a small and finished TA2022 amp. Regarding this device I have a small question: According to the seller the two trimmers inside are for setting the "midpoint voltage". So is this also for adjusting the DC offset, or is this something different?

Thanks a lot,
Alex

 

[Arnie75]

Buy Enthusiast TA2022 T class, digital amplifier, audio amplifier, 2 digital amplifier DIY Enthusiast TA2022 T class 90W at Aliexpress.com

This is the device I'm talking about. Can anyone help?

 

[Pano]

Yes, it's for setting the DC offset. Connect your speakers or an 8 ohm load. With your voltmeter in DC mode, and NO input to the amp, measure between the positive and negative speakers terminals one channel at a time. Tweak the trimmers until you have no more than a few millivolts DC offset.

Just a note: Some old VOMs don't do well on this adjustment as the HF carrier of the class-d amp fools them. Newer meters seem to be OK.

 

[Arnie75]

Thanks. I cannot do this without speakers, just between the terminals at the amp?

 

[wwenze]

The speaker load is often part of the low pass filter to remove the switching noise that will make your meter's voltage jump around.

Short answer: no.

 

[Pano]

Long answer, Maybe. 😉
But Wenze is right, it's much better to do this with a load attached. Any 4-8 ohm speaker will do, as will a resistor of the same value.

 

[Arnie75]

OK, thank you very much.

 

[wwenze]

By the way what's the impedance of a speaker at switching frequency? 😀