There is music...but high DC offset >.<

[longitude]

Just finish amp9-basic,
All channels are OK with music.
However, only one of them with under 10mV DC offset,
others are 45mV, 86mV and 141mV !!!
I took the input diodes out off the PCB.
Still got the same DC offsets.
I close the jumper to operate in class T mode,
Still got the same DC offsets...

Don't know why,
Any suggestion?
Thank you~

[omishra]

It seems OK. I read somewhere anything below 150mV is OK.
BTW, how you mute and unmute the board? It does some offset adjust while unmuting.

Look at this -&gt;

quote:AUTOMATIC OUTPUT OFFSET VOLTAGE CORRECTION
The TAA4100A contains an automatic DC calibration routine that reduces the output offset voltage to a maximum of 25mV when the device is active (mute off). Please note that the DC calibration is done on the transition of MUTEB from low to high. The entire calibration sequence takes approximately 6mS after the MUTEB pin is pulled high.

Also measure it while input pins are grounded.

[V-bro]

It's nothing to worry about.

Did you use any load on the outputs? You should, a speaker or resistor is fine... Did you short the inputs to ground like Omishra said? You should, otherwise the auto offset adjustment can go wild on start-up.

------X-max. can be several meters on any driver, too bad it can be done only once...------

[longitude]

I found that the amp should be muted by default.
Once it unmute the volatge is fine.
Juit one channel is 16mV which is larger than 10mV.

I always defaltly unmute my amp, just control it by the power swith.
They are OK in amp4, amp11 and amp32ps,
Seems that amp9 have different design.

BTW, if I want to operate the amp9basic in T-mode not AM-mode,
I should close the jumper of AM-mode, right?

[omishra]

quote:Originally posted by longitude
BTW, if I want to operate the amp9basic in T-mode not AM-mode,
I should close the jumper of AM-mode, right?

Yes. To use AMP9-BASIC in Class-T mode, you have to short that J2 AM pins by using a jumper

[Scratchy]

BTW, you WILL ruin the chip if you close this jumper with the power applied.
Always remove the power and discharge the amp, before touching the AM mode jumper.

***It's so easy, everyone should be doing it***

[V-bro]

quote:Originally posted by Scratchy

BTW, you WILL ruin the chip if you close this jumper with the power applied.
Always remove the power and discharge the amp, before touching the AM mode jumper.

***It's so easy, everyone should be doing it***

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

Good one Scratchy!!!

I can't stress this more often, I think Jan should have designed a 0 ohms resistor footprint parallel to the jumper so you can't make any mistake with this if you are unaware of the functioning....

------X-max. can be several meters on any driver, too bad it can be done only once...------