Need help with basic electrical stuff

Black on the ground of any input jack, red to red speaker output. Amp should be on. 

Check the DC voltage at the speaker output related to GND (e.g. XLR Pin1)

I think the designer wants you to measure the DC voltage of speaker binding posts to ground.

1. Turn on the amplifier, let it warm up about 15 minutes.
2. Set the digital multi-meter to DC voltage auto range setting.
3. Insert the positive probe into the "+" speaker binding post, place the negative probe on the outer metal ring of any RCA socket, and record the reading, please note that readings may be negative. (I do not recommend placing the negative probe on XLR socket pin 1 to avoid accidentally shorting the probe to other pins and causing more damage.)
4. Insert the positive probe into the "-" speaker binding post and place the negative probe on the outer metal ring of any RCA socket, record the reading, please note that the reading may be negative.
5. repeat step 3 and 4 on another channel.

Hope this helps.

Ty guys. Much appreciated!

@imhififan 

For the black speaker terminal I got -0.05 volt. For the red speaker terminal I couldn't get a reading, it was 0 most of the time. Is this normal?

Not sure if this helps but when checking the Hafler amps, one of the checks is DC offset at the speaker outputs. Put the positive meter lead on positive, negative on the negative meter on millivolt or volt settings. Usually the desired number is less than 100mv +\- .
 

Maybe that’s the information they are seeking? 
 

Refer to the Hafler amplifier DH-200 or DH-220 manual which is available online for free. 

@samureyex 

Without a service manual or schematic for your amp, I don't know if this is normal.

I think you should check with the designer and see what he says.

@imhififan Good idea. Unfortunately the designer seems like he's in a very busy phase. it can take many days for him to respond. 

Regarding if the value is normal. I'm also unsure. The designer has said his amp is neither class A nor AB nor D nor H. He said it's a kind of its own so who knows what's normal or not. What I can say is when the amp turns on, it counts from 10 to 0 until it full engage in. 

I just thought a 0 on the + terminal would mean something.