Poweramp is outputting constant voltage at terminals.

Hi I have a technical question.

I recently got two mono amps (ADE HSA 300) and one of them doesn't output music. Instead it outputs a constant DC voltage. One of the MOSFETS gets extremely hot within 1-minute after turning on the unit. It is only plugged into power and there are no external signals connected (neither RCA or XLR) and it still outputs the constant voltage.

I took a look inside to see if there are any burnt marks or burnt smell but there isn't.

What could it possibly be?

They are both the same type of amp. They are old (around 30ish years) and the working one sounds absolutely amazing.

Thx in advance. If you need further details, let me know :)


2005-10-04 6:14 pm
I suspect the amplifier to have shorted transistors. You need to review the schematic diagram, and check all the transistors, diodes, resistors and capacitors which are associated with that channel. Since amplifiers are DC coupled, one bad transistor often means a lot of others are also bad, so be thorough testing all the parts.


2018-04-17 6:50 pm
Information on these monoblocks appears to be sparse, but here's a photo of the suspects in case it jogs anyone's memory.


  • ADE HSA 300.jpg
    ADE HSA 300.jpg
    205.7 KB · Views: 58
I took a look inside to see if there are any burnt marks or burnt smell but there isn't.
Sadly our natural senses are deaf/blind to Electrical parameters (resistance - capacitance - voltage - signal level - inductance - etc.) so specialized instruments were developed to detect and, most important, measure them.
Sight/sound/smell can not detect 99.99% of problems, except GROSS ones such as sparking/smoking/catching fire/cracking/exploding.

Combine that to not knowing how the circuit works and both lead straight to a tech who is both trained and equipped to solve your problem.