[vlb]

Hi
 
I have an Audio research D250, its a wonderfull amp even though it eats a fortune of tubes and produce to much heat to be used in the summer.
I have changed all the tubes and have done all the adjustments except "Ac balance" and now I need your help.
 
The manual says I should measure  thd or thd+noise when driving a 16ohm load with 10W @1khz and then adjust it for >0.005% THD or 0.02% THD+Noise.
 
I have 4x 4ohm 5W resistors to get the 16ohm load, and I can generate a 1khz signal with my dac, But what kind of intrument do I need to measurre thd or thd+N?
 
Thanks

 

[Avro_Arrow]

Does this help?

 

[Avro_Arrow]

Here is a good website I found.
Looks like they have lots of interesting stuff.

 

[amb]

The most inexpensive (and quite effective) way to do this is to use a good pro-grade computer sound card and RMAA software.  The key is your choice of sound card -- it needs to have lower noise and distortion than the amp you're trying to measure, or you'd just be measuring the sound card itself.

 

[vlb]

Thanks!
Ive tried using the soundcard (xf-fi) but it doesent go as low as >0.005% THD at least not with the software I tried. But ill try the software you suggested.