Rotel Bias ...

20mA sounds a bit low to me. I'd go for at least 30mA.

Graham

**8mV across TP1 & TP3 & Across TP2 & TP4. Those are the figures for the RB970BX. (Not MkII). I'll try to locate the data pertaining to the model you have.

Trevor Wilson

If you have a distortion meter -- especially one that can show the levels of each harmonic (eg, an audio spectrum analyzer) -- you might try adjusting for the lowest distortion or the least odd-order distortion.

Thanks very much Trevor. That equates to not far off Graham's figure of

30mA, so that's where it's now set, and going back to the shop this morning - it's one of those jobs where the owner is panicking the shop for it on a daily basis. Customers, don't you just love 'em !! d;~}

Arfa

I can live with that, and 30 is pretty close to Trevor's figure (see his post).

Thanks Arfa

I do have one, but it only shows THD. I was expecting the figure to be somewhere between 20 and 50mA, and was erring on the side of caution and cool running with 20mA. It's now set for about 30 per Trevor's useful info, and heatsinks are just barely off room temp at idle. I doubt that there would be too much to be measured as a difference in THD between 20 and 30mA, and the owner probably wouldn't be able to tell the difference ... :-)

Arfa

I'd be foolish to suggest there even _might_ be an audible difference. However, the harmonic-distortion spectrum of transistor amplifiers can vary quite weirdly with bias and signal level.

**Some. I have a few clients who are like gold. Some, OTOH, I just never want to see again.

Trevor Wilson

Amen to that, Trevor !!

Arfa