Bias for Jolida 502 P Amplifier

The "break in" period of my Jolida was hard to quantify since it was so subtle and sounded great right out of the box. I noticed more from tube rolling, my most recent being the amazing Psvane 12AX7T-II input tubes...highly recommended. I look at the LEDs when I adjust the bias and it seems that if you turn the bias up to the point where an LED is steady and then back it off until it's almost out, this corresponds to 500mv...in my amp anyway. After that, the house current fluctuations are evident and I ignore that, although the LED blinking indicates a sign of life.

Ejman,
another important thing to remember is that the bias of a tube amp takes 30-45 minutes to settle down after switching it on. During that initial period the tube bias voltage is all over the map so you shouldn't even bother measuring it until it settles down. Hopefully you already knew this & you were measuring after atleast 45 mins....

I used to own a Jolida 502A some time back but I have forgotten what the bias voltages for the output tubes were supposed to be.

Hi Ejman

Please don't start with rolling tubes until you have spent A LOT of time with the 502P first.Definitely let it settle in.

For me I believe the red LED lights should be on all the time indicating that the amp is properly biased. Normally I turn on my system along with the 502P and I don't listen to music until all the LEDs are illuminated and steady.

Regarding tube rolling I say follow what Wolf did and not what I did. Wolf has the discipline to keep his tube set-up pretty constant while I kept swapping tubes. I've got a box of all sorts of power tubes and preamp tubes in my closet ready to swap out for the 502P. I had to write down all the combinations I could do I have that many tubes.

I found a non edgy sound with Tung Sol KT-120s, Tung Sol 12AT7 and Mullard 12AX7 re-issue. It was a bit mellow for me though.

Keep enjoying your Jolida.

Thanks guys. I've doing the adjustments after waiting about 10 minutes for the amp to warm up. (The manual says wait 5 minutes) but I think Bombaywalla's suggestion of waiting 30-45 minutes makes sense as the amp continues to warm up quite a bit over that time frame. But right now it's sounding wonderful so I think I'll just listen and smile...

FYI-upgraded tubes will yield significant improvements. I went to KT88's with great results.