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Bias for Jolida 502 P Amplifier

Just got my new Jolida 502 P yesterday and I'm enjoying it a lot - great sound! (Thanks Wolf and Jedinite for your posts re the Jolida amps) I'm surprised at the amount of bass and slam I'm getting with my Magneplanar 1.7's In fact I'm thinking that for a lot of music I probably won't even turn on my HSU sub.

On setting the bias - how important are small variations? When I got the amp I checked with my multimeter and the amp was set at about 560 mv for all tubes. Moved the bias back to 500 mv per the manual but I'm not sure if it really matters all that much for these small changes? How critical is this?
128x128ejman
jtcf's avatar
jtcf
1,589 posts
 
The higher you set the bias the shorter the tube life will be.I would leave them at 500mv for 50-100 hrs until it's settled into your system,then feel free to experiment.Some folks feel the sound is sweeter with a higher bias setting.Glad you are enjoying your new amp!
wolf_garcia
6,591 posts
 
Seriously great amp. I keep mine biased at 500mv just because it seems the amp was built around that point...with KT120s (which I've been using daily for almost 2 years and they refuse to burn out) you can supposedly bias higher, but it sounds fine at 500 so there it stays. The Jolida guys told me there's at least 50mv in each direction that is still conservatively within spec (I think the manual says that also), so there's that. I check it every couple of weeks and there is rarely much drift...10 mv maybe here and there, but my house AC is nothing special and all over the map (I do a load of wash and the LEDs on the 502 blink a little) and the amp doesn't seem to care.
jedinite24's avatar
jedinite24
1,503 posts
 
Hi Ejman

I'm glad you are enjoying the Jolida 502P. Regarding the bias I keep it around 535MV to 560MV. I do that for a couple of reasons. Around where I live the voltage from the socket fluctuates quite a bit. I think it has gone from 126 volts down to 118 volts depending on the time of day and what else is going on in my house. I don't have dedicated lines and I plug the Jolida right into the wall socket. Initially I tried to keep the bias exactly at 500MV and there were times it dipped below and the red lights on the 502P would go out or flicker. If the voltage in your home is stable I'd just keep it a bit above 500MV.

Also it may be my meter but whenever I tried to bias the Jolida to exactly 500MV I would fail. So if I was biasing it and I got it somewhat over 500MV I was happy.

Enjoy
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