Jolida 302 convrted to a 502?

I have a Jolida 302 that came trashed from shipping. I have it working fine but I'd like to up the output. The pro shops offer an upgrade that does little more than change 4 resitors and 4 tubes. Of course they are not forthcomming with that info. Can any one walk me through this? I posted once before but got no responce.
Try the Tubes forum on AA also, those guys tend not to
pay someone $700.00 for an upgrade with $10.00 in parts,
and an $80.00 quad of Super Super Select Private Reserve
Stock Russian Tubes!
I own a JoLida 502A & bought it over the 302A or B 'cuz (altho' the EL34 tubes have a magical midrange, the power o/p was unlikely to be sufficient for my needs) of the 502A power o/p.
>>"The pro shops offer an upgrade that does little more than change 4 resitors and 4 tubes. Of course they are not forthcomming with that info."

Not true! Either you are not looking diligently or you are but are discounting what they tell you. For example, see this website:
Anyone who reads this will agree that there is a ton of info on this page & that if you are handy with a soldering iron, you could look @ this page & do the mod yourself!!

Anyway, I think that the EL34 ckt can be modified to use a 6550/KT88 o/p tube. I once knew where to find this bit of info on the Response Audio website but seem to have forgotten! If you poke around the above site, you might come across it. Otherwise, email Bill Baker - he's easy to communicate with over email & quite forthcoming.

Just FYI: I tried my 502A with my 89dB efficient speakers this past weekend. Results? Bad!! The volume needed to be around 2 o'clock for reasonable listening & 3 o'clock if I really wanted a little more SPL 9' away for a favourite track. That left very little headroom for dynamics as a result the music sounded rather 2-D. Now, I do have 6550 output tubes => I probably have 45W/ch. The music would probably sound better if I used KT88 tubes. I agree here.
With my 94dB efficient speakers, the JoLida with 6550 output tubes is a pure treat! Completely different animal with a great sound. Let me add that I'm not 1 bit surprised at this outcome. One speaker being 5dB more efficient means that it demands between 3-4X less power as a result the volume control is at 9 o'clock (max)! Plenty of headroom for dynamics.
So, just confirm that the 302 or 302-converted-to-502 is the right amp for your speakers. Otherwise, you'll be wasting your money.
With the KT88 you'll get the rated 60W/ch which might or might not be enough for the type of music you listen to.
Thanks guys, hopefully someone will give me a walk through. I am running a 94db single driver speaker set up I made myself. There better than any over the counter stuff I've tried to date, with the exception of the DAli stuff. By the by, I listen to everything from Django Reinhardt to the Grateful Dead.
Thanks for the feedback Ponterio22554.
Looks like you want a walk-thru on how to change EL34 ckts to a KT88 ckt. Right?
Looks like you are handy too, which is good.
Here's what you can do to help yourself: call up JoLida & ask for the 302A or B ckt schematic. They are pretty good in honouring your request. How do I know? 'cuz I called them up & requested a 502A ckt schematic & they mailed it to me!
Once you get the 302A/B ckt schematic let me know, I can fax you the 502A ckt.
Compare the 2 & modify the 302 to a 502 i.e. convert EL34 to KT88.
Thanks, I have the schematic. Its the same with some exceptions, none of which I can recognized. Please e-mail me and with your generous help I may get through this. I'm at
well, I tried to email you off-line & I got this error message:-

554 delivery error: dd this user doesn't have a account (
Unable to deliver message to (and other recipients in the same domain).

What gives??
Its sorry