Jolida JD9 Upgrade/Mods Clarification.

[nathanjh13]

Hiya, hope all's well. I have the op amps (AD843KN) and capacitors (AMPOHM: FP-CA-1-AU) lined up for replacement in my Jolida JD9 phono stage. I've already rolled the tubes to good effect and the op amps are a doddle to change. It's the caps I'm worried about.

I've been losely following this thread:

Jolida JD-9A phono amp hybrid Magic...



Where is the left hand solder of the left hand cap connected, is it not connected above as it appears different to the pic below?




Trouble is, I can see from the pics where to solder (more or less) and I admit I'm a total newbie but with pictures like these I can get through it no problem. However, the article suggests removal of the "old capacitors", and I could do with someone double confirming which ones these are please.

There's a pic of the layout here and you can see the six op amps in the top right too.



Thanks in advance good people. Ultimately I'll then populate this page with many photo's along the way, hopefully bringing together the info from other sites (which isn't complete in any one instance, there's always the need to trawl around).

[nathanjh13]

There's a small green capacitor next to each valve (they'd be on the right of the valves as viewed in the photo above), these are doubtless the ones to remove but I thought I'd better confirm.

Incidentally, the op amp change alone has made the overall sound much cleaner and more detailed, perhaps as you'd expect with slew rates like that. It's quite a difference. However, it's brought with it a change in timbre at least in the lower frequencies as the bass seems a half step lighter in tone.

I'm hoping the caps will correct/change things further but as the op amps are part of the signal path etc I figure it's better to be as clean as possible as soon as possible then tailor the rest of the system around it (different tubes/speakers etc).

[bigdirty]

The caps your looking for are the output coupling caps. if you follow the wire from the output rca jacks you will find the proper caps to pull.

Very timely thread as I myself have just purchased and modded a JD9. I went with mundorf supreme 1.0uf for the output caps. I had 2 linear technologies LT1028acn which i put in the input position (the 2 right most in your pic). I added some jantzen crosscap 1.0uf bypass the electrolytics in the power supply.

I plan on adding two 1000uf 25v to the power supply, 2-4 more LT1028 to play with, and upgrading the resistors on the gain/loading board. I'll post some pics next time I open it up.

[nathanjh13]

Great stuff, thanks. Here are more pics for other interested parties (this is the unit with the old tubes attached, all prior to modification).

So Photo03 shows the two green caps to remove. Thanks.

[nathanjh13]

Here are the places to solder and the removed capacitor locations. I'll have a look at a few other mods you've mentioned too, thanks. Pics would be great but no prob.

[nathanjh13]

The cap change has made a significant improvement to the positives of enjoying the music, but it's also made a slight contribution to the negative. There's now a background "hiss".

It's not too bad but that's as technical as I can get, it's definitely a hiss and not a hum. Is it my lousy soldering or something else?

Thanks.

[bigdirty]

Originally Posted by nathanjh13

I have the op amps (AD843KN)

in the thread over at audiocircle there is talk of not replacing all 6 opamps with AD843KN. could this be your problem? try replacing the original opamps into the output position. ( the ones on the left in your pic above.)

If your going to open it up reflow your solder joints, and make sure the opamps are seated into the sockets securely.

good luck.

[nathanjh13]

True enough. I replaced the old op amps back in the outputs and the hiss reduced a lot, they're right when they say it's not ideal using the AD843KN in all six slots.

The sound was very sharp with them all in but a little thin, I did a bit more listening with the old ones back in and there's a nicer vbalance overall, noteably more bass 'authority' I guess is the word that seems to fit.

I'll have a look at other op amps now and maybe try the LT or BB's as an experiment.

I'm trawling around at the moment and looking at different datasheets but someone will have knocked up a quick comparison table somewhere I'm sure. The LT1028's you mentioned look pretty damn quiet though.

Thanks

[CalgaryAudio]

I am searching for information about modding my JD9 phono preamp and find the this thread has a world of info, almost too much for a beginner like myself.
I was wondering if anyone out there has created a step by step and parts list for some basic mods and would be willing to post it as a starting point for me.

Regards,

[CalgaryAudio]

I am just in the process of modding my JD9 and was wondering if you could add a list of all the mods you have done, a component list and detail the results you have had?

Regards,