Jolida JD-9 Upgrade

If one wants to go down the DIY Route, then taking time to learn the methods for testing the Components for their values will be the way to go.

Heat, Humidity and the Breakdown or aging of materials used for the the assembly are all factors usually considered. Even a Solder Joint has a limited life?    

Have a look at Tutorials covering Basic Component Fault Finding. 

As a strong suggestion and an option that was not available at the time of original ownership, as an addition to any work being undertaken.

Replacing the RCA's on Both Chassis (Phon' and Pre'), as well as the Cable Terminations, to a Low Eddy Design, is an expense will worthwhile of incurring. If done as a DIY activity the cost is not too much.

Additionally using a PC Triple C wire for the Signal Path within the Phon' can also add real time benefits to the sonic. Add the PC Triple C Wire to the Interconnects using the Low Eddy RCA's and the sonic might just jump to a night / day betterment.

Phon's I have been very used to experiencing and very impressed with, have been taken to another level with the above suggestion adopted for the Signal Path.

My wish today is to hear PC Triple C used for a Cart's Coil and a SUT, I have heard it in use for every other role where Wire is to be used, and its presence is always perceived as a betterment       

First thing is if you've been running the same tubes for 20 years then they probably need replacement. There are lots of options for 12AX7s - I really liked the Sovtek 12AX7LPS. Low noise, readily available, sound great.

I did all my own upgrades on my JD-9, and they're easy to do. It's possible your output caps have deteriorated in 20 years, but they don't get stressed much in the JD-9 so they're likely fine. I replaced my OEM caps with Jupiter Beeswax and it made a noticeable improvement. Again, there are many choices.

Opamps might fail but don't wear out. I originally installed the Burr-Brown (OPA627) op amps and they were better than the OEM but not dramatically. The big change came when I bought 6 Burson V5i on sale; they were majorly better.

If you can solder, you can easily DIY all these changes. Good luck!

@armstrod Burson V5i sounds interesting.  Does the JD-9 take single or dual version?  Thanks

All triode tube units will present a capacitance at the input, if the gain stage is a simple common cathode topology. This is due to capacitance between the anode and grid, primarily, and to a lesser capacitance between the grid and cathode. This is called Miller capacitance. The 12AX7 has very high miller capacitance owing to its high gain factor. So add 50 to 100pF to whatever you think is cable capacitance. A cascode at the input avoids miller capacitance, but usually you won’t have a 12AX7 in a cascode. Transistors and op amps exhibit a similar phenomenon.

Thanks for the advice.  The tubes get replaced regularly.  I'll look into the caps and opamps.