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Hello,I'd like to know how to reduce the gain in my Jolida JD9. I tried several searches on the subject but all I find is information on substituting the 12AX7's with 12AU7's or 5751's. I'm more interested in cutting the SS gain stage by a third. Anyone done this type of mod?
Thanks for any information or leads!
Tom
Edits: 11/30/16Follow Ups:
Solder a 100k tantalum resistor to the RCA input "hot" then on to the "hot" input wire; solder a 10k metal oxide or carbon comp to the RCA input ground and on to the ground input wire.
See what that does and adjust accordingly if necessary. More attenuation change the 10k to 5k or simply solder another 10k in parallel with the first. Less attenuation leave the ground 10k and lower the value of the 100k.
There's too much made of negative effects of attenuation circuits. You're speakers likely have them and I've never noticed any loss of dynamics or other ill effects in a amps or pre-amps. Just lowered gain.
When you say RCA input "hot" are you meaning the high output RCA connection (to the integrated amp) or the actual RCA input connection (from the turntable)? Please forgive my electronics ignorance, I'm just wanting to be sure when I consult a local soldering mentor.
Thanks!
Tom
Hi, kitch29,
Thank you for the suggestions.
I find your comment on attenuation circuits interesting: "There's too much made of negative effects of attenuation circuits. "
From what I've seen posted regarding the JD9's gain attenuation, it relies on trim pots for the "LO" output connection. And those trim pots seem to be consistently criticized by audiophiles posting on a number of forums. But there are people like yourself who consider the trim pots to be a non-issue.
I'm still on the fence; I cannot say for certainty that I notice much (if any) difference using the attenuated output. The problem is that it's very difficult to compare between the "HI" and "LO" settings with the same cartridge, at least with the cartridges I'm currently using; the "HI" output overloads the cartridge and degrades the sound. So I guess the obvious answer is that the "LO" output sounds better. '-)
Regards,
Tom
Don't confuse very high quality resistor circuits with IC or even discrete pots and especially L-Pads.
Edits: 11/30/16
Point taken. :-)
The manual makes no sense to me when it comes to which outputs to use and the dip switch settings. I found the chart posted here a while back to be very helpful when installing a new cart.
Hi, dean_martin,
That chart is something I posted years ago. I have an updated version posted in my gallery.
I want to reduce the overall gain so I don't have to rely on the attenuated low output connections. If I can reduce gain by a third then the high output gain settings would become: ~37, 47, 57, and 64 dB. Perfect.
Regards,
Tom
Sorry I didn't remember. I'll look for the updated version.
Good luck with your project. Sounds like a worthwhile pursuit. Sorry I couldn't help out. I think I'm experiencing too much gain for my new lo cart.
You're welcome! It's gotten a lot of use over the years and I'm glad to see it's still of value.
I kept the JD9 because I consider it to be a fine sounding phono stage, especially for the $450 I paid for it. But the gain is more than I need for any of the cartridges I use. It's currently set up with a Goldring 1012GX and sounds fantastic. But I'm having to run it through the "LO" output connections at ~35 dB of gain. I'd like to be able to run everything through the "HI" output connections.
I'll post any leads I find in my search for a solution.
Regards,
Tom
dean_martin is correct about the manual, use the switch chart he provided. If you use the Lo Output RCA jacks and adjust gain using the setting switches, you should be able to reduce the output.
Easiest (imo) would be to insert a pot into the the output RCAs.
Then adjust them 'till you have the level you desire.
At which point one could meter the Pot position ohmage.
Remove the pots and fit appropriate value wee resistors into the centre of the RCA plugs.
DO! label the resultant modded interconnects though :-0
Edits: 11/30/16
Hi, bare,
Your suggestion is similar to kitch29 's so maybe there's hope. But I was thinking that maybe the gain could be reduced without resorting to attenuation. (Refer to my comment to kitch29 .)
Regards,
Tom
I'm not really an op-amp guy but it looks like you can't mess with IC2 or IC3 without getting into the RIAA EQ.
You could change the amount of FB on IC1. Change the relationship between R2 and R3. I'm not sure what you would have to do with C3 to keep things "right".
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Hi, Tre',
Thanks for the reply. I was hoping that there's a relatively easy modification to reduce gain but I shouldn't be too optimistic. I'll probably have to do some trial-and-error web searches to see if I can find anything.
Regards,
Tom
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