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Duelund JAM paper in oil , Cu foil Capacitors as coupling caps on Tube Amp
Duelund JAM paper in oil , Cu foil Capacitors as coupling caps on Tube Amp
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Old 2nd April 2020, 07:01 AM   #1
Radni is offline Radni  India
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Default Duelund JAM paper in oil , Cu foil Capacitors as coupling caps on Tube Amp

On my tube amp from Cary Audio, I have been happily enjoying sound of Jensen Paper in Oil , Copper foil, Alu Case capacitors ( value 0.22 / 630 VDC ) as coupling caps. I like its lush , liquid sound, not harsh. As they are 9 years in use now, I may need to replace them soon. I just found that Jensen has stopped production so was considering a good replacement to match the sound. I get option of Duelund JAM paper in oil , Cu foil Capacitors which are at present available at good price . I like to know if anyone here has used these caps as coupling caps and how is the experience. What change in sound can I expect going from Jensen PIO caps to Duelund JAM PIO caps?
Or does anyone have other recommendations for substitute of Jensen PIO caps?
My amp has a small chassis, hence may be difficult to put large caps.
Your views, comments , suggestions are welcome.
Thanks
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Old 2nd April 2020, 07:18 AM   #2
6A3sUMMER is offline 6A3sUMMER  United States
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I do not know if your amplifier uses fixed adjustable bias, or self bias.

For output stages that use self bias, it is easy to check the coupling caps for one problem that can arise . . . they start to be leaky.
Check the voltage on the grid leak resistor.
V / Ohms = current.
That current is only from 2 sources, either the coupling cap, or the tube is gassy.
I even find brand new caps that are leaky.

Some amplifier designers use a cap that is rated with enough voltage to work when the amp is up and running, but not work at power-up with B+ voltage high (output tubes not yet conducting current, and driver tubes not yet conducting current). The capacitor gets this high B+, and the other end is connected to the grid resistor to ground.
Not good!
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Old 2nd April 2020, 01:41 PM   #3
Salectric is offline Salectric  United States
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Roughly 15-20 years ago Jensen caps had a bad reputation for leaking voltage after a few years. I installed Jensens in my Cary 40M amps around 2003 and two of the caps failed within the next couple years. Based on that I would be very cautious about Jensen couplers. However I seem to recall Jensen addresses the problem sometime after my experience so later versions may not have the same risk of failure. You say yours are 9 years old so they may be the newer version.

In any case, if I were you I would replace the Jensens just to be on the safe side. I would use Audio Note copper foils. They may cost a bit more but they are worth it, and they should be very reliable.
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Old 2nd April 2020, 03:49 PM   #4
Radni is offline Radni  India
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Salectric,
Thank you for your suggestion. My tube amp had upgraded Jensen oil caps fitted by Cary when amp was bought, they were 0.22/630 v , then after few years two of them went bad (leaked?) so Cary suggested to replace all four. I got all four new Jensen PIO 0.22/1000 V on it by Cary. Now after about 9 years of use, I just apprehend they may fail someday. So looked up to buy Jensen PIO caps , only to learn they are mostly out of stock. So was offered to consider Duelund JAM ( also manufactured by Jensen) PIO caps, and price is good at $47 each.
I see Audio Note copper foil , Mylar in Oil cap , offered at $ 53 each. I am not aware of difference in sound characteristics of paper in oil versus Mylar in oil. Can you help me to understated? Alternatively, what would you choose between Duelund JAM and Audio Note Mylar in oil? ( Price difference being small, it is not an issue here).
Thanks

Last edited by Radni; 2nd April 2020 at 03:52 PM.
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Old 2nd April 2020, 04:19 PM   #5
swich401 is offline swich401  Canada
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Miflex KPCU 0.22uF copper paper in oil - $22 each and highly rated.
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Old 2nd April 2020, 07:15 PM   #6
mctavish is offline mctavish  Austria
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I like Mundorf Zinc foil.....
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Old 2nd April 2020, 09:02 PM   #7
Salectric is offline Salectric  United States
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Radni, Everybody has their own opinions when it comes to coupling caps. I recommended the Audio Note Copper foil caps because they have a similar tonal balance to the Jensen caps but with more detail and they are reliable. At the price they are a real bargain in my opinion. I haven’t tried Duelund JAM but I have tried 4 different Duelund CAST values (much more expensive) and did not like them at all. They are not as natural sounding as the AN Copper. I also don’t recommend the lower priced Audio Note aluminum caps; the copper model is one with the mojo.
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Old 3rd April 2020, 05:17 AM   #8
Radni is offline Radni  India
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Thanks all for your inputs.
I liked the tonal balance of Jensen PIO, and wish to broadly retain it. That's one reason I like to go in favor of AN Cu foil, besides its coming in Copper case. My current Jensen are Cu foil in Alu case, so I expect some change for better. AN is smaller in size than JAM, which is very helpful considering the smaller Chassis. On reliability, I like to trust AN this time better than Jensen( which also made Duelund JAM at its facility , so I learn ).
I will go for AN copper foil in copper case.
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Old 3rd April 2020, 05:50 AM   #9
aardvarkash10 is offline aardvarkash10  New Zealand
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trying to imagine heart surgeons sitting around discussing which caps they prefer in their heart monitors to improve the soundstage and presence of the signal...

Nope, can't do it because the don't.

Not saying you won't enjoy what ever component you settle on. Just putting the idea here as a thought.
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Old 3rd April 2020, 06:55 AM   #10
Kay Pirinha is offline Kay Pirinha  Germany
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For 0.22 µF/630 Vdc coupling caps I prefer these: MKP4J032204J00KF00 WIMA | Mouser. Why? Because the manufacturer is specialized in high quality and reliable industrial products that don't need to be decorated with audiophoolish babble.
Best regards!
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