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In Reply to: RE: Question about Sprague Vitamin Q posted by Triode_Kingdom on January 28, 2025 at 05:48:18
Here is the information my friend's gave me about this cap.
"These super JAN capacitors are designed to operate from '55 deg. C to +125 deg. C. Capacitance tolerance on these glass-to-metal seal high I-R units is plus or minus 10%. Terminals are insulated from case. Exclusive Vitamin Q impregnation means unmatched performance at high temperature." Hermetically sealed; this means 'made airtight by fusion or sealing', not that they were made by hermits. Paper dielectric is impregnated with mineral oil, aluminum foil plates, all units have plastic outer insulating tube over outer metal casing. Q's are the original paper in oil signal capacitors, developed for 'state of the art' military and scientific applications. They cost BIG BUCKS, even back in the '40s. Many D.I.Y. tube audiophiles worldwide still feel that NEW OLD STOCK Vitamin Qs are the best signal capacitors ever made. Curious? Give the Q's a spin in any good tube hi-fi or premium guitar amplifier.
2.5uF/330VAC (about 462VDC...), unusual round metal can type with two insulated solder lugs on the bottom end, circa '62, approx. 2" diameter, 2" tall."
Here is the note in the box with those Vitamin Q he has.
Follow Ups:
"Paper dielectric is impregnated with mineral oil"
PIO dielectrics are inferior in virtually every way to standard (dry) film capacitors. Guitar players love this type for the distortion they introduce into the signal path. Ask your friends about dielectric absorption.
-
What is your comment on Russian KBG-MN? It is also PIO.
which is the ODAM part from VH Audio.
I've seen oil filled parts of various kinds (paper and even Teflon) develop electrical leakage (and I've seen a few simply leak too). The electrical leakage appears as a slight Voltage on the output of the cap that you wouldn't expect to see and might have you chasing other things like grid current in a tube or some such- a mystery Voltage.
The link below is exactly such a problem.
If such parts were installed in an output section it would be no surprise if the power tubes and/or power transformer failed. IOW they can throw off the bias (of course if you checked the bias you might find there's a problem and so avoid such consequences).
Reliability is why I personally feel its a good idea to stay away from such parts.
An oil filled part as shown in the original post is sort of thing you might use for motor run or motor start capacitor. They have a 'self healing' aspect where if they arc internally they can recover if given time. This is helpful in motor start applications.
I have listened to a homebrew linestage that is probably based on the Audio Research SP-10 MKII line section and the tube supply circuitry. It has ASC Blue Line oil cap in the power supply. The output coupling cap has parallel Vitamin Q there. It sounds so good and wonderful! The midrange performance is stunning, it is so liquid and real.
I didn't say anything about how the caps sound. We've tested them a lot over the last 25 years. About half of them we tested exhibited some electrical leakage.
So IMO while your example is likely real, the question is 'for how long?'
The original Vitamin Q capacitors are quite old. I hope this isn't what you have in your line stage; I regard them as untrustworthy.
BTW, FWIW, what we've seen of coupling capacitors over the years suggests that bypassing an audio coupling capacitor is a bad move as it smears the sound (the smaller cap usually is much 'faster' than the larger cap). Better to just give it your best shot with the coupling cap and put in the best one you can get.
I just tested all 15 of these caps and none of the oil caps show any leakage at all on the Sencore LC53. Maybe I'm just lucky? The 47uf 450vdc electrolytic leaks like a sieve.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
It might simply be that we've had really bad luck.
I recently renovated an EV A20-C. It had paper and oil caps throughout; all of them were electrically leaky and one was also leaking oil (Black Beauties).
.
Have Fun and Enjoy the Music
"Still Working the Problem"
Of the caps we've tested, fully half of them exhibited some minor output Voltage where there should have been none.
The exception so far has been the ODAM caps from VH Audio.
NT
This is the picture he sent me about the caps.
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