If I decided to recap by L-65A Jubals, who makes a 13.5µf cap? Most makers on Parts Express seem to jump from 12.0 to 15.0. Any ideas?
If I decided to recap by L-65A Jubals, who makes a 13.5µf cap? Most makers on Parts Express seem to jump from 12.0 to 15.0. Any ideas?
put two standard value caps in parallel, in place of the original.
the values sum (e.g, 12uF + 1.5uF).
The reason the caps jump in value is because the tolerance is low -- probably 10%. 1.2x and 1.5x are standard multipliers for 10% tolerance components.
12uF could be anywhere from 10.8uF to 13.2uF.
15uF could be anywhere from 13.5uF to 16.5uF.
It would be pointless to produce a 10% 13.5uF cap, because its range would overlap with its neighbors. Sorry if this explanation doesn't make sense, here's a link that goes into more detail. It's written for resistors, but the same thing applies to capacitors:
http://www.pc-control.co.uk/resistor-eia.htm
If you really want a 13.5uF cap, you should find someone who stocks them in a higher tolerance. If you don't care about the precision, just choose the next closest value, or sum two smaller caps like Grumpy said.
Try Newark or Digi-Key.
http://www.newark.com/30M8915/non-st...equestid=23130
hey, ive been thru this recently ( upgrading the stock 4430 to MKP) very good deal here on the sweden EVOX-RIFA caps:
http://stores.ebay.com/AudioTek-Shop...QQftidZ2QQtZkm
im still lookin for 0.01 bypass caps, I can source some audionote teflon for basically free though.
The Altec 19 XOs used a 21uF cap but I can only find replacments in 20 or 22uF.
I think either is close enough but am not the expert here by a long shot.
My question goes more to back in the day, is it possible Altec decided upon the 21uF simply because that was what they had available at that time?
Gary
hi , you can just wire caps in parallel, like 3x 6.8 + 0.47 would be pretty close IMHO, though watch out for tolerance readings, the EVOX ones I shown are within 5% of their given micro farad value . Paralleled caps have lower ESR (resistance) value than a single one, now this is where my knowledge stops, what ESR these old mylar / polyester caps had. Parallel MKP is obviously the cheap way, boutique large values are waay overpriced imho.
This is some what of a common practice in better XOs.
In general you would 10% of the total capacitance in a smaller cap in parallel with the larger one.
Large value caps are layers of metal rolled up to get the desired value the can be some inductive loss at high frequencies, buy putting a smaller cap to bypass the bigger one this can reduce the inductive effect. John
.. what in the end could make a funny unintended high-Q Inductance/Capacitance-resonator. I would like to insinuate that common audio knowledge may be quite missleading when it comes to electrical engineering.
As far as I know salable film capacitors rated from 0,1mu up to 220mu will behave near to ideal with audiofrequencies, R.dc << 0,1Ohm, L.ser << 1mikroHenry, nonlinearities (if any) well below 0,01%.
BTW: I personally don't understand why JBL as a reputable sort of institution came to the idea to "bias" film capacitors ... .
Best Regards
Ed Meitner mentioned it to Greg and Greg tried it. He was stunned at the results. I was skeptical but tried it as well. I was quite impressed at the results. Insinuating that Greg is disreputable only serves to make me cranky. I can tell you one thing for certain, Greg is really sick and tired of discussing it at this point. Did I stress the sick and tired part enough? Do what you want with your gear and he'll do what he wants with his and that includes his loudspeaker designs at JBL. I can also tell you that I don't have time to screw around and if I thought I could save time by not biasing my capacitors I'd be all over it. Hopefully that helps you understand?
If not you can read through the links found in this link:
Biased Capacitors aka Charge Coupled Capacitors
This thread was done at post number two.
O/k, I've had read the related pages before. For honest! I really thought it over and over again. But from these pages there is absolutely no evidence for a benefit from biased film capacitors. It seems to be an excessive speculation. The analogy to amplifier topology (class A vs. B) is rather a persuation than an explanation.
If there was an effect as stated a stunning simple measurent would disclose it: the distortion at lower levels would both increase tremendously by absolute amount and not at least its spectrum would give a signature that can't be overlooked even at diminishing levels. You may measure anything directly at the caps as to avoid contamination by the acoustics.
But - You just guess it right, the opposite is true: even with very poor electrolytic caps the lower the level the lower the distortions go. With film types You won't see any crossover (sic!) distorsions no matter how far You go down close to thermodynamic limits of random noise (-130dB). Consequently the pages omit any graphs on that topic or even a simple single number. In spite of this application area would be very very revolutionary!
edit: think of capacitors in microphones, mixing consoles, nearly anywhere in audio. Much lower levels (charge wise), relative more crossover, more distortion, less pleasing right from the start?
To believe in what the paper says does mean to believe that there is the fabulous something that can't be measured but only heard. The most the more it should be hidden by surrounding circumstances. In so far everybody is free to find his own luck. My hearing ain't impressive - that for the affinity to louder speakers? - but I'm happy.
With posting #x ("some inductive loss at high frequencies") the thread reiterated common wisdom in that capacitors where mythical gremlins which one hardly can get under control. Surely they'll break out again, when the next disbelief is on its way: "Does it sound really right?"
I felt free to give the advice to think all that urban ledgends over. You won't challenge that electrical engineering grounds on rational arguments. If so, why not use terms as "inductance" etc as they are intended? Namely as quantities that can be calculated with. Give it a try. There is no use in all that talking without a basic understanding of proportions. What is of paramount importance and what can be omited simply due to its diminishing numbers?
No offense!
edit 2: This reading would tell the story to the end (I hope so) => http://www.aes.org/e-lib/browse.cfm?elib=5175
Last edited by mini; 11-26-2008 at 10:11 AM. Reason: completion II
I think your desire for measurement confirmation of a technical idea is certainly acceptable, but your assumption that a phenomenon does not exist unless you can measure it is not.
My question is--have you aurally compared charge-coupled vs. non charge-coupled versions of the same speaker? If you have not done this, those who have are far more informed on this question than you are, no matter how much electrical engineering you know. Your theoretical objection to someone else's experience is just absurd.
David
I would pass your concerns on to Greg but he honestly doesn't care. Seriously. He just doesn't. He's heard it all before and he has far bigger fish to fry.
More importantly, it really doesn't have anything to do with you unless you are having a problem with your JBL loudspeaker systems and you suspect your biased capacitors are at fault.
I really don't know what else to tell you. It's a deadend discussion.
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