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In Reply to: a solution posted by Dave Cigna on February 27, 2007 at 13:52:06:
I shudder to think that this whole thread has been about nothing. Look at the date of the John Curl article, 1978. I remember the first preamp manufactured by the David Hafler Co., the DH 101. All the output caps at the line and phono stage were two SERIES connected 22uf/16V tantalum caps giving an overall value of 11uf. That preamp was put out around 1979. It got rave reviews. I thought it sounded kind of...'zippy'. The fix to that was very simple, though, you just replace the tantalum caps with film caps. It may be that Cheap-Jack will try to put electrolytic caps back in the signal path, but I don't believe that he will do it for very long. They just don't sound very good.
Follow Ups:
Hi.Time bears no reference to physics. LPs are over 100 years old & still my most favourtie music programme media.
That's exactly what John Curl suggested in his paper: "back-to-back coupling or nonpolar tantalums will reduce this distortion".
So you've heard Hafler's preamp & you found it sound "zippy".
IMO, it would be some design achievement back then considering people were still in the vintage sounding era, "zippy" would be some very contemporary sonic quality to them.Good guess, if it does not sound right, I will surely toss it out INSTANTLY. To me, sound come first, always. Period.
Technically, parallel reversed caps, oil on paper, film or 'lytic regardless, is always better than back-to-back caps due to the the LCR network structure of a practical capacitor.
As I posted before, parallel caps will reduce the caps total DCR,
self inductance, dielectric loss R, insulation loss Rin. It is a win win situation provided that, of course, the DC issue can be resolved as in the sticky case of a polar 'lytic cap.Hence my posts.
c-J
PS: David Haflter has patented hundreds of his audio designs. He is somebody audio indeed.
JackI do like the present incarnation of my Hafler DH 101. It has been running in my living room now for 23 years, 24 hours a day, 7 days a week barring unscheduled breaks by the local power company. It sounds fine to me.
I think it may be difficult to lift John Curl's article out of it's historical context. I believe that tantalum caps will have lower distortion than the industry standard for the low impedance transistor ciruits of that era, the aluminum electrolytic cap. Aluminum eletrolytic caps don't do very well above 500-1,000hz. Tantalum caps will do much better than that, but it is a hard sound. One of the advantages of tube electronics over transistor electronics is the effortlessness of sound reproduction above 1,000hz. Transistor circuits may test well above 1,000hz, but they always sound as if they are working very hard in the higher frequencies. That's what I meant by a 'zippy' sound to the stock DH 101. Replacement of the tantalum caps by similar valued film caps removed that 'zippy' sound.
You can try bipolar tantalum caps in your PC application, but I think you may find that even by parallelling 1uf/50V mylar caps from Digikey will produce a more neutral sound with a composite which will still fit in your enclosure.
Hi.Yes, that's why I already replaced all those throw-me-up mini cans with those nice-looking inverted-pearl-shaped tiny tant caps in all my SS & tube projects recently given no other feasible alternatives.
In fact for my current SS phonostage upgrade, I have decided to replace the orginal cheapie 4.7uF mini cans RIAA I/P coupling cap with two 2uF100V PP film caps, ying-yang parallel. With their pretty small size, I can still manage to squeeze them onto the PCB.
Somehow I find PP film sounds better than those historic mylar stuffs. Of course, sonic is so subjective.
c-J
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