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In Reply to: RE: upgrades to output supplies posted by Banat on April 16, 2014 at 15:45:58
Banat, It's very interesting that you mention "photoflash" capacitors. I was privileged to know Julius Futterman toward the end of his life, and he had discovered the benefits of such capacitors for use as coupling caps in his circuit. I could easily hear the improvement that they wrought in a Futterman amplifier. But the Futtermans were further improved by bypassing the output capacitors with film caps. However, I do take your point that the film bypass capacitors are only helping the treble, usually. And conversely, the transient energy demands are less at high frequencies (at least I think so), so the bypass caps can only go so far.
I had assumed that Photoflash caps of those days were now supplanted by the latest best electrolytics from Nichicon, Panasonic, etc. (In my mind, maybe because there is no demand for large size flash guns as light sources in modern photography.) One no longer sees that term in print on websites like Mouser and Digikey, in the US, which is where I usually buy my electrolytics. As I have mentioned here before, I perceived a benefit by paralleling bunches of smaller value Panasonic TS-ED caps as a substitute for single high value capacitors. The decision after that is whether to bypass and what value to use as bypass. Higher value film caps that fit into the chassis will tend to be metallized film, rather than true film and foil, so that's another trade-off. (Large metallized film caps don't necessarily sound better to me than very good electrolytics.)
Follow Ups:
Lew
I`m sure that Mr.J. Futterman was know very well specific reasons why hi choose just Photo Flash capacitors type for output power coupling cap in his OTL Amps ! , but in the same time I must say that even Photo Flash caps have some finite electric performance ( ESR,ESL ...) so it is not big surprise for me that bypassing that PF cap with relative smaller value of film cap overall Amp sonic performance was increased even more , as is expected mostly in treble range .
Yes PF caps are very rare today as offer in electronics free market places , personally I have impression that they are mass produced even today , but mostly sold on different industries , and used for power laser PSU`s , rail guns and who knows where else , but not to much for photo flash guns any more .
Your tactic of paralleling many smaller Panasonic caps instead of one big cap is very good ! , since that method lower overall filter cap ESR , ESL ... , I would say in that way of connection it `speed up` stored DC E energy delivering on to OTL Circlotron OPS circuit .BTW , I was use Siemens 3100uF/360VDC PF caps in some of my earlier OTL Circlotron Amps with great success , i have eight more left for my new pair of Amps , they are pretty old but in perfect electric condition , they will be connected as last C member in CRC based PSU filter , first one C will be standard Mallory 2000uF/200VDC/85C. caps ,
here is the picture of this Siemens PF caps together with one 6c33c tube secured in the associated socket , only for better physical dimension comparison .
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Enlightened Evolution-Astral Projection
Edits: 04/19/14 04/21/14 04/22/14
Mallory 2200uF/200VDC/85C. cap............
I have 16ea setaside for my OTLs......i have 6ea in my Diyed MA1s.........sound great...vary good bass...........i tryed the smaller caps..i like biger caps....just saying.... sound better to me.
As I have mentioned, I use Panasonic TS-ED, 2200uF/200V/85 degrees C. I have 14 per monoblock. Seven per phase in each monoblock.
Well, now comes the fun part.
I will listen to my present setup for a week. I will play the same albums each night so I etch the sound into my feeble mind.
I will measure the midrange's output with my speaker measuring equipment. I will do this both before and after swapping out the caps (quantitative vs qualitative).
A small edit from a previous post. The HC+, 22000uF 250V 85C caps are 369Euros each, yikes!!!!!, I sure hope this was worth it.
-they do work well, but they don't last very long. They don't do well with ripple current or a little heat. An 85 degrees Centigrade -rated cap will last for years in our amps but photoflashes can die in a period of months.
Also its been my experience that there is no ideal value for the supplies. The larger the better, but there is a point where doubling the capacitance continues to get greater results, but they are diminished, while also making the circuit impractical due to size, cost, survivability of rectifiers and switches, that sort of thing. As it is if we put the Power Supply Boost option in the MA-1, we have to also install 35 Amp rectifiers to survive the inrush current.
Lew
One way i have got a sweeter sound out of the Circlotron.....with polproplen caps was to take 4ea.... 4-6mf 630v an put them on each leg of the outputs + an - to ground......right at the 600ohm res.go to ground...
an then like most of us .....put 2mf foil caps on the diode bridgs that feed the big caps in the PS.....
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