| seventenths |
Hi all,
While working on a GC and digging thru my rapidly growing parts, bin I found a couple of caps that are labeled "photo". These are 120mfd @ 330V.
Are these useful in audio circuits?
TIA
7/10 |
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| Conrad Hoffman |
| Photoflash caps are designed for high discharge rates, and I've seen admonishments not to use them for regular cap service. I don't know why not, as they seem to perform the same as a conventional cap of the same value and voltage. Anybody know of a reason to avoid them? |
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| FastEddy |
| An example: http://www.capacitorindustries.com/web/CD17S.htm ... note that these "photo flash" types are special purpose electrolytic capacitors and may be of only slight value for DIY audio ... but experimentation may be in order. :smash: |
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| seventenths |
Conrad & F-Eddy,
Thanks for the replies...
In an effort to keep moving forward, I've left a terminal strip in the PSU section to facilitate easy CAP experimentation. I will
:smash: er-uhhhh ...test them
Onward,
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| Poindexter |
Seven, what I've heard is that in normal service photoflash caps are charged all the way up, then completely discharged; this once a minute or so, episodically. They are designed and constructed uniquely for this odd sort of service. Put in a power supply, where they are charged most of the way up and then partially discharged and recharged sixty times a second, their service life will be very short.
If you're looking for very good, very economical electrolytic caps, have a look at Panasonic ED, TSHA, TSHB at Digi-Key. I have found nothing better, and I have A-B'd them with the heavy hitters.
Aloha
Poinz |
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| seventenths |
Mahalo P-Dexter,
Seeing your location makes me think I should fly out for a personal A-B test :D
I'll follow your advice on my next order... I have a handful of chips and a Big trafo, but still need to decide on a project. Hmmmmmm
Aloha
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| juergenk |
| hm, I find the values to small to be useful in a chipamp design |
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| seventenths |
... mine are; 120mfd 350v.
Maybe I'll make a flash;)
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| juergenk |
| yes, with 120uF/350V you can't do much exept flashes |
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| Poindexter |
Juergen,
How big are you guys using? The original schems I've seen are calling for about 1KuF as the last tank, which looks pretty small to me. 18v into an 8 ohm load is 3 amps, which is going to drain a thousand mic cap pretty quickly.
Aloha,
Poinz |
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| juergenk |
I'm currently using 1000u at the amplifier board and 10000u as charging capacitor after the rectifier
regards
Juergen |
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| lineup |
| quote: | Originally posted by juergenk
I'm currently using 1000u at the amplifier board and 10000u as charging capacitor after the rectifier
regards
Juergen |
might do for you
a bit too much for a simple chip amp
in my book
of course for heavy metal music :rolleyes: we may need 20mF!!!
PS. It is NOT anything bad with high voltage rating for caps
In fact, it is good when a cap can take 200-1000 Volts
- a sign of quality. This is true for example for Polypropylene, 2.2 -10uF = input capacitors.
But for electrolytics, power Supply Caps, higher voltage means BIGGER & More Expensive.
So a waste of space and your money.
If a power Supply Cap is rated 10-20 volt above the V+ it is most cases good enough.
For a +/- 40 VDC rectifier bridge (4 diodes) supply
we can use for example 4.700uF/ 50VDC or 4.700uF 63VDC.
Regards lineup :) |
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| Zen Mod |
I remember ads from old periodics where Croft mentioned using photo elcos in his best models of preamps;
I have no intention to say that photo caps are better or worse than some "audio" grade ones.......but I really can't imagine worst scenario for one cap use than heavy discharging.......... charging and discharging it 100 or 120 times/sec in ordinary PSU must be piece of cake .........or easy task for them....... |
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