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Old 13th February 2012, 07:12 PM   #21
Kei is offline Kei  Wales
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Spent some more time today looking at various capacitors for the psu filtration. I've come up with a few different options. I've listed them in order of their total cost:

4x 18000uF 100V united chemi-con ESR = 0.0123Ω Ripple = 17.4A

12x 5600uF 100V united chemi-con ESR = 0.003Ω Ripple = 8.3A

4x 15,000uF 100V Evox Rifa ESR = 0.017Ω Ripple = 17.3A

4x 22000uF 100V BHC ESR = 0.013Ω Ripple = 18.4A


I've also been wondering if having the transformers stacked is better, worse or indifferent to having them separated. (together like they are here) These are the rough designs i've come up with based on the various capacitor combinations.

12x 5600uF with the transformers apart.
Click the image to open in full size.

12x 5600uF with the transformers stacked.
Click the image to open in full size.

4x caps with transformers apart.
Click the image to open in full size.

Last edited by Kei; 13th February 2012 at 07:17 PM.
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Old 13th February 2012, 08:06 PM   #22
Tajzmaj is offline Tajzmaj  Slovenia
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This is good price....
And how can be done.
Cheers, Taj
100pcs Cornell Dubilier 80v 2700uf snap in Capacitors | eBay
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Old 13th February 2012, 08:15 PM   #23
Kei is offline Kei  Wales
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Cheers for the info you sent Taj. Not sure i'm going as far as that with 2700uF. (too much like hard work with all those holes and soldering) I'd prefer screw terminals which is pushing the cost up. I just noticed from the image on quadblog that they use 63V capacitors and they are also 63V in the service manual which will save me a lot more.
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Old 13th February 2012, 08:25 PM   #24
Tajzmaj is offline Tajzmaj  Slovenia
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Capacitors with screw terminals are good choice but price is high. In case that you decide to go with those I have p-cad file for those boards....
Performance is good with such amount of smaller caps.
I hope that you get my email yesterday.
Cheers, Taj
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Old 13th February 2012, 08:27 PM   #25
Tajzmaj is offline Tajzmaj  Slovenia
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p.s.
If you get good price for 80V caps just grab it because at lower voltage will last longer.
Regards
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Old 13th February 2012, 11:08 PM   #26
Kei is offline Kei  Wales
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Yes i got the email, and your pm too. Excellent info. Was looking at the many small capacitor route but prefer not to exceed 12 in total as space inside the case will become a problem. (i'm looking at the 300mm deep modushop 3U case, the 400mm depth is too big for the shelving)

I quite like the look of the evox rifa capacitors as they have the longest life rating as well as high ripple current and low ESR.

12x BHC 6800uF 63V caps, quite like the simple layout. 63v caps have also allowed me to increase the transformer size up to 500VA. (probably overkill but just to be sure to be sure )
Click the image to open in full size.

4x 22000uF Evox Rifa 63V caps
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Old 14th February 2012, 04:08 AM   #27
PB2 is offline PB2  United States
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About T15 and T16, note that the transformer does not have a center tap:
Bob Cordell's Power amplifier book
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Old 14th February 2012, 09:12 AM   #28
Kei is offline Kei  Wales
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I reproduced the psu circuit yesterday. I also created a second supply using two rectifiers for each secondary winding. The circuits have their simulated voltages shown. (AC supply shown in place of the transformer secondary)
Click the image to open in full size.

Not so sure i've done things right with this one though, but the rails come out equal.
Click the image to open in full size.
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Old 14th February 2012, 08:29 PM   #29
Tajzmaj is offline Tajzmaj  Slovenia
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About modushop 400mm deep.
I don't like it because it has actually 2 200mm heatsinks in line...so there is not only one big sink per side. i don't know how bad is thermal coupling but I don't like it. I managed to squeeze similar amp with 1200VA transformer in such case.
It might not look best from inside but connections are short and it works well. Very well in fact.
Cheers, Taj
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Old 14th February 2012, 08:35 PM   #30
Tajzmaj is offline Tajzmaj  Slovenia
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Ah attachments...
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