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Old 18th August 2008, 10:07 PM   #21
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Edited Excel Sheet.
Thanks everybody.
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File Type: zip capacitor size for ac side of rectifier.zip (9.9 KB, 197 views)
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Old 18th August 2008, 10:25 PM   #22
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Here's one with the values changed over to match up with available capacitors. . .
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File Type: zip full chart -capacitor size for ac side of rectifier.zip (9.9 KB, 295 views)
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Old 18th August 2008, 10:35 PM   #23
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Thanks so much for the information!!

One of my little amplifiers was running on a 36vct, 1 amp transformer, I tried snubbing the rectifier to cool it off (less heat at heatsink), which it did, but it didn't sound right.
I had mistakenly tried using the same 10nF that I had seen in my big amplifier's service manual.
Now I find out that the needed value for the little amplifier was 820pF. OMG!! That's a huge difference.
Well, no wonder.
EDIT: Yes, the right size works nicely.

Thanks again!!!

EDIT: As promised, a photo, because not everyone has Excel software.
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File Type: jpg 1cap-on-the-ac-side-of-a-rectifier.jpg (92.7 KB, 2003 views)
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Old 18th August 2008, 11:23 PM   #24
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Quote:
Originally posted by danielwritesbac
Thanks so much for the information!!

One of my little amplifiers was running on a 36vct, 1 amp transformer, I tried snubbing the rectifier to cool it off (less heat at heatsink), which it did, but it didn't sound right.
I had mistakenly tried using the same 10nF that I had seen in my big amplifier's service manual.
Now I find out that the needed value for the little amplifier was 820pF. OMG!! That's a huge difference.
Well, no wonder.
EDIT: Yes, the right size works nicely.

Thanks again!!!

EDIT: As promised, a photo, because not everyone has Excel software.
Any first impressions on the tweak?

Regards
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Old 19th August 2008, 12:13 AM   #25
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Quote:
Originally posted by konstantin


Any first impressions on the tweak?

Regards
My little LM1875 project didn't improve nor degrade the sound, but did run cooler.

I don't have any that are technically gainclone style, so I couldn't comment on what the tweak does with a gainclone.

Hey, thanks for the lower temps!!

I think that this will be mighty helpful on getting my new parallel+bridge amplifier more compact and affordable.
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Old 19th August 2008, 07:34 AM   #26
Baka is offline Baka  Montenegro
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Quote:
Originally posted by AndrewT
Every PS since then has AC caps, both before and after the transformer.

Hi Andrew,

Would you share your experience in that respect.

What is the capacitance you use before the transformer?

Do you use only X rated caps and do you use them between hot and neutral?

Do you use Y rated caps - between phase or neutral and earth?

Most often heard critics are that the use of these affects the dynamics. What is your impression?

Thanks, Baki
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Old 19th August 2008, 07:40 AM   #27
Nordic is offline Nordic  South Africa
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Something else you may want to try... use a 11 to 17W 1R resistor in series with a 220nF mains rated cap, these connects in parallel over the primary... Be sure to insulate and heatshrink all exposed bits as this is at mains potential...
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Old 19th August 2008, 08:13 AM   #28
Baka is offline Baka  Montenegro
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Quote:
Originally posted by Nordic
Something else you may want to try... use a 11 to 17W 1R resistor in series with a 220nF mains rated cap, these connects in parallel over the primary... Be sure to insulate and heatshrink all exposed bits as this is at mains potential...
Thanks, Nordic, I'll try that.
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Old 19th August 2008, 09:44 AM   #29
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Nordic,

I forgot to ask: is that calculation for 220~240 AC?

Thanks, Baki
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Old 21st August 2008, 03:46 AM   #30
Pocoyo is offline Pocoyo  Indonesia
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Default Use for Class AB PSU

Hiii

Is this work great for class ab psu ?

i have calculated for 230vac, 2x45vdc
500 va need 64nF - 68 nF

Can someone share this information for me ???
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