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Old 16th February 2014, 02:44 AM   #1
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Default Adding bigger caps to classic LM3875

I built a good sounding LM3875 classic with stock parts and 300VA 22/22 transformer.

I'd like to add a little oomph to the bass response.

I was thinking of adding 10,000 63v caps to the PSU. This is done at C1 and C2 on the board, correct?

Do I need to adjust/change any other components when adding these caps?

Thanks.
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Old 16th February 2014, 03:13 AM   #2
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just take out the 10uf that come with it and add the 10000uf instead
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Old 16th February 2014, 02:00 PM   #3
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You can find discussion on bigger caps here: Commercial Gainclone kit- building instructions

Some people like to add snubbers when using large caps. My board will accommodate those too. Info on snubber components valu can be found here: http://www.audiosector.com/lm4780%20psu.pdf
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Old 16th February 2014, 07:23 PM   #4
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Thanks for the pointers. I know this has been discussed a lot previously (years ago!).

I want to add a little to the low end without coloring the sound (much). According to your (Peter's) testing, the snubber changes the neutral tone of the amp.

I just ordered some Nichicon KG type I 10,000uF 63V. I'll try to alligator clip them to test the difference.

Maybe just adding a summing circuit and a powered subwoofer is a better choice.
Like page 42 (vol 14 #4)?https://community.klipsch.com/forums...%20HOPE!!!.pdf
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Old 18th February 2014, 01:54 PM   #5
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It all depends on your speakers, but sometimes adding powered subwoofer is indeed best option.
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Old 4th March 2014, 05:54 PM   #6
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Just an update that others may find helpful.

The 10,000uf Nichicons didn't seem to affect the bass, but some detail was definitely sucked out of the music. Maybe they weren't the ideal caps.

I removed them, then replaced the basic resistors with the ones from the premium kit (caddocks and riken).

Pronounced improvement in the clarity.

If you're looking at Audiosector LM3875 kits, don't skimp. Go for the premium kit.

I also added a small subwoofer to my bookshelf speaker setup and it works great to fill in those lower frequencies.
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Old 11th March 2014, 03:00 PM   #7
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Hi Peter, hope all is well with you. Based on the discussion above I was wondering if this is still your opinion:
"I'm coming to conclusion that the less stored energy the amp is dealing with, the fresher the sound becomes".

And are you personally still using only 100u BG N near the amp and nothing at the bridges (different than in the Patek)?
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Old 11th March 2014, 07:12 PM   #8
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Yes, this is still my opinion. However, I would be using BG N 100uF caps only at the chip if the amp was intended for mid or high section of multi amp setup. For full range BG STD 1000/50 at the rectifier are still needed.

If I'm not using BG caps, Panasonic FC 1500/50 are my first choice.
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Old 11th March 2014, 07:43 PM   #9
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Quote:
Originally Posted by Peter Daniel View Post
If I'm not using BG caps, Panasonic FC 1500/50 are my first choice.
Thanks, and what at the rectifier in this setup?
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Old 12th March 2014, 01:46 PM   #10
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Those are MUR860
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