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Class D Switching Power Amplifiers and Power D/A conversion

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Old 29th May 2009, 07:27 PM   #301
aszu is offline aszu  United Kingdom
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New cap in the PSU:
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Old 29th May 2009, 08:05 PM   #302
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Hi Aszu, happy you had good results with the tweaks. I agree, how can this little ugly thing sound SO good?
The little film cap is

"used to bypass (shunt) unwanted signals to the ground. A common use is in power supplies where a bypass capacitor is connected in parallel with the main filter capacitor to shunt noise and other high frequency interference to ground which the main capacitor may not be able to do."

http://wiki.answers.com/Q/What_is_the_function_of_a_bypass_capacitor_in_an_a mplifier

It is a very common practice.

Please look for a film input cap, you can find it very easily on e*ay and you'll certainly notice the improvement in sound. If you PM me I'll send you with pleasure a pair of my NOS Wima MKA.

Finally please allow some burn in time to get a very full bass.
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Old 29th May 2009, 09:01 PM   #303
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Default the kitchen system

I'm testing the amp in the kitchen (oh yes I love cooking with music). I fixed up an amazing lilliputian vintage system. Actually yesterday I found a glorious Sony D-50, the first portable cdplayer ever...
Ohmygod I want them in every room!
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Old 29th May 2009, 09:13 PM   #304
cheric is offline cheric  United States
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Calamaro,

Can I use the same resistors (on board ones) to by pass the tone control or MUST I replace them with 22k resistors?
Also, can I use 0.33uf film capacitors instead of 2.2uf caps, due to the space?
Thanks for your help.
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Old 29th May 2009, 09:20 PM   #305
aszu is offline aszu  United Kingdom
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Many thanks for the explanation Calamaro

I attached this small 100nF film capacitor under the board - very quick and easy job. I didn't expect to hear any difference, but it looks like stereo separation is now a bit better.

Regarding big (2.2uF) film capacitors, I have found this one

Do you think it will do the job?

Are there any other mods of this board you can recommend?
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Old 29th May 2009, 09:23 PM   #306
aszu is offline aszu  United Kingdom
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BTW: I am ultra-mega happy with the sound at the moment.. It was amazing before mods, but now it is much more refined, almost perfect

Bypassing tone controls is definitely a way to go!
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Old 29th May 2009, 09:37 PM   #307
Gmorris is offline Gmorris  United States
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Quote:
Originally posted by cheric

Also, can I use 0.33uf film capacitors instead of 2.2uf caps, due to the space?
I'm pretty sure caps under 2.2uf will start acting like a high-pass filter resulting in rolled off bass.
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Old 29th May 2009, 09:50 PM   #308
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Yes, that's right. At 2.2uf, the input caps are already acting as hi-pass, but the frequency is low enough not to interfere with the audio range.

Cheric, if you're tight for space, you can parallel two 1.0 uf caps and get something that will work just fine. I remember some people in these forums getting good results with the blue-colored 1.0uf film caps sold at Radio Shack. Also, some film caps are larger than others--usually related to the voltage rating.

BTW, if you know you're only going to use the amp with speakers that don't produce much bass, cutting off the frequencies below which the speakers don't do any useful work is not a bad idea and leaves more energy for frequencies where it does.

--Buckapound
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Old 29th May 2009, 10:03 PM   #309
cheric is offline cheric  United States
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Thank you Gmorris and Buckapound for quick replies.
I will try to find the 2.2uf caps in a smaller package.
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Old 29th May 2009, 11:10 PM   #310
col is offline col  Australia
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you can get 2.2uF Hi Quality Metalized / Polypropylene Capacitors from Jaycar (thats the ones I use). They have a UK branch.

https://secure.vividcluster.crox.net...T&SUBCATID=866

theres a phone number there too.

edit: you can also get the Taiwan Alpha B100K log pots that I used (which are much better quality) from here.

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