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Class D Switching Power Amplifiers and Power D/A conversion

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Old 16th October 2004, 10:32 PM   #781
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I've already some PK in my DEQ2496 for coupling. Works fine.

For Peter: modules works very fine. Tested and approved.
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Old 18th October 2004, 06:32 AM   #782
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Default Power Transformers available

Hi:

I have moved the listing for my transformers for sale to:

http://www.geocities.com/dmfraser77/parts4sale.html

Please have a look for some power transformers suitable for the UcD180 amplifiers.
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Old 18th October 2004, 10:04 PM   #783
tiki is offline tiki  Germany
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Default quick and dirty

Hi,

here you may find my first approach to an 4-channel amp with UcDs. It is foreseen to drive the smaller 3-way-speaker during its "tuning", using a behringer dsp crossover. After that it may be used by my son for his band, therefore the 19" case.

Please forgive me the dirty design, I was very keen to hear both channels together. First I was surprised about the very different sound, compared to my simple Technics SU-VX500 - until I noted the activated loudness. After that I was not able to spot a significant difference, which I could describe well. The main reason was the lack of a A/B-switch behind the amps. The bigger speakers are not well suited for that comparison, too.
But I liked the Japanese drums of Ondekoza very much at that volume level!
After a while I noted the remarkable temperature of the output chokes, more than 50 degC. They seem to be the hottest, most lossy part of the whole module.

I wait for the gold plated XLRs still. The volume control I realised with double log pots in series, it works satisfactory.
The PS is not ideal, the next will have only double 2way-rectifiers instead of bridges. The 330W-transformer seems to be symmetrical up to 0.1V. I should implement a softstart too, now I need 4A-fuses on the primary side minimum.

A thought about caps: I tried to find cheap ones with low ESR and small dissipation factor. I believe, these are their main characteristics for audio purposes. On that score aerovox and other "audiophile" caps are not the best. Bruno described already, that the ESL of the standard caps is low enough, so why slit foil and T-caps? Is anybody really sure to hear that? Remember Bruno's blind test of PS-caps together with his father.

Thank you, Bruno, Jan-Peter, JohnW and all the others for your useful hints and explanations.

edit:
I connected the mute-contact to ground hard-wired. Sometimes there is a remarkable "thunder" while switching on. A few seconds after switch off a small chirp occurs. I do only hear noise, if I creep into the tweeters, 20cm away I don't hear anything - very good! I like the UcDs very much and hope, they and their successors will conquer the audio scene.

Best regards, Timo
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Old 18th October 2004, 11:19 PM   #784
tiki is offline tiki  Germany
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edit button is gone...

Forgot to add, that I used Schottky rectifiers MBR10100 (yes, with small Cs in parallel). I hope, the Schottkies perform even better than fast rectifiers due to their lack of recovery time issues. Additionally, they have lower Vf. The results should be a lower supply output resistance and less possibility of spike generation (will check that with a scope sometimes, or the input ac-coupled to the supply ).

regards, Timo
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Old 19th October 2004, 07:42 AM   #785
koldby is offline koldby  Denmark
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Hi Tiki

IMHO the best solution is fast soft recovery diodes for the bridges (BYV79e) . You don't need the small capacitors then. And they sound best

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Old 19th October 2004, 10:44 AM   #786
tiki is offline tiki  Germany
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Default rectifiers

After a little search i found that:
I did not verify the measurements yet, maybe in the future. But I do not hear any hum, if the inputs are properly connected, even with this old, asymmetric DIN-connection.

Best regards, Timo
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Old 19th October 2004, 12:43 PM   #787
koldby is offline koldby  Denmark
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Hi Tiki

Good thread you found there. John Curl says excatly what I feel in post #77 (page 8)

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Old 19th October 2004, 01:37 PM   #788
matjans is offline matjans  Netherlands
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finally finished the casework ...
the top case is just a source selector and volume pot, i still have to build a decent pre.

Click the image to open in full size.

why isn't the image being shown? i did enclose the link in img tags !?
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Old 19th October 2004, 01:42 PM   #789
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matjans, can you post a picture of the inside of your amp? I have the same cases and I was wondering about layout

Thanks
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Old 19th October 2004, 02:02 PM   #790
matjans is offline matjans  Netherlands
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here ya go

My original plan was to mount the xformer in the centre and the psu caps bbehind it, also in the centre. That way you can have really short wires from the psu to the modules. Alas, i miscalculated the size of the psu board by a centimetre and it just wouldn't fit nicely.

a bit messy. I think Usvr posted a pic of the internals of his amp somewhere around page 70 of this thread.

Click the image to open in full size.

found usvr's post: http://www.diyaudio.com/forums/showt...744#post462744
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