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Class D Switching Power Amplifiers and Power D/A conversion

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Old 25th October 2006, 02:39 PM   #11
v-bro is offline v-bro  Netherlands
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I wouldn't worry about 8 ohm loads, all it can result in is a bit less power, but since it has plenty i would change nothing and just enjoy it. (a 4 ohm capable amp can drive tougher loads and will keep up the compatibility of the amp...)
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Old 25th October 2006, 02:40 PM   #12
niiico is offline niiico  France
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I'm speaking about the output caps.

For the input caps, you may test the Paper in Oil caps without any problems.
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Old 25th October 2006, 03:14 PM   #13
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alright, sounds good! now for a far simpler question!

does anyone seggest a good power transformer for this amplifier (Preferably a torodial)? because I have found one with a 25v secondary, rated at 300VA, it has the right current, but it would require unwinding quite a few wires off the transformer to make it suitable. does anyone seggest a transformer? (in a decent price range, the 25v 300VA is 19.95)
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Old 25th October 2006, 04:18 PM   #14
niiico is offline niiico  France
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I may be wrong, but...

25 V AC secondary means 25x1.41=35.25 V DC at least.

And this is far beyond specs. (33V is the maximum voltage before damaging the amp)

To get a 24V DC you must find a transformer with 18V AC output.
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Old 25th October 2006, 04:56 PM   #15
heady is offline heady  Singapore
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Quote:
Originally posted by alexmoose
I was thinking and almost positive I going to make Amp5. I looked at amp 9, but was dis-enchanted when I saw it is designed for a 4 ohm load, has anyone run it with an 8-ohm load? do you still seggest the amp9 for my 8-ohm speakers?
Just finished a amp5 and using it to drive 8ohm speakers. Sounds very good and goes louder than I need. Easy to build as well.
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Old 25th October 2006, 07:01 PM   #16
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Quote:
Originally posted by niiico
I may be wrong, but...

25 V AC secondary means 25x1.41=35.25 V DC at least.

And this is far beyond specs. (33V is the maximum voltage before damaging the amp)

To get a 24V DC you must find a transformer with 18V AC output.
I know, you're right, which is why I would have to resort to unwinding part of the Transformer, but if anyone had a good one in mind I am open to seggestions

Heady,

how does the high-range of Amp5 hold up? it looks like the distortion kinda looses it above 5k, does it sound really nice in the high range?
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Old 25th October 2006, 10:50 PM   #17
v-bro is offline v-bro  Netherlands
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If it's a really good deal on that tranny you can try more diodes in the rectifier bridge to drop the voltage a little....
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Old 25th October 2006, 11:01 PM   #18
v-bro is offline v-bro  Netherlands
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I don't think this solution can be rendered as very "audiophile" though...

This link shows that the chip can handle an absolute maximum of 40Vdc:
http://www.tripath.com/downloads/TA2022.pdf

Maybe the best way to go is indeed unwinding the secondary on the tranny...

Or maybe there's the possibility you can upgrade a few components to be able to handle it, but beware, the chip/amp/parts can have a very short lifespan this way...
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Old 26th October 2006, 02:26 AM   #19
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I think the best chance is to add ADDITIONAL windings to the transformer secondary in the reverse direction, then nothing would be lost powerwise. I think I would need to add about 70 windings in the oppisite direction to lower the secondary from 28v tro 18v with, the transformer has a power rating of 500VA, so at 19.95, its a really good deal
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Old 26th October 2006, 02:49 AM   #20
heady is offline heady  Singapore
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Quote:
Originally posted by alexmoose

Heady,

how does the high-range of Amp5 hold up? it looks like the distortion kinda looses it above 5k, does it sound really nice in the high range?
When I first built the amp, I used the supplied electrolytics for the input caps. The treble was horrible, very artificial and screechy.

I then substituted them for a pair of Solens polypropylene caps which was by-passed with Vishay-Roedenstein caps and the high end really cleaned up. Now with the burn-in, the high end sounds very tame, maybe a little too tame but that could be due to my other equipment.

You can see the pics of the mods I made in this link:
http://www.41hz.com/Forums/topic.asp?TOPIC_ID=742
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