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Class D Switching Power Amplifiers and Power D/A conversion

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Old 19th April 2007, 02:51 PM   #1
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Default T-amp POWER AMP Mod + VERY LOUD

I've just modded a t-amp to make a power amp via audio 1st diagram (stealth badd modd with new 2.2uf caps and new power cap).

I've added 100k resistors from input.

Everythings working well and sounds great but it seems extremley loud.

I previously reboxed a t-amp with a alps 50k pot but this power amp seems way louder.

With my marnatz 63se cd player I can't even turn the volume past 3. previously I could have both the cd player and the amp on full volume.

Justed wanted to knnow if anyone else had experienced this.

I attached a couple of pictures if your interested
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File Type: jpg amp inside1.jpg (47.6 KB, 582 views)
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Old 19th April 2007, 02:59 PM   #2
Puffin is offline Puffin  United Kingdom
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Have you wired it like this ? (see attachment) I have modded 3 S.I's as power amps without the loudness problem you have ?
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File Type: pdf scan pot.pdf (57.6 KB, 97 views)
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Old 19th April 2007, 03:35 PM   #3
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I've wired it as in this picture (below) with 100k resistors , i'm not saying its a problem i just didn't expect it to be this loud.
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Old 19th April 2007, 04:38 PM   #4
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Picture attached now
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Old 20th April 2007, 07:12 AM   #5
Puffin is offline Puffin  United Kingdom
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The way you have done it is different to mine. I carried out the "classic" mod and then removed the pot and substituted the 100k resistors.
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Old 24th April 2007, 04:12 PM   #6
Seraph is offline Seraph  United States
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Wondering Puffin, did you remove R1 and R2 ?
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Old 25th April 2007, 07:30 AM   #7
Puffin is offline Puffin  United Kingdom
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Yes. R1 and R2 are replaced by 22kohm metal film resistors attached to one of the pads vacated by R1 and R2. This is a very tricky soldering job. It pasy to be patient and make sure you glue the resistor to the edge of the board before soldering. Any movement of the resistor is likely to pull the very small pad you have soldered it to, off the board and then....goodbye S.I !

Check out the input mods "Classic" on Michael Mardis's site.
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Old 25th April 2007, 12:00 PM   #8
Seraph is offline Seraph  United States
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Thanks Puffin. I will check out the Classic mod on M. Madris' site.

I wonder if it'd be feasible to drill a small hole through or near the pad to secure the resistor without ultimately saying bye bye to the SI! I'll look into that when I get round to it. Anyhow, It does pay to be patient and careful when working on such small boards.
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