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Old 4th August 2005, 01:11 PM   #1
Nuuk is offline Nuuk  United Kingdom
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Default AMP-3 DC offset (high)

I'm measuring 113 mV DC offset on one channel of the AMP-3 that I have here. The other channel measures 10 mV.

Is this normal for the AMP-3? And how safe is it to connect the amp to some speakers?
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Old 4th August 2005, 06:44 PM   #2
jkeny is offline jkeny  Ireland
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I had 149 mV dc offset on one channel of my SI amp(other channel was 10mV) and it was ok connected to Rogers speakers although a slight bump was heard at power on.

I had another SI amp with low dc offsets on both channels < 20mV, which was going to be my preferred amp but I blew the chip experimenting with output inductors when OUTM1 & OUTM2 connected while running.

I'm hoping to order a chip (from 41Hz?) and try to desolder old and solder in new - has anybody had success with this operation?

John
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Old 4th August 2005, 06:58 PM   #3
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Well that makes my 113 mV sound not too bad John!

I think I am correct in saying that Leo managed to desolder a chip from his AMP-3 and replace it with another one!

Isn't the chip in the SI amp the 2024 though? The AMP-3 chip is the 2021!
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Old 4th August 2005, 06:59 PM   #4
t. is offline t.  United Kingdom
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My Amp3 also has 70/80mV DC offset both channels.
So I wonder whats causing this

I have just replaced the TA2021b chip in my Amp3, unfortunately it isn't easy but is possible, just make sure you take your time
I didn't know 41hz sold the chip suitable for the SI amp
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Old 4th August 2005, 07:00 PM   #5
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Good Timing Nick
BTW you are correct, the chips are different
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Old 4th August 2005, 07:35 PM   #6
jkeny is offline jkeny  Ireland
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Oops,
Thanks guys - anybody know where 2024 chip is sold - SI board has thiis chip sitting on solder slug - this might make desoldering it v difficult

John
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Old 4th August 2005, 07:41 PM   #7
t. is offline t.  United Kingdom
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Hi John,

Maybe these could help http://www.autocostruire.com/catalog...roducts_id=262
All the other class-T amp kits I've seen use mainly the Tripath TA2020 and 2021 chips
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Old 4th August 2005, 09:25 PM   #8
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Default SI repair

I would have to say forget repair unless you have access to a modern facility with all the correct hardware. Even then it would be a coin flip. The board is extremely fragile and can be easily ruined, this is experience speaking. This is not the quality found in the amp3.
Roger
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Old 4th August 2005, 09:32 PM   #9
t. is offline t.  United Kingdom
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Hi Roger,

What sort of DC offset do you get on your Amp3?

Cheers
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Old 4th August 2005, 11:33 PM   #10
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Quote:
Originally posted by t.
Hi Roger,

What sort of DC offset do you get on your Amp3?

Cheers
79 MV on one and 67 MV on the other, not great but passable.
Roger
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