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Old 6th November 2003, 08:31 PM   #1
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Default Aleph ripple voltage

Hi,
Just a question:
How much ripple voltage is ok for an aleph?
I'm getting 75mV ripple pp at the output. The bias current is 4A

Is this normal for that circuit and a power supply ripple of 350mV pp??

Christian
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Old 6th November 2003, 09:11 PM   #2
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Pumuckel

Recently, the topic of power supplies for the Alephs has become interesting again. See here and in the Aleph-X wiki for more information. 350mA from the power supply seems high to me and I would look to quiet that before looking further up the amp. I would ask some of the other members in the thread above their opinion since they may know more about the pre-X Aleph.
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Old 6th November 2003, 11:29 PM   #3
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With that much ripple on the supply, you should be seeing
maybe 300 micro-volts of ripple, or about 1/1000 of the
supply ripple, or less.
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Old 7th November 2003, 09:42 AM   #4
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Default Re: Aleph ripple voltage

Quote:
Originally posted by Pumuckel

I'm getting 75mV ripple pp at the output. The bias current is 4A
Christian
Hi Christian,

Your descripion sounds like you are collecting "hum" somewhere

not ripple!

Look if this is 50 or 100Hz!

-> 100Hz is maybe some PSU induced hum.

-> 50Hz is maybe grounding problem.

Put away all input cables make a shortcut on all 3 input pins

and look if the hum changes.

Uli
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Old 7th November 2003, 03:28 PM   #5
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Thanks for the replies.

I already thought that it's much too much.
It's 100Hz ripple.

What coud be the reason for that.
I matched the input fet's not only by their gate/source voltage but by their characteristics.

Any Ideas??

Christian
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Old 7th November 2003, 09:15 PM   #6
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HI,
Here are a few measurements of the ripple I took right now. the funny thing is that the left and right channel behave different.

What in the aleph circuit is responsible for the PSRR?
How does the bias current of the first stage affect PSRR?

Any ideas??
I'm sitting in the lab right now, so I can try things out and give feedback.

Christian
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File Type: jpg l channel supply and output hum.jpg (51.8 KB, 373 views)
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Old 7th November 2003, 09:17 PM   #7
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other channel
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File Type: jpg r channel supply and output hum.jpg (51.6 KB, 361 views)
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Old 7th November 2003, 09:19 PM   #8
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... I forgot to say that I'm using a LC Filter now. That's the reason why the ripple is much lower, but the ratio of supply ripple vs output ripple didn't change much.

Christian
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Old 8th November 2003, 12:36 AM   #9
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What's the noise figure on the good channel?
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Old 8th November 2003, 09:20 AM   #10
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I wouldn't say that there's a good channel, because the ripple of the output is 1/10 of the supply ripple.

The traces are averaged, to only see the 100Hz ripple.

noise is about 15mVPP
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