Aleph ripple voltage

Pumuckel · 6th November 2003, 08:31 PM

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

yldouright · 6th November 2003, 09:11 PM

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.

Nelson Pass · 6th November 2003, 11:29 PM

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.

uli · 7th November 2003, 09:42 AM

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

Pumuckel · 7th November 2003, 03:28 PM

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

Pumuckel · 7th November 2003, 09:15 PM

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

Pumuckel · 7th November 2003, 09:17 PM

other channel

Pumuckel · 7th November 2003, 09:19 PM

... 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

Nelson Pass · 8th November 2003, 12:36 AM

What's the noise figure on the good channel?

Pumuckel · 8th November 2003, 09:20 AM

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

6th November 2003, 08:31 PM	#1
Pumuckel diyAudio Member Join Date: Aug 2002 Location: Graz, Austria	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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6th November 2003, 09:11 PM	#2
yldouright diyAudio Member Join Date: Aug 2002 Location: New York, NY	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.

6th November 2003, 11:29 PM	#3
Nelson Pass The one and only Join Date: Mar 2001	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.

7th November 2003, 03:28 PM	#5
Pumuckel diyAudio Member Join Date: Aug 2002 Location: Graz, Austria	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

7th November 2003, 09:19 PM	#8
Pumuckel diyAudio Member Join Date: Aug 2002 Location: Graz, Austria	... 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

8th November 2003, 12:36 AM	#9
Nelson Pass The one and only Join Date: Mar 2001	What's the noise figure on the good channel?

8th November 2003, 09:20 AM	#10
Pumuckel diyAudio Member Join Date: Aug 2002 Location: Graz, Austria	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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