Power supply

Lichoo · 31st July 2003, 10:22 PM

Hello,

I'm going to tweak the power supply in my CD6000 and put another 10VA +/-12V trasformer for the analog section. I'd like to improve also filtering in the supply so I'm going to put larger capacitors. What is the best way to do it:
1) put 4700uF before stabilizer and leave 470uF after stabilizer
2) leave 470uF before stabilizer and put 4700uF after stabilizer
3) put 4700uF before and 4700uF after stabilizer
4) any other combination?

Regards,

Piotrek

djmiddelkoop · 1st August 2003, 12:25 AM

What kind of regulator ?

A LM317 outperforms a 78XX easy.

For the electrolytics, quality is more important than value.

Dick.

Peter Daniel · 1st August 2003, 12:34 AM

You might try to read those threads:

http://www.diyvideo.com/forums/showt...5&pagenumber=1
http://www.audioasylum.com/audio/twe...ges/36827.html

Lichoo · 1st August 2003, 06:46 AM

>What kind of regulator ?
According to the scheme, L7812/L7912.

> For the electrolytics, quality is more
> important than value.
There will be Panasonic FC caps.

Regards,

Piotrek

Guido Tent · 2nd August 2003, 10:09 AM

Quote:

Originally posted by djmiddelkoop
What kind of regulator ?

A LM317 outperforms a 78XX easy.

For the electrolytics, quality is more important than value.

Dick.

Hi

An LM317T is quite noisy, it depends on the application if it is OK

Measurements show output current noise in a band of 20 kHz = 0,7mA. This is never published in the datasheet........

best regards

Guido

Terry Demol · 2nd August 2003, 10:41 AM

Quote:

Originally posted by Guido Tent

Hi

An LM317T is quite noisy, it depends on the application if it is OK

Measurements show output current noise in a band of 20 kHz = 0,7mA. This is never published in the datasheet........

best regards

Guido

Hi Guido,

Can you elaborate on this. Normally current noise is at IP
of a device and reacts with driving impedance to develop
a noise voltage. How does OP current noise work, with an
OP Z that is very low I don't see how it can develop any voltage?
Or are you referring to current at ref point (to gnd).

Cheers,

Terry

fmak · 2nd August 2003, 11:35 AM

[QUOTE]Originally posted by djmiddelkoop
[B]What kind of regulator ?

A LM317 outperforms a 78XX easy.

For the electrolytics, quality is more important than value.

-----------------------------------------------------------

No longer true. LM317 is very noisy compared to new generation 78xx such as NJM. The 5V one is 40 uV wideband. Also new generation doesn't mind large lytics and likes low impedance output caps.

Guido Tent · 2nd August 2003, 03:27 PM

Quote:

Originally posted by Terry Demol

Hi Guido,

Can you elaborate on this. Normally current noise is at IP
of a device and reacts with driving impedance to develop
a noise voltage. How does OP current noise work, with an
OP Z that is very low I don't see how it can develop any voltage?
Or are you referring to current at ref point (to gnd).

Cheers,

Terry

Hi Terry

The noise source behaves as a current source generating output noise current on top of the DC voltage.

Shorting it (with a cap) will reduce the output voltage noise, but will still force noise current to the point of decoupling (often ground)

A series resistor of 10 ohm helps, but still isn't working out like I would like to see it

Bricolo · 2nd August 2003, 03:34 PM

[QUOTE]Originally posted by fmak
[B]

Quote:

Originally posted by djmiddelkoop

No longer true. LM317 is very noisy compared to new generation 78xx such as NJM. The 5V one is 40 uV wideband. Also new generation doesn't mind large lytics and likes low impedance output caps.

how can you see if a 78** is from the old or the new generation?

Guido Tent · 2nd August 2003, 03:36 PM

Quote:

Originally posted by fmak
The 5V one is 40 uV wideband. Also new generation doesn't mind large lytics and likes low impedance output caps.

Hi Fred

What bandwidth is used when specifying 40uV?

Guido

31st July 2003, 10:22 PM	#1
Lichoo diyAudio Member Join Date: Jul 2003 Location: Krakow	Power supply Hello, I'm going to tweak the power supply in my CD6000 and put another 10VA +/-12V trasformer for the analog section. I'd like to improve also filtering in the supply so I'm going to put larger capacitors. What is the best way to do it: 1) put 4700uF before stabilizer and leave 470uF after stabilizer 2) leave 470uF before stabilizer and put 4700uF after stabilizer 3) put 4700uF before and 4700uF after stabilizer 4) any other combination? Regards, Piotrek

1st August 2003, 12:25 AM	#2
djmiddelkoop diyAudio Member Join Date: Feb 2003 Location: Noord-Holland	What kind of regulator ? A LM317 outperforms a 78XX easy. For the electrolytics, quality is more important than value. Dick. __________________ Music is the best F.Z.

1st August 2003, 12:34 AM	#3
Peter Daniel diyAudio Member Join Date: Jul 2002 Location: Toronto, Canada	You might try to read those threads: http://www.diyvideo.com/forums/showt...5&pagenumber=1 http://www.audioasylum.com/audio/twe...ges/36827.html __________________ www.audiosector.com “Do something really well. See how much time it takes. It might be a product, a work of art, who knows? Then give it away cheaply, just because you feel that it should not cost so much, even if it took a lot of time and expensive materials to make it.” - JC

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1st August 2003, 06:46 AM	#4
Lichoo diyAudio Member Join Date: Jul 2003 Location: Krakow	>What kind of regulator ? According to the scheme, L7812/L7912. > For the electrolytics, quality is more > important than value. There will be Panasonic FC caps. Regards, Piotrek

2nd August 2003, 11:35 AM	#7
fmak diyAudio Member Join Date: May 2001 Location: London UK	[QUOTE]Originally posted by djmiddelkoop [B]What kind of regulator ? A LM317 outperforms a 78XX easy. For the electrolytics, quality is more important than value. ----------------------------------------------------------- No longer true. LM317 is very noisy compared to new generation 78xx such as NJM. The 5V one is 40 uV wideband. Also new generation doesn't mind large lytics and likes low impedance output caps.

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