Confusion on home made buffer, one channel clear, two channel not? - Page 2

Destroyer OS. · 13th May 2010, 11:49 PM

I get a lot of noise if I touch the inputs on the JFET's.

Destroyer OS. · 14th May 2010, 12:53 AM

If I so much as plug in the power cord with the amp on I get noise. I got no idea why. That is with the power off.

I have no idea what is wrong, I give up. I am just going to have to wait who knows how much time and get a PASS B1 I guess.

robertor · 14th May 2010, 08:39 AM

the lm317 is only for the positive supply.

the output will be xx volt/0 volt or GND.

Joris · 14th May 2010, 10:42 AM

robertor, I disagree with you, it IS possible to create a positive and a negative voltage with 2 pieces of LM317. It would be nicer to use LM337 instead, but it should work without trouble.
I think since it is a shared power supply for both channels, the problem isn't in the power supply, it must be in that left channel. You should check the circuit board for bad ground connections.
You could also try to swap the amp inputs, so left channel becomes the right and the right becomes the left, this eliminates any doubts about the amp itself.

Could you post me a picture? So I have a clue what we're talking about exactly..

Best regards

Joris · 14th May 2010, 10:45 AM

Quote:

Originally Posted by Destroyer OS.

If I so much as plug in the power cord with the amp on I get noise. I got no idea why. That is with the power off.

I have no idea what is wrong, I give up. I am just going to have to wait who knows how much time and get a PASS B1 I guess.

If I understand it correctly, you get noise when you plug in the power cord of the amp that is connected to your circuit? If that's true, you certainly have a ground loop.

Destroyer OS. · 14th May 2010, 03:00 PM

Yeah well I put the whole thing into the closet until I need the box again... I can not even imagine how a ground loop was being created without the circuit even on.

robertor · 07:31 PM

re-build the power supply with 317/337 and try another time.

don't work fine?

search for another problem.

must to go for exclusion: that work fine and the problem persist? check the fet or buy some j-fet buffer PCB come from china.

jims-audio have the borbely.

p.s.: i'm not able to build a power supply work fine then i buy from some Chinese ebay seller. the price is absolutely absurd and make their work.

14th May 2010, 08:39 AM	#13
robertor diyAudio Member Join Date: Nov 2007	the lm317 is only for the positive supply. the output will be xx volt/0 volt or GND. __________________ rob

14th May 2010, 07:27 PM	#17
robertor diyAudio Member Join Date: Nov 2007	re-build the power supply with 317/337 and try another time. don't work fine? search for another problem. must to go for exclusion: that work fine and the problem persist? check the fet or buy some j-fet buffer PCB come from china. jims-audio have the borbely. p.s.: i'm not able to build a power supply work fine then i buy from some Chinese ebay seller. the price is absolutely absurd and make their work. __________________ rob Last edited by robertor; 14th May 2010 at 07:31 PM.

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13th May 2010, 11:49 PM	#11
Destroyer OS. diyAudio Member Join Date: Nov 2005	I get a lot of noise if I touch the inputs on the JFET's.

14th May 2010, 12:53 AM	#12
Destroyer OS. diyAudio Member Join Date: Nov 2005	If I so much as plug in the power cord with the amp on I get noise. I got no idea why. That is with the power off. I have no idea what is wrong, I give up. I am just going to have to wait who knows how much time and get a PASS B1 I guess.

14th May 2010, 10:42 AM	#14
Joris diyAudio Member Join Date: Aug 2009 Location: Noord-Holland	robertor, I disagree with you, it IS possible to create a positive and a negative voltage with 2 pieces of LM317. It would be nicer to use LM337 instead, but it should work without trouble. I think since it is a shared power supply for both channels, the problem isn't in the power supply, it must be in that left channel. You should check the circuit board for bad ground connections. You could also try to swap the amp inputs, so left channel becomes the right and the right becomes the left, this eliminates any doubts about the amp itself. Could you post me a picture? So I have a clue what we're talking about exactly.. Best regards

14th May 2010, 03:00 PM	#16
Destroyer OS. diyAudio Member Join Date: Nov 2005	Yeah well I put the whole thing into the closet until I need the box again... I can not even imagine how a ground loop was being created without the circuit even on.