BOSOZ Hum Problem - Page 2

hifileslie · 18th September 2007, 03:39 PM

I would not say I am an expert with an oscilloscope, but I can see ac on the lines after the rectifiers and none at the outputs of the PSU.

Whare should I look next please? Any advice gratefully received!

mpmarino · 18th September 2007, 04:17 PM

1. Do you have hum when only one channel is connected to the pre psu?

2. Have you tried re-locating the transformers far away from the rest of the pre?

You could try lifting your earth varistor and let the pre psu float - thereby eliminating the possibility of a loop thru earth.

Are you sure it's an ac HUMMM? Could it be noisy protection zeners, or maybe protection zeners (if you have them) are the wrong way around?

Zenny's right, a pic is worth a book.......

hifileslie · 18th September 2007, 04:28 PM

I never said it was an ac humm-just trying to eliminate the obvious!!

Can anyone help narrow down the cause by the fact it is the same in both channels, does not vary with volume and is there with all inputs grounded etc.

18th September 2007, 04:17 PM	#12
mpmarino diyAudio Member Join Date: Jun 2004 Location: Crunchville, where I don't fit in.	1. Do you have hum when only one channel is connected to the pre psu? 2. Have you tried re-locating the transformers far away from the rest of the pre? You could try lifting your earth varistor and let the pre psu float - thereby eliminating the possibility of a loop thru earth. Are you sure it's an ac HUMMM? Could it be noisy protection zeners, or maybe protection zeners (if you have them) are the wrong way around? Zenny's right, a pic is worth a book....... __________________ Crazy Yankee.

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18th September 2007, 03:39 PM	#11
hifileslie diyAudio Member Join Date: May 2002	I would not say I am an expert with an oscilloscope, but I can see ac on the lines after the rectifiers and none at the outputs of the PSU. Whare should I look next please? Any advice gratefully received!

18th September 2007, 04:28 PM	#13
hifileslie diyAudio Member Join Date: May 2002	I never said it was an ac humm-just trying to eliminate the obvious!! Can anyone help narrow down the cause by the fact it is the same in both channels, does not vary with volume and is there with all inputs grounded etc.

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