Aleph-P(roblem)

Pawel · 4th August 2004, 03:14 PM

Hi!
I've recently finished building Aleph-P preamp and I have a little problem with it. When I use unbalanced input the sound is distorted and I can hear hum, when standing very close to the speaker. When I disconnect negative input from the ground everyting seems to be OK. Does any of you had similar problem before? I need some advise, what to do? I've checked all connections and components twice. Voltages are very close to PSpice simulated ones... so everything seems to be OK but it's not

Nelson Pass · 5th August 2004, 10:29 PM

Normally grounding the negative input is what prevents
this. Is there potential for oscillation due to no Gate resistors
or no series output resistors? Is it on both channels?

Maybe what you think is ground is not a good ground.

Pawel · 6th August 2004, 08:19 AM

Thank you for your reply Mr. Pass.
Yes, it's grounding problem. Changing ground connections helped a little bit. Sound is no more distorted and there is much less hum. I'll try to apply star ground topology to my board. Maybe this will help to remove hum completely.

4th August 2004, 03:14 PM	#1
Pawel diyAudio Member Join Date: Apr 2004 Location: Poland, Wroclaw	Aleph-P(roblem) Hi! I've recently finished building Aleph-P preamp and I have a little problem with it. When I use unbalanced input the sound is distorted and I can hear hum, when standing very close to the speaker. When I disconnect negative input from the ground everyting seems to be OK. Does any of you had similar problem before? I need some advise, what to do? I've checked all connections and components twice. Voltages are very close to PSpice simulated ones... so everything seems to be OK but it's not

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5th August 2004, 10:29 PM	#2
Nelson Pass The one and only Join Date: Mar 2001	Normally grounding the negative input is what prevents this. Is there potential for oscillation due to no Gate resistors or no series output resistors? Is it on both channels? Maybe what you think is ground is not a good ground.

6th August 2004, 08:19 AM	#3
Pawel diyAudio Member Join Date: Apr 2004 Location: Poland, Wroclaw	Thank you for your reply Mr. Pass. Yes, it's grounding problem. Changing ground connections helped a little bit. Sound is no more distorted and there is much less hum. I'll try to apply star ground topology to my board. Maybe this will help to remove hum completely.

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