old Parasound ZAMP

Senn · 3rd December 2005, 03:31 PM

My sis gave me an old Parasound zone amplifier (ZAMP) that was sitting in a closet for years. It is in very good shape as it was barely used. I intended to use it as a headphone amp but, as soon as I incorporated it into my HT setup it caused a nasty ground loop hum all around the system.

I troubleshot the problem with the usual solutions - ground loop isolator; plugging into different outlets; cheater plugs; etc. - with no luck.

I noticed while checking the Parasound homepage that there are 2 newer versions of this amp, the V2 & V3. Both of these units have "ground lift" switches on the rear panel.

Do ya' think Parasound knew the early version of the ZAMP causes a ground loop hum and remedied it in later models? Can this amp be modded in such a way to eliminate the problem? Anybody else have any experience with this particular amp and a possible solution? Thanks in advance.

anatech · 3rd December 2005, 04:06 PM

Hi Senn,
The case must remain grounded to the third wire on the plug. You can interrupt the circuit ground and try a 10 or 100 ohm resistor to reconnect those two points. That should get rid of your ground loop.

-Chris

anatech · 3rd December 2005, 06:39 PM

Hi Senn,
I have serviced many amps in the past, including Parasound, but can only speak in general terms. The chassis ground is a safety feature and must remain. Somewhere, the circuitry inside is connected to the chassis. The generally occurs as a wire coming off a "star" ground. You need an audio tech to correctly identify this point and insert some resistance to stop the circulating ground currents.
Parasound may be able to assist you by providing a technical description of what needs to be done. The description of what needs doing is fairly straight forward, the work may not be. A good audio technician should be able to do this.

-Chris

In response to an email

3rd December 2005, 03:31 PM	#1
Senn diyAudio Member Join Date: Mar 2005 Location: Northeast U.S.	old Parasound ZAMP My sis gave me an old Parasound zone amplifier (ZAMP) that was sitting in a closet for years. It is in very good shape as it was barely used. I intended to use it as a headphone amp but, as soon as I incorporated it into my HT setup it caused a nasty ground loop hum all around the system. I troubleshot the problem with the usual solutions - ground loop isolator; plugging into different outlets; cheater plugs; etc. - with no luck. I noticed while checking the Parasound homepage that there are 2 newer versions of this amp, the V2 & V3. Both of these units have "ground lift" switches on the rear panel. Do ya' think Parasound knew the early version of the ZAMP causes a ground loop hum and remedied it in later models? Can this amp be modded in such a way to eliminate the problem? Anybody else have any experience with this particular amp and a possible solution? Thanks in advance.

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3rd December 2005, 04:06 PM	#2
anatech diyAudio Moderator Join Date: Jun 2004 Location: Georgetown, On	Hi Senn, The case must remain grounded to the third wire on the plug. You can interrupt the circuit ground and try a 10 or 100 ohm resistor to reconnect those two points. That should get rid of your ground loop. -Chris

3rd December 2005, 06:39 PM	#3
anatech diyAudio Moderator Join Date: Jun 2004 Location: Georgetown, On	Hi Senn, I have serviced many amps in the past, including Parasound, but can only speak in general terms. The chassis ground is a safety feature and must remain. Somewhere, the circuitry inside is connected to the chassis. The generally occurs as a wire coming off a "star" ground. You need an audio tech to correctly identify this point and insert some resistance to stop the circulating ground currents. Parasound may be able to assist you by providing a technical description of what needs to be done. The description of what needs doing is fairly straight forward, the work may not be. A good audio technician should be able to do this. -Chris In response to an email