Hum diagnostic assistance?

weinstro · 31st March 2009, 10:13 PM

Hi,

I have an annoying hum/buzz that I'd love to get rid of.

Details:

Audio Refinement Pre2DSP connected via RCA to Marantz MA-5, Marantz SM-6, and Hafler DH-200 amplifiers. The Pre2DSP is connected to 1ph. 120Vac power, as is the Hafler. The Marantz amplifiers were acquired in Europe and are currently operating on 2ph. 240Vac power (a dryer outlet in the US).

In this configuration, the Hafler is very quiet, but not totally silent.

The Marantz amps hum like mad, about +12dB.

If only the Marantz amps are powered on, the hum is about +6dB.

If the input cable is disconnected, the amps are silent, and I measure about 60mV ac between the cable shield (still connected to the Pre2DSP) and the chassis of the Marantz. Between the chassis of the two, I measure 80mV.

I can try adding a loop breaker circuit, such as shown here...............http://sound.westhost.com/earthing.htm

Any thoughts?

31st March 2009, 10:13 PM	#1
weinstro diyAudio Member Join Date: May 2003 Location: California	Hum diagnostic assistance? Hi, I have an annoying hum/buzz that I'd love to get rid of. Details: Audio Refinement Pre2DSP connected via RCA to Marantz MA-5, Marantz SM-6, and Hafler DH-200 amplifiers. The Pre2DSP is connected to 1ph. 120Vac power, as is the Hafler. The Marantz amplifiers were acquired in Europe and are currently operating on 2ph. 240Vac power (a dryer outlet in the US). In this configuration, the Hafler is very quiet, but not totally silent. The Marantz amps hum like mad, about +12dB. If only the Marantz amps are powered on, the hum is about +6dB. If the input cable is disconnected, the amps are silent, and I measure about 60mV ac between the cable shield (still connected to the Pre2DSP) and the chassis of the Marantz. Between the chassis of the two, I measure 80mV. I can try adding a loop breaker circuit, such as shown here...............http://sound.westhost.com/earthing.htm Any thoughts?

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