noise problem..help

markC · « **on:** 31 Mar 2003, 03:14 am »

I'm experiencing an annoying, quite audible noise problem-sounds like a 60hz buzz. Heres the situation: I was over at my friends place listening to the new diy speaks he built, (see sharp looking diy speaks in the lab), and I liked how lively they were and how much attack they had compared to mine. So when I got home I gave my system a go and decided to change the normal laid back sound to a more lively, aggressive sound. I can do this by switching my Decware ZT pre from normal to high gain. When the first disc was over, I got up to change it and noticed quite a loud hum from the speaks as I approached them. After some testing I found that with the gain switch on high and no program material playing, The hum got louder as I increased the volume on the preamp. This was not the case with the cdp turned off. The increased hum volume, (over the normal gain switch position), was still there, but constant. Now for the strange part-with the cdp AND the pre switched off the increased hum level was still there. With the cdp and the pre off or on and the gain switch set to normal, the hum goes back to being barely audible. You can only hear it when you bring your ear within 4"-5" of the drivers. Before I start tearing things apart, could someone please offer some advice. Thanks.

audioengr · « **Reply #1 on:** 1 Apr 2003, 01:21 am »

Since the hum increases as you turn up the preamp, this means that the noise is being introduced a the preamp inputs. You probably have a ground-loop there. This ground loop is caused by your CDP or other device that is an input to the pre that has a grounded power cord. The fact that your pre has a grounded power cord creates the loop. If the pre and the other sources that are AC-grounded are plugged into different circuits in your house, this will aggravate the situation. Plug everything into the same circuit first. If this does not solve it, then float the source component with an ac cheater plug.

markC · « **Reply #2 on:** 1 Apr 2003, 01:41 am »

Thanks for the response. All of the components are plugged into the same dedicated circuit. I may sound niave here, but I assume that a cheater plug is a device that has a 3 prong plug and accepts only 2 prongs in its back alowing the ground prong to remain unconnected. Would this be correct?

JoshK · « **Reply #3 on:** 1 Apr 2003, 01:55 am »

mark,

The other way around. A cheater plug accepts 3 prongs and plugs only two into the wall.