RFI/EMI Problem - Head-Fi: Covering Headphones, Earphones and Portable Audio

thebikingengineer · 04-10-2008, 01:06 AM

I just got a Beresford which I am enjoying quite a lot. The only problem I have with it is there is a persistent hiss and a dull buzz and I'd like to get rid of them.

The hiss seems to be coming from the circuitry of the amp itself. It doesn't change with a change in the volume control which tells me that it occurs after the potentiometer in the circuit (though I may be wrong).

The buzz is volume dependent and goes mostly (acceptably) away when I cover the RCA inputs on the back of the unit with my fingers. I was browsing TTVJ and saw in the tweaks section that they have RCA caps to combat this, they seem expensive for what they are.

All of the noise goes away when I plug 600 ohm AKG 240 monitors in, but they are my roommates and just mask the problem. Does anyone know of any (college student budget) tweaks that I could do that may minimize or eliminate these noises?

Thank you,

Mark

breakfastchef · 04-10-2008, 01:58 AM

Aside from contacting Beresford, the first thing I would do, I would initially consider there to be a grounding problem. Try running the TC off the same circuit as the source equipment. Maybe try plugging all you equiment into a surge protected outlet strip. It is always possible you got a dud. Let us know how this turns out.

thebikingengineer · 04-10-2008, 02:51 AM

I've got my source plugged into a different outlet than my DAC/amp. That should rule out a ground loop. Everything is on a power strip. The hissing is there even with no source plugged in. I think I may just have dirty power in my house (it's pretty old and has rather antiquated wiring). Maybe a power conditioner would help.

infinitesymphony · 04-10-2008, 04:23 AM

Originally Posted by thebikingengineer

I've got my source plugged into a different outlet than my DAC/amp. That should rule out a ground loop.

Plugging equipment into different outlets is one possible cause of ground loop problems. You say that the source and DAC/amp are plugged into different outlets, then you say that "everything is on a power strip." Which one is it?

From your description, it's almost certainly a ground problem.

thebikingengineer · 04-10-2008, 09:45 AM

Everything is on different power strips. From what I had read a ground loop results from equipment sharing a common ground. Regardless, this didn't change any of the hissing.

infinitesymphony · 04-10-2008, 06:09 PM

Has the buzz gone away? That sounded like a ground loop problem, but the hiss might be inherent in the design, as you said. Maybe someone who has modified the Beresford can chime in... You might ask about it in the DIY forum, or try e-mailing the company.

thebikingengineer · 04-10-2008, 08:46 PM

There's still a bit of a buzz, but I think I can safely say it's coming in through the RCA jacks, it goes completely away when I cover the jacks with my fingers. I tried a bunch of different outlets in my house and the hiss seems to be present everywhere. I'm thinking that I probably just have some dirty power. I may try to bring the system into work where we have plenty of power conditioners (high-level rack mounted Furman units). That should allow me to rule out dirty power.

dvw · 04-10-2008, 11:43 PM

Originally Posted by thebikingengineer

There's still a bit of a buzz, but I think I can safely say it's coming in through the RCA jacks, it goes completely away when I cover the jacks with my fingers. I tried a bunch of different outlets in my house and the hiss seems to be present everywhere. I'm thinking that I probably just have some dirty power. I may try to bring the system into work where we have plenty of power conditioners (high-level rack mounted Furman units). That should allow me to rule out dirty power.

If you are covering the jacket, and the buzz goes away, then you have a ground loop. Ground loop comes from when the ground are not of equal potential. The hiss came from the equipment design or manufacturing, I don't think a power conditioner will help.

My Dell laptop got a hiss even when it's running off a battery.

LostOne.TR · 04-10-2008, 11:58 PM

Did any of the other beresford tc-7510 owners have these same problems? Maybe something's wrong with the unit?

Uncle Erik · 04-11-2008, 12:27 AM

Sounds like a grounding problem. Also, do you have a fan or other AC motor near your gear? You might want to move your setup around. Fluorescent lights are a potential problem, as well.

If you want to filter line noise, try one of the RF/EMI filters from Mouser. They're $3-$5 and easily installed into a project box.