NV112 connecting to laptop question

Jim Saunders · Post by **Jim Saunders** » 14 Aug 2006 5:46 pm

I'm trying to get a good connection from my laptop, with BIAB, to my NV112 CD input. I'm getting a good buzz from it. I realize the laptop output is a stereo and the 112 has a mono 1/4 jack. Advice?

Jack Stoner · Post by **Jack Stoner** » 15 Aug 2006 2:06 am

Sounds like a "ground loop" hum. You will have to isolate the AC power ground in either the PC or amp. If it were me, I'd isolate the AC power ground in the amp with a "ground lifter" AC plug converter.[This message was edited by Jack Stoner on 15 August 2006 at 03:06 AM.]

Andy Sandoval · Post by **Andy Sandoval** » 15 Aug 2006 2:36 am

Jim, I had the same exact problem when I hooked my laptop to my amp. Jacks advice is the way to get rid of it. On my current setup my amp has two input channels so I used an adaptor which splits a stereo mini from the laptop headphone jack into two 1/4" guitar jacks for the two amp inputs.

John Daugherty · Post by **John Daugherty** » 15 Aug 2006 7:08 am

I built a small passive mixer for that purpose. The computer stereo output connects to 2 volume controls. The outputs of the controls(center terminal) are connected together through 2 resistors. Then a single, shielded cable connects to the amp.
This mixer can also be used to connect a CD player to your amp. It can be built in a metal box the size of a cigarette pack.

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www.home.earthlink.net/~johnd37

Jim Saunders · Post by **Jim Saunders** » 15 Aug 2006 12:42 pm

Thanks Jack, it worked. Appreciate the response. Andy thanks for the input. And, John, thanks too, but looks like I got by with a simple fix. I need electronics for dummies. [This message was edited by Jim Saunders on 15 August 2006 at 01:44 PM.]

Gareth Carthew · Post by **Gareth Carthew** » 15 Aug 2006 2:06 pm

Removing the ground from the amp will solve a ground loop problem but you'll be removing the safety earth.

Better to remove the ground connection from the Laptop power supply. It should be double insulated anyway.

Try running the laptop on battery power first while connected to the amp to make sure it solves the problem.

Is it a 60Hz "mains hum" or a higher pitched hum?
A friend had the same problem when using his laptop with a karaoke setup. I first thought of some sort of ground loop problem and suggested the high pitched hum he was experiencing could be a result of the switched-mode power supply for the laptop. When running on batter - no more problem.[This message was edited by Gareth Carthew on 15 August 2006 at 03:09 PM.]

Dan Dowd · Post by **Dan Dowd** » 16 Aug 2006 5:18 am

Hey Guys, I think you need a 1/4 stereo plug for the rear jack on the 112. I use a stereo RCA (2 RCA pin plugs)or a 1/8 inch stereo plug to the computer out, to a 1/4 inch stereo plug. Plug it in to the PRE AMP IN jack on the rear of the amp. The Peavey manual shows this connection. If you dont have the manual go to the Peavy web site where you can download it.