I have a switching box that I use with my Beogram 8002 and 8000 connecting them to a Beomaster 4500. Both Beograms suffer from a distinct electronic hiss and I suspect it is due to the fact that I have attempted to ground both Beograms to the single ground source on the switch box.

Is this improper and how should I go about correcting this issue?

Jeff

Most ground problems I've seen involve hum rather than hiss. My guess is that the hiss is due to using a switchbox; using a switchbox to switch two turntables is usually discouraged, due to capacitance issues and/or noise. If you're going to use a switchbox, use an inline phono preamp between each turntable and the switchbox's inputs, and run the switchbox's output to a line-level input. That way, the switchbox will be dealing with line-level inputs, as (probably) designed.

-Adam

Adam,

I stand corrected, the sound is definitely a hum.

I removed the ground wire from the Beogram 8000 leaving the 8002 ground to the switch box and the hum disappeared. I am assuming that one can not ground two Beograms to the same ground.

So where do I go to ground the 8000? I am thinking that I can connect it to the metal shell of the Beomaster 4500, but I am unsure about this.

Any advice?

Thanks,

Jeff

Does indeed sound like some sort of ground loop. Which input was selected when you removed the 8000's ground wire, and the hum went away? Did hum go away for one, or both? I've seen amps with two grounding screws and two phono inputs, but I'm not sure if they ground to the same place or not. Grounding one to the 4500 might help, but I'm not sure. One thing you might want to try is reconnecting the grounds together, and reversing the prongs on the Beograms, to see if that has any sort of effect. Radio Shack sells a ground loop isolator, but I'm not sure whether or not putting that between the switchbox and 4500 would have an effect.

-Adam

If you removed the ground from one TT and the hum disappeared, that means you never had to ground the TT in the first place.  Grounding is necessary only if you experience hum.  Well designed electronics in a good topology don't need separate grounding to be connected.

Adam,

I connected both Beogram 8000 and 8002 ground wires to the available ground screw on the back of a switchbox with unsatisfactory results. Both Beograms had a mild hum.

When I removed the ground wire from the 8000 leaving the 8002 alone grounded to the switchbox, the hum on the 8002 disappeared.

However the hum on the 8000 got considerably worse. I need now to find an appropriate ground for the 8000.

My first place to look was on the back of the Beomaster 4500, but unless I missed it the 4500 doe not provide a ground.

Jeff

Yep, definitely a ground loop; the results with the 8000's ground disconnected proves it. One option is to build a separate switchbox for the ground leads using a single-pole double-throw toggle switch with each turntable ground lead connected to one of the outer terminals, and a wire from the switch's center terminal going to the switchbox's ground screw. Another is to find an available screw of any sort on the back of your Beomaster 4500, and use that as a ground screw (not sure if it'll do anything about the hum, however). Last option would be to just use one turntable with the 4500, and switch between them manually (probably your best option, IMO). Hope this helps.

-Adam

Hi Adam,

I found a metal screw on the bottom of the Beomaster 4500 and connected the Beogram 8000 ground wire and PROBLEM SOLVED. 

With the Beogram 8002 grounded by itself to the switchbox and the Beogram 8000 to the Beomaster 4500 both are no hum-free.

Apparently we can not ground two Beograms to one ground source.

Thanks for your help!

Jeff

Glad you were able to fix the problem. I've never messed around with using two turntables on the same phono input, but I'm glad you were able to find a solution. I'd still compare the switchbox with using a single turntable on a single input, since I'm concerned about signal degradation due to the low voltage and capacitance levels involved with a phono input. Anyway, glad I was able to help.

-Adam

Hi Adam,

Today is Canadian Thanksgiving and I was using both Beogram 8000 and 8002 with exceptional results during dinner.

The Beogram 8000/MMC6000 was more than up for a Bach organ concert with E. Power Biggs, while I had the 8002MMC2 playing a Spanish guitar piece that was simply wonderful. Since both turntables do multiple plays, as the concert only served as background music for dinner, it was nice just to let the Beograms do there thing…… with the repletion completely unnoticed.

I love your footer and would like to copy you, however I feel that Beogram 4000, 4002, 4004, 8000, 8002, 1602, CDX, Beocord 8004, and 9000 is a bit too long.

Thanks again for your help.

Jeff