Ok are you guys ready. Here is my situation. In this clients house I have two receivers (1)Denon AVR-883 and (1)Yamaha 530 At the Yamaha side there is a cd player. The client wanted cd audio at the Denon side, so I ran a line level. Everything is perfect when both systems are running, however, when the Denon is shut down the audio is slightly distorted at the Yamaha side. Can some one help me figure this out.

Thanks in advance,
Dean

Now you've got me racking brain... had the exact same situation about 2 years ago. Something about a Yamaha receiver not liking the load disconnect when the receiver at the other end of the CD player's Y-adapter gets shut off. We used a special Y-adapter to solve the problem, but damned if I can remember the specifics.

I documented it on the job sheet, lemme dig it out today & post again later.

Doug Butler
HomeWorks Group, Inc.

Sound like you are dealing with a potential ground loop! Try disconnecting the power cord for the Denon receiver when the humming noise is there. If it goes way, try using a ground lift adapter for the power cord at the denon receiver.

You never mention, is there Cable TV in the system?

You need a buffered "Y" connector(s).

Tributaries is one manufacturer that makes them.

Or you could use the digital out (if the cd player has one) for one system, and analog out for the other.

Should take care of the problem.

JJP

The reason for the distortion is that when you shut down the Denon it is shorting its inputs. Most receivers do that. I would connect a buffer to the CD player. A better fix will be if one of the receiver's has a digital input use that and RCA on the other.

John
I must be blind I did not see your post.
Zinon

Thanks your all your input. I'm going there tomorrow to try the buffered "y's". The cd player does not have a digital out

Dean

Here's more detail about what happens, just to help avoid this sort of problem --

The signal goes into the amp input, probably through a resistor, then on to a transistor. When the amps are on, voltages are present on the transistor that make it look to the signal like a linear high impedance load -- like a resistor.

When the amps are turned off, the excitement begins. The power voltages inside the amp drop to zero, at very low impedance, so now the + side of the transistor looks like a ground to the audio coming in. Since the voltages in the amp are at zero, the transistor's current flow now only comes from the input, limited only by the input voltage and the input resistance. Basically, the transistor now looks like a resistor in series with a diode across your audio signal. This will definitely cause distortion!

This does not happen with all amplifiers. In my experience, most since the mid 90s do not give you this kind of problem. It happens when you are trying to give your customer a break by using his old two-channel receiver for the second zone amp.

I have solved this by building a little harness that places a 1K resistor between the CD output and EACH input. This way, the effect of the "shorted diode" is minimized. In some cases, you might have to go as high as 4.7K. Suddenly you are spending your time and money to solve a problem caused by saving your customer the price of a new amp. I now avoid this when I can.

The Tibutaries piece will definitely solve this, and should be included in the initial price, just in case.

Audioplex also makes them. It's called the "Buffy".



More info can be found HERE

JJP

It becomes a reflex when you know the answer. :)

Sorta like raising you hand and shouting "OOOOO, OOOOO" before the teacher gets the whole question out of their mouth.

JJP