Hum and noise with CD-4 and....me

[Lucanu]

My CD-4 setup is working 50%.

The setup is this:
Sony PS-LX350H, low cap cables (RG58) and my JVC 4DD-5.

My setup suffers of a form of hum&noise, very close to what you hear when GND is not connected to TT.
Noise come and go as I come near my turntable, or when I turn on my plasma tv, which is at 10 meters from my quad unit.

Ground is wired and working, I tried to swap AC plugs but, nothing.

The odd thing is that even my pc is not disturbing the tt and the demod.

p.s. I live in Italy and AC here is 220V at 50Hz

 

[ArmyOfQuad]

I feel your pain, I've had so many hum issues in the past, it's absolutely horrible. If only home audio equipment was actually made to be decent, with balanced connections instead of this unbalanced bs. Anyways, I found that many factors came into play with hum. disconnect everything from the amplifier. Add components 1 by 1. Anything that's hooked up could possibly be causing the hum, finding the cause is half the battle.

 

[aquadad]

Hello,
If it is coming from the demodulator picking up a high frequency from the environment (i.e. TV, flourescent light etc.) the radar would light up without a cd-4 record playing. If that's the case you can start turning things off until you lose the radar.

 

[ArmyOfQuad]

That just reminded me of something. I usually have to switch my turntable back and forth from the demodulator and the amplifier, depending on whether or not I'm listening to quadradiscs or not. I found that if I didn't move the ground wire with it, that is if I hooked the turntable to the demodulator, but the ground from the turntable to the amplifier, even though the demodulator is going into the amplifier, this would cause a hum. And it caused a hum that would become greater if my computer monitor was turned on, and would also light the demodulator lamp. So, you might want to make sure the turntable is grounded directly to the demodulator.

 

[Lucanu]

Thanks everybody for help.
Demodulator will make noise in two cases (not always BTW):
1. if I'm near the TT
2. if I turn on plasma TV.

Another experiment was to put the demod in 2-channel mode, pump up volume on the amplifier. Still here noise so I'm not sure what this is coming from.
I checked everything comes to my mind....
I'll try to change wires from demod to receiver (maybe those cables will do the trick...)

thanks,

Luca

 

[Lucanu]

Finally, a good news.

Hum and noise are no more in my house.

my TT has a ground wire with a "Y" connector both plugged in TT and demod.
I looked better to TT. It has a "Q" shaped GND, and if ground wire doesn't touch that tiny thing it won't work.
This is what I have.

 

[The Quadfather]

It sounds like the shield is disconnected from the demodulator to the amp or it could be a bad shield connection on the turntable wiring. A bad ground inside the demod also could do this. Possibly ftrom the jack to the board. Also check capacitors in the power distribution circuits in the demod. I have had this problem. Better just to recap the whole thing. Mine has developed a problem and I will have to work on it soon. This will give me a chance to look for potential trouble spots. Something's definitely not right, as these units are normally rather quiet.

The Quadfather

 

[The Quadfather]

Hey Surround Hound:
I like that moniker! Did you ever get your CD-4 straightened out? If so, what was the problem? Just curious.

The Quadfather

 

[Lucanu]

Hi Quadfather
well, I solved the problem.

First, I saw on SH forum a guy who has the same setup I had, which was a comination of the sony TT, 4dd-5 and the AT440ML.
He didn't had that problem so I had to change my cd-4 TT with an old "unreliable" italian clone, that I paid 5€.
Changed all wirings and connected it to the jvc and it sound pretty better, but still some noise.
So I connected my Sansui QRX-7001 gnd to the shelf where the tt is and the noise disappeared.
I don't really know what happened but it works now.:banana:

BTW the Sony still buzzes when I touch it or I'm near it.

Here you can see both TTs

 

[The Quadfather]

Hey Lucanu:
I was reading some older posts and ran across this thread. I would like to add: It is good that you got rid of most of the hum. However, you mentioned you still get some when you approach the turntable. I suggest you borrow an ohm meter from an electrician, or buy one and check between the tonearm shaft and the ground wire. Be sure to touch a metal part on the tonearm. Also, check between the chassis and the ground wire. In either case it should read close to zero ohms. (dead short) If not, and it is a high resistance, find out why. You can also have a technician do this. It sounds like you really haven't solved the problem, just gotten around it. Good luck.

The Quadfather

P.S. To answer your question, I never got a chance to work on that demod, but in the meantime I picked up a Technics SH400 and that is what I am using now.

 

[Lucanu]

Hi Quadfather,
fortunately I have a tester and an ohm meter, so I checked with those and seems it's okay.
The demodulator is fine too because the sony is the only one which makes that noise if I'm near....
Well WTF... I've got other two to play with

P.S. I'm curious to hear the difference from the JVC and the Technics

 

[The Quadfather]

I probably need to get a new stylus before I make that judgement. My first impressions are that the SH400 is a little softer sounding in the high end. This works well with the overly bright AT440MLa I am using. I need to align my cart also. I have not done so.

The Quadfather