Weird interference on my audio system

Stephen_74

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Jul 13, 2016
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Weird one here. I bought a Technics SL QT turntable second hand. I put it through a Panasonic SU-CH80 amplifier which I also got second hand. The turntable doesn't have an integral pre amp so I bought a cheap one new. It doesn't have much in the way of a name, just a capital H integrated with a star icon, but it was made in Taiwan if that helps.

In the morning the system is unbelievably good. There is no background noise at all and when I put a vinyl record on it is just like listening to a CD.

In the evening, however, there is lots of crackling interference together with a French radio station. During the evening the system is unusable. This noise is constant, whether a record is playing or not.

Anyone got any ideas?

This is in The UK BTW.
 

Ironsounds

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Jul 31, 2011
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Hello... Just aluminum cooking foil as a TEST... Use some wire and Tape / paper clip?...to to the turntable ground or stereo ground thumb screw... we used Aluminum foil around "English" made... OLD Marshal tube Guitar Amps... when we were playing near radio towers or downtown areas... they would pick up Police and emergency radios B D
 

Ironsounds

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Hello... IS the Phono Pre-amp metal shielded Box or plastic?
Does it have a grounded plug? or Wall/DC convertor?

1) Try a different placement for it and/or some "grounded" aluminum foil around it.
2) Did you hook up the ground wire on turntable too?
3) Poorly constructed shielded audio cables could cause this too.
 

Stephen_74

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Jul 13, 2016
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Thanks for answering. Yes, the ground wire is hooked up to the pre amp. How do I ground aluminum foil? Is it just aluminum cooking foil or do I need to get some from an electronics shop?

Also, have you any idea why it's perfect in the morning but unlistenable in the evening?

Have the lizard people woken up by then and are listening in to my Bach records ;)
 

Stephen_74

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Jul 13, 2016
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Thanks mate. I will have to try this later because it is working perfectly now. I am just listening to Fidelio on it.

Out of general interest, have you any ideas why the interference comes in the evening. It is every evening as well, so it couldn't be atmospheric conditions.

 

Stephen_74

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Jul 13, 2016
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Ha, it worked! Slight buzz which isn't there in the morning but not audible when you are two metres away.

I just wrapped the preamp in cooking tin foil and made sure it was in contact with the turntable ground.

What is that all about then? Is it the quality of the preamp that is the problem?
 

Ironsounds

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Hello... Well... you say the Musical and Sound of the pre-amp are Good... but the "shielding" is NOT... The "Signal" from a Turntable is a very low output, and needs a extra stage of amplification... so you need a Good/Great shielded path for this "Signal"... You can "spend a lot" on Pre-Amps and cabling that eliminate noise from the "Radio wave spectrum".

Guitar Pick guards have to be "Shielded", and people will custom wrap their cavities with "adhesive copper" for those problem area's they Play a lot.

Early days of "Wireless" MICs, "Guitar belt transmitter's", And TUBE amps had these problems... like I said we would get Police and Emergency channels start blasting through a Marshal tube amp... when we played a certain place in a Downtown area.
 

Stephen_74

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Jul 13, 2016
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If it works with tin foil I will go with that. Probably about 10p worth of tin foil!

 

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