Amplifier & fm tuner operation query

[augean-4354]

Hi all

I have a Linx Theta fm tuner running into a Roksan K2 amplifier acting as a pre amplifier. When cd input is selected, but not active, I can hear the tuner at a very low volume through the speakers. I do not perceive it as a problem while cd is playing.
Powering off the tuner stops this.
Also: when I power on the tuner I hear an ultra low hum from the tuner itself.
My chief concern is whether the tuner is an electrical hazard to the amplifier or speakers.
A secondary concern is whether anything is failing in the amplifier to allow the spillover of sound.

Any thoughts?

[Fran]

I'm not familiar with either bit of kit - but what you are describing is not uncommon. Typically there can be some cross talk on inputs, but it normally is very faint. Its been a while since I looked this up, but from memory, what is going on is that the grounds aren't switched on the inputs, only the signal side. The ground still carries a bit of the signal though, or a tiny amount bleeds through the switch. The vast majority of amps are wired this way. Chances are all that is OK - if you play CD, with tuner off then you might well hear the CD very faint in the same way. Or connect another source and you'll hear that coming through as well.

The hum is harder to say - if its mechanical hum from the tuner, ie you are not hearing hum through the speakers.... well often transformers vibrate a bit and can cause that. If you are hearing it through the speakers then you could have some ground loop etc or it could be something in the very early stages of going wrong.

Not much help I know!

[augean-4354]

Hi Fran

Thanks for reply.
It is very helpful.
The ultra low hum is from tuner alone.

(so much for inky black darkness...)

[Fran]

So are you hearing the hum through the speakers when tuner is selected, or is it just coming from the tuner box itself?

[augean-4354]

From the tuner itself.
Not through the speakers.
It is very low and I probably only noticed because I switched off all, checked all connections for tightness then switched on fm tuner and was listening carefully.

[Fran]

Probably nothing to worry about so....

EDIT - on a related note - what are you using as an aerial?

[Saxman]

Have you tried disconnecting the antenna.
If the hum disappears you likely have a short between the coax shield and signal cable

[Saxman]

Another thought as far as hum is concerned have you tried disconnecting the tuner from the system and plugging it into a socket outlet remote from the rest of your system
If the hum persists the hum is obviously being caused in the tuner.
Could be as Fran says the transformer. Maybe the best bet is ask hifi hospital to have a look at it in case it could result in something more major