Why is this happening?

I came home from school this afternoon to find my sister worried that the hifi and/or the PC was broken.

She'd turned all of my separates off, but when I turned it all back on my amp was set to the auxillary 2 input, which isn't connected to anything whatsoever. She insisted that she could hear music using this though, just very very very quietly and it necessitated turning the amplifier up to maximum. I had a mess with the DAC, and that was set to SPDIF output, receiving a toslink signal from the computer, yet the DAC is connected to the CD input.

I was just in total disbelief at this point, surely theres no way you'd hear music from it like this - the amp set up to receive a signal from an input that nothing is plugged into. But no, if I start playing a file through the computer and the DAC, and I can hear it really quite clearly through the speakers if I turn the volume up loud enough.,

I'm presuming this must be down to either rubbish internal shielding around the different inputs, or poor amplifier design where the input selection isn't very clean at all. Certainly made me appreciate how noise could get into the amplifier from external sources or 'leak' through other connections, which must somehow impact the sound. I found the same problem with both aux 1 and 2 inputs. The inputs connected to other bits of kit (tuner) didn't exhibit the same thing.

Is this sort of problem/issue typical of relatively low end kit (the amplifier in question is a Marantz PM7000, cost £300 almost 2 years ago).

Is there anything I can do to improve the shielding inside the amplifier fairly easily (I was thinking of a DIY addition of copper shielding - seems fairly straight forward but is it likely to help, and I am worried about heat since the amp runs warm enough anyway?).

Cheers, apology for the long post, just thought I'd best explain what was happening properly

 

could be crosstalk, wich can be caused inherantly by the layout of the internal components.

 

Nah, it happens all the time..about 50% of the kit I've heard does it some of the time.
I imagine people like Madhippy can spend ages tracking down crosstalk in PA/pro/recording situations. Lamp dimmers are a nightmare for buzzes in PA etc.

 

both my nait 5 and nac 82 did / do this so i'd not worry too much - in fact i thought i'd bollocksed my 82 a few days ago when i plugged the cdp into the wrong socket - could hear it very faintly and had palpitations that i'd blown the output stage on the cdp by being a lazy git and not switching it off only to have another look round the back and saw that i'd been a div. that'll larn me...
cheers


julian

 

Yep, it's crosstalk and sadly it's normal. This is why you should only switch on the source you are listening to, otherwise you'll get a little bit of the other sources mixed in.

ps. Never let women near your hifi

pps. Always check the volume control is at minimum before you switch on or your speakers could get a nasty surprise

 

HMMm usually Jap kit and Marantz are pretty good, tends to be more 'cottage' stuff that this sort of thing affects.

Though if you look inside, you will find lots of pcb tracks, and they are very find and close to each other.
The green in between acts as the dielectric of a capacitor, being an insulator, between conductors, and something could leak through their, unlikely, but poss., or it could be happening in the ribbon cable, or the selector switching.
I don't think a bit of copper would help, it is a design issue, and I would expect Marantz to be ok, maybe there isn't a lot they can do about it economically.

 

My Rotel did this. I'm fairly sure (due to the layout and relay switching) that the S300 won't, but haven't tried. I discovered it on the rotel by being sure I could hear something that wasn't right in the background on quiet passages. Stopped the CD and there was something there. It was the tuner....

 

my Shearne does it with tuner.

Isaac, how was the holiday mate?

 

Ah well, I'm comforted to know its normal and not something especially bad with my kit, even though I can't do anything about it (not that its of much consequence during normal listening ).

My sister has been tought to respect the hifi (cos if she breaks it, she's paying for it ) though she still moans about having to select the input on both the DAC and the amplifier ('My stereos so much easier to use blah blah blah....').

With regards to your p.p.s, i accidentally turned the input to cd whilst I was messing around with the volume at max, and I was playing something at the time :nuno:. Lets just say I scared the hell out of myself, but the speakers are fine.

Welcome back Isaac mate, hope you had a good holiday

 

If her stereos so much easier to use, whats she doing playing about with your one then??

 

I'm still on holiday. It's just too hot to go outside right now

Back Tuesday. Then back to looking for gainful employment...

 

my Plinius amp does it too...except you can hear it at 12 o clock!!


ah well, never mind eh

 

My hifi's connected to the PC, which she uses now and then....if she wants any sound at all from the computer, then she has to use it (I did have some cheap PC speakers connected at one time as well as the hifi, so she wouldn't have to mess around with my kit, but they broke and I never replaced them).

 

I've just checked. As I suspected, the S300 doesn't do it at all, even with the volume cranked up to full. However, the relay-switched inputs and large amounts of space between inputs should prevent it, as they seem to.

 

There's always one

I thought most systems do it, well mine does.