XA1 problem

Discussion in 'Hi-Fi Stereo Systems & Separates' started by themoid, Jul 29, 2002.

  1. themoid

    themoid
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    Hi guys,
    Looking for your help. When i turn on my musical fidelity XA-1 amp there is a humming noise coming out of the speakers which gets louder as you turn up the volume. The speakers are OK as they work with the AV amp. I'm hoping someone can tell me its a simple fix, but i'm worried I've damaged the amp by plugging and unplugging the speakers while its powered up.

    Any ideas / suggestions ?
     
  2. buns

    buns
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    I wouldnt worry about damage.......i have the same problem from a brand new amp. In fact im told it is not a problem, rather it is perhaps more of the truth!

    My amp is slightly high end, when i got it i was a bit owrried about the humming.....in fact i had radio 1 playing as well!!! Anyhow.....after a bit of work i got confirmation that i was suffering both RF interference and crappy mains noise. Im not sure whether one or both would be your problem though...... i am informed that UK devices shouldnt suffer since they should have all sorts of shielding and nonsense to cut out these effects (which also effect the sound of course!!)

    So what i did was move things about a bit....... my pre turned out to be very sensitive to proximity to its power source and the cd player couldn't be anywhere near the power amp. This did some good.... however...... the real difference i got was using some speaker cable i made some years back from braiding cat 5 cables..... if you look on www.tnt-audio.com you can find similar designs...... they are time consuming but do work. Altenatively and easier, just arrange your cables differently, if you have a power cable and signal cable parallel, well, just dont!! I promise you its a bad thing!

    Basically play about a bit. I was told i should just fiddle with every factor....cable lengths, types, design, structure. Power feeds, system position, other hardware in your circuit (such as hair dryers which are spawn of satin in audio terms.....) so have a play and if you cant sort anything, gimme a bell!

    good luck!!

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  3. tomson

    tomson
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    As buns says - fiddle around with your erm.. parts and the problem should dissappear.

    I had exactly the same problem when I first got my XA-1 and I spent hours buggering about trying to find out what was wrong. In the end I tracked it down to a signal booster plugged into the same 4-way as the amp. I plugged it in somewhere else and the problem was gone.
     
  4. themoid

    themoid
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    Thanks for the info guys. I had a play with it all yesterday, but it looks like there may be some kind of earthing problem with the cd input connections on the amp. If i plug the interconnects into the Aux 1 sockets everything is OK, but plug them into the CD sockets and the humming begins. If i pinch the connectors on the amp the humming decreases, but if I just touch the casing the humming increases. Really frustrating !!

    Do you know if the aux 1 port is set up differently to the CD port. I can use that OK but i'm not sure if the sound will be as good. Anyway, I think I may need to get it looked at. I've had it for 4 years or so, perhaps it may be wear and tear. I'm going to have another play at the weekend, and i'll let you know if I make any progress.

    Cheers again guys :)
     
  5. stranger

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    sounds like you need an attenueated pair of phono leads cd to amp, try russ andrews pbj a great interconect in its own right and just a few quid more for the attenuation (tell them the make of your gear) money back if not satisfied.
     
  6. themoid

    themoid
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    excuse my ignorance but why would I suddenly need an attenuated pair of phono leads when my normal ones have been working OK ? why would making the signal (as i understand attenuation) weaker reduce the hum ?

    i dont have a lot of technical knowledge in this area, but im always looking to learn
     
  7. stranger

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    excuse me for trying to answer your query but how the hell was I to know your setup had been working correctly and you hadn't just aquired your equipment?
     
  8. themoid

    themoid
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    Stranger,

    looks like the tone of my post may have been slightly mis-understood.

    as I said, I do not have a lot technical knowledge and was just asking why you thought an attenuated cable would be required

    really sorry to have so obviously p****d you off

    still interested if knowing what difference an attenuated cable can make though ?
     
  9. stranger

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    apparently some cd players outputs can overload an amps cd inputs-when this is a problem an attenuated cable can balance things out.
     
  10. mickey moo

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    you have an earthing problem somewhere - I would guess that tho only piece of equipment in the system that is earthed is actually the amp (IEC plug, round three core cable) and everything else is just two core (slightly oval cable).
    Is everything connected to the same wall socket and have you got tv/vid/dvd connected to the amp. Trouble often comes from having a tv booster in the loft which is on a different ring main and having a different earth voltage which comes down the co-ax into the tv and finding its way through scarts/interconnects back to the first piece of equipment earthed - often the amp.
     
  11. buns

    buns
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    Just browsing and i notice this problem still being discussed.

    I agree that earthing may be a problem, but i beleive it is not your main problem. Earthing is more commonly a reason if the amp is humming, not the speakers (though i wont argue that it could still be important). With my amp, I have speaker hum and transformer hum. The transformer hum i have traced to messy mains, a good filtered mains lead will sort this. The speaker hum does not appear to be so linked. The magnitude of my speaker hum appears to be dependent mainly on positioning of the componenets and their leads. If my power amp is near anything else, the noise is bad, presumable due to induced currents from neighbouring electronics. This subject is very much a difficult one, there is no definitive answer seeing that everyones set up varies. Fiddling is your best way. If you email Geoff at tnt-audio, he may well have answers and was very helpful with me.

    keep trying!

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  12. themoid

    themoid
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    thanks for the help guys, i'll move some stuff around this week and see if i can sort it out and let you know how i get on.

    just on the subject of mains filters, anyone recommend one ? my dad has recently had problems with a new washing machine, and as he works for the power company was able to get it traced back to a fault street light, which is kinda interesting as if it can affect a washing machine it will certainly have an effect on sensitive audio equipment i gu
     
  13. buns

    buns
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    Sometimes it can make a big difference, to other the difference will be totally negligible! Russ andrews seems to be the leader in this type of thing for mainstream use, plus he does a mone back garantee. You can get far higher end mains solutions but i assume you arent looking to spend thousands!

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