Loud Hum Through speakers when playing Dual Turntable

I'm very close to upgrading my system, mainly to play Vinyl, but will have to start with either an amp or turntable.

As mentioned previously, I have a Dual 505 turntable and a Cambridge Audio Azur 540A amp, which has a gentle hum when turned up to 3/4 power, which was necessary to hear vinyl records even via a preamp, but not for CD via my Monitor Audio Bronze B2 speakers.

I was very close to deciding that the amp was the first thing to upgrade, but today, while playing the turntable the gentle hum became a very loud buzz through the RH speaker. This stopped when I put the tonearm back on its rest and did not happen at all with the CD.

Am I right to think, now, that the problem is in fact with the turntable? In which case, that's the first upgrade to make?

Thanks for any suggestions,

Stephen

You have an earthing issue by the sound of it. That should be simple enough to sort.

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Originally Posted by walpurgis

You have an earthing issue by the sound of it. That should be simple enough to sort.

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Thanks Geoff, any advice on how I do it. I have the ground wire from the Dual securely wrapped around the screw on the preamp, in fact double-check it today.

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Originally Posted by RothwellAudio

Either a wire within the tonearm has broken and moving the arm causes an intermittent contact (hence the loud buzz stopped when you put the tonearm back on its rest), or the tonearm has a mute switch which silences the cartridge when the arm is on its rest (hence the loud buzz stopped when you put the arm back on its rest).
Either way, the arm wiring needs to be checked.

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Thanks Andrew. I'd be fairly sure (but not certain) that the old Dual doesn't have a mute switch in the tonearm, and I'm leaning towards the wiring problem. I think I have to accept that my Dual has seen better days (I bought it second-hand in 1985). In which case my decision is made easier and I'm going to upgrade the turntable first...I'll probably buy a Rega Planar 1.

If your Dual is an earlier one, it likely has a cartridge carrier that slots into the headshell. The little metal tags/tabs on these can make poor contact sometimes. That could be something to look at.

I'd not give up on it too easily. The 505 is a decent enough little turntable.

Thanks again Geoff and Andrew. To be honest, I think I'm ready for a new turntable and probably an amp too! I'm getting too old not to treat myself to decent sounds!

This is the headshell with the cartridge attached.

http://gallery.adareimages.com/cartridge.jpg

Get yourself a P1, sit back and enjoy the trouble free sound.

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Originally Posted by hifi_dave

Get yourself a P1, sit back and enjoy the trouble free sound.

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Going to the London Saxophone festival weekend after next and when I get back, I'll be placing the order. :)

I have stock..:)

Another thing to point out is to get the right pickup for the riaa.
To play 3/4 loud for normal listening points out that your riaa have a wrong amplfiering of the signal according to your pickup.
Some pickups need more gain than others.
Some good riaa have several different gain stages and ohms to best fit pickup. So you don't need to crank up the volume so much.
It's important for the best sound possible to get this right.
If your riaa don't have this so check the manual for the data and buy the best pickup for that.

Tommy