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New member Username: CactusjoePost Number: 1 Registered: May-09 | I just inherited a Dual 505-2 in near mint condition, fitted it with an Ortofon cartridge and set it up. Sounded brilliant for about half an hour then developed a humming that got louder and louder until I couldn't hear anything but that. I shut it down for the night and started it up in the morning again, but same hum was present but at a much lower rate. I've got it connected to a Sony receiver, however, the RCA cord is about eight feet long and runs behind some electronic equipment and one pretty large floor standing speaker. I'm wondering if it's generating some kind of static electricity or something like that. Thing is I had a Kenwood turntable that I've had for 30 years in the same spot, also with an Ortofon cart, but never a problem at all. I'm at a loss. Oh, and yes, I have it grounded. |
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Gold Member Username: ArtkAlbany, Oregon USA Post Number: 9521 Registered: Feb-05 | Did you connect the ground wire? |
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Platinum Member Username: NuckPost Number: 12252 Registered: Dec-04 | What happens when you touch the tonearm? |
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Platinum Member Username: Jan_b_vigneDallas, TX Post Number: 13566 Registered: May-04 | . The Dual tables have problems with too many connections. They sound quite good when they are working but tend to require a more than average amount of attention paid to cleaning of contacts. Since you have the table grounded to the receiver and this problem developed over the course of thirty minutes, I suspect you have just stirred the pot of oxidized connectors. If you still have the other table, use it as a test just to isolate the issues down to the Dual or your pre amp/receiver. If you determine the problem is with the Dual, check these pages; http://www.dual-reference.com/index.html This sort of problem with a 505 typically requires a technician who will tear the table down and clean all the connection points, and there are quite a few in a Dual. You can begin, if you feel confident, by taking the headshell off and cleaning all the connectors you see there. A pencil eraser will do the job nicely. If that doesn't solve the problem, you'll need to move on to the connections downstream. Duals had poor RCA cables and quite often they need to be replaced. After twenty plus years, it wouldn't be a bad idea to do so. This will require removing the bottom plate which will give you access to the rest of the connections. When you replace the RCA interconnect, use a cable no longer than one meter as anything longer has the potential to degradate the sound quality of the table. The Dual originally came with the proper length of cable. Whatever you or someone else did to extend this O.E.M. cable could easily be the point where your problem now resides. . |
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New member Username: CactusjoePost Number: 2 Registered: May-09 | Thanks for the responses. Yes, I have it grounded and nothing in particular happens when I touch the tonearm. I did go to that Dual reference site and checked and cleaned the contacts. No results. It appears that there is some problem with the cd player that is sitting next to the turntable. The RCA cables that connect to the receiver were running behind it; I moved the two so that that was no longer the case. After moving the cables, the ground wire and the power cord around in different configurations, the hum actually went away and I was able to play the turntable without any problems for well over an hour. I'm just gonna go with that and hope that the hum doesn't reoccur. If so, you'll be hearing back from me. |
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Platinum Member Username: Jan_b_vigneDallas, TX Post Number: 13567 Registered: May-04 | . " It appears that there is some problem with the cd player that is sitting next to the turntable. The RCA cables that connect to the receiver were running behind it ... " If you come back, you might mention relevant specifics such as this. Your CD player should be switched off when playing your turntable as digital ciruits will interfere with the low level analog from your table, even to the point of injecting noise through the AC lines. If your CD player has a "standby" state, this won't solve your hum problem but will remove a bit of hash from the signal. Power transformers placed too close to cartridges will cause hum. You need to shorten that RCA cable no matter what. . |
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Platinum Member Username: NuckPost Number: 12255 Registered: Dec-04 | I was going to mention the crossed cables and quality in general, whether the items or the housekeeping and arrangement. Who has a good link for arrangement and routing? |
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New member Username: CactusjoePost Number: 3 Registered: May-09 | Thanks for the advice. I did mention that the cables ran behind some electronics, but either way, I'll take your advice and shorten the cable. That should take care of any other problems as the turntable should be away from everything but the receiver at that point. |