that’s paying attention to the true meaning of things!
Or, is it the true nature of things?
Turntable Right Channel Dropping Out; Grounding Cartridge Body Brings It Back
I’m running an old Numark Pro-TT1 DJ-Style turntable which I have modified in the following ways:
(1) Added a switch to toggle between Signal and Chassis Ground (to solve a Ground Loop issue with another cartridge)
(2) Falling Weight type of Anti-Skate
(3) Balanced Tonearm XLR Cable made for me by a company in England (I think it was Iota)
(4) Added a new ‘The Vessel’ cartridge with an elliptical stylus on an aluminum cantilever.
(5) Replaced the original tonearm wires with Cardas clear tonearm wires,
I’m currently using an ELAC Alchemy phono stage that has balanced inputs; but I’m going out from it on unbalanced RCA cables to my McIntosh C100 preamp. The input on the McIntosh preamp can be configured as either a Moving Magnet phono input or an Auxiliary input; I’m using it as an AUX input. The C200 passes the signal to two MC252 stereo power amps. Each power amp is bridged to mono so that they operate as monaural amplifiers.
There are pictures and descriptions in my profile.
Currently, there is a ‘breakout box’ of sorts installed on the unbalanced line for the purpose of taking voltage readings and oscilloscope traces while using my Analog Production’s Ultimate Test Record to dial in my new cartridge.
What’s driving me nuts is that while I’m listening to music, I suddenly realize I’m not hearing anything from my right channel. I can see the needles moving on the ‘big, beautiful blue’ gauges on the MC252, but the voltage on the multimeter (if connected) is way down, and there is no trace on my old analog Tektronic oscilloscope. Eventually, the signal on all indicators fades to zero confirming what I’m already (not) hearing.
But, if I touch my stylus brush to either side of the cartridge body that is metal, I hear a brief, fairly loud, hum from the right speaker. After that the system works fine again. Sometimes the problem comes back on the next side, but after a few cycles of this ‘hum draining’ exercise, the system is good to go for as long as I care to listen, two or three hours, usually.
I can touch the metal cartridge with my finger, but that doesn’t generate the hum or bring my system back. It’s only when I touch, or when my stylus brush touches, both the cartridge and the headshell that the hum is generated and the system’s function is restored.
Does anyone know, or have an idea, of what is going on here? I have another identical Numark turntable that still has its original unbalanced RCA cabling, and to which I have performed the same modifications (except the grounding switch), it has none of these problems. Am I forced to revert from a balanced to an unbalanced interconnect? Why? What is going on? Anyone know?
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- 24 posts total
A few suggestions - 2. On the tonearm - if you have rewired the tonearm internally with Cardas wire, it is highly possible you have melted the inside of the tonearm bayonet fitting that the headshell goes into, that would explain the sticky pins. Those bayonet fittings do not take heat at all, and are easily damaged, given that the Cardas needs very high temperature to solder properly, it's a recipe for disaster. On some vintage arms that I have had with sticky pins I have successfully freed them up by spraying CRC lubricant into the fitting and pushing the pin in and out ( gently ). The CRC evaporates off. I would also check the tonearm earth for continuity at each point along the path. Another simple test to see if there are any dry solder joints, which can also cause these problems, particularly on the earth leg, is to simply wiggle the cables ( with low volume ) to see if you can induce the problem. |
@dover Thank you for responding. I especially appreciate your experience with soldering tonearm wires, Cardas wires in particular. I can confirm that the tonearm connectors are very sensitive to heat. Immediately after soldering, everything is free and loose, after cooling, everything sticks. I really missed the little aluminum heat sink clips that came with my first Weller soldering kit purchased from Radio Shack many years ago. I learned that the Cardas wires can be tinned before soldering, and it helps, but even better, it seems to me, is pulling the solder tab out (compressing the spring), clipping on a heat sink, and THEN applying solder. I’ll apply the CRC with confidence based on your experience. Again, I can’t tell you how grateful I am for your contribution to the discussion. @elliottbnewcombjr That contraption looks like a holder I could use! I’ve never had much luck with the two-armed + magnifying glass type rigs. |
- 24 posts total