by Record-changer »
Thu Mar 19, 2009 8:36 pm
It is quite likely that either the speakers are out of phase, or one channel on the cartridge is wired backwards.
Use the mono switch on the amplifier to find out which. (If the amp has no mono switch, use a Y cables to connect both turntable outputs to one preamp input.) If the centered main vocalist on a stereo record disappears with the mono switch on, or if all sound on a mono record but quiet distortion disappears, one channel on the pickup is wired backward. If the sound is permanently disoriented with the mono switch on (it sounds like it is stuck to the back of your head), no matter what record is played, one speaker is wired backward.
If the cartridge is wired wrong, check the connections. The pickup wiring is as follows:
White: Left hot
Blue or Black: Left ground
Red: Right hot
Green: Right ground and headshell ground
I got this off an actual Dual headshell I have in my hand as I type.
If you have a Shure cartridge, the correct order of wires, top to bottom is:
Left hot
Right hot
Left ground
Right ground
If the speakers are wired wrong, check the wires. There should be a marking that tells which wire is the ground wire - a color stripe, silver tinning, or a molded ridge. Connect the marked lead to the - terminals on both ends. But I was upset several weeks ago, because the wire I bought had no markings at all. I had to use an ohmmeter and mark the ends. #&$%#*&!
Also note that mono records made before stereo was introduced DO sound awful when played on a stereo player. There was no quality control over what the groove sounded like when played with a cartridge sensitive to vertical motion. Before stereo, it was not necessary to check that. That's why stereo amplifiers have mono switches
One other thing to check in the indistinct sound area:
When you play a record, is the tonearm constantly bobbing up and down, causing the stylus assembly to flex? (I don't mean the motion caused by a warped record.) If so you have an arm resonance problem. This usually means the arm and the cartridge are mismatched. I never had this problem with any Dual, but it might be that you have a pickup that doesn't like the mass of that tonearm.
If the arm is trying to move while you are balancing it, check the following:
1. Is the turntable level?
2. Are the pickup leads trying to move the arm? If so, they might be caught on something, or the insulation might be hardening.
3. The antiskate on that unit doesn't ever fully turn off. You might be seeing the residual force when the arm is not on a record. It means the bearings are in excellent shape.
4. The arm tries to pull away from the spindle right at the rest post because it is activating the power switch there. But it should not do this when over a record.