Dual 721 ?'s [Archive] - Audio & Video Forums


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Bill K Davis
04-20-2007, 06:06 AM
What does the 5th black wire coming from the tonearm of the Dual 721 connect to? Where is a good place to get those tiny clips, that connect the tonearm wires to the cartridge pins? Would gold plating on these pins make a difference? Thanks.

04-20-2007, 07:16 AM
When there's a black ground wire, it usually has a small terminal soldered to it. It usually connects to the screw that holds the headshell in place. The terminal might still be there... It's purpose is to ground the metal tonearm and make it a shield around the signal wires.

Needle Doctor has cartridge clips. http://www.needledoctor.com/Online-Store/Cartridge-Lead-Clips

I had the lower-priced Cardas on one of my tables. Didn't seem to grab very tightly. Had to mess with them to get a good connection after only a few months. Sucks since they're the only fairly priced ones I can find on the market anymore...

You have to have a small soldering iron tip, smaller gauge solder definitely helps... You have to work VERY quickly in order to prevent melting too much casing off of the tiny tonearm wires that heat very quickly. Don't apply too much solder, it will take too long to cool. Small heat-shrink tubing can cover a little wire that becomes exposed. Tonearm wire sold for do-it-yourselfers generally has Teflon insulation that won't melt and makes it much easier to work with. Soldering clips to stock wires while on the turntable is one of the most difficult soldering jobs there is. Not trying to scare you... You'll have a better chance of success knowing what to watch out for.

Good luck!!!

Bill K Davis
04-30-2007, 05:17 PM
Thank you Royalphil. Super answer, covered it all. I am going to use that cold solder paste. I assume, from your answer, that there can be no exposed wire at all. I am a klutz,but if the cold stuff is ok, then I can manage.

04-30-2007, 08:08 PM
Exposed wire is no big deal. It can easily get to the point where you'd have problems with bare wires touching each other or a ground though. Like I said, as long as you know about the problem... and you're pretty quick (carefully crimping the connectors on if possible before soldering helps minimise problems with wires needing to be repositioned while soldering).. it should come out OK. A little heat shrink tubing can help... Put something on the turntable to give you a stabile surface to work on... A small pair of needle-nose vice grips might come in handy...

If you're new to soldering... The best way to strip the tiny wires without breaking them is probably to melt a little insulation off.... To solder... Just touch the tip of the iron to the cartridge clip where the wire enters and heat it to solder melting temperature. A second or two should be enough for this job... Without removing the iron, apply a little fine gauge, rosin core electrical solder where the wire enters the cartridge clip... A very small drop is enough... A small, inexpensive 25 watt iron would be about right...

Cold solder paste is probably not a good idea for audio. Just won't give you a perfect connection. Many people would use nothing less than silver solder for tonearm wires. I think silver solder is harder to work with and not really necessary.

Good luck!!! :)