Adding RCA Jacks to a Technics SL-1401

[MCM_Fan]

As a little project to kill some time, I plan to add some RCA jacks and a ground lug to my Technics SL-1401 to replace the original captive interconnect cables. My Harman Kardon T60 came this way from the factory, and I like this feature. A few months back I made several pairs of double shielded, low capacitance interconnect cables using Blue Jeans LC-1 and Canare LV-77S cable and some Canare F-09 connectors. I am using one pair with my T60 and would like to use another pair with my SL-1401.

I have some nice Rean color coded, insulated RCA jacks on hand:

but before I start drilling holes in my table, I have some questions about the ground lug. First, recommendations of a source for a nice looking, affordable ground lug would be appreciated. I was thinking about this Vampire BP-.5 from Parts Connection:

Or maybe this Zavfino:

but wouldn't be opposed to something less expensive.

In any case, the upper half of my Technics plinth, where this will be installed, appears to be made out of some type of light cast alloy, which I suspect will be conductive once I drill through the paint. The current ground wire does not appear to be connected to chassis ground, it seems to go right into the tonearm. So, like the RCA jacks, I assume I need to insulate the ground post from the metal chassis to avoid creating a ground loop. Since these ground lugs don't come with plastic insulating washers, like the Rean RCA jacks, any suggestions how to accomplish this in a clean, attractive way?

 

[MCM_Fan]

When in doubt, make your own. Here's something I threw together this afternoon:

1" x 10-32 brass screw, #10 ring lug, 1/2" diameter #10 nylon washer, 2x 3/8" diameter #10 washer, 1/2" diameter #10 nylon washer, #10 star washer, 10-32 brass nut, #10 spade lug, 10-32 brass knurled thumb nut.

The two stacked 3/8" diameter black nylon washers are a perfect for match the thickness of the table. To install this ground post, plus the two RCA jacks required drilling three 3/8" holes in the back of the turntable. Here's how it turned out:

Now, I just need to solder the lead wires onto the jacks and lugs and the put the whole thing back together. I completely disassembled the turntable so I wouldn't risk getting any metal shavings in the motor, transformer or any of the printed circuit boards. That took longer than drilling the holes.

Maybe I'll get one of the fancy ground lugs the next time I order from Parts Connexion, but this will do for now.

 

[MCM_Fan]

Inside connections:

And back in service:

 

[MCM_Fan]

A little more info, in case anyone wants to attempt a similar mod to their Technics turntable.

Unless you are 100% comfortable completely disassembling and reassembling your turntable, do not attempt this mod.

As mentioned above, I completely disassembled the turntable prior to drilling the holes. This mod requires drilling three large (3/8" diameter) holes in the rear of the cast aluminum alloy top deck of the turntable. This produces a lot of small metal filings that could ruin a motor, short out a transformer or a printed circuit board. That is why I removed everything from the top deck of the turntable before drilling the holes.

If you're comfortable proceeding, the parts for this mod run around $6 - 7. I purchased the REAN/Neutrik RCA jacks from Mouser. I use a lot of these for my various projects, so I buy them in Qty = 10 each (to get the quantity discount), and tack them onto my Mouser order whenever I start to run low. Here's the ones I used:

Red: NYS367-2

White: NYS367-9

or, if you prefer black for the left channel: NYS367-0

The hardware for the grounding lug all came from my local Ace hardware store.

After disassembling the turntable, I used a 5/64" drill bit to drill pilot holes for the larger 3/8" bit. I placed a towel on the work surface and took it outside and shook it out after every hole (to prevent any shavings from scratching the painted finish of the turntable). I then used a 3/8" brad point dill bit to drill the 3/8" holes. Brad point bits are generally used for drilling in wood, but the light cast aluminum alloy of the Technics is very soft (even softer than billet or extruded aluminum), drills very easily and the brad point bit leaves a nice clean hole with no rough edges.

Here's the bits I used:

Once the holes are drilled, take it outside and blow out any loose metal shavings. Then install the RCA jacks and ground post, cut the original leads short enough to solder what's left to the jacks, reassemble the turntable and you are ready to go. For anyone comfortable disassembling/reassembling a turntable, using basic hand tools and a soldering iron, it's a pretty low cost, straight forward mod. As mentioned the part that takes the longest is carefully disassembling and reassembling the turntable. Other than that, it's pretty basic stuff.

 

[Montycat]

Very nicely done, both in execution and description, and a fine upgrade. That model is one of the best looking Technics tables in my opinion. If it had the more adjustable arm of the 1200 etc I would like it even more.

 

[MCM_Fan]

Very nicely done, both in execution and description, and a fine upgrade. That model is one of the best looking Technics tables in my opinion. If it fit had the more adjustable arm of the 1200 etc I would like it even more.

Thanks. Yes, it's a very clean, elegant looking table, and not one you see everyday. VTA would be nice, but I'm used to tuning it using spacers and mat thickness. This is my first suspended direct drive turntable (to go with a pair of belt driven suspended models) and I am very pleased with the sound quality.

I've tried several different carts on it, but so far the Signet TK5E with original TKN1 stylus is my favorite (even its looks are a good match for the SL-1401).

The table came with a Shure V15 Type IV. The original stylus was long gone and the seller had a local dealer install an inexpensive Pfansteihl VN35E in it's place. Eventually, I will get a JICO SAS for that cart and give it a proper try to see if it can unseed the Signet as top dog.

 

[MCM_Fan]

Brief update: Someone on another forum correctly pointed out that the PCB is grounded to the chassis though its mounting screw:

This makes isolating the ground stud from the chassis using the nylon washers completely unnecessary. They don't hurt anything, but are completely superfluous. You can just go with a smaller mounting hole for the ground stud and skip the nylon washers.

 

[lokerola]

Brief update: Someone on another forum correctly pointed out that the PCB is grounded to the chassis though its mounting screw:

This makes isolating the ground stud from the chassis using the nylon washers completely unnecessary. They don't hurt anything, but are completely superfluous. You can just go with a smaller mounting hole for the ground stud and skip the nylon washers.

This is a great write up, thanks. I've often wondered what it would take to do this to my Denon table.

 

[BillWojo]

Very nice and clean job. Looks like it came from the factory that way!

BillWojo

 

[scorpio333]

Sorry to drag up an old post. I have a 1400MK2 and added jacks on the rear panel. I'm confused when it comes to the grounding. Instead of adding a lug at the rear, I simply left the ground wire alone, routed back through just as it was. Everything back together and time to test it out...IF I attach the ground wire to the integrated amp, I get a hum. I disconnected the wire from the amp and let it hang loose, no hum.

I have no issue not using the ground wire, but I would like to make sense of it all. Honestly, before doing all this I always used the ground wire and never had any hum issues. Why do I now get hum if I just snipped the old cables off and attached them to the RCA jacks?