Building Some Interconnects, Part II

6 04 2010

So I realized that I hate being suckered into buying mega-cost interconnects whose ability to improve the sound I hear is suspect at best.  On the other hand, there is the tactile and visual niftiness that comes with having a cable of high quality in the system.   Couple that niftiness with solid construction and good quality shielding, and it seems to me you have a winner.

So I elected to go with Belden 89259 coaxial cable, some Monster-made RCA connectors I found at the local electronics supply, and some woven nylon cable sheathing to make it all look ever so cool.  I also bought some heat-shrink tubing to tie down the ends and make it obvious which cable is right (red) or left (blue).  Finally, I used silver solder to make the joints.  This ensures a corrosion-free and sturdy connection.

I determined that I needed 10 cables in all, two of which needed to be split (these are the ones that run from the woofer output on the ASP to the two channels on the ATI amp that drive the two woofers on each speaker).  I determined that the interconnects between a source and the preamp, and between the preamp and the ASP,  would be 0.75 m, while those from the pre- to the power amp would be 1.0m each. For simplicity’s sake, I defined a 1.0m interconnect as one whose unterminated cable was 1.0m, so in fact each cable is about 5 cm longer than its nominal length due to the RCA plugs on either end.

In case you want to do the same at home, here’s a rough guide.

1.  Measure and cut your coaxial cable.

2.  Align the coax and the RCA connector such that the bitter end of the coax is flush with the center pin solder point on the RCA connector.

The Belden wire and the RCA connector.

3.  Strip the outer jacket from the coax.  Be careful not to cut too deep; you need to solder the outer contact to the woven shielding later on.

Cut back the thin outer jacket. NOT TOO DEEP!

4. Peel back the outer woven shielding.  strip a small portion of the centre conductor, just enough to get a good solder connection to the centre pin of the RCA conector.  Tin the centre conductor just a bit.

Belden wire prepped for soldering to RCA plug.

5.  Solder the center conductor to the center pin.  Clamp the woven shielding to the outer conductor and solder that too.  Don’t overdo it on the solder – use just enough to get a good connection; too much may drip and create shorts that will be very painful to track down later.

An ugly example with a reused plug.

An ugly example with a reused RCA plug.

6.  Cut your woven nylon sheath slightly (2 cm) shorter than the length of coax.  Slide two 7.5 cm pieces of heat-shrink tubing over the ends.  Slide the RCA plug ends over that.

The assembled cable sheath, comlplete with RCA plug back covers.

7.  Slide the whole sheathing assembly over the unfinished end of the coax-RCA plug assembly you have just created, snugging one end of the nylon sheath right up to the threaded part of the RCA plug.  Slide one piece of  the heat-shrink over that, such that when you heat it up, you will still be able to place the back cover on the RCA plug.

One end of the cable with nylon sheathing and heat-shrink in place.

The nylon sheath and the heat-shrink should both be snugged up to the threaded portion of the RCA connector.

8.  Shrink the tubing using a heat gun.  Protect the nylon sheath with teflon tape or other suitable substance; it may melt at the temperature necessary to completely shrink the heat-shrink tubing.

9.  Attach the back cover for the RCA plug.  Congratulations – you have completed one end of the cable!

One end finished!

10.  The other end should now look like this:

The unfinished end.

The unfinished end.

11.  Solder on the other RCA plug and finish as in steps 1 to 9.

12.  IMPORTANT!  DO NOT CONNECT THE CABLE TO YOUR STEREO UNTIL YOU HAVE DONE THIS! Use a multimeter to test that the centre pins are connected to each other, that the outer collars are connected to each other, and that the centre pins do not short to the outer collars.  Your stereo equipment is a very expensive tool for discovering shorts in your RCA cables.  Do it this way instead.  Trust me.

13.  Repeat as often as necessary to make the number of cables you need.

You will recall that the Orion plans call for the bass output from the ASP to be split into two inputs on the amp – one for each woofer.  I was at a loss as to what to do about this for some time;  I couldn’t think of a way to make a Y-connector that wouldn’t look shoddy or makeshift.  Then I hit upon the idea of using two blocks of wood, hollowed out in the centre, and making the joint inside.  You may still think what I did looks makeshift.  You may be right, but bite me anyway.  Maybe I’ll cryo-something them, or put green paint on them, and they will sound like Bog and all His Angels themselves singing in the firmament.

I cut three pieces of wire:  two of 40 cm (output side) and one of 60 cm (input side).  I cut two pieces of oak, left over from a chair I made for my wife a couple of years back.  I clamped them together in a vise.  I drilled one hole from the left hand side of the clamped assembly (for the input wire), along the plane of the joint between the two pieces, to approximately the middle of the block.  I drilled two similar holes from the right hand side of the clamped assembly (for the two output wires).  When the assembly was unclamped, I used a chisel to sculpt out a largish hollow connecting the three holes.  It was in this hollow where I placed the joints among the wires, soldering together on the one hand all of the twisted woven shielding, and on the other all of the centre connectors.  I coated the whole section of exposed wire with many coats of liquid electrical tape from West Marine to prevent shorts.  I added nylon sheath and heat-shrink to the wires, placed the resulting structure between the two blocks of wood, glued them, and clamped them very tightly for an hour or so.

I then sanded and stained them.  Not bad for a first effort, although a slightly more elegant shape might have been possible had I the time and/or patience to create one.

My "wood block" Y-interconnects.

My "wood block" Y-interconnects.

Time Flies

4 03 2010

OK, OK.  I can tell from my stats that there are at least 3 people out there who are hanging on my every post.

I received the Analog Signal Processor (“ASP”)  unit and speaker wires from Don Barringer some time ago.  As I expected, it’s got a homemade feel about it, but the workmanship with respect to the population and soldering of the PCBs is first-rate.

The unit is black painted metal with a transparent Plexiglas top.  The only external control is the low filter switch, which is designed to get rid of inaudible low-frequency sounds that might cause excessive woofer excursion (and consume a substantial amount of amplifier power at the same time).

Simple but robust workmanship.

There are three output channels per side – woofer, mid, and tweeter.  The woofer output is meant to be run into a Y-adaptor and to drive two channels of the power amp – one for each woofer.

Gold RCA outs all around.

The ASP is driven by an AC adaptor – supplied with the system, and is on whenever it is plugged in, as evidenced by two green LEDs mounted directly to the PCBs.  The ASP also comes with rack-mount adaptors that can easily be affixed to the left and right front panel.

Finally, one can adjust the output of the various channels with respect to one another by means of trim pots that attenuate or boost the sound for that channel in, I believe, 0.5 dB increments.  You can see one of them in the background in the shot above – sort of a blue-and-white round dial immediately behind the reflection of the light fixture.

I’ve tested it and it seems ready to go.

Also from Don Barringer came the speaker cables, made of eight-lead Belden wire, terminated at the amp end with 4 pairs of banana plugs and at the speaker end with a Speakon connector.

20-foot Orion cables by Don Barringer.

That’s it but for the wood, which is coming from Wood Artistry, and hopefully soon, as I ordered it back in December.