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June 26, 2011

Custom Audiophile Power Strip

Audiophiles can be very finicky about their power source. There are countless products available for music listeners to replace their receptacles, power cords, line conditioning and even the faceplate with audio-branded merchandise. Companies like PS Audio, Furutech, Oyaide, Wattgate, Neotech and Onix (just to name a few) all have extensive power-related products made specifically for audio enthusiasts. There are other companies that offer well-made products for a variety of consumers and are still very worthwhile for the discerning audio listener who isn't interested in paying the high prices of audio-niche gear. These companies include Marinco Industrial Group, Hubbell and Schurter.

In this post, I'll be putting together a custom audiophile power strip from a variety of low-cost but high quality components. Please note that this post is for entertainment purposes only, attempting to replicate anything shown here has the potential to be a fire or electrical hazard. I've selected a Hubbell 20A 4-Plex Box in a nice dark-brown color to mount to a generic 2 gang steel box to be the base of this "audiophile" power strip. Some other parts I'll be using are 5 rolls of Teflon tape, a Marinco 8215 hospital-spec 3 prong plug, a run of military-spec 10 gauge silver-plated copper in Teflon wire, some tinned copper braided shielding, a small amount of bus wire and some sleeving and heatshrink.

Oddly enough, it's not too often that you find silver-plated copper or Teflon in power products marketed to audiophiles. PS Audio had a very substantial power cord called the Premier SC that was released in 2006 with silver in it, but it was quickly discontinued (possibly due to people not biting on the $999 SRP). Also, many audio power cords come with cheap high-loss poly vinyl chloride (PVC) dielectric, as one moves up the line, the quality of the copper gets better, but the dielectric remains the same. Nordost actually pays quite a bit of attention to the quality of their dielectric, but it's not terribly common with other companies; you're lucky if they even tell you in the specifications. One would think if these companies agree that the difference in power cords is audible, and I hope they would considering how much some of them cost, that they would consider the quality of the dielectric a little bit more.

This cord starts off nearly identically to my Right Angle Power Cord, so I won't be covering those initial steps in this post. There is basically the twisting of the geometry of the three 10 gauge wires, wrapping with several layers of Teflon, covering with a full-coverage braided copper shield, soldering a bus wire to it, then wrapping with several more layers of Teflon. It's a very time-consuming process, but nice to do while listening to some music. Below you will see the power cord after all these steps are complete.

Powercoated 2 gang box, Hubbell 4 Plex outlet and Marinco plug.

Once all these parts are ready, it's nice to dress the cable with some techflex. I chose to use one layer of red and two layers of black on top to give it a dark brown look and match with the other parts to some extent.

Cable dressed with three layers of heatshrink

Once the dressing process was complete and heatshrink was applied, it was time to attach the Marinco 8215 plug. The silver plated wire was stripped and the bus wire that's conductively attached to the shield is wrapped around the bottom of the ground wire and soldered in place. This allows the braided shield to act as a floating shield (it's not connected at the other end) and protect from EMI / RFI.  

Bus wire soldered to ground conductor

The Marinco plug is installed completely by screwdriver. Pressure allows the contacts to work without soldering. I personally prefer soldering, but soldering terminals are fairly uncommon with these DIY type electrical plugs. If these conductors were pure copper, I would tin them with solder before installing them in the plug to prevent oxidation. The strain relief system is tightened with screwdriver and the plug is ready for use. Before the Hubbell 4 Plex sockets are installed, a small strain relief collar is installed on the two gang box and I used some epoxy to hold it in place, fed the cable through it, installed a clamp and added additional epoxy around the clamp to ensure this cable wasn't going anywhere. The wires were then stripped and screwed down to the corresponding screws on the Hubbell 4 Plex.

Hubbell 4 Plex installed

I was going to use some vinyl dye on the blue collar, but I kinda like it as an unusual accent, it's about the same color blue as the Zynsonix heatshrink. Now that these conductors were fastened on, the 4 plex outlets needed to be screwed down and the unit tested.

Outlet testing device approved

Hardware stores have a very handy outlet tester that gives you a three LED readout to let you know if everything is wired correctly. The two LEDs above indicate that the outlet is in working order. Below is the finished unit ready to feed a hungry amp ;)

The Fine Print:
The above steps detailing the creation of a power cord are for entertainment purposes only, and not to be performed under any circumstances. Please remember that attempting to use homemade power cords can be dangerous to you and/or your surroundings. The owner of this blog and all associated parties can not / will not be held responsible if you attempt the process posted above and cause physical harm to yourself or your surroundings. Many electronics contain high voltages that can kill, and DIY power cables can be a fire hazard. Please keep this in mind.

June 15, 2011

A Customized Dynaco ST35 Kit

The ST35, also known as the Stereo 35, was released by Dynaco in 1963. It's the baby brother of the Dynaco ST70 and tends to be overlooked by many vintage amplifier aficionados. I think the main reason this is the case is that there isn't a large price difference between the two units, and with a tube rectified power supply, power choke, bias system and twice the wattage, it's hard not to want to step up to the ST70. For those of us with relatively sensitive speakers, the ST35 is a nice little unit with a small footprint and more than ample power (17.5 watts x 2). I've also read from more than one source that the ST35 is the best sounding of the Dynaco units stock, for whatever that's worth ;)

Because there are a lot less ST35s floating around, there aren't really any boards with modern circuits that fit into the original chassis. Shannon Parks of DIYTube has created a brand new circuit board that is similar to the ST35 circuit with some modern sensibilities if one would like to go that route. I prefer the looks of the original ST35 chassis myself, with the exposed PCBs on the ends. For this, I turned to Dynakit Parts. Dynakit Parts is a company based in Clifton, New Jersey and has an impressive selection of old school reproductions of Dynaco products. The kits are about as close to the originals as you can get, from the can capacitor to the screw-down terminal strips.

Dynakit Parts ST35 Kit

The original Dynaco ST35 Schematic

Rather than purchasing the whole kit, I purchased a number of the parts a la carte, as I was interested in adding a little bit of customization to the kit with a power choke, power switch, triode / ultra-linear switches, a C8 power inlet for a custom C7 removable power cord and a number of boutique parts. I also added the ST35-BCU bias control upgrade kit which fits nicely above the chassis. As stated on the Dynakit site:  The ST35-BCU employs an adjustable fixed bias circuit which allows for user adjustment of the bias setting of each (EL84) output tube via (4) separate on board precision bias pots. This allows you to not have to purchase a matched set of power tubes. And even if you did purchase a matched quad, power tubes tend to age differently, so they can be adjusted after this occurs. 

Kevin of Dynakit Parts was working on a brand new brown PCB board for the ST35 when I contacted him. I really appreciate it when a company isn't resting on their laurels but investing in new products and innovations. The new PC-13 boards from Dynakit is made from aerospace grade 240 degree Centigrade brown Polymide mil spec material and features silk screened component designations. The brown will go very nicely with the vintage patina powdercoat scheme that I had planned. I wish the bias board was made of the same nice brown material, but we can't have it all, can we? ;)

Brown Polymide boards with a few parts in place
I elected to populate the small driver / power boards with Kiwame carbon film resistors, Obbligato and Mundorf Supreme film capacitors and Teflon and ceramic tube sockets (the Teflon sockets even have beryllium copper contacts). The caps fit pretty much perfectly, although the Mundorfs will have to be mounted once the boards are mounted due to sizing constraints. The Dynakit build calls for nicer silver mica capacitors in place of the ceramic disc capacitors that were in the older units. These can be found just about anywhere (Mouser, Digikey, Partsconnexion, Handmade, etc.). 

I chose to go with the cadmium metal chassis as opposed to the newer stainless steel version as the chassis is going to be powder-coated; no need to pay extra for that chromed-out finish when no one's going to see it ;) Below you will see the chassis, I've enlarged the holes to fit the Cardas binding posts and RCAs, and the center hole has been enlarged to hold a piece of FR4 material that will then hold the C8 inlet in place. I then gave the chassis a nice sanding and labelled it for the powder-coater. 

A few chassis mods and a bit of sanding prep
One thing I would be painting myself was the power choke. A choke is a nice cheap upgrade for the ST35 and helps reduce ripple in the power supply. A number of people have used the C354 to replace the 50 ohm resistor, I chose a Hammond 156R with 56ohms DCR, which is pretty much the equivalent. Chokes tend to be on the ugly side, so if they aren't hiding in the chassis (there's absolutely no room in this case), they need to be dressed up a bit. I was prepping two at once, one for the ST35 and one for the Millett Jonokuchi

The first step in this process is to sand down the metal frame on the choke. Then painters tape is cut and applied to mask off the inside. I've seen some builders just paint the whole thing, but I don't really care for that look. 

Chokes masked off with painters tape
Next I apply two layers of primer, one per hour, then multiple coats of Hammertone paint. It can be difficult to get the Hammertone paint to lay correctly without making the coat too thick. Any over-spray is corrected using black permanent ink. 

Chokes painted with copper Hammertone paint

Once dry, I measured and cut some strips of black leather and used some epoxy to keep them in place, wrapping around the spool of the choke. I use a couple layers of leather when possible to give the spool a fuller look, it's more aesthetically pleasing.

Completed chokes with leather wrapping the spool. 

UPDATE (6/19/11): The parts arrived for the ST35 power / driver boards, so I went ahead and populated everything except for C4 and C5, which will be 0.1uF Mundorf Supremes that will hang off the board just a bit and will need to be installed once the boards are fastened to the chassis. C1 was not used per Bob Latino's suggestion as its purpose is DC input blocking and nearly all modern-day preamps already have a DC blocking output cap, so I used a pair of thick leads to short C1. As you can see below, the Teflon tube sockets have blue PCB boards installed to ease the soldering process. The sockets had a rather long ground pin that I trimmed down and sanded smooth as there would have been a clearance issue in the height challenged chassis. 

ST35 boards mostly populated and ready for installation

UPDATE (7/8/11): The chassis is pack from the powder-coater so I was able to fit the boards in place. I opted to install them rotated 180 degrees as I wanted the RCAs on the rear of the chassis and there wasn't sufficient clearance with the power tube sockets blocking the way. I took some generic gold-plated RCAs from my parts bin and trimmed off the back with a cutting disc, rendering them nonfunctional but small enough to squeeze between the tube socket and the chassis front, simply for the sake of aesthetics. I was also able to position the painted Hammond filter choke, attach the Cardas copper binding posts and install the Cardas rhodium plated RCA jacks. Also installed was the large silver multicap and the bias control board from Dynakitparts. 

Getting started assembling the parts on the chassis
In the interest of making things convenient, I installed a small 6A SPST toggle switch on the front panel of the chassis so the amp can be powered on and off conveniently.

A 3 Amp power switch installed on the front of the unit
The ST35 Bias Control Unit from DynakitParts makes use of an adjustable fixed-bias circuit, allowing for adjustment of the bias setting of each EL84 power tube via four separate precision bias potentiometers. 

Wires run to the Bias Control Unit from DynakitParts

The initial wiring was completed using Kimber TCSS 19 gauge stranded copper in teflon dielectric. I opted to drill out the area originally designated for the fuse holder and the cable in the interest of fitting a C8 power inlet. Because the re-purposed real estate on the chassis back was a little too large for the C8 inlet, I mounted it to a piece of FR-4 material and then mounted the combo to the chassis. This adds a degree of convenience, allowing a removable C7 power cord to be used to power the amp. The fuse was then moved inside the unit and mounted to one of the chassis braces, really a perfect place for it in my humble opinion. Grounding lugs were added to both chassis braces to connect to the RCA grounds (the Cardas RCAs are insulated from the chassis unlike the stock Dynaco RCAs) and the negative connector of the speaker binding posts. 

Initial wiring of the ST35 complete
UPDATE (7/28/11): The transformer bell-ends arrived back from the powdercoater and were reattached to the iron with brass hardware. Rather than using the cut transformer wire, I prefer the Kimber TCSS Teflon wire for all extraneous point-to-point wiring. The dielectric doesn't melt, it's a little thinner so it's easier to route, and I'd imagine the copper's of a higher purity. I opted to add a set of three 1uF 630V Solen film capacitors as bypass caps for the can capacitor. The Solen film caps are only a couple bucks a pop and have the potential to add refinement to the power supply. It's a narrow fit in the ST35 case, no room for zip tie mounts for the caps. 

Transformers wired in place, Solen bypass caps added
The wiring was finalized by adding a pair of DPDT switches to manage the triode and ultralinear switching. This was wired based on the following advise from Bob Latino and Tazsmonn on the DynacoTubeAudio Forum: Remove green or green white wire from pin #9 of each tube and solder to separate poles of DPDT switch on the same end, Solder wire from pin #9 to center pole of DPDT switch, Solder 100 ohm [resistor] from pin #7 to DPDT switch opposite end from green or green white wire, All wiring to and from switch side must be to same tube.

Triode mode switches wired up
Now that the wiring is complete, a final checkout of the circuit is performed, tubes and installed, the unit is powered on and the tubes biased using the ST35-BCU. The tubes installed were Mullard EL84s and Phillips EGC 12DW7. The sound is quite excellent, very resolving and holographic imaging. It actually sounds quite "hifi" for a circuit from the early 1960s. I could use a tiny bit more bass, but I was listening on a small set of Tektons with 4" Fostex full range drivers. Here's some additional progress pics:

Dynaco ST35 front view
Final Dynaco ST35 back view

Dynaco ST35 side view

UPDATE 8/8/2011: I was able to have a pair of custom engravings made for the unit. A 1" gold circle with the word "Dynaco" engraved in black and a small rectangle with a Dynaco Stereo 35 logo that I made in Adobe Illustrator. These are the final touch.

Final Dynaco ST-35 front view

Final Dynaco ST-35 top view

Engraving detail on quad-cap

Final Dynaco ST-35 rear view

To recap, the customizations to the kit were as follows:
  • Teflon tube sockets with Beryllium copper contacts
  • Ceramic gold plated driver tube sockets
  • Mundorf and Obbligato driver board capacitors
  • Solen power bypass caps
  • Kimber TCSS internal wiring
  • Kiwame / Koa Speers carbon film resistors
  • Hammond 156R Choke - 56ohms DCR
  • Dynakit Parts ST35 BCU (Bias Control Unit)
  • Front power switch
  • Triode / Ultralinear Switches
  • Cardas RCAs and Binding Posts
  • C8 power inlet jack with custom C7 power cord
  • Custom powdercoat color-scheme
  • Alternate fuse holder and placement
  • Custom Brass Engravings

The Fine Print:
Please remember that building circuits and performing circuit modifications can be dangerous to you and/or your surroundings and should only be performed by a certified technician. The owner of this blog and all associated parties can not / will not be held responsible if you attempt a build or modification posted above and cause physical harm to yourself or your surroundings. Many electronics contain high voltages that can kill, and mods, if performed improperly, can be a fire hazard. Please keep this in mind. 

June 13, 2011

Pure Silver RCA Interconnects

Audiophiles have had a fascination with silver for as long as I can remember. Silver is about 7% more conductive than annealed copper (59 x 10^6 siemens/meter for copper versus 63 x 10^6 siemens/meter for silver). So on paper, silver is better than copper, but in regards to sound, it's more a preference issue to the listener. Your average silver interconnect tends to be a bit more smooth and detailed than the average copper interconnect. Because the cost of silver continues to increase year after year, silver interconnects will, unfortunately, continue to get more and more expensive. Even still, the sonic qualities are well worth it to many music lovers. 

A silver interconnect starts out with a number of cut strands of pure silver wire. The number of strands varies depending on the geometry of the cable. In this case, each interconnect will be using three wires, one for the signal and two for the return. Typically, silver wire is rated at at least four nines (99.99% pure) and some of the more expensive wire can get as high as six nines. 

High purity silver wire

Silver wire will sometimes come pre-sleeved with Teflon, and in some cases you have to sleeve it yourself into empty Teflon tubes (or your dielectric of choice, some interconnect builders use unbleached cotton). I find a general rule of thumb is to get a Teflon sleeve at least a couple of gauge sizes larger than the wire itself (eg: 22 gauge Teflon tubing for 24 gauge wire), otherwise its far too difficult to sleeve. Once one gets about 3 feet in, the friction gets to be too much, so it's better to get the silver pre-sleeved if one is making a long cable. The advantage of sleeving the wire as opposed to pre-sleeved wire is that you are actually getting pockets of air where the silver is not touching the Teflon. Since air is a better dielectric than Teflon, it's more ideal. You may be thinking to yourself "well, with air touching the wire, doesn't it become oxidized over time?". Copper oxidation can deteriorate the conductivity of the wire, but silver oxidation is highly conductive, so there's nothing to worry about ;)

Teflon sleeved silver wire

Once the wire has been sleeved with Teflon tubing, it can be braided. I've chosen a standard Litz Tri-braid for these interconnects. Electrical tape is used to hold the braid in place before the decorative outer sleeve is placed on the cable. 

Completed braiding process

Soft black nylon multifilament is now added over the cable for a more attractive and finished look. A hot knife is used to cut these sleeves to size to prevent fraying at the ends. 

Cable Sleeved with black nylon multifilament

As an added touch, a piece of custom labelled heatshrink is added to each cable to denote the brand. 

Custom blue heatshrink

Color coded heatshrink is added and Cardas GRMO Rhodium and silver plated RCAs are soldered to the ends using Cardas Quadeutectic solder. As described in more detail in the Cardas RCA Interconnects post, a large amount of heat is necessary to really make sure the wire is well attached to the barrel of the RCAs. Once these are secured, black adhesive heatshrink is added to act as a strain relief system between the cable and the RCAs.

Cardas GRMO connectors
After a signal test with the multimeter, these are ready for action. 

Finished silver interconnect cables

Craving a set of solid silver interconnects of your very own? Contact Zynsonix Audio today.

The Fine Print:
The above steps detailing the building of a cable are for entertainment purposes only, and not to be performed under any circumstances. The owner of this blog and all associated parties can not / will not be held responsible if you attempt the process posted and cause physical harm to yourself, your surroundings or your property. Please keep this in mind.