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November 30, 2012

Pure Silver Mini to Mini Cable

A short mini to mini cable cable can be very handy when connecting a portable audio player to a portable amplifier. In some cases it's worthwhile to use a digital audio output, but not all portable devices offer this, so the venerable 3.5mm mini to mini will work perfectly well. In this particular post, I will be assembling a mini to mini cable using Cardas 5N (99.999% pure) silver wire and a pair of Neutrik mini connectors, the Neutrik NYS-231 BG to be exact. The B in the nomenclature stands for the black shell, and the G stands for gold contacts. This particular connector is chosen over the Switchcraft 35HD and the Canare F12 as the body is smaller and more easily fits on the face plate of portable amplifiers. You'll notice below that the connectors come in three parts, the connector piece with solder tabs, a barrel and a small tube that acts as a dielectric so the left and right solder joints do not short to the barrel, which is connected to ground.

A pair of Neutrik NYS-231BG

You may notice that the barrel inlets are rather small and not completely ideal for thicker sleeved cable. Because of this, I dremeled out the barrel inlet to create a larger opening. 

Barrels dremeled for larger diameter cable

Once this is complete, it is necessary to sand or file the rough areas so they don't grind up against the wire during use. Once the barrels are prepared, the solder tabs should be identified with a multimeter. In this case, the shorter leg A is the left signal (aka tip), the longer leg B is the right signal (aka ring), and C is ground (aka sleeve). 

Pinout of the Neutrik mini connector

As mentioned above, this cable will be using solid silver wire from Cardas. This wire will be sleeved with Teflon (PTFE) tubing. 

Cardas silver wire and Teflon tubing

Each wire is trimmed to the appropriate length and the Teflon tubing is then slipped over top. The Teflon acts as a dielectric and prevents the strands (aka conductors) from shorting to one another. It's a very good idea to get Teflon that's for a larger gauge than the wire you are using so it slips over it easily. In this case, 24 gauge silver is covered with 22 gauge Teflon.

Silver wire sleeved with Teflon

The three wires are braided together and soldered to the Neutrik connector. It's important for the Teflon tubing to go right up to the solder taps to prevent shorting.

Silver wire soldered to the Neutrik connector

Next comes the black nylon multifilament sleeving made by Techflex. This is 3/16" size, cut to length using a hot knife from Partsexpress. The hot knife prevents fraying at the ends by slightly melting where it cuts. Also note the dielectric material is slid in place before the barrel is screwed on. 

Black Nylon Multifilament

The barrel can then be screwed in place, and the other Neutrik connector installed the exact same way. In the photos below, 1/2" heat shrink is slipped over the barrels to provide additional strain relief and to offer the feel of a "rubberized"-type layer.  

Completed mini to mini cable

This can now be the connection between a portable audio player and a portable amp and not take up much real estate at all. Thanks for taking them time to read this post. If you are interested in purchasing a completed mini to mini cable, please contact Zynsonix.com.

For more pure silver goodness, check out a previous post detailing the build of pure silver interconnects

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.

September 14, 2012

DIYTube Get Set Go 300B Headphone Amp

It's been a little while since the last post, and there's a good reason for that; I've been gathering parts for a very special DIYTube Get Set Go made specifically for the Audeze LCD-2 headphones. The Get Set Go is a single-ended triode design made first-and-foremost for high-sensitivity speakers that only need a few watts to fill a room with sound, such as the Planet 10 Audio Frugel Horn. I did have the fortune to build the Get Set Go for speakers previously and was impressed with the overall tonal character and quality of the sound.

The Get Set Go Board from DIYTube

You may be wondering why someone would be using a speaker amp for a pair of headphones. A typical headphone amplifier will output relatively a small amount of power compared to the speaker amplifiers (in small fractions of a watt measured in milliwatts). The Audeze, as well as certain other planar magnetic headphones like the HiFiMan, really benefit from some added wattage to sound their best as they aren't the most sensitive drivers. Hense, using a low-powered speaker amplifier makes sense, but there are some changes that are necessary.

The biggest change is the output impedance. While speakers are typically 4, 8 or 16 ohm, headphones often range between 32 and 600 ohm. The Audeze headphones that the amplifier is being made for are 50 ohm (although I have also seen them listed as 60 ohm). Since 50 ohm single-ended output transformers don't really exist on the market, you can either have one custom wound, or try and find something that would have an equivalent turn ratio. There's a handy calculator that Shannon of DIYTube recommended that will give the equivalent turn ratio for this purpose. A 3.5K / 50 ohm output transformer would have a turns ratio of 0.12, or 8.367:1. Gery at Transcendar offers a 1.6K / 16 ohm single-ended transformer, the TT-023-OT, which is a 10:1 ratio and close enough for our purposes. Per Shannon, The reflected load would be a touch more linear and lost max output would be minimal.

Secondly, learned from previous experiences like with the Millet Jonokuchi, and to a much lesser extent, the ECP Audio Torpedo, headphone amplifiers do not like their output transformers to be close to the power transformer. When they are too close in proximity, there is something called flux interaction when the magnetic waves interfere with one-another and cause an audible hum with certain headphones. So not only will the output transformers be moved to the opposite side of the chassis, but rather than using an EI transformer for power, a toroid will be used instead as they create much less of a magnetic field. Antec is one of the few manufacturers out there that builds certain toroids specifically for tube amplifiers. The Antec AS-2T300 would be a good substitute for the PA774 with a bit higher ratings.

So other than the transformer choices and their position, this build will be fairly similar to the previous Get Set Go. To make things a little different, 300B tubes will be used rather than 6B4Gs. Also Mundorf Silver Oil capacitors will be taking the place of the Jupiter wax paper caps. The Mundorfs should be a little more detailed, which the Audeze can benefit from with their warmer/darker presentation.

The first action-item on the list was the chassis. I always like to create a virtual mock-up of the chassis layout to see different set-ups and settle on what I feel will work the best. Note that in this layout, the output transformers are distanced from the power toroid and chokes.

Virtual Chassis Layout

Once this is settled, I forwarded the dimensions over to Keith (ebay seller po1019) to fabricate the chassis. The virtual layout is then used as a guide to lay out the parts, take measurements and make markings, and ultimately start drilling / cutting away. After prepping a number of aluminum and steel chassis, I have a small collection of very handy Greenlee punches, which are ideal for making clean holes for tubes and sockets. The metal area (which will be behind the little red tab on the Neutrik locking plug) to release the headphone plug was recessed a bit by sanding using a Dremel and by hand for adequate clearance.

The prepped aluminum chassis

I decided that this chassis would have a more unique and artistic finish. Something more worn and rustic looking. I was actually inspired when I was scrapping off the dark grease on an old baking sheet. This finish starts with some black engine enamel that is then sanded and scrapped by hand minutes after spraying. It produces and interesting texture in my humble opinion.

Textured Bottom Plate

Texture Detail

The texture is achieved by hand using worn out sandpaper at different times of paint dryness, along with the sharp point of a scissor to get the longer lines. Once the texture was where I wanted it, I gave the chassis two coats of clear satin enamel. The parts can now be dropped in place. I began with the smaller pieces, including the headphone sockets, which were flush mounted and secured with black oxide screws. The switch, pilot light, RCAs, binding posts, IEC, Teflon 300B sockets and hole grommets were all installed next.

Part installation on the chassis

Next comes the fun part, the population of the PCB. Varying from the BoM, we have Elma Silmic II caps, Nichicon FineGold caps, Kiwame and Mills resistors and Mundorf Silver/Oil Caps. Slight changes to the circuit includes the Wima 0.1uF snubber cap and a pair of Solen 630V 5.6uF bypass caps in the power section.

The populated Get Set Go Board

On the bottom of the board, at Shannon's suggestion, we have a few of the Mills power resistors to help distribute the heat a little better. 

Bottom of the board

Now comes the long process of preparing the wood side panels. I decided on an antique silver leaf finish for these pieces. Since there is no off-the-shelf option for antique silver leaf that was readily available, I'm using some Speedball brand silver leaf pieces and some Old World Art brand leafing and antiquing materials.

Leafing Materials

Below are the wood side panels for the chassis before any prep.

Wood Chassis Panels

The first step in the antique leafing process is a red basecoat. This is typically used with a gold foil, so we'll see how it performs with silver. Below is the wood with the basecoat applied.

Red antique basecoat

 After two basecoats and a layer of adhesive size, the wood is covered with the silver foil sheets. This is a very unusual process, the foil is incredibly thin and will tear apart if it catches your fingers, so you have to be delicate. each foil sheet is laid down with a little bit of overlap.

Silver foil sheets laid in place

The foil is then burnished with a cheesecloth to have it form the curves of the wood. This is a messy process and the foil flakes will end up everywhere. They are so thin that you'll find them floating in the air. Once this is complete, a layer of sealant is used to protect the foil. 

Silver foil after burnishing

The antiquing kit included an antique glaze that is made for gold so it's a brownish hue. It didn't look right on the silver. Instead I chose to rub it down with powdered graphite before sealing it again. Then two layers of satin clearcoat were added for additional protection of the finish.

More to come

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. 

August 14, 2012

Decware Zen Head ZKIT3 Portable Headphone Amp

The competitive portable headphone amplifier market can be a difficult one to approach. Manufactures quickly churn out new designs and form factors so quickly that unless you spend lots of time on HeadFi, it's difficult to keep track of them all. Between Ray Samuels, HeadAmp, HeadRoom, iBasso, Fiio, and many others, there are enough offerings to make your head spin.

The company Decware, known mostly for their non-portable, tube-based amplifiers, released a portable headphone amplifier back in 2008. While it was only four years ago, there have been hundreds, if not thousands, of portable amplifiers released since then that may have made some headphone enthusiasts forget about it. It was reviewed favorably many moons ago by HeadFi member Skylab whose opinion I respect, and Decware is offering the PCBs and chassis on his website, so I figured it would be a nice diversion to put one together and have a listen, even if it is a few years old ;)

The Decware Zen Head PCB

One of the nice things about the Zen Head PCB is that there's no SMD soldering to worry about, which is almost a given with more modern portable designs. Just regular old through-hole components here. This may not be the best beginners project as there isn't really any online documentation other than a bill of materials to populate the board. Also unusually, the parts values are printed directly on the board rather than part designations.

Rather than simply ordering the BoM, I opted to try a few other parts. All the resistors are Takman REX carbon film, and there are quite a few of them as seen below.

Takman carbon film resistors - pretty in pink

The capacitors were switched with Nichicon / Wima equivalents. Also added were a pair of gold sockets so the OPA2132P op-amps could possibly be rolled in the future. All other parts remained identical to the BoM except for items that were out of stock and necessitated a substitute. After the population of all the parts the board is quite colorful!

The populated PCB

The chassis is a little long compared to other portable amps as the battery doesn't fit on or over the board, but in a plastic battery holder in the back. Compared to something like Ray Samuel's Shadow, this amp is massive, but it will still fit in your pocket or transport just fine in a case. A pattern was drilled on the top of the case for heat dissipation, although it's doubtful that much will be generated.

Zen Head in PCB in case

I noted that the PCB was a little long and ran into the battery compartment. Since there's no traces at the end of the board, the PCB was sanded down a bit so everything would fit nicely. The battery strap was then soldered in place.

Attachment of the battery strap
Next the front plate needed to be drilled. A template was printed from the Decware site that was printed at actual size (not fit to page, very important!) and taped to the front of the plate. The plate was then drilled using a drill press and the holes de-burred.

Drilled front plate

More to come!

Need a custom cable for your iPhone or portable amp? Check out Zynsonix for some great sounding options.

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 15, 2012

MC Step-Up Transformer using Altec 4722

Despite the extreme convenience of computer-based audio systems, the turntable has not lost it's place in the hearts of many audiophiles. Sometimes that extra effort can be worth it, balancing the plinth, brushing the dust off the record, cleaning the stylus, flipping the record after a few songs, the list goes on. There's just something nice about that analog warmth of that teeny tiny stylus wandering through the grooves of a well pressed record.

One of the requirements for owning a turntable is a phono pre-amp. A phono pre-amp brings the low-level signal from the record player up to a point where it can be run to a standard amplifier. Equipment like CD players and DACs don't have this requirement because their output is already at a suitable level. So, a very small gauge wire runs from the cartridge through the tone arm and goes to whatever jacks are on the turntable, generally RCAs on more modern decks. A pair of RCAs are run from these jacks to the phono pre-amp, which amplifies the signal and passes it on to the main pre-amp or integrated amp in the users system. Occasionally, the pre-amp or integrated amp will have a built in phono input, but many enthusiasts prefer a separate unit as the quality can be better. To complicate matters further, many phono pre-amps only amplify the signal of a moving magnet (MM) cartridge. There are also moving coil (MC) cartridges that have an even lower signal that the phono pre-amp simply does not have enough gain to play at a proper listening level. In order to remedy this, one can use an MC step up transformer.
A common step-up transformer, the Ortofon ST-80 SE

An MC step up transformer is completely passive, no electricity is needed to run it. The signal runs from the turntable to the MC step up transformer which amplifies the signal a small amount, then the signal runs to the phono preamp, which amplifies it further to the point where it can be run to the main-pre amp or integrated amp, where it is amplified yet again before it makes it's way to the speakers. So the flow would be Record Player > MC Step Up > Phono Pre > Pre / Integrated.

Many DIYers have taken to the fact that vintage microphone transformers can be used as an MC step-up device. As JELabs has stated: "Moving Coil cartridges behave very much like condenser microphones - low impedance and low output - requiring a voltage boost. Step-up transformers are passive devices and as long as they are wired properly, they are virtually noiseless. To me a wide bandwidth input transformer is the most elegant way of boosting MC output to MM phono level." There are a variety of units that fit the bill, from the Altec 4722 and 15095, Denon AU320, RCA MI12399A, Tamura TKS83, and Thordarson T-43606-A just to name a few. Below you will see a variety of these units in step-up devices made by JELabs.

A Variety of Step Up transformers

I'll be making use of the Altec Peerless 4722, it's one of the most popular vintage units and commands a price because of that demand, but from the way JELabs described it, it seemed that the units have a bit more of a euphoric warmth than the others, which I always appreciate. The Altecs are in the shape of a vacuum tube with eight pins at the bottom designed to fit into a vacuum tube socket. The chassis was custom-made by Keith, eBay seller po1019, and is a very fetching little unit. Holes were drilled for the RCAs, ground posts and switches and punched for the tube sockets that would be holding the Altecs.

Prepped Chassis
Cardas RCAs (GRFA) and ground posts (GRND) will be adorning the petite chassis. These were secured using a small socket wrench.

Some Cardas bling
More to come...

Need a pair of low impedance cables for your turntable? Contact Zynsonix Audio today.  

The Fine Print:
The above steps detailing the building of a MC step-up transformer 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.

June 8, 2012

Custom RCA Switch Box for Audio

So in any given audio setup there may be multiple amplifiers (e.g. a headphone amp, speaker amp, etc.) or possibly multiple sources (e.g. a record player, CD player, DAC from a computer, etc.). A switch box keeps it simple so one doesn't have to reach in the back of the rack and manually switch interconnects to listen to particular equipment. They will commonly have multiple RCA jacks (or in some cases XLR jacks) for both input and output and a switch which is commonly 2 pole (stereo with common ground) or 4 pole (stereo with isolated grounds).

They may be handy, but not all switch boxes are created equally; audio enthusiast know that using a generic one can potentially degrade the audio quality, a situation which just isn't worth the added convenience. All the ingredients need to be of high quality to ensure there is no notable degradation of the signal.

This post will be detailing a simple 6-to-1 switch box making use of high quality parts to ensure transparency. Parts include a Swiss-made Elma 04-1264 switch, EAR isolation feet, Philmore Teflon insulated gold plated RCAs, Neotech UP-OCC sold-core copper wire in Teflon and a lovely custom-made chassis from Keith (ebay seller po1019).

The first task was to take the chassis and drill holes for the switch, feet, and RCA connectors. It may be easy to use a ruler and mark where each hole is going to be, but drilling the holes perfectly in line *probably* won't happen, even on a drill press. When there are multiple items lined up, the eye can very easily identify any slight aberrations to a straight line. I was able to get them pretty close in this case. The chassis was then powder-coated a nice cream color.

Chassis prepped for the build process

The next process is installing the RCAs. Because the powdercoat insulates the aluminum, the back of the holes were filed so the RCAs would ground to the chassis so the chassis would act as a shield. You might be gawking at the Philmore RCA blister pack and thinking "wow, that looks like dollar store garbage"... Looks can be deceiving; under the homely packaging are a pair of very nice quality gold RCAs with Teflon insulation. I like to use Cardas RCAs in many of my builds, but when one is using seven pair, like in this case, that would be quite costly; that's where the Philmores come into play. Each one is cranked on using a socket wrench and the ground washer bent at 90 degrees. 

The chassis populated with Philmore RCAs

Each of the ground washers is then tweaked together with a pair of pliers and a ground wire is run through them, then soldered in place. This particular wire is silver but any bus wire would be fine. This ensures that there is a common ground between all inputs and outputs. 

Ground wire connected to each RCA

Now comes the fun part; wiring up each RCA to the Elma switch. Seeing which solder lug corresponds to each switch position is relatively straight forward, simply look through the transparent plastic at the location of the gold contacts. Each wire is soldered in place and a small amount of heatshrink is placed over the connection. 

Beginning the wiring process

The Neotech wire was kept nice and short for each connection. On the bottom, EAR isolation feet were fitted with a screw, lock washer and nut.

Wiring complete

The box could now be assembled and the nicely finished wood panels placed on the sides. Below are a few photos of the finished product.

Switchbox complete!

Switchbox Front

Switchbox Rear

Switchbox Bottom

Some nice points about this design are the short signal paths thanks to the small chassis, the Teflon insulated wire and RCAs, the gold contacts on the switch and the point to point wiring with no circuit board for the signal to run through. This box could either be used to allow 6 inputs and 1 output, or 1 input and 6 outputs. With a larger box and a second switch, there could be both multiple inputs *and* outputs. Or there could be two of these boxes daisy-chained, allowing for 6 inputs and 6 outputs. Tons of options!

Update: I created a nice little logo "iO" standing for input output and had it custom engraved on a brass plate for the top panel. Looks rather sharp I think :) Some additional photographs with the plate are below.

Need a great sounding passive audio switchbox to tie your system together? Please contact Zynsonix Audio for details. 

The Fine Print:
The above steps detailing the building of a switch box 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.