DIYTube Budgie SE 3W Single Ended Amplifier

Our good friend Shannon Parks over at DIYTube has designed another great tube-based amplifier, this one using a pair of EL84 power tubes and a single 12AX7 driver tube.The Budgie has been designed from the ground up to be an affordable build, the power and output transformers (sourced from Edcor) run a measly ~$100 or so dollars for all three! Throw in the parts ($35), tubes ($35), PCB ($39), and build your own chassis ($20), and you should be able to scrape by under $250. Granted, this would be a bare bones build, but it just goes to show you that this is an affordable design. You can go hog wild and add Shannon's top custom printed top plate and a Hammond chassis with walnut sides, and maybe some boutique coupling capacitors, and we're still looking at a reasonable price tag for a single ended tube amplifier.

Budgie SE with custom printed top plate and walnut sides

The DIYTube Budgie SE Schematic

I chose to skip the top plate as I enjoy building my own chassis (it prolongs the whole building process which I find inherently enjoyable anyway). I had a scrap piece of copper which I trimmed to 7" x 12", which is a little larger than the custom printed PCB and will allow a little more air between the components. The base would be an intricate mitered wood frame made from chair rail molding from the hardware store. 

The copper plate was cut, punched, drilled, Dremeled, etc. to hold all the parts in place. The layout used to plan the initial plate size was used to determine where each hole would fall. Small holes were drilled using the drill press, larger holes for tubes and the Neutrik locking plug were punched using GreenLee punches, the extra-large holes for the capacitors were cut using hole saws on the drill press, and square holes, like for the transformer and IEC inlet were cut using a Dremel metal cutting disc. The copper is a little denser than aluminum and requires a bit more effort to cut through.

Once the chassis plate had all the holes necessary to accommodate the parts for the build, it was sanded down, starting with 80 grit sandpaper and ending with 600 grit. Next, a coat of clear satin finish was sprayed on each side to protect the copper, otherwise it tends to pick up fingerprints and oxidize. I've had good luck with the clear satin enamel from Krylon. I tried the Valspar outdoor clear satin and it clouded up and flaked off, so I won't be using that again. Gloves needed to be used after the sanding process so my fingers wouldn’t leave any oil on the copper. Once the clear coat was dry, parts could finally be fastened onto the plate.

Copper Plate with myriad holes

First the various connectors and jacks could be installed. The RCA females are nice quality Philmore gold plated units with a Teflon dielectric. The binding posts are generic heavy duty gold plated brass with clear plastic on top, made to look like WBT's early binding posts I assume. Also installed is the ubiquitous Neutrik 1/4" TRS locking jack, which I elected to install with the release up front for ease of use, the IEC inlet with built in fuse, and a small toggle switch for power.

The Budgie gets some cost effective connectors

Populating the PCB were a number of parts I had lying in the parts bin, some Koa Speers resistors (green) from Mouser, and some spiffy Elna RFS Silmic II electrolytic capacitors from Digikey. Both the Koa Speers and Elna Silmics are considered to be "warm" sounding parts (the opposite of bright or harsh), which is usually what I'm going for. The big blue caps are 150uF Cornell Dubiliers that have good ripple current ratings, which will help smooth the power supply a bit in addition to the Triad choke called for in the design. In addition, I added some surplus Nichicon 0.1uF film caps bypassing the power caps, which would help ripple to some minor degree as well. I also found some oddly shaped Mundorf EVO Aluminum 1uF film caps that I installed on the side of the board. These were relatively low cost and a bit more interesting to look at than a standard film cap.

Top of the PCB with Tube Sockets, Film Caps

Bottom of the PCB

The PCB could now be fastened to the copper plate with short aluminum standoffs.

Directly beside it would sit the 1H Triad choke which I pulled from an ST70 when I upgraded that choke to Classic Valve's heavier duty model.

Sitting directly beneath the output transformers are a pair of matched vintage Russian silver mica capacitors. If a manufacturer was making these today, I'm sure they'd be pricey, but given that they are old military surplus, they're downright affordable. Some audiophiles feel these sound comparable to the Russian Teflons, so I figured I'd give them a shot. They are certainly interesting looking little metal brown boxes.

Check out those Russian silver mica caps!

With all the small parts in place, I could secure the Edcor power and output transformers. I purchased some unpainted bells from Edcor (I'd imagine these are popular products on their page for anyone who doesn't want blue) and had them powdercoated with an antique copper color, then replaced the nylon washers and the nickel hardware with brass for a more uniform look. These were secured to the copper chassis with rubber washers to dampen a bit of the vibration they produce.

You can always hide a depth mounted screw under an xformer

Since a copper plate cannot sit on its own, a wooden base was fashioned out of some decorative molding from the hardware store, the edges rabbited with a router so the plate could sit on top via "gravity mount", and then mitered to be a perfect fit for the plate. Once the four pieces of molding were secured together with woodglue and allowed to dry, I went through the process of copper leafing and antiquing the wood. If you'd like to see more details on this process, please check out my Bottlehead Crack Coppermine project.

Completely wired up

And the photos of the finished unit:

Front

Rear

I had a listen with a pair of Sennheisers and really enjoyed the quality of the headphone output. I'll be testing the unit with some speakers shortly. Looks like Shannon has another winner on his hands!

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. 

Balanced XLR to RCA Cable

Balanced XLR interconnects are what many people consider to be a superior connection between components. Typically found in Pro-audio equipment, they feature three wires rather than the two in an unbalanced RCA interconnect. The three wire system includes hot, neutral and ground. Current flows through the hot and neutral with both an inverted and non-inverted version of the signal. The component only needs to sense the difference between the two signals which assists in rejecting common noise. Common noise includes RF and ground loops, both of which can be quite annoying.

Some higher-end components have taken notice that balanced XLR interconnects can be more ideal and include them as optional inputs and/or outputs. Unfortunately there are many components that do not offer them, so you may end up with a component with XLR outputs and another with only RCA inputs. In this case, an XLR to RCA cable can be used.

The parts needed are relatively self explanatory. An XLR connector on one side (may be male or female depending on the component), an RCA plug on the other side, and three wires to connect them. One can also use only two wires and short the XLR internally between pins one and three. Note the diagram below that pins one and three are connected to the sleeve of the RCA and pin two is attached to the tip.

Starting with a Neutrik NC3-FXXB (3 pin female XLR connector), each of the pins are identified by the small number that's actually printed on the front of the plug.

The inside of a Neutrik NC3-FXXB

If you follow this blog, you've already seen countless litz braids of silver plated copper in PTFE, so we will skip that and move on to the soldering of the individual wires to the solder tabs on the Neutrik XLR connector. Each joint should be heated quickly but adequately (not too long which could melt the plastic casing) which will result in nice shiny joints.

Wire soldered to the Neutrik XLR

Next comes the sleeving. In this particular case, the braided wire is covered with soft black nylon multifilament. The black nylon multifilament is made by the company TechFlex and has a nice vintage look. It can be purchased from online retailers like Cable Organizer and WireCare. In order to sleeve the wire, a hot knife is used to cut the sleeve to prevent fraying, it is then slowly slipped over the braided wire and once completely covered, the other end is cut with the hot knife. To hold the sleeving in place, adhesive heatshrink is used on the ends where the strain relief from the plug will eventually cover the cable.

Sleeved cable

As you will note below, the strain relief system is placed over the heatshrink to give it something to "grip" to. The metal barrel is then slipped over the front of the XLR plug.

Barrel and Strain Relief

The boot can now be slipped over the other end of the cable and screwed in place to secure the barrel and strain relief system. Neutrik does offer the FXX line with a number of different colors. I'm using red here to denote the right channel. 

XLR side is complete

Moving on to the other side of the cable, the RCA connector will be attached to the cable. First, the metal barrel for the RCA is slipped onto the cable, then the RCA connector soldered in place. Both the number 1 connection and number 3 connection from the XLR side are soldered to the ground or "sleeve" in this particular configuration. The number 2 connection is soldered to the signal or "tip". Once soldered in place, a small piece of heatshrink (in this case red) is used to prevent shorting between the ground and signal. The nylon sleeving is then slipped as far forward as it can go and the strain relief on the sleeve is crimped around it.  

RCA connector soldered in place

Now another piece of adhesive heatshrink is placed over the bottom of the RCA connector to act as additional strain relief and further secure the sleeving.

Heatshrink sleeving in place

Now the metal barrel of the RCA can be screwed on. The cable is now complete and can be tested. 

A single completed cable

The pair of XLR to RCA cables

I hope you enjoyed this post. If you are interested in purchasing a completed XLR to RCA cable, please contact Zynsonix.com.

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.

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.

Custom C7 Power Cable

If you're familiar with a standard IEC inlet, it has three separate connectors for hot, neutral and ground and is on nearly all audio equipment worth its salt, with a few exceptions of course. But we just can't be lucky enough that all equipment has an IEC three prong power inlet, can we?

Furutech gold IEC power inlet

Older equipment and certain newer universal disc players, among other things, have a C7 inlet. A C7 inlet does away with the safety ground connector, and is unpolarized, meaning that the hot and neutral is interchangeable as the cord can be aligned either way on the inlet. There are certain C7 connectors that are polarized which have a square end on one side and a circle on the other to ensure the hot and neutral go through the appropriate route.

Polarized C7 power cord

In my case, I'm currently building a Dynaco ST35 kit which combines the circuit ground with the chassis ground. When this is the case, there is a good chance for hum if attaching a preamp and amp on the same breaker if the circuit ground of each is attached to the safety ground of the power cords. Many of the forums I've visited recommend not attaching the chassis ground to the safety ground on the power connector to prevent hum on Dynacos. Please note that safety ground is called safety for a reason, if it's not connected and the circuit shorts to the chassis, it can be very unsafe.

I'm using a Shurter C7 inlet for my ST35, and it would be blasphemous for me to connect an ordinary C7 power cord to my tricked out new Dynaco ;)

Schurter C7 Power Inlet

So, what are the options for aftermarket C7 cables? PS Audio produces the 12 gauge Jewel power cord which is offered in a C7 configuration and runs ~$70-80 on the street, then there is the Audioquest NRG-1 power cord, which has a similar street price and comes in 16 gauge. Both are larger than the typical 18 gauge unshielded C7 power cord that comes with most equipment and are of course much more attractive.

In the interest of DIY, I chose to build my own. There are sparse few choices for a cable-end plug. Furutech offers a very attractive one, but at $45 as of this writing for a C7 plug is a little rich for my blood ;) It's also a little large for my purposes.

Furutech C7 power plug

Luckily, a builder in Japan offers a low cost C7 connector with solder connections that accept anything up to 16 gauge. These are floating around on that auction site if one searches for "C7 solder".

The power cord starts off a little differently than my other power cords. Rather than twist 10 gauge wires together in a spiral, I chose to use 16 gauge wire and braid it in a tri-braid configuration.

A bundle of 16 gauge silver plated copper in Teflon

Tribraided conductors

Then came the Teflon tape insulation, which covers the braided cable twice over.

Initial Teflon wrapping

A shield is then added over the top, which is connected to the source side ground via a soldered bus wire to create a floating shield.

Wrapped with a tinned copper mesh shield

The next step is two additional layers of Teflon are added to the top, over the braided mesh shielding.

Teflon wrapped 16 gauge power cord

Finally, the decorative techflex sleeving is added to the top, in this case both Chrome XC and black PET sleeving was employed to give a low-level shimmer. The low-cost Marinco 5266 is screwed down on one end and the C7 connector is soldered to the other. A piece of heatshrink is used as a strain relief, and in this case, the joint was bent at 90 degrees while the heatshrink was still hot for ample clearance behind the amp.

High quality DIY C7 power cord

Reverse shot detailing Techflex covering

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 below 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.