Donate to a Great Cause and Win!

My good friend and fellow DIY'er Nate Maher (who goes by n_maher on many audio forums) has a wonderful cause that he's working toward. He's going to be raising money for the upcoming 3 Notch Century, which is a challenging and scenic ride through the White Mountains of New Hampshire that benefits the disabled via Northeast Passage, an organization that works with everyone from individuals born with disabilities, accident victims, wounded combat vets, etc. 

I think this is a wonderful cause and encourage you to participate. If you need a little more encouragement, Nate will be raffling off an ECP/Beezar Torpedo headphone amplifier, a pair of vintage recabled AKG K340 headphones, and a custom pair of interconnects. 

Win Nate's Torpedo!

Please head over to: http://www.active.com/donate/threenotchcentury13/natemaher to participate. Each $10 donation is worth a ticket in Nate's raffle. Once you're donated, be sure to send n_maher a personal message on HeadFi with the # of tickets that you ”purchased” via your donation and the name under which you donated to enter his raffle.

About Northeast Passage
Northeast Passage, founded in 1990, is a nationally recognized leader in the provision of innovative therapeutic recreation services. Northeast Passage delivers disability-related health promotion and adapted sports programs throughout New England. All proceeds from this event directly benefit their participants.

Fine Print: The owner of this blog does not have any affiliation with Northeast Passage and/or the Three Notch Century event and will not be personally providing any of the prizes mentioned above. 

Bottlehead Crack Coppermine Edition

I’m going to guess that the Crack is Bottlehead’s all time most popular kit. A great little tube headphone amplifier at a price-point nearly anyone can afford that sounds very good for the money, it’s really hard to go wrong here. The Crack has gone up in price a little bit since its introduction 3+ years ago, but it’s still quite a value. I also highly recommend the Speedball upgrade, which replaces the plate loads on the tubes with a constant current source and brings this amp into its own with added detail and transparency. I built a Crack shortly after its release and of course replaced a number of the parts with racier versions and it sounded quite good. Years later, I reminisced how much fun it was to put together that point-to-point Crack and decided to build a new one from the ground up with fancy parts and give it a layout that would accept that added girth.

While I normally would have turned to Keith Kirby to shape me up a new chassis, it was time for me to step up and build my own, despite not being crazy about working with wood. The first task was to figure out what the size of the top plate would be with the additional room for larger capacitors (in both coupling and power supply positions) and a pair of large-ish Hammond chokes for the power supply as well. This ended up being 12” x 12” (more than twice the stock 10x6 size!), which is perfect as sheets of metal can be ordered in 12” x 12”. Rather than go with the typical aluminum plate, I spent a few extra bucks and went with a 12” x 12” x 0.1” copper plate. The copper provides even better grounding and conduction than aluminum and comes with a nice natural color. Despite the fluctuating metal market, a copper plate this size isn't too bad at about $40.

The next chassis-related task was to create the wooden box that the plate would sit on top of. This is not the most trivial of tasks for those of us not blessed with nice power tools and a garage. So, I drew up the dimensions of the plate, where the plate would sit on top of the routed edges on the wood, noted how deep the route would be, and based on that drawing I found the appropriate sizes for the wood to be cut and added about a 1/16” of an inch for wiggle room. For the wood itself, I decided I wanted something a little more intricate (“fussy”, as someone I know would call it) than flat sides, so I went with a flat piece of pine and a piece of decorative molding and glued the two together. I then used the router to make a decorative route along the outer top edge and used a rabbeting bit to make the inner route that the plate would sit on. Four sections of this piece could then be cut at 45 degree angles to make the box. Since I was cutting the wood by hand, I used a plastic miter box and did my best to cut at a straight 45 degrees all the way down to get the corners to line up properly. Obviously, this never works out perfectly, so that’s what wood filler is for.

Wood frame for metal plate "gravity" mount

Wood frame corner detail

Once the box was assembled with wood glue and the wood filler sanded down smoothly, four small wood blocks were glued to the bottom corners to provide adequate surface area for the EAR damping feet to be placed. For the finish, rather than simply staining the wood like I normally would, I opted to use a copper leafing kit from Old World Art to bring the copper theme into the base. The leafing kit is a multi-step process including a red base coat, adhesive size layer, application and burnishing of the metal leaf, a sealer coat, application of an antique top-coat, and then another sealer coat. The nice thing about copper leaf is it's incredibly cheap; a set of 25 sheets runs less than $10. 

Old World Art Leafing Kit

Red base coat

Copper leafing process

Once complete, it looks like the texture you would find on an old frame on a painting in an art gallery.

Copper leaf after burnishing

Copper leaf over the whole frame

Now the copper plate could be 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. 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 after sanding and satin finish

Aside from the PT-3 transformer from Bottlehead, a little bit of the wiring, and the Speedball upgrade, all other parts were swapped. For the wiring, silver plated copper in PTFE/Teflon was used for power connections, including the heaters, Cardas 20.5g internally litzed copper in Teflon for the signal, and Kimber 19 gauge copper in Teflon for capacitor connections, etc. Shielded Cardas copper in Teflon was used for the input and output wiring with the copper mesh shield grounded. A few of the nice gold plated solder posts from VT4C were used in place of the tin plated ones, and short turret boards were used to handle the power supply connections, which I find a little more robust for multiple connections. The tube sockets were Teflon with gold plated copper contacts and matching miniature PCBs. Coupling caps were a combination of a 47uF Obbligato Gold Premiums and 70uF Obbligato Film in Oils, both good values for the money. The final power supply capacitor was replaced with a set of three 75uF Axon caps wired in parallel (simply because the three together were a bit cheaper than a single 220uF film cap). The volume control was a relatively low-cost Taiwanese ladder stepped attenuator. Resistors were all of the Kiwame / Koa Speers carbon film 2 watt variety. The knob was a solid aluminum one with set screw from Kilo. Finally, the switch was a nice little brass plated 3A DPDT that was made for guitars.

Wiring up the unit went just like a stock unit aside for a few things. The Hammond 159M chokes (measuring 254 ohms resistance) replaced the 270 ohm resistors, the Obbligato Gold and Film Oil caps were wired in parallel and soldered in place of the coupling electrolytics, the pilot light was wired up to the 6.3V heater , and a few of the ground connections were moved about.  Also is the 6SN7 driver tube. A big thanks to Grainger who posted the alternate wiring information at Bottlehead which is duplicated below:

12AU7 PIN                          Wired to 6SN7 PIN

1                                                                                             2

2                                                                                             1

3                                                                                             3

4                                                                                             7

5                                                                                             N/A

6                                                                                             5

7                                                                                             4

8                                                                                             6

9                                                                                             8

I assume it is correct as it was confirmed on the forums by Caucasian Blackplate, but I make no personal guarantees ;)

Initial parts installation on the copper plate

Even though the stock Bottlehead PT-3 looks great as-is, I wanted to try something a little different for this build, so I opted to use a transformer cover from VT4C. The transformer cover base had to be trimmed to fit the PT-3, but it's a perfect fit length and width wise. 

Bottlehead PT-3 sitting on top of VT4C transformer cover base

In order to make a nice clean install for the three 75uF film capacitors in the power supply, I fabricated a piece of FRP (fiberglass reinforced plastic) with a few turrets that would sit on top of the caps and accept solder connections so they could be cleanly wired in parallel. The three caps wired in parallel give about 228uF (75x3 plus a little bit of tolerance wiggle room), very close to the 220uF electrolytic they are replacing. 

Fabricated FRP board

Fully wired up in stock configuration

After firing up the build in stock configuration and making sure it held smoke. I powered it down, removed the tubes and installed the very worthwhile Speedball upgrade. As mentioned earlier, the Speedball is a constant current source upgrade that replaces the plate loads of the input and power tubes. I also took the time to wire up the big 70uF oil filled Obbligato film caps.

Here's a shot of the completed amplifier sitting on the copper leafed base. I really love the look of the copper color and black on this build. 

Completed Coppermine Crack

Some nice little embellishments were a custom logo I made for the Coppermine Crack which I had engraved on a 3" wide copper plate, as well as some copper plated earrings which I attached to the top of the oil capacitors. 

Engraved plate and copper plated earrings on top of the oil caps

The final product looks and sounds great. I hope you enjoyed this build. 

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. 

Audio Note DAC 2.1 Level B

As mentioned in previous posts, much of the audiophile world has really moved from compact disc players to a computer-based digital audio setup, whether it's streaming over the local area network or coming directly from the output on your desktop or laptop. As we all know, the built-in digital audio converter in a computer generally leaves a lot to be desired for an audiophile. The sound card is generally an afterthought built into a computers motherboard with some of the lowest-cost chips available, likely doesn't have a very low noise floor and probably has gimmicky features like 3D sound processing. The best option is to bypass as much of this as possible, either through a dedicated optical output from a reputable sound card (something like the ESI Juli@), or to use a USB to coax converter (there are TONS of these on the market from companies like M2Tech, Musical Fidelity, Stello, etc.) and get that digital signal to a high quality external DAC.

An external DAC (digital analog converter) effectively converts a digital binary signal (think 1s and 0s) to an analog signal that you can send to your speaker or headphone amplifier. External DACs started to gain momentum in the late 80s when used with CD players with a digital output.

A handsome old Sony DAS R1 DAC (circa 1987)

Now with computer audio, there are thousands of DAC offerings on the market. There are non-oversampling (NOS) DACs from makers such as MHDT and Valab, and oversampling DACs (also known as interpolating DACs) which use a pulse density conversion technique, from makers like Benchmark, Lavry and Audio Note Kits. Some feature tubes, some are solid state, some are warm sounding, some are bright or analytical. Really the best thing you can do when selecting a DAC is read a review from someone whose ears you trust (tends to enjoy gear that you enjoy) or preferably test one at an audio meet, as the source really is the cornerstone of your audio system and it's important to get one you really like. When a warm sound is preferred, often a tube DAC is the best answer; tube-based implementations tend to add harmonics and distortion to the sound that's very pleasant to the ear. Since this blog is all about DIY, I will be building a tube-based DAC kit.

The company Audio Note Kits has been offering tube-based kits online for nearly ten years now and has been around for much longer. The available number of kits is impressive; there are a number of push-pull amplifiers, single-ended amplifiers, DACs, pre-amplifiers, phono pre-amps and speakers. A rather interesting new product is the HiFiMan HE-6 headphone amplifier that runs on EL84s. As of this writing there were over 20 different kits available. The current DAC models are the L2.1, L3.1 and L4.1. Each model is offered in a few different flavors, the standard and signature versions, and there are a few options available balanced transformers and a USB converter. The different versions feature different tubes (6922 in the L2.1, 5687 in the L3.1 and L4.1), different transformer configurations and the parts quality is predictable higher in the more expensive L3.1 and L4.1.

In this post I will be assembling a DAC 2.1 Level B kit. The difference between level A and level B is simply the optional I/V transformers. These transformers handle the current to voltage conversion. These can improve sound quality in a digital system for three reasons, as stated by Sowter:

• The usually rather poor operational amp chips which are fed by the I/V resistor are eliminated.
• The digital and analogue grounds can be isolated which can remove some complex distortion mechanisms.
• The unique frequency characteristics of the transformer can provide improved filtering of the quantization noise.

The starting block of any build is the chassis. Audio Note Kits had the intelligent idea to create a relatively universal chassis that could be used for many of their builds. Any holes that are unnecessary are covered up by the front and rear plate or are on the bottom where no one can see them. This "universal" chassis is a very thick gauge and is quite heavy, which is necessary to prevent bowing if it's holding a number of bulky transformers. The stock chassis comes in a nice textured black, with black front and rear panels (these appear to be plexiglass or lexan) and screened gold logos and text. I opted to have the chassis powdercoated gold to match the gold logos and make my unit a little different.

Gold powedercoated chassis

When the unit is powdercoated, it's necessary to leave the exposed metal areas for proper grounding and protect the screw holes so they are still usable after the process. These can be done by using screw hole inserts and stickers that are compatible with the powdercoating process. Below is an example of a chassis hole with exposed metal surrounding it after the gold powdercoat.

Exposed metal for grounding purposes

Concentrating on the chassis inputs and outputs, it was already decided that the chassis would use a balanced AES-EBU digital input in one of the D-flange holes. To make use of the other two D-Flange holes, I'll be using a pair of Neutrik recessed RCAs for the analog output of the DAC. The RCAs themselves would be replaced with the higher quality copper body Vampire RCA jacks (as seen in lower right).  

Neutrik recessed RCAs

Also used is a Vampire XLR-CF jack with gold plated copper alloy contacts for the AES / EBU digital input. Do note that the holes on the chassis need to be enlarged a bit for these items. 

Installed input and output jacks

A view from the back of the unit

Next, the power switch and power inlet could be installed on the back panel of the chassis. I opted to upgrade to a Furutech IEC inlet FI-103(G) with built-in fuse holder which has some nice gold-plated copper alloy conductors. Included in the kit is some nice high quality silver plated copper in Teflon wire which is used for internal hookup from the. This wire is used to wire up the ground connections (which short to the chassis) and the power transformer. Also mounted during this process is the power choke which takes the place of a resistor to help smooth ripple in the power supply.

Transformer and choke mounted

The printed circuit boards are thick and of good quality, which is useful if one ever decides to change / upgrade parts later on; there's nothing worse than desoldering parts on a cheap PCB and losing a solder eyelet in the process. It's also nice that the real estate given for coupling capacitors is very ample, so the builder can easily fit some big paper-in-oil caps if they'd like. Also note the little holes in the board near the capacitor area so they can be secured with zip ties. Zip ties are not included with the kit but are readily available from hardware stores or places like Partsexpress.

The line board

The power board

The DAC 2.1 is offered with Mundorf Supreme film capacitors but you can request the Audio Note Tin caps for the line board. Below are the Audio Note tin caps shown next to a nickel for scale. These are not small by any means, but typically sized for oil caps. These are not paper in oil but make use of mylar film and are assembled by Audio Note UK. 

Audio Note mylar film and tin foil capacitors

I decided to begin the build by populating the boards. Brian Smith of Audio Note Kits was able to offer me some nice Takman carbon film resistors for the line board. You'll also notice the AN tin caps and Elna Silmic II electrolytic capacitors. Interestingly, the ceramic tube sockets here are the chassis mounted type which are mounted on aluminum standoffs. The reason for this is so wires can be soldered to eyelets at the bottom of the socket to power the heaters on the tubes. 

Populated line board

Next the M2 power board would be populated. I dropped a few parts that I had in storage in these, including Kiwame resistors which are rated to 2 watts and typically measure very close to the printed value. Also added were Elna Silmic and Nichicon Fine Gold capacitors. 

Populated M2 power board

Once the boards are completely populated, it's a good idea to clean off the solder flux. My favorite way to do this is to splash some isopropyl alcohol on a cheap toothbrush, in this case a Snoopy themed kids toothbrush (they're like a dollar for a four pack) and scrub away on the bottom of the board, then dab with a paper towel to remove the flux. After doing this 2-3 times the board is suitably clean. 

Circuit cleaning supplies

Once the boards are clean, they are wired up to the unit. As the M2 Power Board has quite a few wires connected to the bottom of the PCB, fly leads are all soldered in place before the standoffs are secured to the chassis.

Bottom of the M2 Power Board

Below is the top-down view of the unit after the fly-leads from the power board were soldered to the transformer.

M2 Power Board in place

Once the M2 Power Board is secured, the line board can be wired up. As shown in photos of the internals of the unit, heatshrink was placed on the leads travelling to the line board for a more uncluttered look.

Bottom of the line board

Next up is the line transformers and DAC portion.

And the finished product from the outside:

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. 

Beyerdynamic T5P Recable

Beyerdynamic is a family-owned audio equipment manufacturer based in Germany that produces headphones, microphones and wireless audio systems. The headphones produced by Beyer feature great build quality and the sound produced by their top-tier headphones is something the discerning audiophile can really appreciate. The DT770, DT880 and DT990 models are ideal choices for the listener on a budget, and if one likes what they hear, there are the pricier Tesla-based models that Beyer introduced over the last four or so years: the T1, T5p, T50p, T90 and T70.

Beyer's Tesla lineup

The Tesla nomenclature comes from the redesigned transducers that achieve efficiency values of over one Tesla, which is the unit of measurement for magnetic flux density. This provides the listener with nearly double the volume at the same input level as typical headphones. Also unique to the Tesla line are the drivers which are angled toward the listeners ear.

Today I'll be recabling the luxurious Beyer T5p. The T5p is effectively the mobile version of the T1 (The "p" standing for portable) and with it comes a few changes, including a short 4 foot cord and a 32 ohm impedance which can be driven easily from sources like the iPhone / iPod and other portable music players, and leather pads to help attenuate outside noise.

Beyerdynamic T5p

Something I've found with some Beyer headphones (especially the DT880 / 250ohm) is the upper-midrange can cause me ear fatigue over long listening sessions. This certainly doesn't affect everyone, but a few other people with sensitive ears have mentioned the same finding to me. I've found the best remedy for this is to recable the headphone with Cardas enameled copper wire, which effectively warms up the sound signature and subtly rolls off those frequencies which I personally find fatiguing.

Cardas copper wire

The first step is to braid the Cardas copper wire in a litz-braid. I've chosen three different colors in this case, red for right signal, blue for left signal and black for ground.

Braided Cardas wire

The cable is then sleeved with the soft black nylon multifilament sleeving. You'll notice below that electrical tape is over the ends of the wire, this prevents the small conductors from snagging the sleeving while they are fed through by hand. 

Sleeved with black nylon

Once the leather earpad and sealed ring are removed, that gives access to the driver housing. Note the angled driver in the photo below. 

The T5p angled driver

Take a look below at the beautifully machined Tesla driver housing, I've never seen anything like it. 

T5p Telsa driver backside

The existing wire and solder is removed. This is done using as low a temperature as possible as to not damage the delicate drivers. Next the Cardas wire is prepped. The Cardas wire is enameled, so it has to be either dipped in a solder pot or heated up with solder on the tip on an iron to tin it and remove the enamel. Once appropriately tinned, it is soldered in place. 

Cardas wire soldered in place

Once the wire is soldered in place, a stain relief system and adhesive is used to keep the wires in place (and helps prevent the tugged cable from yanking on the solder tabs). The headphone is then put back together with extra attention paid to the sealed ring (the seal is very important to the sound). Below is the completed product. 

Recabled T5p

The T5p has a incredibly clear, detailed and coherent sound signature. Color me impressed. I hope you enjoyed this post, if you'd like to have your headphones recabled, please contact Zynsonix for a quote. Since Beyerdynamic T1, T5p, T70 and T90 are all quite similar, the same mods /recables can be performed on all of them. Here is a Beyer T90 that has been recabled for balanced listening with dual XLRs.

Beyerdynamic T 90 balanced with dual XLRs

The Fine Print:

The above steps detailing the recabling of a headphone 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.