Steampunk Modified Bottlehead Crack DIY Headphone Amp

If you're here you're probably a fan of steampunk, DIY audio, or hopefully both. I wanted to show off my buddy Greg's absolutely beautiful Steampunk themed Bottlehead Crack. I guess technically you might not be able to call it a Crack anymore given nearly every piece of the kit has been swapped out, but the amplifier section of the circuit the same, a simple tube buffer design. 

The Bottlehead Crack has been a popular staple for aspiring DIYers thanks to the lowish price and accessible build. Bottlehead includes step by step directions with pictures so you don't need to know how to read a schematic (although it's fairly easy for tube amps as they are typically simple circuits, so I recommend learning if you can). The stock Crack has very few parts and lacks output transformers so most can complete it in a single evening. 

That being said, many users like Greg like to customize their Bottlehead gear, so bespoke wooden bases or unique paintjobs aren't uncommon. Others choose to modify the internals to enhance performance.You will see the frequently replaced electrolytic capacitors with big honkin' film caps. Greg also designed a lovely pair of custom brackets to nestle around the Clarity Caps. 

Lots of audiophile goodies inside

You will see a small power filter near the power IEC socket, then a CRCRC high voltage power filter with Nichicon electrolytics, and near the front switch is a rectifier board. The stock crack has you mount the rectifier circuit on solder tabs around the transformer so this is a nice little improvement. Some people also elect to install ultra-fast diodes as another option. The tube sockets are replaced with the high quality CMC Teflon PTFE sockets which can help dampen tube vibration. These were directly soldered to however you can find PCBs on eBay or AliExpress to make things a little easier. CMC is also now making Bakelite versions of the socket if you are feeling especially vintage.

The stock Alpha potentiometer has been replaced by a higher quality Audio Note version, and Greg let me know he has ample real estate there to mount a larger stepped attenuator. You'll notice this Crack does not have the Speedball upgrade. While the Speedball enhances the performance of the amp as a constant current source for each channel, some people prefer the more "tubey" sound of the stock circuit. I can tell you they are two different flavors and each have their charm. I prefer to mate a Crack with the Speedball upgrade with some warm tubes and a I feel like it's a nice compromise.     

While there are plenty of improvements on the inside of the amp, the outside is the bee's knees. You'll see a polished copper chassis adorned with brass acorn nuts, a custom copper heatsink, the obligatory steampunk gears, and an old fashioned double pole knife switch. There is a reason why knife switches have been relegated to Frankenstein films and not household electronics; they are inherently unsafe and can arc when connected to high voltage. A shame as they look bad ass. This one is just for show.  

You will also notice there transformer is a little larger above. In fact Greg installed a dedicated heater transformer for the tube heater pins rather than requiring the single transformer from the kit to do all the work. 

An earlier version of the unit before the heater transformer was added

The whole unit is a work of art and has great personality. Despite being Steampunk, there were unique choices. For one much of the copper and brass is shiny and polished vs. aged/scuffed. I think it's great to not force yourself into one line of thinking; make it unique, make it you! Now Greg might have to make a pair of headphones that look equally amazing.    

For more steampunk related audio gear, check out this post.

Creator's Bio: Greg Ritacco started mis-wiring audio kits in the 1980's. Gradually fire became smoke and smoke became music. Encouraged by this, Greg briefly pursued a career in audio, first building speakers and later working for Threshold in the "lab". Family pressures and a desire to have his own back yard caused Greg to become more "serious" about his career, and as audio became the stepchild to home theater, and CD's washed vinyl away, Greg gave up and bought a Walkman. These days, he has rekindled his love of LP's and exploding electronics, built a few projects, and he and his daughter share their discoveries of new artists.

Please remember that building/modifying circuits 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. 

Octal OTL DIY Tube Headphone Amp

Another day, another headphone amp :) One of my life's pleasures is digging around on eBay for exciting finds, whether it be obscure vintage tube equipment or interesting/useful PCBs. This article covers the latter, a very nicely made PCB which features an octal (8-pin) tube OTL headphone amp circuit. Specifically, this is an Aikido input with a White Cathode Follower output, based on John Broskie's design. The circuit is designed to power most headphones, including those with a 32 ohm impedance. This is relatively uncommon with OTL headphone amps, which usually get along best with headphones ~300 ohms.

Top and Bottom of PCB

The tube compliment is a pair of  6BX7 or 6BL7 output tubes, a pair of 6SN7 input tubes, and a 5AR4 rectifier... because tube rectifiers are fashionably old school. Using all these tubes requires a hefty transformer, the 8.6lb.Hammond 272JX, which has a 5V, 6.3V and 600V secondary outputs. Yes, 600V, so this is not an amp for beginners. 

One can utilize the 6BX7 or 6BL7 tubes by switching two pairs of jumpers on the board, or the circuit can be configured to only work with one of the two tubes, but you can select between 32 and 300 ohm outputs using the jumpers. I personally chose the 6BL7 tubes and two different impedance outputs. 

One nice thing is that getting pairs of vintage 6BX7 / 6BL7 tubes is pretty reasonable ... $25-30 a pair for many different brands and vintages. Same for the 6SN7. You can get the GTB variants which are built to a slightly higher spec. For the 5AR4 you'd probably want to get new construction from Sovtek or similar. Guitar center is a good source. 

All the stuff on the BOM is of great quality: WIMA film caps, Vishay resistors, Nichicon electrolytics... all the good stuff. I ended up digging around the workroom to see what I had first... mostly Kiwame and carbon comp resistors, hand matched as carbon comp values can vary by 10% or more. Film caps are compact Panasonics. For the power resistors I think I went with Koa Speers as the Vishays were oddly overpriced on Mouser.

PCB populated with the smaller components

Ceramic tube sockets soldered in place

For the larger film caps, I wanted to incorporate some of the EVO oil Mundorfs. The sizing is tough, as the Mundorfs are fairly compact, but wide, and the chassis is about 3" tall, so some unique fitting was required. As most of the area underneath the caps on the circuit board doesn't have any traces running through it, I used a cutting disc and Dremeled away the area on each side... this would give an extra 1/4" to 1/2" height lost from the PCB and standoffs for extra clearance. I drilled a hole on each side of the PCB as well so a zip tie could hold each cap in place. 

The chassis I selected is from IAG DIY Tube Audio Products. He lists his chassis on ebay and on his website. Hand-made in the USA and built like a tank. The chassis gauge is relatively thick, but aluminum so easy to work with. I chose to cover up the pretty polished aluminum with painters tape to try and prevent any scratches.

Using a step drill bit to make holes in chassis

Using a Greelee punch to make the holes for the headphone outputs

Dremelled out area for IEC power inlet

I accidentally inverted the drawing when punching the holes, so we have an extra hole here. No big deal, it can be covered with a 1 1/8" Hillman hole cover.

Interior of the chassis

The populated PCB slips right in place. There aren't too many wire connections needed, just the transformers, pot controlled RCA input, and headphone output. Shielded Cardas 2 x 21.5 was used for the input and output (as they no longer make the 2 x 24 for some reason). I also wired up a pilot light to the 6.3V heater. The Hammond comes with a 115V and 125V primary. Typically you use the one that closest matches your house's voltage. As mine is 120V on the dot, I used the 125V as it didn't really matter. You dial in the voltage via the two adjustable resistors inside anyway.

When adjusting the 300V secondary, I noticed R24 was dissipating a bit too much heat and starting to smoke. Per the seller, R24 has been changed to 22K, so I went ahead and swapped that out.

Ignore the power wiring in this image, the ground is isolated on the board and is wired differently

By default for a tube amp, I wired in a filtered IEC outlet, however these are incompatible with this design as there is a ground isolation circuit built in. Once everything was corrected, I ensured the secondaries were dialed in correctly, but was getting a high DC offset. Chatting with the designer, he suggested just loading the circuit with 32 ohms on each channel. Upon measuring this, all was well. The unit started up without any issue and sounds excellent.

Completed headphone amp rear

I had a nice little brass tag made for the nameless amp, simply calling it "High Voltage OTL Aikido Octal" as the seller's eBay name is HVforless and it employs an Aikido circuit. The front features a 4 pin XLR for convenience with a shorted left and right ground.

Completed headphone amp front

You can get vintage driver tubes for this amp on the cheap, so that's another nice bonus.

Please remember that building/modifying circuits 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. 

Tube Kits, Solid State Kits, PCBs, Transformers, and Where to Buy

I've been quite busy over the last couple of years and haven't been able to build as much as I would have liked, but now that I'm getting back into the swing of things, there are a number of DIY providers who have left the space, so I wanted to put together a list of all the great companies who still offer DIY kits, boards, transformers, etc. I hope it's of use to you, and please try to support the DIY community in any way you can. There's not much money in selling just boards, it's more of a community service in many cases. This is a growing list and I'll be adding more as time goes on. If you have one you'd like to see here, please add in the comments section.

ACTIVE BUSINESSES FOR THE DIYER

AMB Labs (Solid State board and part provider): Ti Kan has lots of great solid state options including headphone amps (desktop and portable), power amps, DACs, power supplies and more. The famous β22 (Beta 22) balanced headphone amplifier is here, as well as the portable Mini³ headphone amp which shouldn't be too hard for beginners. Tons of boards and parts available and a good forum.

Antek (Transformers): My favorite provider of toroidal transformers, Antek has fantastic pricing and a large variety of values, most of which are typically in stock. You'll find tube-friendly 6.3V and 12.6V heater secondaries here as well.

Audio Note Kits (Tube amplifiers, Preamplifiers, DACs, etc.): A little higher end than the typical DIY kit, ANK has quite a few nice offerings, most of which are based around universal chassis that work with several different configurations. Also one of the very few kit providers that offer a DAC, perhaps the only tube-based one I am aware of.  Prices range from $1,300 - $6,850 per kit, so these may be out of reach for the budding audiophile, but I still consider them a good value for the parts that are being provided. One thing to note is that the tubes are hidden within the chassis on some models (many of us like the tubes out in the open because they not only look nice but it's easier to roll them).

AudioSector (Chip Amps): Nice simple circuit PCBs designed around Texas Instruments LM3875 and LM4780 chips.

Beezar (Tube Amp Kits): Tom (Tomb on HeadFi) runs Beezar and offers great, proven designs from ECP Audio (The Torpedo I and II headphone amps) as well as other DACs and headphone amps. Tom puts together a great kit and the documentation is unbelievably good. Every step is illustrated similarly to the Bottlehead kits. Highly recommended and beginner friendly.

Bottlehead (Tube and Solid State Kit Provider): Bottlehead provides mostly tube builds, from headphone amplifiers, to low-wattage speaker amplifiers, to pre-amps, etc. This is a good company for the budding DIYer as the directions are very explicit with color photographs and the support is quite good. Most of the builds are point to point with a few small circuit boards here and there for constant current upgrades usually. I'm certain they've sold a truckload of Cracks, a very affordable headphone amp offering. Below is Tyll Hertsens of InnerFidelity (great site) building a Crack.

Cinemag (Transformers): Very nicely made signal conversion and moving coil step up transformers.

DigiKey (General Supplier): Carries all the various passive and active components you'll need to fill a circuit board (resistors, capacitors, op-amps, sockets, etc.). If they are out of a product, try Mouser.

DIYAudio Store (Solid State PCBs, Kits, Chassis): Never to be overlooked, DIYAudio.com has its own store with some great little accessory PCBs like the soft start board, a universal power supply, as well as some legendary Nelson Pass designs and big hulking chassis you'll need to house them in. Pricing is very reasonable.

DynakitParts (Tube Kits, PCBs, Transformers): Kevin at Dynakit parts is an incredible guy. You can build Dynakits just like you used to back in the 1950s thanks to his incredible efforts. Dynaco, if you aren't familiar, is likely the most legendary audio kit manufacturer of all time. The ST70, their 35 watt-per-channel amplifier is a ubiquitous favorite, and their other models, including the ST35, MKIII, MKIV, and PAS pre-amp all have a very strong following. Dynakitpart's uses the original circuits, which are excellent, but perspective buyers may also use alternative boards from a variety of producers (and will need to in the case of the PAS pre-amp and SCA35 integrated). The newly designed boards have some nice attributes in some cases, but are becoming harder to obtain lately. The Quad-caps are very cool and vintage looking, but some people prefer cap boards on the inside instead. The beautiful thing is that this is DIY, and you can do whatever you like.

Edcor (Transformers): Affordable custom-made "E I" transformers with iconic blue bells. Everything is made to order at Edcor and takes 6 weeks to get produced. If you need something immediately, Hammond may be a better bet.

ElectraPrint (Transformers): Well-made custom "E I" and moving coil transformers at reasonable prices and excellent customer service. Check out the ebay page for ready made units.

Glass Jar Audio (Solid State Kit Provider): Jeff is kind enough to assemble kits with designs from AMB, Cavelli, Toole and others. It's much easier to order through him than sourcing all the parts all over the place and the pricing is very reasonable.

Glassware Audio Design (Tube PCBs and Kits): Glassware has an impressive collection of designs, mostly around the Aikido circuit. You'll find pre-amps, phono pre-amps, headphone amps, volume attenuators, and power rectifier boards. Nice really thick PCBs that are well laid out and some offer the ability to fit bypass capacitors and large coupling capacitors (for DIYers who have strong opinions ;) ). Manuals and schematics are included with purchases. Not as friendly for beginners, start with Bottlehead unless you have some experience under your belt.

Hammond (Transformers and Chassis): Hammond offers a great array of transformers, inductors and chassis which are perfect for small to large DIY projects. Hammond is carried by a number of suppliers such as Angela, Digikey, Mouser, Allied, and others.

Magnequest (Transformers): Some of the best custom wound "E I" transformers for audio. Magnequest transformers are used in designs by Wavelength Audio, Curcio Audio, Alessandro, and other well-known makes. Check out the site for Bottlehead upgrade transformers as well.

Mouser (General Supplier): Need to populate a PCB? Mouser likely has everything you need aside from tubes and traditional tube sockets. If they don't... try Digikey.

Neurochrome (Tube and Solid State PCBs): The Modulus86 seems to be a popular design based around the LM3886 chipamp with some performance enhancements. Very low total harmonic distortion, if you're into that ;) Also a very cool 300B SET (single ended triode) PCB set is available.

Oddwatt (Tube Kits): Oddwatt is a two person team (Bruce and Rodney) offering a number of tube amplifiers and a preamplifier with simple but effective circuitry. The kits include Edcor transformers and custom chassis and PCBs. I don't know too much about the company,  but there is a nice write up on DIYAudioProjects.

Pete Millett (Tube PCBs): Tons of great designs for tube amplifiers, pre-amplifiers, headphone amplifiers and the like. Some beginner friendly designs like the Butte and Jonokuchi headphone amps, as well as expensive, esoteric amplifiers designed around unusual tube compliments. Definitely worth checking out!

Transcendant Sound (Tube Kits): I havent purchased a kit from Transcendant Sound (yet), but have heard many good things. From what I see they look to be a tremendous value. The Grounded Grid pre-amp is quite popular, and the OTL (output transformerless) tube amp designs are said to offer treble clarity rivaling solid state.

Triode Electronics (Tube PCBs and Kits): Dynaco-based amp kits as well as some guitar amplifier kits. Very nice selection of parts and tubes as well if you are building a vintage amp. Directions not quite as perfect as Tubes4HiFi or Beezar, but still very good.

Tube Audio Lab (Tube Amp Kits and PCBs): Great and not overly complex tube-based point-to-point kits and PCBs using the classic 300Bs, 45s, 2A3, etc. Parts selection based on your preferences.

Tubes4HiFi / Bob Latino (Tube PCBs and Kits): Roy and Bob run a really great DIY amp and preamp site. There are models based on the Dynaco ST70 and MKIV, as well as some higher wattage versions if you have some pretty demanding speakers or a big room to fill with sound. Lots of great kits, excellent directions for most offerings (some of the pre-amps have more basic schematics, etc).
Great products at reasonable prices from my experience.

NO LONGER PRODUCING DIY PRODUCTS / IN HIATUS

ChipAmp (Solid State PCBs and Kits): Allen at Chipamp has a fantastic array of chipamp / gainclone builds based on the LM1875, LM3886, and LM3875. He also has some great power supply, volume and switcher PCBs. Very simple and easy builds. Beginner friendly except the power amps use high amperage and would be dangerous if safety measures aren't followed carefully. UPDATE: per communications at DIYAudio.com and HeadFi.org, it seems there may be issues with order fulfillment in 2016-2017.

Classic Valve (Tube and Solid State PCBs): Geek at Classic Valve is getting out of the PCB business to shift his attention to building turn-key amplifiers. I encourage you to buy up what he has left. There are a number of very unique Dynaco boards for the PAS, ST70, MKIII and MKIV as well as power filters and other great stuff.
UPDATE: It looks like the supplier CK Magnetics is also clearing out their leftover PCBs, so grab em while you can: http://www.ebay.com/usr/ckmagnetics

DIYTube (Tube PCBs): Shannon at DIYTube is getting out of the PCB business to shift his attention to building turn-key amplifiers. You will still find excellent documentation on DIYTube.com and a semi-active forum, however the boards are no longer available.

Transcendar (Transformer Producer): Once an extremely high value "E I" transformer producer, this maker appears to no longer be producing new products.

The Fine Print: DIYAudioBlog and Zynsonix Audio, LLC does not represent or have any business affiliation with any of the above businesses or individuals. Building/modifying circuits 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. 

Bottlehead Fix for Full Range Speakers

The Bottlehead Fix is a passive baffle step corrector and treble compensating device that sits between your source and your integrated amplifier, or between your pre-amp and amp. Baffle step correction (if the baffle is narrow) and treble compensation can benefit the sound of full range speakers in particular, so if you are into Fostex or MarkAudio drivers (or even Planet10 / Feastrex modified drivers), this is a great device to check out. Do note, in some cases, the compensation is already being handled by a network of capacitors, inductors and resistors within a full-range speaker.

There are four switches in total. As stated on the Bottlehead website: two of switches on the Fix controls the adjustable baffle step corrector that compensates for the bass roll-off in narrow baffled speakers. The first switch is used to set the bass turn-over frequency for the baffle width of the speaker you are using (selectable in inches). The second switch controls magnitude of the cutoff frequencies for passive bass compensation (which flattens a falling frequency response below baffle step frequency).

The third and forth switch compensate for treble roll-off with typical full range drivers. One switch selects turnover frequency, and the second switch chooses 0,2,or 4 dB of treble compensation above that frequency.

Curious if your speakers could benefit or not? The Fix is only $75 so it's not a big gamble, and given the popularity of full range speakers lately it wouldn't be a tough sell either. 

Normally, the Fix comes with a random colored piece of plexiglass (or similar material) and you either make the base yourself, or order one of Hammond or Bottlehead's for a few extra bucks. The build should be pretty quick as there aren't many parts, and would take the average person a couple of short nights to put together. 

Since I like everything on my rack to be "matchy matchy", I'll be using some alternative materials to put mine together, namely the typical copper leafed wood base and a copper plate. The copper plate I ordered was a remnant online, nice and heavy at 1/8" thick. I taped the plexi plate to the copper one and used it as a drilling template on the drill press. 

After drilling the holes, I sanded with 60, 180, 300 and 600 grade sandpaper, then spray painted it with a matte clearcoat from Krylon, otherwise it would be oxidized with hand-prints the very next day. 

Drilled copper plate

The base is made from 2 inch tall decorative molding from the local hardware store, cut with a miter saw, adhered with wood glue, and braced in the corners with square pieces of pine. It's then copper leafed using generic copper leaf and Mona Lisa Speedball base coat, adhesive size, sealer and antiquing glaze. These items can be found at your local Michaels craft store or online. 

Sitting in a copper leaf base

The first step in assembling the Fix is fastening on the switches and RCA female connectors. A socket wrench is especially handy in this step, however if using the plexi base, caution is advised in the manual as it can crack. In addition, the switches have plastic threading, so they could strip easily if too much pressure is used. 

Switches mounted

Once these items are secure, it's then time to mount the solder tabs. The manual shows corresponding letters and numbers for each solder point, so it's great to write these directly on the plate for ease of assembly. 

Labeling the solder points

I ran a solid piece of Cardas magnet wire for the ground plane and tied any solder tabs that needed to be grounded to it using bus wire. The polystyrene caps supplied are very nice quality. Polystyrene was commonly used for capacitors in the 50s up through the late 70s. You'll still find them today, many of them surplus from overseas. In vintage tube amps you may find them in glass-sealed tubes. This variety has the leads laid-in, and you need to be careful in higher values as they will create inductance based on the way they are built. Also polystyrene caps can melt, so don't put them in areas of high temperature! Those are the cons, but many feel that polystyrene caps are second only to Teflon in sound quality, so it may be worth it to experiment with them.

The 15,000pF caps in the Bottlehead kit are polypropylene, I opted to order some polystyrene to match the rest of the build. These came from Israel and are a little larger as they are 125V (no particular reason, just the smallest value I could find).

I opted to use some Cardas hookup wire and carbon film resistors for the build, just based on my own preferences. The ethernet wire that Bottlehead supplies is extremely high quality, so go with that unless you are a die-hard Cardas fan ;)

Bottlehead Fix interior

With the 15000pF caps installed

Bottlehead supplies a nice piece of black vinyl that has the functions printed on it, as well as an "I" and "O" for input and output. As a final touch, I added the iconic Bottlehead badge to the lower center.   

The completed Bottlehead Fix

I hope you enjoyed this post. Please visit Zynsonix if you need some sweet sounding interconnects for your Bottlehead gear, or any other custom audio cable. Until next time! 

The Fine Print:

The above steps detailing the build of a Bottlehead Fix are for entertainment purposes only, and not intended to be used as assembly instructions. Zynsonix Audio LLC is in no way affiliated with Bottlehead. 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. 

The Bottlehead Mainline

If you are not already familiar with Bottlehead, they make some fantastic audio kits, mostly tube-based, to power sensitive speakers and headphones. They have some other cool stuff too like a guitar amp, so check them out if you haven't already.

The good people at Bottlehead have a slightly unusual naming convention for their products... sex, drugs, and I'd imagine the rock and roll is when you fire up a build for the first time. The Mainline continues this tradition, and if you are ignorant to these references as I was, mean intravenous injection, which I surmise alludes to addictive sound quality... or something like that ;)

Stepping away from the marketing side of things, the Mainline is a headphone amp... and yes, I am building ANOTHER headphone amp. I'm beginning to think I might need to grow a few more ears. The Mainline should be good enough, refined enough, that I won't have to build another for a while... we will see.

The Bottlehead Mainline

The Mainline offers a balanced output for those of you lucky enough to have balanced headphones. If your headphones aren't balanced, you can contact Zynsonix Audio for the conversion, or just take the boring route and use the single ended output on the amp.

The Mainline has 3 tubes in total. A 12AU7 is used for power duty and two 6C45-Pi tubes take care of the signal. The signal tubes each get their own C4S board (often an upgrade on other Bottlehead kits) which provides an active load for the tubes and improves sound quality.

The output is a healthy 600mW with adjustable impedance. Doc, the head honcho at Bottlehead, has stated that the amp works well with the more power-hungry Audeze LCD series. It features the same volume attenuator as the BeeQuiet upgrade that Bottlehead offers on their top-of-the-line BeePre pre-amp. Using a pair of knobs labeled "coarse" and "fine", you adjust the volume. The coarse attenuation has 9dB steps (from 0dB to -45dB) and the fine adjustment has 1.5dB steps (from 0dB to -7.5dB).

The Bottlehead gear makes use of a gravity mount, which uses a wood frame with a rabbeted edge to hold up an aluminum plate, which all the parts are mounted to. It's a nice easy way to make a chassis if you don't have a metal bender and it looks nice too. I like to build my own with some decorative molding and then copper leaf it, which is a process where you take extremely thin sheets of metal and adhere them to the wood surface.

Copper leaf being applied

If you've seen my other builds, I tend to switch out some of the parts for my own personal favorites I've found over the years, namely Teflon tube sockets, Cardas wire, Kiwame resistors, and various boutique capacitors. That being said, the quality of the parts included with the Bottlehead kits is perfectly good, so don't feel like you have to swap things out.

Below is the initial mounting of the parts with a little bit of wiring done. The teflon tube sockets have blue PCBs mounted that give you some extra room for soldering. The blue wires are Cardas 23.5 x 2. The design calls for shielded wire, so the mesh shields are grounded to the chassis.

Additional progress pics below:

You'll note the large Jupiter beeswax flatstack 10uF capacitor mounted on the right. I initially was going to mount a piece of FRP material then mount the caps to that, however I ended up with a standoff and a capacitor mount instead, it offered a slightly cleaner look. The cap narrowly avoids touching the transformer and the clip on heatsinks, and the leads are just long enough to reach. The cool gold colored zip ties are from Michaels craft store.

Very precise mounting of Jupiter capacitor

I re-oriented the capacitor for the final build when I was satisfied with the fitment (outer foil faces inward on the right cap). These are big caps (big and beautiful!) so they needed a second standoff with capacitor mount to keep them nice and secure.

Final interior photo

After some listening tests with the resistor and the choke, I couldn't really tell a difference, but since I had the choke already, I went ahead and installed it. It fits so nicely in the corner. 

This is the final photo of Bottlehead's most sophisticated headphone amplifier to date (at least publicly available, maybe they have something spectacular going on behind the scenes).

The knobs, if anyone is wondering, are matte aluminum made by KILO. You can purchase them from Digikey or Allied Electronics. The copper colored tube shields I believe were from Angela Instruments.

Hope you enjoyed this post. Be sure to visit Zynsonix Audio if you need a great sounding headphone cable or some new interconnects to connect your Bottlehead gear.

The Fine Print:

The owner of this blog and Zynsonix Audio LLC do not have any affiliation with Bottlehead. Please remember that building/modifying circuits 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.