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. 

Xtension Retro Arcade Cabinet - SNK Neo Geo Edition

Given that you’re on this page, you likely spent a good portion of your childhood in the 80s and 90s. There are few things more nostalgic than a standing arcade cabinet, perhaps running a classic like Galaga, Pac Man, Street Fighter II, or something else from the canon of truly awesome arcade games. With arcades now being few and far between, you may be reminiscing about “the good old days”. Now you could plan out your own cabinet, however not all of us have the time or the tools necessary to create the panels to assemble an arcade cabinet. Fortunately, there are few companies out there that will help give you a relatively authentic arcade experience back without breaking the bank.

The company that I’d like to single out is RecRoom Masters. This is a small, bustling company that is constantly bringing new products to the market. There is a large range of pricing and cabinet sizes so you can purchase based on your budget and the amount of space you have available. Wayne Scheiner at RecRoom Masters and I exchanged numerous emails so I could get a good feel for the decisions I needed to make so that the product came out the way I wanted. Even though I already settled on the larger Xtension Arcade with the 27” screen, I had to decide if I wanted to light the top, if I wanted a coin door or a cabinet drawer, if I wanted graphics on the sides and over the stick, and if those graphics would be vinyl or a more permanent adhesive.

When I was younger, one of the most exciting cabinets to find at an arcade, bowling alley, or restaurant was an SNK Neo Geo Multicade MVS System. The Multicade would usually be stocked with 2-4 different games like Samurai Shodown, Sengoku or King of Fighters. The Neo Geo home system, which was famously expensive when released ($650 for the system and $200+ for each game), was out of the price range of anyone I knew, so the only opportunity to play many of these classic releases was on an MVS System. Now that a couple of decades have passed, the only time I see an MVS is occasionally at a convention.

A few iterations of the MVS Multicade Cabinets

For the sake of nostalgia, I decided that I wanted my Xtension arcade cabinet to have the same look and feel as an SNK MVS, in all its red and white glory. I opted to have RecRoom Masters apply the permanent stickers on the side panels, and prepare me some stickers and vinyl for the front of the cabinet and the Tankstick, which is X-Arcade’s larger joystick with the trackball in the center for playing bowling, golf and marble games. (As an aside, X-Arcade and RecRoom masters are two different companies, RecRoom Masters fashions their cabinets so the X-Arcade sticks can be dropped in quickly and easily.)

The X-Arcade Tankstick

The X-Arcade Tankstick is built like a … well you know. It has a nice heft to it, the finish feels durable, and accessing the interior doesn’t require much effort. Spending some time reading the reviews online, most people like X-Arcade offerings, but don’t care as much for the included joysticks, which are actual X-Arcade branded units. Many suggested switching over to Happ branded units as they tended to be more responsive. Since purchasing a pair of these would only run about $20, I decided to take the plunge. The HAPP units feature Cherry switches, and are actually easier to install and uninstall because of their smaller girth around the bottom.

The Happ versus the XArcade Joystick

Switching out the joysticks in the Tankstick requires you to pull the little rubber nubs out from the center of each rubber foot, then unscrew the screw under each one.

You can then access the interior, which may look like a rat’s nest of wires to the uninitiated, but it isn’t too hard to visually follow each wire. I took a photo of the interior for a reference of the color coding, then unclipped the leads, unscrewed the bolts, removed the spring clip at the base of the x-arcade joysticks, and removed them from the unit.

Stock X-Arcade Stick

Removal of the existing joystick

The Happ sticks have the same hole pattern and are easy to drop into place. 

Installation of the Happ Joystick (note I like zip ties!)



Another consideration while the joystick was open was wiring up the coin door on the unit so dropping a quarter in would actually register in-game. The Happ coin door from X-Arcade has a pair of leads that you wire up to one of the buttons within the joystick for that purpose. I decided I would be fancy and sleeve this lead with Techflex sleeving rather than leaving the white and green wire exposed. Now that the joystick was all set, I could concentrate on the Xtension cabinet.

Coin door leads needed a good Techflexing

Tankstick Interior

The Xtension cabinet comes in three relatively large boxes that have a good heft to them. If you’ve ever purchased set of shelves to assemble from a department store, that would give you a good idea of what to expect. Upon opening the boxes, everything was well packed with lots of foam and bubble wrap. Putting together the unit is largely like putting together furniture from Ikea, just follow the diagrams and put in the bolts, pegs, etc. While the directions could have been slightly more explicit in a couple of places, I’d give them a solid rating.

Below are some photos of the base of the cabinet being assembled:

Base with coin drawer opening facing front

Interior support for X-Arcade Stick

This little board helps keep the joystick in place during play

The left side being fitted in place

Adding the bolts before standing up

And finally standing up

Dropping in the Happ coin door didn't require much effort. Six metal pieces are screwed in place and that's all she wrote. The unit has an LED that lights up, this needs to be plugged into an electrical socket.

Back of the coin door

Open the coin door for access to the interior cabinet

Joystick Sitting on Base

One of the trickier parts of the build was getting everything situated in the small marquee area. I mounted a GE metal body light that was a bit less deep than the GE light that comes with the unit so I could allow room for a pair of speakers.

GE Metal Body 24" Under Counter Light

Mounted to backboard

The speakers are a pair of MarkAudio full range CHR-70 4” drivers, full range meaning that they’ll reproduce the whole frequency of sound. These are popular units in the DIY world, you’ll see them being used by Planet10 hifi and other full range enthusiasts. If you like the Fostex sound you’ll probably like these.

MarkAudio CHR-70 4" full range drivers

Adding Dynamat damping around drivers

Wiring up the Kimber TCSS to the speakers and 4 pin XLR

I mounted the MarkAudios behind the routed holes in the board behind the marquee, dampened the board with Dynamat Xtreme, and then mounted a 4 pin XLR above the light and ran Kimber TCSS wiring from the speakers to it, that way it’s one quick, easy locking connection to attach a 4 pole speaker cable to the back rather than four binding posts... it's just a cleaner look with less fuss. Below is the rear of the marquis area with the four pin XLR connector and a handsome litz braid of Kimber TCSS wire. The wire is 19 gauge thick, which is is ample for the application.

Custom 4 pole speaker cable connected via XLR

Once all these items were secured in place, getting the plexi and graphic to stay put as I closed the unit was a doozy. I ended up putting very small pieces of electrical tape on the top and bottom of the plexi glass to hold the pieces sandwiched together, then slowly slipped them into place. The tape is hidden by the routed wood area, so no worries there.

Testing the backlight on the marquis

The monitor was the last think I needed to situate before pulling everything together. RecRoom Masters recommends a 27” monitor that has screw holes facing the back and connectors that face downward for the sake of clearance. You could obviously use something else if you wanted, but you’d have to modify the board that it mounts to. I chose a Viewsonic VA2703 monitor, it was the only one I could find that fit all the criteria. You can find these going for as low as $180 refurbished to $230 new, so not a tough investment.

Once the top part of the cabinet has all the goodies in place, it can be a bit heavy. I’d recommend a second hand to help pick it up and put it in place, then do some final tightening of the bolts (but not too tight, they can cause the graphics to buckle).

One everything is put together, you have ample cabinet space in the back to put a PC and whatever else you need. I added a little wifi antenna unit and my purpose-built Gainclone amplifier and USB DAC, who’s switches are easily accessible from the front of the unit when opening the coin door.

Below is my hand-built Gainclone amplifier from ChipAmp based on the LM3886. I built this nice and small specifically to go into the arcade cabinet. It puts out 68 watts which is more than ample for the 4" Mark Audio drivers. Within it is a USB DAC (the GrubDAC) which converts a USB digital signal to analog before the amplification stage. I installed a little switch and pair of RCAs so analog inputs could be used as well. To see more about this build, go here.

Hand-made Gainclone / Chipamp 68 watt amplifier

The PC inside uses a small form factor case by Rosewell - The Legacy U3-B, with a low power Intel i3 so it doesn't generate too much heat. You can see more details on the case and PC here.

Rosewill Legacy U3-B

Below are photos of the completed cabinet in all its glory:

Keyboard drawer open

Below is the slide-out keyboard tray that holds a full-size keyboard and mouse. I chose a Corsair Raptor K30 which has the nice light-up red keys, and the mouse is a laptop wireless unit from Microsoft. You can actually control the cursor using the track-ball, but it's a little slow. 

Close-up of the keyboard tray

With keyboard tray closed

Opportunities for tweaks

For the cost, the Xtension is amazing. You’re not going to find a better product out there for the price. That being said, there are a couple of areas that you could make some tweaks or mild improvements if you wanted to put a little more money into the project. I picked up a longer 24” light for behind the marquee that was less deep to give more room for the speakers.  I also mounted a small black kitchen knob on the keyboard area, as it can be a little stubborn to open without one. Another thought is that you could mount a higher end drawer slide that extends a bit further for better access to the keyboard.

Hope you enjoyed the post. As always, if you are in need of some custom audio cabling to take your rig to the next level, contact Zynsonix Audio. Custom work is a Zynsonix specialty, even if you need a 4 pin XLR speaker cable for the back of an arcade cabinet ;) 

The Fine Print: The above steps detailing the building of an arcade cabinet are for entertainment purposes only, and should not be used as directions / instructions. 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. Zynsonix Audio does not have any affiliation with X-Arcade, Recroom Masters, or any of the other companies mentioned above.

Steampunk Grado with Turbulent X Drivers

I've heard plenty of good things about the Turbulent X drivers made to fit Grado Labs and Alessandro headphones, so I thought it would be fun to build a new pair. Anyone who's modded a pair of Grados and ran a few Google searches knows that there are hundreds of options out there, from Sennheiser pads to aftermarket leather headbands, to wood cups from numerous manufactures large and small. So if you don't want your Grado to look like everyone else's Grado, there's nothing stopping you from some serious customization.

I'm no stranger to modding Grados, my last being an Alessandro with custom wood cups and a cable made from Cardas copper. This time I decided to do something that I'm pretty sure no one else has tried, a Grado with copper leafed mahogany cups. Copper leafing is process where you put down a base coat of paint, sand, then put down adhesive sizing, then lay extremely thin sheets of copper down and burnish them onto the wood, then cover with some protective sealant. You'll see some other examples of this in my custom built tube amplifier bases.

I began with a pair of mahogany wood cups and performed the copper leafing process. You'll note that the look is not perfect, it has a unique weathered look that make it nice for a steampunk-esq look. It actually weathers over time a bit as well, which only makes it look better in my humble opinion.

Copper leafed Grado cups

Inside the cups, I'd be using some unique grating I had powdercoated a copper color. This was cut for a tight fit and affixed with adhesive.

Powdercoated grates

Since Zynsonix is known for it's audiophile quality wire, I wouldn't be using any run of the mill cable, but some really impressive wire that was custom-made for Zynsonix, particularly for headphone and portable cable applications.

Custom Zynsonix Trebuchet wire

This is a special 24 gauge wire with high flexibility and low memory properties called the Trebuchet. It uses a high-flex clear PE dielectric and ultra pure ohno continuous cast copper for the finest sound quality. 

The mini connector is the well-made Amphenol 3.5mm. Unlike many other mini connectors, it works well with portable DAPs and iPhones in thick cases. This was braided into a litz, then into two twisted pairs, one for each cup. 

Each wire was run into the cup, soldered directly to the Turbulent X driver, then test fit to verify where the wire would fall. The wire was then secured with a zip tie and some hot glue. If it's good enough for Grado, it's good enough for me ;) It is nice to use hot glue as it is removable later for future mods. 

Turbulent X Drivers - Green marks positive in this case

I needed a donor pair of Grados, this would be a pair of used SR-60s I located online.

Some of the best value cans out there, the SR-60

The headband was removed with a twist of the plastic, then the Turbulent Labs headband was installed. This is much comfier than the stock headband, although not the finest Grado headband I've used. That honor would go to JMoney. I do like the color on this one though. 

Next was the process of removing the stock SR-60 cups and installing the copper leafed cups. The forks on the stock unit needed to be dremeled down a bit for adequate clearance, but other than that, pretty straight-forward.  

Well now I have a very unique Grado build with some great sounding Turbulent X drivers and the superlative Zynsonix Trebuchet wire, a match made in heaven for my ears. The sound is crisp and detailed yet full-bodied and dynamic. 

Please feel free to contact Zynsonix if you'd like your headphone recabled with the Trebuchet wire, or if you'd like a custom cable made from it, you won't find it anywhere else.

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.