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The stock Alpha potentiometer has been replaced by a higher quality Audio Note version, and Greg let me know he has ample real estate there to mount a larger stepped attenuator.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. 

Emotiva BasX A-100 Stereo Flex Amplifier Review

This is a review of the headphone output of the Emotiva BasX A-100 Stereo Flex Amplifier. If you’re not familiar, Emotiva makes some great audio products at incredibly attractive price-points. They offer a host of speakers, headphones, amplifiers, processors, and other gear. I have owned their portable DACs which are a tremendous value; I ended up parting ways for lack of need. They were quite good sounding though and offered a robust build quality. I currently have some of their power equipment which is also well built. If I were a home theater afficionado, I’d likely have even more of their gear.

Emotiva has a value-oriented 2 channel amp called the BasX A-100. Normally it is a speaker amp providing 50 watts per channel into 8 Ohms and 80 Watts per channel into 4 Ohms, which is plenty for most setups. What is also pleasing for those with limited in-house real-estate is that the unit is half width, so 8-1/2” wide x 3.125” high x 15” deep. That saves half of your shelf for another piece of equipment/some headphones or something else.

Perhaps what is most interesting about the A-100 is that it can be used as a high-powered headphone amp. Granted, very few people would need this capability, but it is there. The unit does need to be internally jumpered for this operation as it is unsafe for standard headphones. The output is:

8 Ohms:  50 watts / channel
33 Ohms:  12 watts / channel
47 Ohms:  8.5 watts / channel
150 Ohms:  2.6 watts / channel
300 Ohms:  1.3 watts / channel
600 Ohms:  0.6 watts / channel

So, what headphone owners would be interested in this feature? Owners of low-sensitivity headphones like the HiFiMan Susvara, HiFiMan HE-6 or HE-6se, the HEDDPhones, the Abyss AB-1266, and others.

Normally I use an external box with some high quality resistors to convert a speaker amp’s output for headphones (it has some protections built in for amps with output transformers) but given the low cost of the A-100, it was a no-brainer to at least try it out.

Starting with the good news, the A-100 produced plenty of usable volume with the HE-6se and drove them with spades. There are some caveats though. The first, I noticed the amp takes a bit of time to warm up. When listening immediately, the midrange wasn’t well defined. After 10-15 minutes this seems to go away. Second, I found the sound to be fairly cool/bright and slightly lacking on the low end. This isn’t a big deal if you don’t mind EQing. I found reducing the upper midrange and increasing the low range to help make the sound more agreeable for my personal preferences. If you are listening from a computer, you can use the free program PEACE to make adjustments, if not, you can pick up something like the JDS Labs Subjective3 or the Schiit Loki. Neither of these offer an ideal level of control to get the A-100 exactly right (for me), but they are well made and get the job done affordably.

Running the HifiMan HE-6se with the Emotiva A-100

It seems that perhaps the weakest link of the A-100 is its potentiometer (volume control). Early into turning it, there was very noticeable channel imbalance. This seemed to subside quickly as the volume rose; however, it is important to note. A good potentiometer can be costly, so this was likely a price point issue. Given an Alps Blue Velvet (RK27), a frequently used entry-level potentiometer for audio, is around $12 per piece in bulk, it would be very hard to implement at this price level.

You get a lot for your money in terms of parts and build

Overall, the Emotiva BasX A-100 Stereo Flex Amplifier is impressive at its price point given the heft, solid and attractive build, and ability to send 50 WPC to a pair of headphones. Also the internal rectified power supply (no wall wart) is typically reserved for more expensive gear. If you were in the position to have purchased some HiFiMan HE-6 or HE-6se and had very little left over for a suitable amp, this is probably the only game in town, aside from potentially the balanced output of the Schiit Magnius which I haven’t yet tested.

If you were only interested in powering speakers and don’t mind purchasing used gear, you might want to cross-shop an older receiver from a reputable brand like Yamaha, Onkyo, Outlaw, or Denon. If you are DIY-minded, a chip amp like Akitika is a good route to investigate for speakers.   

If you are trying to power low-sensitivity headphones via a speaker amplifier, please check out the CBOX at Zynsonix.com. It provides a safe consistent load for your amplifier while delivering the juice your headphones need. 

Chipamp Dual Mono LM3886 Gainclone Speaker Amp

I'll be dipping my feet in the chip amp waters again. I enjoyed the results of my previous Chipamp.com LM3886 build, so I decided to build another, more serious version. You can visit that post to read a little bit about the history of the chipamp, also known as the Gainclone, based on 47Labs Gaincard topology.

As you are likely aware, DIYers have created chip-based builds using a variety of power opamp or audio opamp chips including National Semiconductor LM1875, LM3875, LM3886, and LM4780. The most popular chips being the LM3886 and LM3875. You'll find a number of these designs at Chipamp Electronics.

This more serious build features a pair of Antek 300VA torroids, each with their own shield, integrated amp functionality with an Alps Blue Velvet and multiple selectable inputs, film capacitors on the driver board, and higher end parts like Nichicon Gold Tune power caps, Cardas binding posts, and Cardas RCA connectors.

Cardas wire, RCA connectors and binding posts

Other nice additions to the build include a 6 position Grayhill selector switch and the Alps Blue Velvet RK27 (100K) volume potentiometer, both with the corresponding ChipAmp BrianGT PCBs. The RK27 board is handy as you don't have to discern which pin is which (the white screen tells you which wire goes where). It's also a little easier that soldering to the little pins. The Grayhill switch's pins are so minuscule that you really have to use the board, it's not like an Elma or Goldpoint with larger gold solder lugs. The nice thing is the combo is a fraction of the price of the fancier selector switches.

  

Chipamp's PCBs for pre-amps / integrated amps

This project would require a larger box than the Bud 7" x 12" x 3" aluminum box I used previously. Rather than build my own gravity mount chassis, I wanted something a little different this time. I turned to Horace Atkinson of www.iagaudio.com for a robust 17.5" W x 10"D x 3.75"H chassis. I stumbled upon his chassis work on eBay: it's a nice combination of aluminum and wood panels for sides, as well as attractive wood accents on the bottom. The metal used in these chassis is a thicker gauge, one piece .125" aluminum tubing, so it can support heavy transformers without any bend or flex. (FYI IAG offers thicknesses up to .188"). The bottom features perforated sheet metal for adequate air ventilation reaching the heatsinks cooling the LM3886. A unique feature is the wood side panels actually act as feet, holding the aluminum portion up higher to allow for ventilation, very cool!

IAG Audio aluminum and wood chassis 

A view of the bottom with the perforated sheet metal removed. Note the bottom of the chassis is not completely open due to the rigid, tubular design, however underneath the wood side panels, there are removable metal panels that can be removed by unscrewing two flush mounted screws to give you adequate access for drilling, etc.

Chassis interior

As noted, the wood panels are all easily removable if you decide you want to access the sides of the chassis interior or change the wood stain, etc. Horace found some beautiful figured maple for me, as you can see below:

Figured maple side panels and accents

After much internal debate, I decided the chassis would be colored to match some of my other equipment with a red and cream color combo, so the wood was stripped down and stained a deep red hue, then given a number of generous coats of MinWax Satin Clear Urethane.  

Red stain and urethane on Maple

Now that the wood is my a nice shiny red, it's time to drill the chassis. After planning out the layout in Photoshop, the chassis is prepped with a ruler and sharpie and taken to the drill press. Many of the holes will be countersunk for this project. The others will be deburred using a Skaviv deburring tool with Cobalt bits. The IEC hole is trimmed using the typical combo of drilling four holes in the corners and using a Dremel cutting wheel to remove the rest. 

Chassis prep

For the heatsinks, I found some reasonably priced ones on eBay that had mounting holes for screws. The instruction manual from Chipamp says you can also use a 3"x3"x1/2" piece of aluminum in free air in certain applications. I installed 1" aluminum standoffs on the heatsinks so I could mount them to the chassis. Small drilled venting holes will be above them so when heat rises it can escape the chassis. 

Below is the chassis after a nice cream colored powdercoat. 

Since the amp is dual mono, it gets not one, but two chunky toroids. The transformers are always what weigh down an amp (big magnets with large quantities of copper wire spun around them aren't the lightest of materials). The pair, with steel cases, weigh in at a healthy 22 pounds. These are 300VA rated units from Antek.

Below is one of the toroids in a steel case. I had these powdercoated brick red as it makes a nice accent color for the cream. Typically the steel cases are used as a shield within a chassis, however I'm using them as both a shield and external transformer covers. I don't think I've ever seen a solid state amp with external transformers (usually they're just hulking boxes) so this will be a unique design choice.  

I'm adding the Power Supply Soft Start Board (or SSB for short) from DIYAudio for this build, this allows a gentle inflow of power on startup, which protects the power caps and should offer a more reliable service life for the amp. 

With everything ready, the chassis can start to get filled in. Shiny Cardas RCAs adorn the back of the unit, the binding posts would have been a bit tight on the back, so they were mounted to the top of the chassis right behind the transformers. Four large film caps will be residing in this chassis as well, so you'll notice some zip ties within the chassis as well.

Getting everything in place was a tricky predicament, as the sides of the chassis which held the heatsinks were screwed in place, then the wood panels were screwed to them, but the capacitors would have to be slid in to be held and secured, so order of operations took precedent. 

The power capacitors were a bit tall, so I had to use some minuscule PCB standoffs so they wouldn't come in contact with the chassis. The film caps, as you can see, were a perfect fit. I made a few small turret boards to keep the wiring neat. Cardas wiring handles all the signal work and thicker power wires as well. If you look carefully you'll notice one of the blue wires exists after the potentiometer to the RCAs to handle subwoofer duty. 

And the final product, see what you think:

Final weight was about 40 lbs. thanks to the hefty transformers and very solid tubular chassis. It's a unique take on a solid state amp, not the typical big black box with heatsinks on the side, but a more vintage tube-amp looking chassis. The sound is excellent, will be looking forward to putting it through the burn-in process and most more impressions.

The Fine Print:

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. 

Custom Audio Cables Make for Great Eye Candy

I've been spending a bit more time experimenting with paracord sleeving, it performs quite similarly to nylon multifilament and comes in all sorts of different shades. Below are some cables assembled with a fun splash of color, along with some choice audiophile componentry like Cardas ultra pure silver and Neotech ultra pure ohno cast copper. Perfect for your headphone or speaker amp. They are available for sale on ebay, first come first serve ;)

Pure silver (Cardas Silver) mini to RCA, Switchcraft right angle mini, Vampire RCAs - 1 1/2 feet

Ultra pure ohno cast copper in Teflon, right angle Switchcraft mini, Vampire RCAs - 2 feet

UPOCC Copper headphone extension cable with Neutrik 1/4" male, Switchcraft 1/4" female - 6 feet

Pure Silver (Cardas Silver) mini to mini cable with Neutrik gold mini connectors - 5 inches tip to tip

UPOCC Copper Mini to RCA Cable with Switchcraft straight mini and Vampire RCAs - 2 feet

If you like what you see above but need something custom, Zynsonix Audio is welcoming requests for any audio cable solution you need. Until next time!

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. 

Steampunk Art & Design

I wouldn't necessarily call all of my electronics work my own creations; many of the amps and preamps were existing circuits or kits that I may have modified the parts list or made a few minor circuit changes. As enjoyable as it is to build them, it's preferable for me to stick with tried and true circuits created by the experts and not come up with new schematics of my own volition. There tends to be more enjoyment in the final presentation, the color scheme and the chassis work and even the way the inside looks. A number of people have told me that my builds have a Steampunk look to them. I'm familiar with the movement, and I wasn't even aware of the fact that my design choices tend to follow that look, but perhaps was subconsciously making the design decisions with Steampunk as an inspiration.

Steampunk?

I suppose my designers manifesto is that I feel that amplifiers with older technology like vacuum tubes should have a vintage look and patina, even if they are being assembled in the 21st century. Vintage has a different look for different people, but I tend to think of copper and polished brass, gold plating, brown and copper hues with a crinkled / hammered texture, wood and metal grating and leather. These seem to be the same facets that find themselves in the psuedo-Victorian era Steampunk movement of design. I'm not sure that future projects will have the telltale brass gears and non-functional pipes that Steampunk gear tends to have, but I may think up other embellishments as time goes on.

I think that the main inspiration for vintage electronics was a company called Moth Audio that produced a number of designs from 1996 to 2007. There are many purveyors of audio gear that make really beautiful work, but in my minds eye, the aesthetics of Moth Audio gear is second to none. Craig Uthus was the head of Moth and at the time, the work was considered to be "retro-styled", the designs were highly distinctive and still highly sought after today. Craig's partner at Moth was Joel Marshall, a Hollywood prop designer, who designed the beautiful chassis you'll see below. 

Moth Audio NiteLite with 15E Radar Tube

Moth Audio Sphinx balanced line-out amp and phono preamp

I almost feel that these amplifiers belong in an exhibit somewhere. Perhaps someone out there could open up an audiophile museum one day, the cable section alone could take up a whole wing ;)

There is at least a few audio builders out there that fully embrace the Steampunk aesthetic; Aevil at Coppersteam Labs put together the best looking S-5 Electronics K-12G I've ever seen. I'd imagine there's more money invested in the copper than the amp itself, it's a real beauty that looks like it came right out of Bioshock.

AEvilMike's K-12G Amplifier 

I also found a lovely "effect-pedal" if you will made by Peter Groenewoud at Hilltree Productions called the Steampunk Doomsday Machine. The top features two 230V DC bulbs that carry the music signal and create the effect. Lots of wood, brass and copper in this Steampunk design. Peter will not share a schematic on this device as the 230V DC going across those lightbulbs is fairly dangerous.

Hilltree Productions Steampunk Doomsday Machine

Also, a new addition after the 2012 Bay Area HeadFi Meet was Frank Cooters amazing looking headphone amplifier. I don't know too many details about this one, but the glorious copper piping and top-plate and nicely figured hardwood really set this apart from other builds. Evidently all the work inside this beast is point-to-point, and Frank has a matching one that powers electrostats. In this photo it looks like someone has an Audeze LCD-2 headphone plugged in.

Frank Cooter's steampunk-styled headphone amp

In conclusion, I'm not sure that my builds are Steampunk. They may look like it to a certain degree, but it's nebulous where the line of vintage and Steampunk merge, intersect and share common facets. What do you think?

Looking for some steampunk-esq audio cables and equipment? Contact your friends at Zynsonix Audio.