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The stock Alpha potentiometer has been replaced by a higher quality Audio Note version, and Greg let me know he has ample real estate there to mount a larger stepped attenuator.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

The MOD Rock Bottom Guitar Effects Pedal

Today's post is a guest post from my bud Ryan Price and covers the MOD Rock Bottom Pedal. Ryan's been getting his feet wet in the DIY audio scene and doesn't shy away from some classic point-to-point wiring.

Please excuse the possible lack of common decorum for a post.  This is my first one and it’s a learning process.  I picked up a DIY guitar pedal build kit by MOD from Amplified parts.  I chose the Rock Bottom pedal for a few reasons.  First is I wanted an analog Fuzz.  Second is the extended low end so I can use it with both bass and guitar.  the “3” rating seemed like a challenge for a pedal build novice with some soldering experience.  Considering that I have plenty of time to kill as I’m currently recovering from a recent heart transplant, I went for it even if it was gonna be just outside my skill set so far.  I was able to finish it over the course of about 4-6 hours over a few nights. 

The Pedal Kit

Now for the breakdown.  The MOD kit comes with everything you need minus tools and solder.  I used a Hakko 888D soldering iron but for this application most would suffice I believe.  Hand tools I used were a MusicNomad guitar multitool, strippers, dikes, hemostats, and some modified pliers.  I put a bit of shrink tube around the jaws so as not to damage wire and components.  While the kit comes with everything you need the wire is not easy to work with if you don’t have a solder pot.  I own one but did not have access to it at the time of the build.  I substituted the wire with some I had left over from a previous project.  Its if a smaller gauge but of much higher quality.  That’s the only substitution I made. 

Tools of the Trade

The build is rather straightforward.  Starting with terminal strips, switches, and connectors.  The layout is very straight forward and with some planning can be a super clean build.  

Classic Turret Strips

Next they have you measure out the wire.  As I followed the directions closely up to this point I found the lengths a bit on the long side (editors note: you can make the wires shorter depending on your OCD level). But I can see why as its easy to trim to size.  Not so easy to add length!  Now I got ahead of myself and terminated both ends of the runs as I was building.  For my next build I plan to take things a bit slower.  Before terminating any connection I will dry fit all components, bend and run, then get a plan of how to go forward.  The directions are decent there are a few times you run into overlapping components. 

Wired Up

Component layout is definitely the most difficult part of the build and you should take your time.  Plan ahead and follow the directions.  That will make this build a breeze.  Don’t get ahead of yourself and begin terminating at a whim like I did as you will regret it.  It will also take more time than doing a layout before assembly.  Trust me on that one!  

All Parts Installed

Once I fixed all my errors (there were many) it came together nicely. Powered right up and gave me sweet, sweet two transistor Fuzz! This pedal is a massive bang for your buck win. I can recommend it 100% to all but the most novice of DIY people. I can’t wait to build another MOD pedal in the near future. Amplified Parts has a great selection of all related components and tools (Editors note: if you're a knob snob they have a nice selection). As well as super solid shipping. I can’t recommend them enough.

Finished Up

So if you’re got some soldering skills, desire to DIY, and a few hours I say go for it!  

I left the sticker off.  My wife is an artist and I’m going to have her paint and label the pedal!

(Editors note: we'll update the story when Ryan and his wife are all done.)

 

Overnight Sensation DIY Speaker Kit Assembly Step by Step

In this post I’ll be building Paul Carmody’s Overnight Sensation DIY speakers from a kit. The Overnight Sensations are an extremely popular DIY bookshelf speaker for a few different reasons. One, cost; they are a mere $120-140 a pair at the time of this writing. Two, they sound great. It’s hard for me to recall hearing such dynamic sound from a diminutively sized form factor. Three, the build is super easy. If you have some basic tools and know how to solder, you’re all set. This post is going to be written for a beginner in mind, so if you are already experienced feel free to skip along.

There are three places I know of to get a kit. Partsexpress which includes the full kit with wood panel flatpack and accessories, MeniscusAudio which does not include the flatpack but comes with tweeters with screw-in frames, which I feel is preferable should one need to replace them down the line, and DIY Sound Group, which appears to have a similar kit to Partsexpress.

A typical Overnight Sensation kit

What will you need besides the kits? Each one is a little different, so pay attention to the parts list, but you will likely also need a set of binding posts, 5/8” black wood screws, sandpaper, wood glue, wood filler, and solder. Optionally, you will also want sealing caulk, polyfill or similar solution, and either paint or staining supplies depending on how you’d like to finish the speaker. Tools you will need include bar clamps (or trigger clamps), soldering iron, electric sander, and a power drill.

If you don’t already own clamps, they are going to be a bit of an investment. You ideally need 6 or so and they run about $15 each, so potentially check with a friend to borrow a set if that’s a problem. If you decide to buy a set, get a couple that are longer than you need as well so they’ll be around when you go to make a bigger speaker later 😉   

If you purchase a unit with a flat pack, the wood will be trimmed for easy assembly. You will simply add wood glue between the joints, clamp the enclosure together, and wipe away any excess wood glue with a wet paper towel. Ideally you will leave one side open so you can finalize the internals before sealing it up. Some people also prefer to only screw-in the rear panel with a few modifications, that way you can get in there later if need be. If you follow this route, be sure to find a good solution to seal the edges so only the port is allowing air out of the chamber. Some people also like to mount the crossovers outside so they can modify them later. If that floats your boat, the world is your oyster.

For my assembly, I found a set of crossover PCBs on eBay which I believe are made by DIYSoundGroup. They are very reasonable, and I highly recommend them as they make things so much faster and easier than drawing out the arrangement from the schematic, figuring out a good layout, gluing the parts in place and then wiring everything point to point. 

PCB Crossover for Overnight Sensations

Populated Crossover

That being said, there is absolutely nothing wrong with going that way, and you have more freedom to use larger caps if desired. Some will also say point to point sounds better than going through PCB traces, but that subject is better left for squabbling on audio forums somewhere.   

For my build I chose to assemble the crossover first and mount the PCB on the bottom panel. The Dayton caps are solid and work perfectly well here. I prefer Mills wirewound over sandcast resistors, they're worth the extra if you can swing it, and I had a pair of surplus Mundorf capacitors for the 0.22uF position, but sticking with all Dayton caps is fine too. This is a budget build so you won't get too much yield from bumping up the parts quality. The interior of the other panels is adorned with Dynamat-like sheets for internal damping. There are plenty of brands out there at different price points, but try to get thicker ones for the purpose of adding mass. I personally like to use a staple gun to really keep the sheets on there. Not necessary, but low cost insurance they won't move. It’s important to not completely cover the panels as wood glue, then later caulk will be used to ensure all the corners of the cabinets are sealed. 

Once the panels are all prepped, then they can be glued and clamped. The low-cost Titebond wood glue in the red and clear bottle works well and is inexpensive. For clamps, generally I like to leave them on overnight while the wood glue completely dries, however with most brands you can disassemble after about a half hour or so, so long as you aren’t putting any pressure on the panels.

The more clamps the better!

I left off the front baffle so I could get my hands in for the removal of excess glue and caulking of the corners. The binding posts I’m using are Partsexpress’ gold heavy duty ones along with the nice-looking mounting plates. Normally I use Cardas copper billet posts however this is a more affordable build, so I wanted to keep it that way. Most binding posts are gold plated brass so will sound pretty similar; however, you don’t want anything flimsy that will fail overtime or loosen up inside as once the speaker is sealed. Once it is, you’ll have trouble getting back in there to fix anything.

Partsexpress Heavy Posts

Measure before drilling as the plate takes up some real-estate.

Also, while the speaker is still open, I ran wiring from the PCB to the areas where the drivers and binding posts will be. Again, it’s important to get the lengths and connections right as it will be difficult to access later. You don’t need thick wire as the lengths are going to be short so the resistance is minimal. I used 19 gauge for the tweeter and 16 gauge for the woofer and binding posts.

Wires running from the PCB

Note placement of damping sheets

When everything is ready inside, the front baffle can be glued and clamped in place. 

Once dry, now is a good time to sand where the panels meet to ensure the transitions are smooth. Start with rougher grade sandpaper (60-80 grit) and working your way up. Using finer than 100 grit can sometimes cause issues with this type of wood taking stain, so consult the kit manufacturer if you are staining the wood. There will be small gaps in some cases where the wood touches. This is fine and can be fixed by using wood filler. There are plenty of varieties out there like Elmer’s, Minwax, DAP, etc. and all work well, but if you are staining, you will want a stainable filler.

Sanded down after filler has been added to gaps

Given I hardly have time for personal projects these days, getting the finish done quickly is a major boon. I like to use a product called Duratex from Acry-tech. This is a paint that’s similar to truck bed liner and covers up any surface imperfections with a texture. It dries quickly (about 3 hours) and provides a durable finish. Two to three coats are all that is needed and there is no sanding required between coats. Because these speakers will be in my workroom, there isn’t much point in giving the speakers a museum grade finish, but the Duratex looks nice and is very serviceable. You can either buy Duratex from Partsexpress or directly. Custom colors are available direct, like this nice bright orange.     

Speakers with a few layers of orange Duratex coating

If you’d like to add internal fill, now is the time to do it. I used two handfuls of fluffed Acoustastuf per speaker. The drivers can now be soldered in and placed. The HiVi mid-drivers come with foam surrounds that stick in place, be sure to use these for a good seal. The tweeters will require a little bit of effort to do right and should be handled carefully. First, if any paint or stain ended up in the cavity for the tweeter, you may need to lightly sand to ensure clearance as the fit is very tight. The tweeters do not include a foam surround so a very thin layer of caulk should be placed between them and the wood cabinet to create a seal. On the back the binding posts can be soldered and the plate can be drilled in place.

Drivers soldered in place

Finally, we can plug them in and have a listen. Most speakers have a little bit of burn-in time where the drivers settle in. This is highly dependent on the driver. I found the Overnight Sensations didn’t need much time at all to sound great. The sound is fun and large, full, and on the warm side, but there is a good amount of detail. Given the cost, these are insanely good. Despite a sensitivity rating of 83/dB, they are sensitive enough to get quite loud with my Dynaco ST-35 running in either 17.5 watts per channel push-pull or ~9 watts triode mode in a smallish room.

At the end of the day, there are plenty of great sounding speaker kits out there, and many will sound better than the Overnight Sensations, however I think the price-to-performance ratio and ease of the build makes them a tremendous introduction to first time speaker builders who are looking to get their feet wet in the space. If you’re looking to add some handmade speaker cables, try out some silver-plated PTFE surplus wire, it’s a nice value. 

As always, thanks very much for checking out the blog. If you are looking for custom audio cables, headphone cables, and line or headphone switchers, please check out Zynsonix.com. Until next time!

Dynaco PAS Full Function RCA Jack Kit from Dynakit Parts

Likely the most popular tube amps in existence, Dynaco has many fans both young and old. Given how well they have stood the test of time, I hope they continue to be sought after for many decades to come. There are a number of companies offering kits resembling the originals with modern bits and pieces, but if you want to build or restore a Dynaco as close to the spirit of the original as possible, Dynakit Parts offerings are a great choice. 

Dynakit Parts is a company based in Paramus, New Jersey and has an impressive selection of reproductions of all the most popular Dynaco vacuum tube products. The kits are about as close to the originals as you can get, from the can capacitor to the screw-down terminal strips but have the benefit of using freshly made transformers and other modern parts.

If you are familiar with the older Dynakits from the 60s, you will remember they featured RCA inputs that are a little different than what we typically see today. On the pre-amps and integrated amps, they were spaced very close to one another and it is hard to find RCA cables that fit them now-a-days, not to mention middling quality (though good for the time).

There have been several attempts to reproduce the RCA board on the PAS using higher quality materials, however because of the spacing, not all the RCAs were able to fit in these offerings. Now that we're in 2020 that is not the case. Dynakit Parts has created a very nice-looking solution for those of you looking to feature all the inputs of the original while also providing a high-quality solution. Best of all, you do not have to cut or modify the existing chassis in any way, the kit fits like a glove. 

Above you'll see the items that are included in the kit. You get the handsome brown polyimide board with integrated grounding scheme, nine pair of gold RCAs, two pair of half-watt resistors, a bag of hardware, some detailed instructions, and a nice decal to identify the connections. The cost is a very reasonable $75, especially considering how many gold-plated RCAs are included. Last I checked they run about $6 a pair at PartsExpress, so you can do the math.

Something else that $75 bucks buys you is you don't have to wire up all the ground connections. Just tightening on the RCAs makes electrical connection with the integrated grounding. The image below gives you a better look at the traces.

So what do you have to do to get this puppy ready for install? Simply populate the RCAs onto the board and lightly tighten with a socket tool of your choice. Next you add the resistors and solder in place, and viola! you are done. So simple you can knock it out in 5-10 minutes. You'd then install on your PAS chassis using the provided hardware, or if you prefer a permanent install you can use pop-rivets to fasten the board in place.

Here is the other side of the board when completed.

...and here are a couple of images of the unit installed in a chassis (the nice ground lug is included in the parts):

So what's the verdict? If you are looking for an RCA board that features all the connectivity of the original PAS, this is a no-brainer. It's well made, easy to use and the gold RCAs look like they'll withstand the test of time. You could make a similar board yourself by drilling out a FR4 board, but you'd end up paying the same or more and it probably wouldn't look as nice. 

Now, if you're not a purist and don't need every connection available for the PAS, Dynakit Parts makes a nice kit with a couple less RCAs for a very reasonable $50 (as of this writing). 

If you're interested in the PAS RCA board or other Dynaco-related items, whether building a kit or performing a restoration, Dynakit Parts should be on your short-list. I've ordered quite a few things from Kevin over the years and everything has been superlative.

Hope you enjoyed the write-up. For more PAS related entertainment, you can check out this restoration I did several years ago.


Review disclosure: Dynakit Parts provided a reviewer's sample of the PAS RCA Board to DIYAudioBlog for an honest review. 

DIY Headphone Switchbox

It's a head-scratcher why this hasn't been requested before... a switchable headphone output box. I know so many people in this hobby who have more headphones than fingers and toes, so something like this should be commonly on headphone enthusiasts desks across the world! Haha, well maybe not...

Anyway, I had a client approach me who wanted a switchbox so he could switch easily between four headphones. Obviously you don't want to have all four headphones connected at once due to various drive and impedance issues, hence the switch. In addition, the unit should be as transparent as possible as sound quality is paramount in this hobby... so we have a point-to-point 1 to 4 headphone switch, so up to four headphones can be connected simultaneously to an amp, and switching between them is as simple as the click of a switch (and swapping them on your head).

For the box I used a Hammond extruded aluminum box with aluminum endplates, anodized black (everyone likes black). It needed to be a wider model for enough panel real estate for the switch and four 1/4" connectors.

While 4 pole, 3 throw switches are as plentiful as flatulent passengers in airplanes, 3 pole, 4 throw are a little more difficult to find. I used one made in the U.S. by Electroswitch, found on Mouser. If funds permitted we would have gone with Elma/Goldpoint, but this is a great switch with smooth operation. For the 1/4", I went with the super common Neutrik NMJ6HC-S, which is the more attractive jack from their M-Series and is very reliable. It has switching ability as well, but that wasn't needed in this application.  

Here's a few progress pics below: 

Lining up the jacks 

Drilling the pilot holes

Mounting the jacks and switch

Installing the Kilo aluminum knob

Everything was wired up using solid core silver-clad wire in PTFE. I highly recommend this wire for internal chassis work. It sounds excellent and is easy to work with. Just be sure not to be too aggressive when stripping it as if you nick the solid core wire, it can break off and you'll end up with an open circuit. You'll note below the ground is tied to the chassis via a screw and locking solder lug. This is important to ensure the metal chassis has active shielding from noise no matter which output is selected. 

Interior wiring

This is a simple, effective switchbox which hopefully the client will enjoy. 

Final Product

Hopefully you have fun reading this, and who knows, maybe someone will want an 8, 12 or 16 headphone switchbox in the future! You guys will be the first to know ;)

To purchase this product, visit Zynsonix.com


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.