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June 1, 2021

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. 

May 4, 2021

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

Partsexpress binding 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!

March 30, 2021

Headphone Switchbox in a Compact Chassis

A few years ago I made a headphone switchbox. It was popular enough that I added it for sale on Zynsonix. It uses a standard Hammond chassis which is made in Canada. There have been people looking for a more compact version. Unfortunately Hammond doesn't make a super compact extruded chassis from this line, however a fellow over at HeadFi, ScornDefeat, was able to find a smaller chassis that fits everything (just barely). I believe it's the same chassis as the Objective 2 headphone amp. The size is 3.15" x 5.25" x 1.37" / 80 x 134 x 35mm (LWH) and it comes in anodized black, silver, or blue. 

Rather than Electroswitch in the previous build, the similar 3 pole Lorin CK-1460 is used, and rather than the flashier Neutrik NMJ6HC-S with silver hexagon design, the plain black NMJ3HF-S is used. These are all about the same size so should be interchangeable. 

The knob is a 1/4" Kilo machined aluminum knob. I prefer the selector on the right as it's a little more natural to use the right hand to switch outputs. 

One oddity to note is the chassis that came from Amazon had tapered head silver screws and the chassis screw holes needed to be threaded (Hammond chassis comes pre-threaded). 

If you'd like to build one of these yourself, it shouldn't take longer than 2-3 hours. I recommend solid core 24 AWG wiring for headphone signal wiring inside of a chassis. 

If you'd like one of these built for you for your headphone switching needs, reach out to Zynsonix

Zynsonix Headphone Cable Video Reviews from AB's Sound Advice

Here are a few video reviews of Zynsonix headphone cables from AB's Sound Advice AZ/AU. You get to enjoy a brief review and Ashley's nice New Zealand accent all at once. These videos are also a great way to check out the different sleeving options to see which you prefer. 

Ballista custom headphone cable for Denon headphones featuring denim remix sleeving and balanced 4 pin XLR

Ballista custom headphone cable for Sony MDR-Z7 headphones featuring soft black nylon sleeving and balanced 4 pin XLR

Ballista custom headphone cable for Klipsch HP-3 headphones featuring Viablue sleeving and balanced 4 pin XLR

Be sure to check out AB's Sound Advice Channel for more great reviews on audio gear. 

NEOGEO Arcade Stick Pro Seimitsu Joystick and Button Replacement Mod

If you're like me and previously purchased the SNK NEOGEO Mini back in 2018, you might have seen the Arcade Stick Pro and figured it is just another similar device. To some extent, you'd be right... this is an emulation system that houses a handful of popular SNK games that you can play on a modern HDMI TV. On the other hand, I'd argue that the ASP is a much better product for the typical fan who wants to play the device rather than collect it, so long as you have space to store the larger form factor. 

One, you'll notice right off the bat that the HDMI output is far better looking than the NEOGEO Mini with crisper edges vs. the slightly blurry NEOGEO Mini. The second is rather than having a novelty mini arcade unit, you get a very solid joystick instead with nice clicky movement, responsive buttons and some weight to it.

Opening the unit up, you can see that SNK did not take shortcuts when they designed the unit. There's a metal plate on the bottom to provide that much appreciated extra weight, a clean layout and plenty of reinforcing pillars that make the stick very solid and sturdy. As a bonus, SNK set up the interior so you could easily switch out the buttons and joystick for aftermarket options should you wish. 

Personally I'm not the type that can tell much difference between a Sanwa stick vs. a Seimitsu stick or any other arcade brand out there. I don't play competitively so any enhancement to my guiding a character around the screen would be minimal at best. That being said, I love to mod things and this seemed like a fun little project to kill a couple hours and would hopefully make an informative post. 

The first (and actually most time consuming) part of the mod is to remove all the little plastic bits and screws from the bottom of the unit. I'd advise you put them all in a zip-lock bag so you don't lose any.

Once you have all ten screws removed, you can separate the top from the bottom. Below you will see the stock unit with the included joystick with square gate. Highlighted in red are screw holes that SNK included purposefully so you can install an aftermarket joystick. 

Removing the buttons is very simple and straightforward. You put a little bit of pressure on the center of the metal tab connecting the wire to the button. This dislodges a small metal protrusion that holds the tab in place via the little gap on the button contact. You can then remove the metal tab and wire from the button. Do not force these off or it will damage the metal tabs and you will have to bend them back in place or replace them. With the wires out of the way, you can use a channel lock wrench to press against the two sides of each button at the same time to clear it through the opening.

Replacing the buttons is even simpler, just pop them in place and replace the connections to the corresponding buttons. If you forgot what color goes where, simply use the image above as a reference. I personally used the Seimitsu PS-14-K buttons from the bounceback series just because I liked the concept that the buttons bounce back quickly if you were playing something like King of the Monsters and needed to win a grapple or something. You'll notice in the image below all the buttons are lined up identically in orientation, this is just for neatness and not required. 


The joystick requires a little more effort, mostly because you probably won't be able to find a current replacement joystick with the quick-disconnect tabs. For the joystick to mount within the Arcade Pro Stick, you'll need the MS style mounting plate. This will run $3-4 depending on where you get it. The joystick I chose is the Seimitsu LS-58-01-CR-SS, which is the LS-58 (a popular mid-ground stick) with red hardware and a 5 pin wiring harness socket. If you are having trouble finding the stick you want, you can replace the spring to a different weight without much issue. Also with the Seimitsu units, you can change the gate on the back. I chose a circular gate (called an Octoplate) rather than the square one it came with. Better for dragon punches I assume...? 

Before you remove the joystick, set your multimeter to continuity and set the probes on each of the four pairs of metal tabs where the quick disconnects are. Move the joystick to see what orientation shorts each and makes a beep, write these down so that way you'll know what to solder where. 

To remove the stock joystick, you'll simply need to remove the 5 screws circled below:

The new joystick is going to be agnostic to its orientation so long as you solder the wiring the same way you noted above. Rather than the pair of disconnects, you have two big solder joints on each corner of the PCB. You can test these with your multimeter with the wiring harness in to see which color is which direction. The return is common (all the pairs share the return connection). 

Each wire can be soldered now, you can use the color guide in this picture if your 5 pin harness is facing the buttons. One drawback is that the bottom of the joystick has a plastic tube that interferes with this placement, so you'll need to trim it off with a cutting wheel or your tool of choice. Each wire should be covered with some adhesive heatshrink tubing and then the bundle zip-tied together. 

Note there are four black adhesive circles in the corners of the image below. They like to fall off while you are working, so make sure to put them back before reassembly. 

Once complete, you can screw the unit back together and replace the little plastic screw-hiders. Final photos coming soon.