What is that sound?

Posted on May 25, 2020 by Kenny Shen

Music became an integral part of my life when I was about 14 and got my first PC and 28.8kbps modem that connected me to the Internet. Napster was still around, and I was slowly discovering the world of alt/grunge rock with MP3 downloads one slow byte at a time. My first pair of speakers were a cheap pair of computer speakers that came bundled with the system, and they were constantly blasted at high levels.

I hung around IRC in those days, chatting with various folks around the world, noting down every new artist/track that was thrown about - breadcrumbs that I would follow later on when my current download queue allowed me to. My Winamp playlist grew steadily over the next 2 years. I discovered drum and bass through a IRC friend, and soon was trying my hand at crafting tracks with the help of FruityLoops.

When my dad threw out the system, because my grades were noticably degrading with the constant grinding in Diablo with my fellow guild members, I would not have access to another computer until some 7 years later.

Discovering electronics, and a rabbit hole

I got a soldering iron sometime in the middle of 2017, wanting to put together a mechanical keyboard. The result was rather satisfying - assembling together a loose bag of parts into something functional. It felt oddly like programming, but with less room for mistakes. Desoldering for example, is not entirely a trivial task! Frustrations aside (where’s my undo!), the entire joy of putting things together led me thinking - what else could I put together with a soldering iron?

At this point, I was back to listening to music from my laptop/desktop over headphones (a Beyerdynamic DT150), driven by a DAC/AMP dongle. When I got to work from home, my study wasn’t air conditioned, so under the hot humid Singapore weather, keeping headphones on for extended periods can be quite challenging. Speakers would be totally cool (pun intended!), so I surmised. I did some reading and figured that getting a DIY audio chain going might be possible.

I started with the simplest piece: source. The Raspberry Pi has become popular at this point, offering an accessible palm size computer. Flashing Volumio onto a RPi 3 with a DAC “hat” (I opt for the HiFiBerry DAC+) was straightforward; I found a 3D case that I sent off for printing with a local 3D print shop.

The bountiful ecosystem of DIY Audio

A preamp was next, and I began to realize that the ecosystem around DIYers in the audio space was vast. I spent a fair amount of evenings reading/lurking at the DIYAudio forums, and eventually stumbled on Pete Millett’s DIY Audio pages, which has a treasure trove of data along with his PCB projects. I settled on a buffer PCB that uses the the Korg Nutube.

At this juncture, I started familiarizing myself with reading BOMs, or bill of materials that accompanied projects. Sites like Mouser and Digikey were used to put together orders of what I needed and they arrived fairly promptly in little labelled ziplock bags.

I’m down to the last (and biggest) hurdles of the chain: a suitable amplifier and pair of speakers. I had done enough reading at this point to feel like I could probably take on a sales job at a HiFi store, and amongst the different speaker designs, one that really called out to my minimalist ideals was the concept of full-range speakers. Essentially, you just have a single driver element, instead of conventional two/three-way setups where we separate the sound frequencies and designate them to multiple drivers (woofer, tweeter).

So one driver, and how would we mount them? I found a spartan concept known as “open baffles” (or a dipolar speaker if you want to sound techy) - here you simply take a flat board and mount the driver on it.

Open Baffle Full-range speakers

I ordered these baffles from Caintuck Audio. Since they were flatpaks, the shipping was manageable. The recommended drivers were a pair of Betsy from Wild Burro Audio Labs. The assembly was dead easy - all I needed was a screwdriver and a hammer. I bought some connectors and a roll of speaker wires; a wire stripper/cutter was necessary for this.

OB Betsy assembled
Speaker wires with connectors
Testing the speakers

Full-range rear-loaded horn speakers

Another interesting project that I came across was the Frugel-Horn. I placed an order for these and put them up in the living room for the TV.

Assembling the flatpaks with glue and clamps
Cross section showing the Mark Audio Alpair 7.3 driver

Getting on the tube

This was the part of the journey where I often caught myself asking “Am I out of my depth?”. I had decided to take on building a tube amplifer, which involves dealing with high voltages. I settled on the Novar Spud from Neurochrome (Tom has since discontinued this and other vacuum tube circuits) - a circuit that features the use of a pair of 6LR8 tubes.

Assembled Novar Spud PCB

After I had the circuit assembled, I waited around 2 months before my Edcor transformers (or iron as they’re are often referred to in the forums) arrived in the mail. These are heavy! I assembled the entire amp naked on my workbench and carried out various voltage readings to make sure everything was in order. The amplifier circuit was hooked up to a speaker post that had ceramic wirewound resistors that acted as dummy loads in place of actual speakers.

Testing the circuit

To house the entire amplifier, I needed a chassis sturdy enough to hold the transformers, and provide vents over parts of the circuit that would get hot when in operation. I dug into the world of CAD drawings and made a first draft using LibreCAD. These were sent over to the folks at Landfall Systems who made suggestions/revisions.

The chassis I receive was very well made (pretty sure they would outlast the internal circuitry!

Completed Novar Spud amplifier
A look on the inside

It’s been two years plus a couple of months now and the entire setup is serving me well. I reserved an IP for the RPi/Volumio box on the router and bookmarked it on the browser. Between SomaFM streams, Spotify and using my own desktop as a MiniDLNA server, I’ve hardly been able to run out of listening material. There was a day when the tubes didn’t light up some months ago, but opening up the chassis revealed a weak solder joint on the wires had fallen off, nothing a resolder didn’t fix.

More-Fi? Chi-Fi!

I can’t take my speakers with me all the time, so I still have a portable setup. One of nicest listening experiences I can recall is when my friend Yang loaned me his pair of Staxs for a week. I didn’t run out and get one, for reasons mentioned before - I tend to sweat easily with the climate and headphones don’t appeal to me for that reason. After DIY-ing my way through the above projects, I’ve also come to learn that the world of audiophiles can be a confusing and weird one to navigate. There’s a lot of misinformation out there for the uninformed - cables with a price tag in the thousands, folks claiming audible differences in circuits without the right science to back their claims and in general, just a lot of snakeoil to wade through.

I’ve been happy with a pair of Etymotic ER4SRs that I got last year after my Beyerdynamics died and I like the simplicity of just plugging it into my phone for Netflix and Spotify on the commute without a whole bunch of supplementary devices. More recently, I stumbled on the world of Chi-fi and have been amazed at the build quality coming out of these small outfits in China. It’s so awesome that great sounding IEMs are available in all manners of tuning at prices below $100.

Thanks for reading this. If you embarked on building similar projects I’ll love to hear from you, please drop me a mail.