JWT Audio

Hi and welcome to my website. This is essentially a personal blog - maintained mostly just for fun - where I am documenting some of my experiences building my own audio/hi-fi equipment. I started keeping a hard copy notebook with details about what I have been working on but found it much easier to use Google Sites to build a set of web pages. It is very easy to add and edit content. It also allows me to keep references and links in one place. It has some good features but also some limitations if you are looking to build a fancy website. For my purposes, it works fine and best of all is free.


The COVID lockdown prompted me to re-engage with long-time hobbies, namely electronics, and audio. I typically do not design all my stuff from scratch; I pull together components others have designed and shared where it makes sense to do so. When a special component is needed to accomplish a certain goal, then I will design and build it myself. You may find yourself in a similar situation as you get deeper into the hobby, and that is what makes it fun. 


I have also scribbled down some musings and personal opinions about what I know (or think I know) concerning various related topics in my articles section of the website.


In addition, I have started writing about some of my other interests. Who knows, maybe someday one of the grandkids may find them amusing.

My Background in Audio and Electronics  (click to expand)

My Background in Audio and Electronics 

Early Days

We got a real stereo when I was around 7. I don't recall the brand, but it consisted of two cabinets, one large one with the LP record changer (crystal phono cartridge), a tube amplifier (probably around 10 Watts), a speaker, and a second smaller floor-standing speaker cabinet. I only mention this because it was a very different experience from listening to 45 RPM records on a small record player. RCA came out with their "Living Stereo" LPs and soon everyone wanted a stereo system. I must have worn out my parents' copy of Beethoven's Fifth Symphony playing at high volume when they were out of the house because it sounded so cool.

My interest in electronics started around the age of ten when I was given a subscription to the American Basic Science Club, which sent a kit every month with some simple circuits to build, like a one-tube radio. I should also mention that some of my older, extended family members had dabbled in HiFi before it was a thing. I had an uncle who built amplifiers from scratch in the 40s and 50s - his father (my grandfather) built cabinets for the systems. He was also a Ham radio guy and gave me an ancient copy of the ARRL Handbook, which I found fascinating. Another uncle gave me a very early FM tuner which he had built from a kit in the 1950s. He also gave me a copy of a book titled "Amateur Craftsmans's Cyclopedia and Log Book of Things to Make", published in 1937. Most of the articles were not very interesting (crafty stuff) but there were a few electrical and electronic projects that were neat - like "Build a Picture Frame Radio". So there was a bit of electronics DNA in me.

Then I started fixing radios and televisions and building Heathkits, Knight-kits from Allied, and some EICO gear. I also did some experiments on my own with circuits, often inspired by articles in magazines like Popular Electronics. My dad bought me an old used oscilloscope when I was 12. This was like turning on a lightbulb because I could actually visualize electrical waveforms.  I credit my parents for being patient and supportive of my hobby. I also taught myself some digital circuitry, building transistorized flip-flops and logic gates (this was before integrated circuits were available).

Hi-end audio became an interest when I was in high school and worked part-time at a hi-fi shop setting up and repairing equipment. We sold Wharfdale, Klipsch, Altec, Marantz, Revox, Ampex, McIntosh, etc., so I was "spoiled" at an early age. I built up a tube-based system, consisting of two used Fisher monaural tube preamps, a used BO turntable, two hand-built Williamson tube power amps, and custom speaker cabinets containing 12" coaxial drivers from Allied Electronics. I lugged all this to college, only to sell it off to raise money for necessities. A few years later I replaced that with a modest system, consisting of a Heathkit AR15 receiver, a Dual record turntable, and Dynaco A-25 two-way bass-reflex speakers from Denmark. This was fine for casual listening of my LP collection. Meanwhile, I was working as a circuit designer and honing my electronics skills, although in fields unrelated to audio. After that, I went to work for a computer company (where I would spend the rest of my career) and gained lots of knowledge about processors, computing systems, and networking.

Later in life, I became a fan of live musical performances, particularly orchestral music, We attended many concerts performed by the Boston Symphony Orchestra in Symphony Hall, regarded as one of the finest acoustic venues in the world. These experiences became the benchmark for experiencing "perfect" live sound, so I put together an audio system that I felt could reproduce live music as faithfully as possible, given reasonable budget constraints. This consisted of Martin Logan Aerius i electrostatic speakers, a McCormack DNA amplifier (a good match for the Aerius speakers, since it can produce up to 500 Watts into low impedance loads), a Yamaha passive preamp, and a Sony ES CD changer. The Aerius speakers can be tricky to set up in a room and have a fairly narrow "sweet spot", but certain recordings can raise the hair on my arms with realism, especially voices and stringed instruments. There are times when I can close my eyes and imagine a performer in the room with me, and the soundstage is sometimes three-dimensional. This system is still in use today and is very satisfying to listen to.

Digital Audio Adventures

In the 1980's we began to collect CDs and started listening to them more than LPs. I was not always happy with CD sound, but the convenience and lack of scratches, clicks, and pops were the most compelling reasons. We had a mid-Fi Technics single CD player but later switched to a much better Sony "ES" 5-CD changer. We discovered that CDs produced by Chesky Records were particularly good. In the 1980s the Chesky brothers built a successful independent label by initially issuing analog remasters of older recordings. Their attention to detail led to digital conversion techniques such as 128x oversampling and 24-bit A-to-D conversion using custom electronics, unheard of at the time. They also were particularly mindful of microphone placement for live recordings and avoided "over-micing" in order to simulate the most faithful soundstage possible. More recently, they created HDtracks, an online music service providing downloads of high-resolution recordings with thousands of offerings.

In the early 2000's I bought a Squeezebox audio player from Slim Devices. This was my introduction to streaming digital music over Ethernet and WiFi and I began to digitize my CDs using lossless compression encoding (mostly FLAC, which is "bit-perfect").  The server portion of the system was open-sourced and could run on any PC or server. For a number of years, I used Windows 2000 as a server for the music and then switched over to a Linux setup. This introduced a better level of usability (no shuffling of CDs and jewel cases) while maintaining sound as good or better than CD players could achieve.

When Logitech bought Slim Devices (and soon after discontinued the hardware product line), the server portion became known as LMS, for Logitech Media Server, and the company continued to offer it as a free open-source platform. It is still available for download today for multiple platforms and is maintained.

My Squeezebox lasted for about 15 years and died, so I decided to build my own device using a Raspberry Pi processor based on a project called piCorePlayer. This was a software emulation of the old Squeezebox players running on a version of Linux. Details are in the Projects Section. Also in that section are details of a second DIY streaming player which improved over my initial attempt.

It began to be clear to me that there were inherent limitations to the "Red Book" 16-bit CD format and I started acquiring downloads of higher-resolution recordings in 96KHz 24-bit formats. To me, these consistently sound much better if done right. I jumped over the SACD/DVD-Audio craze and went straight to digital storage of downloaded music.

Recent Endeavors

As I was looking to get back into DIY audio, I thought about tube-based amplification and I have a fairly complete set of old Glass Audio magazines with many circuits for the DIYer. Since I had "grown up" with tubes, I would have been completely comfortable building tube-based equipment, and I was well aware of the high regard that tube amps have in the high-end audio world. But then I began delving into the world of Nelson Pass, the famed audio designer who founded Threshold, designed the Adcom amps, and later started Pass Labs and First Watt. His approach to amplification is generally to use MOSFET devices in output stages running Class A since they can exhibit triode tube-like characteristics. This combined with simple circuit topologies (simple circuits sound better according to Nelson) results in a purity of sound that is highly regarded by audiophiles. Long ago I had read articles about his early Zen amps which were super simple, although they dissipated prodigious amounts of heat, but did not have the time at that stage of life to experiment. I discovered that Nelson freely contributes his ideas and helps in the DIY Audio forums - there is one dedicated to just Pass Labs and his designs, and it has hundreds of thousands of thread responses, many by Nelson himself. I was so intrigued by this level of interest, that was the path I initially took.

My overall goal was to build an integrated system of well-matched components, consisting of DIY Sigfried Linkwitz speakers which would be bi-amplified, with the high-end transducers driven by a Class A amp and the low-end by a more powerful Class AB amp. The crossover function would be handled within a passive preamp using an analog crossover tailored specifically to the Linkwitz speakers. The crossover was designed by Nelson, an outcome of his discussions with Linkwitz, who had been using a digital signal processor previously.

I started with the class A power amplifier inspired by the First Watt F7. You can see the construction details here. This amp is not very powerful (about 25 Watts, so has to be used with efficient speakers) but sounds very musical and has a level of sweetness rarely heard. 

Next came the preamp build, which is detailed here. It can be used with or without the crossover in the audio path.

Next came a 100-watt class AB power amp project, detailed here.  This is not a Pass design but also came from DIY Audio. It was meant to be a high-performance amp using low-cost components

As of this writing, the Linkwitz speakers are a work in progress. I have several parts, and will soon order the transducers. Once this is well underway, I will document the build process.

I also got interested in constructing audio test equipment to evaluate the performance of the projects I am building. As time allows, I will document these in the Projects Section.

So in a nutshell, I have been lucky to have combined my technical background with my interest in good music reproduction.

My Projects  (click to expand)

My Background in Audio and Electronics

Early Days

We got a real stereo when I was around 7. I don't recall the brand, but it consisted of two cabinets, one large one with the LP record changer (crystal phono cartridge), a tube amplifier (probably around 10 Watts), a speaker, and a second smaller floor-standing speaker cabinet. I only mention this because it was a very different experience from listening to 45 RPM records on a small record player. RCA came out with their "Living Stereo" LPs and soon everyone wanted a stereo system. I must have worn out my parents' copy of Beethoven's Fifth Symphony playing at high volume when they were out of the house because it sounded so cool.

My interest in electronics started around the age of ten when I was given a subscription to the American Basic Science Club, which sent a kit every month with some simple circuits to build, like a one-tube radio. I should also mention that some of my older, extended family members had dabbled in HiFi before it was a thing. I had an uncle who built amplifiers from scratch in the 40s and 50s - his father (my grandfather) built cabinets for the systems. He was also a Ham radio guy and gave me an ancient copy of the ARRL Handbook, which I found fascinating. Another uncle gave me a very early FM tuner which he had built from a kit in the 1950s. He also gave me a copy of a book titled "Amateur Craftsmans's Cyclopedia and Log Book of Things to Make", published in 1937. Most of the articles were not very interesting (crafty stuff) but there were a few electrical and electronic projects that were neat - like "Build a Picture Frame Radio". So there was a bit of electronics DNA in me.

CLICK TO READ MORE

Then I started fixing radios and televisions and building Heathkits, Knight-kits from Allied, and some EICO gear. I also did some experiments on my own with circuits, often inspired by articles in magazines like Popular Electronics. My dad bought me an old used oscilloscope when I was 12. This was like turning on a lightbulb because I could actually visualize electrical waveforms.  I credit my parents for being patient and supportive of my hobby. I also taught myself some digital circuitry, building transistorized flip-flops and logic gates (this was before integrated circuits were available).

Hi-end audio became an interest when I was in high school and worked part-time at a hi-fi shop setting up and repairing equipment. We sold Wharfdale, Klipsch, Altec, Marantz, Revox, Ampex, McIntosh, etc., so I was "spoiled" at an early age. I built up a tube-based system, consisting of two used Fisher monaural tube preamps, a used BO turntable, two hand-built Williamson tube power amps, and custom speaker cabinets containing 12" coaxial drivers from Allied Electronics. I lugged all this to college, only to sell it off to raise money for necessities. A few years later I replaced that with a modest system, consisting of a Heathkit AR15 receiver, a Dual record turntable, and Dynaco A-25 two-way bass-reflex speakers from Denmark. This was fine for casual listening of my LP collection. Meanwhile, I was working as a circuit designer and honing my electronics skills, although in fields unrelated to audio. After that, I went to work for a computer company (where I would spend the rest of my career) and gained lots of knowledge about processors, computing systems, and networking.

Later in life, I became a fan of live musical performances, particularly orchestral music, We attended many concerts performed by the Boston Symphony Orchestra in Symphony Hall, regarded as one of the finest acoustic venues in the world. These experiences became the benchmark for experiencing "perfect" live sound, so I put together an audio system that I felt could reproduce live music as faithfully as possible, given reasonable budget constraints. This consisted of Martin Logan Aerius i electrostatic speakers, a McCormack DNA amplifier (a good match for the Aerius speakers, since it can produce up to 500 Watts into low impedance loads), a Yamaha passive preamp, and a Sony ES CD changer. The Aerius speakers can be tricky to set up in a room and have a fairly narrow "sweet spot", but certain recordings can raise the hair on my arms with realism, especially voices and stringed instruments. There are times when I can close my eyes and imagine a performer in the room with me, and the soundstage is sometimes three-dimensional. This system is still in use today and is very satisfying to listen to.

Digital Audio Adventures

In the 1980's we began to collect CDs and started listening to them more than LPs. I was not always happy with CD sound, but the convenience and lack of scratches, clicks, and pops were the most compelling reasons. We had a mid-Fi Technics single CD player but later switched to a much better Sony "ES" 5-CD changer. We discovered that CDs produced by Chesky Records were particularly good. In the 1980s the Chesky brothers built a successful independent label by initially issuing analog remasters of older recordings. Their attention to detail led to digital conversion techniques such as 128x oversampling and 24-bit A-to-D conversion using custom electronics, unheard of at the time. They also were particularly mindful of microphone placement for live recordings and avoided "over-micing" in order to simulate the most faithful soundstage possible. More recently, they created HDtracks, an online music service providing downloads of high-resolution recordings with thousands of offerings.

In the early 2000's I bought a Squeezebox audio player from Slim Devices. This was my introduction to streaming digital music over Ethernet and WiFi and I began to digitize my CDs using lossless compression encoding (mostly FLAC, which is "bit-perfect").  The server portion of the system was open-sourced and could run on any PC or server. For a number of years, I used Windows 2000 as a server for the music and then switched over to a Linux setup. This introduced a better level of usability (no shuffling of CDs and jewel cases) while maintaining sound as good or better than CD players could achieve.

When Logitech bought Slim Devices (and soon after discontinued the hardware product line), the server portion became known as LMS, for Logitech Media Server, and the company continued to offer it as a free open-source platform. It is still available for download today for multiple platforms and is maintained.

My Squeezebox lasted for about 15 years and died, so I decided to build my own device using a Raspberry Pi processor based on a project called piCorePlayer. This was a software emulation of the old Squeezebox players running on a version of Linux. Details are in the Projects Section. Also in that section are details of a second DIY streaming player which improved over my initial attempt.

It began to be clear to me that there were inherent limitations to the "Red Book" 16-bit CD format and I started acquiring downloads of higher-resolution recordings in 96KHz 24-bit formats. To me, these consistently sound much better if done right. I jumped over the SACD/DVD-Audio craze and went straight to digital storage of downloaded music.

Recent Endeavors

As I was looking to get back into DIY audio, I thought about tube-based amplification and I have a fairly complete set of old Glass Audio magazines with many circuits for the DIYer. Since I had "grown up" with tubes, I would have been completely comfortable building tube-based equipment, and I was well aware of the high regard that tube amps have in the high-end audio world. But then I began delving into the world of Nelson Pass, the famed audio designer who founded Threshold, designed the Adcom amps, and later started Pass Labs and First Watt. His approach to amplification is generally to use MOSFET devices in output stages running Class A since they can exhibit triode tube-like characteristics. This combined with simple circuit topologies (simple circuits sound better according to Nelson) results in a purity of sound that is highly regarded by audiophiles. Long ago I had read articles about his early Zen amps which were super simple, although they dissipated prodigious amounts of heat, but did not have the time at that stage of life to experiment. I discovered that Nelson freely contributes his ideas and helps in the DIY Audio forums - there is one dedicated to just Pass Labs and his designs, and it has hundreds of thousands of thread responses, many by Nelson himself. I was so intrigued by this level of interest, that was the path I initially took.

My overall goal was to build an integrated system of well-matched components, consisting of DIY Sigfried Linkwitz speakers which would be bi-amplified, with the high-end transducers driven by a Class A amp and the low-end by a more powerful Class AB amp. The crossover function would be handled within a passive preamp using an analog crossover tailored specifically to the Linkwitz speakers. The crossover was designed by Nelson, an outcome of his discussions with Linkwitz, who had been using a digital signal processor previously.

I started with the class A power amplifier inspired by the First Watt F7. You can see the construction details here. This amp is not very powerful (about 25 Watts, so has to be used with efficient speakers) but sounds very musical and has a level of sweetness rarely heard. 

Next came the preamp build, which is detailed here. It can be used with or without the crossover in the audio path.

Next came a 100-watt class AB power amp project, detailed here.  This is not a Pass design but also came from DIY Audio. It was meant to be a high-performance amp using low-cost components

As of this writing, the Linkwitz speakers are a work in progress. I have several parts, and will soon order the transducers. Once this is well underway, I will document the build process.

I also got interested in constructing audio test equipment to evaluate the performance of the projects I am building. As time allows, I will document these in the Projects Section.

So in a nutshell, I have been lucky to have combined my technical background with my interest in good music reproduction.

Some Useful Audio Links  (click to expand)

This is nowhere near an exhaustive list, just some of my favorites. In the  DIY Audio Forums alone, you can spend hundreds of hours and only scratch the surface.

General Interest:

Books:

Software (these are all freely available):

Parts Sources:

Tools:

Other: