Beezar Audio/ECP Audio History

Discussion in 'Beezar' started by TomB, Oct 26, 2018.

  1. TomB

    TomB MOT: Beezar

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    Marv graciously created a subforum for Beezar so that Dsavitsk (ECP Audio) and I could tell you a bit about ourselves, how we got started, and maybe some of our ideas for the future. So, here goes about me:

    I'm an Engineer by trade and have built things for as long as I can remember. I spent a lot of my youth in building model airplanes. I built plastic model airplanes, and then flying ones later on. These were control line models when I was young, because my family couldn't afford for me to do radio control. I also dabbled in model railroading and slot cars when they were popular. I guess that's where I really learned to solder - building brass slot car chassis with an Ungar soldering iron (and lots of flux).

    After finishing high school in the early 70's (yep - I'm an old fart) and like a lot of guys that age, I got very interested in high-fidelity audio. My freshman college year was spent visiting lots of stereo stores and reading every issue I could get my hands on of Stereo Review, High Fidelity, and Audio magazines. (No Internet back then) My first high-fidelity stereo setup was a Sherwood S8900A receiver (with DynaQuad!), an Elac Miracord 50H MkII turntable with an Empire 1000ZEX cartridge, a pair of the original Advent bookshelf speakers and a Koss Pro 4AA - the original one with the fluid-filled cushions. Back then, the smart stereo consumer would audition in the stereo store, then go home and call up Illinois Audio for a mail order that was 30% discounted from what you'd find in the stores. (Advent speakers were dealer-only, however.) Later on, 47st. Photo and J&R Music World sort of wiped up the market for discounted mail order electronics. I guess it's B&H Photo or Adorama these days or simply Amazon.

    A few years after I got married, I upgraded to a Sony VX6 receiver, a Technics SL-7 linear-tracking turntable, and a pair of Polk monitor 10 speakers. The cartridge was a Shure V15 LT. About this time, I added a Sony cassette tape deck with Dolby C. Back then, the idea was that you ran an album in the turntable long enough to record it on the cassette deck, then you put the album away to preserve it and the cartridge stylus and played the recorded cassette from then on. I still have this equipment:
    [​IMG]
    I also acquired a pair of Sony MDR-80T headphones. Unfortunately, I do not have those headphones anymore, dang it! To me, they were as revolutionary as the Sennheiser HD414:
    [​IMG]
    They were the ultimate Walkman-style headphones.

    I also got a pair of Koss Pro 4X, which led me to stop buying Koss altogether until the KSC-75s. The Pro 4X were a horrible pair of headphones. The cushions (still fluid-filled at first) were glued to a chrome-plated, slotted plastic plate and were attached to another slotted plate on the headphone frame through a thin layer of foam. This allowed the cans to "float" on the foam, supposedly increasing comfort. The foam dissolved in a few years, though, leaving nothing but a ruined pair of phones. Here's a typical pic from ebay:
    [​IMG]
    Look at the area between the two chrome plates and you can see the dissolved foam mess. I shipped mine off to Koss, only to discover that their famous lifetime warranty didn't apply to the 4X.

    Navigating the early 2000's, Headwize, the Millett Hybrid, Starving Student and more in the next post ...
     
  2. TomB

    TomB MOT: Beezar

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    In the booming 80's, my wife and I were blessed with the birth of two girls. Needless to say, between that and work, I had little time for hobbies. I continued to dabble in model airplanes, however, and finally had enough money to try radio control. (Hey - I worked for Lockheed at the time!) It was fun, but the wife and kids didn't like the idea of me driving to Timbuktu every Sunday to fly. Plus, it was still very expensive. Maybe when I retire some day …
    [​IMG]
    The youngest daughter in that pic now has a PhD in molecular biology. The older redhead was born musically talented. In 8th grade, she became the top violist in the state. I began driving her on weekends to practice with a symphony orchestra. I even began recording some of her concerts - with that same Sony cassette deck and Dolby C. Gradually, high-quality stereo and headphones became important to me again. This was sometime in the early 2000s.

    The Pro 4Xs had disintegrated and the MDR-80Ts didn't offer any isolation. So, like everyone does without thinking these days, I went online to find out the latest about headphones. I discovered Headwize. Pretty quickly, I learned that the Sennheiser HD580 was probably the pinnacle of headphones and there was a brand new one that had been out for a couple of years - the HD600. I also learned that these headphones were 300 ohms impedance and they needed headphone-specific amplifiers. Back then, specific headphone amplifiers generally didn't exist unless you built one. Building a headphone amplifier seemed insurmountable to me at the time, despite a lot of headphone amplifier designs and building instructions available in the Headwize library.

    But then there was Chu Moy's brilliant CMoy. Chu Moy founded Headwize and he developed the opamp-based headphone amplifier. Chu Moy did this because he was frustrated at the inability of portable CD Walkmans to sufficiently power the Sennheiser headphones:
    [​IMG]

    Later on, someone took his design and built it in a Penguin Mint tin. I think it was user Apheared who first did that, but I could be wrong about that. Regardless, it became the standard for building a CMoy. Apheared was definitely one of the pioneers of the CMoy and built upon the design by adding more opamps as buffers. Many familiar names (and some that have been forgotten) were on Headwize at that time - Apheared, Tangent, Morsel, PPL, AMB, Tyll, pmillett, n_maher, rickcr42, Steinchen, cetoole, Drewd, and Dsavitsk. (There were many others, of course.) Tangent had already teamed with Morsel and PPL to produce several DIY headphone amplifier designs. Most importantly to me at the time, Tangent had his brilliant CMoy tutorial online:
    How to Build a CMoy Pocket Headphone Amplifier

    This was simple, cheap and almost everything could be purchased at Radio Shack. I already knew how to solder, so this seemed like the ticket. I was hooked and dove right in. Also around about that time, Sennheiser reduced their pricing on the HD580 to $120! I picked up a pair, soon ready to power them with my first CMoy:
    [​IMG]

    It's a jumble of wires, because I was afraid of not having enough lead length to fit everything in the mint tin. When I realized it was too much, I was afraid to un-solder everything to shorten the leads, so I just packed it all in there as best I could. Hey - at least it worked!

    I was off and running and built a couple of PIMETAs from Tangent, next:
    [​IMG] [​IMG]
    These were basically identical and incorporated a trickle charger for charging the batteries. They weren't very practical, though. With the double-BUF634s biased into Class A, a full battery charge would last for about forty-five minutes, while charging took 8-10 hours. I still use them plugged into Jameco linear-regulated walwarts.

    All the while, I was lusting after tubes, but was scared to death of the high-voltage and point-to-point construction. I wasn't ready for that. Then I discovered the Millett Hybrid.
     
  3. TomB

    TomB MOT: Beezar

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    I know Marv wants me to get to the point of describing how Doug and I got together - I'm building to that, I promise. ;)

    Millett Hybrid. In November, 2002 an article was published in AudioXpress magazine (http://www.audioXpress.com). It was authored by Pete Millett and was titled, "Build a Low-Voltage Tube Hybrid Headphone/Line Amp." That's sort of an un-assuming title for the change it eventually wrought in the early days of DIY-ing in the headphone community. I think AudioXpress has long buried this article where I can't find it anymore, but I have a copy of it preserved here: http://www.http://diyforums.org/MAX/history/ax_hybrid.pdf. A very kind customer even sent me an actual hard copy of the actual magazine issue - I cherish it. Pete Millett saves a copy of it on his website here: http://pmillett.com/file_downloads/ax_hybrid.pdf. Here's a pic of the original:
    [​IMG]

    I'm guessing about some of this stuff, but several people became friends at the early CanJams started by Jude and Head-Fi. Nate Maher (n_maher) became friends with Tyll and also Pete Millett, among others. I guess Drew Dunn was there, too, and was an early seller of small, portable solid-state headphone amplifiers. Tyll eventually started selling a super-duper version of the Millett Hybrid as one of Headroom's headphone amplifiers. They still have the manual online and you can download it here to get an idea of the amp: Headroom Desktop Millett Hybrid Headphone Amp.

    Pete sold a couple of high-voltage tube headphone amplifiers under the brand name Wheatfield Audio. I think Headroom sold those, too for awhile. Drew got banned from Head-Fi (Jude could ban someone from his forum?) and started a forum site on his own - diyforms.org. Somehow he got together with Nate and produced a 2nd version of Pete's design. Pete's version used heat sinks and an open-PCB, bottom-only case style. On the other hand, Drew's revMH version used simple opamp sockets and was sized to slide into the slots of the popular Hammond 1455-series of cases:

    [​IMG]
    [​IMG]

    I found out about it all through the Group Buy on Headwize. Here was a real tube amplifier that was entirely based on low-voltage - no killing yourself while trying to learn! I was hooked and ended up building four of them. Many, many others built them, too. Nate built and sold several that were works of art:

    [​IMG]

    Notably, this was also when AMB (Ti Kan) was getting involved in the headphone community and one of his first forays was building a revMH Millett Hybrid. AMB also provided some really great work in performing baseline measurements for the Millett Hybrid and its various options. AMB's Millett Hybrid is still documented here: https://www.amb.org/ti/audio/millett.html.

    A builder from Germany, known as "Steinchen," designed the Diamond Buffers for the revMH. The Diamond Buffers were based on Walt Jung's famous design and Steinchen designed them to plug into the opamp sockets on the revMH PCB:

    [​IMG]

    While addressing BUF634 shortages at the time, this put the performance of the Millett Hybrid on another level. However, while excited about this change (I built four of them again.), I was a bit disatisfied with the current state of the DIY headphone amplifier progression. Tangent, AMB, and even Pete seemed to design and build DIY amplifiers without power supplies. For awhile there was the Elpac linear-regulated power supply, but it quit being made soon into this era. Tangent probably became more famous for his STEPS and TREAD power designs, the ultimate in low-noise power supplies. The STEPS was a full-blown, transformer and mains equipped power supply, while the TREAD was a tiny 2" x 1" board intended for supply with an AC walwart, with a slightly reduced noise performance. Its size also meant it was more flexible and there was the possibility of locating the board inside an amp, which many did. Or in my case, I actually built a couple of custom walwarts using Jameco plastic walwart cases and the TREAD:

    [​IMG] [​IMG]

    All of this required a lot of creativity on the part of the builder. There was really no single solution for a desktop, all-inclusive headphone amplifier design. The power supply was always separate - separate parts, separate designer, separate sources, possibly separate casework, etc., etc.

    Meanwhile, while impressive, the plug-in diamond buffer boards were difficult to build, a bit touchy, and including the power supply, meant three completely separate design sources (or more) in obtaining boards and parts just to build a single Millett Hybrid. Around about this time, I became acquainted with the user "cetoole." Cetoole was Colin Toole, a young guy with a talent for PCB design with Eagle. Lo and behold, he posted a draft Eagle layout design for a new Millett Hybrid design that incorporated an onboard power supply (fed with a universal AC walwart), a completely integrated diamond buffer with onboard heat sinks and sized to all fit into either a Lansing or Hammond standard case. This was the answer!

    [​IMG] [​IMG]
    [​IMG]

    I immediately started trading posts and PMs with Colin and helped him as much as I could with the new design, even building the first prototype. This eventually evolved into the Millett Hybrid MAXed, which ended up as the largest Group Buy (I think) that Head-Fi ever had with a DIY design PCB. There's a picture somewhere that I lost showing Colin's bedroom covered with all the sealed envelopes of the MAX boards ready for shipment.

    Not too long after that, I started Beezar Audio.
     
    Last edited: Nov 2, 2018
  4. TomB

    TomB MOT: Beezar

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    After the initial Group Buy, I approached Colin with the idea of continuing to sell the boards and perhaps some extra parts with my own business, sharing some of the profits with him. This is when I started Beezar Audio/beezar.com. My youngest daughter (the one with the PhD, now) had an interest in website design and blogging when she was a pre-teenager. I bought her a domain and web hosting service as a birthday present one year. At the time, she also had an Abyssinian guinea pig pet. Back when she first saw the guinea pig, and how its fur was sticking out into all directions, she exclaimed, "Beeeezzzarr (bizarre)!":

    [​IMG]
    (That's not a pic of her own guinea pig, but you get the idea.)

    She named the guinea pig, "Beezar." When I bought the domain and web hosting site for her, I gave it the domain name, "beezar.com." As things often happen, she lost interest when she became a teenager, but we still owned the domain name. I asked her if she'd mind if I took over the site - she said no. I thought beezar was a pretty unique name and that I wouldn't have much conflict with anyone in using and registering it as a business name. That's how Beezar was created. ;)

    After a period of selling the Millett Hybrid MAX, Colin developed the MiniMAX. I helped him get the design of the power supply even quieter. Measurements using Tangent's Low Noise Measurement Preamplifier (LNMP) were better than even Tangent's STEPS power supply. I also designed a pretty elaborately machined case design using one of Lansing's extruded aluminum cases:
    [​IMG] [​IMG]
    [​IMG]

    This gave me invaluable experience into case design and sourcing manufacturing runs from major manufacturers. We sold quite a few MiniMAX boards and I eventually started selling them as full kits, so that I could incorporate the cases. Colin designed the Bantam DAC for me also, which eventually led to the onboard DAC PCB design of the MAX V1.2 PCBs that are available today.

    Eventually, Drew Dunn left the hobby and Nate Maher approached me about buying the DIYForums.org website from Drew. Nate was concerned that all of the MH information would be lost unless someone else picked up the gauntlet and kept it running. So, I purchased DIYForums.org. I ran the forum for awhile, but like at Headwize, it got hacked a couple of times. The phpbb software had some updates, but like a lot of software, it wasn't necessarily backwards compatible. Since the other forums were much more successful and beezar.com kept me pretty busy anyway, I basically de-activated the forum. However, I kept it available in a static form so that all of the info is still there. Since then, I have used the site as the documentation platform for building instructions, BOMs, etc. for all the designs that I sell at Beezar.com.

    Along the way, I became acquainted with other designers who wanted an outlet to sell their PCB designs. One of these was Doug Savitsky, otherwise known as Dsavitsk.
     
  5. TomB

    TomB MOT: Beezar

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    Before continuing further, I just wanted to point out a post that Doug made recently. It encapsulates the best about his standards for excellence and the fact that no one is doing what he does with designs these days, either with tubes or especially lately - transformers:
    https://superbestaudiofriends.org/i...4-headphone-amplifier.6720/page-3#post-231633

    Back to the story -
    I had followed Doug for a long time on the forums. In the early days, he was modding a Melos SHA-1. Later on, he built the revMH Millett Hybrid as his first, true DIY headphone amplifier project. On Head-Fi and Headwize, his username was dsavitsk. On diyforums, it was "drs." He developed his own website and began posting one article after another about a headphone amplifier (DACs later) he had modded or built. One early instance that caught my eye was what he did to a Grado RA-1. Not content with fixing a volume pot issue, he completely gutted the amplifier and installed a PIMETA in its place in the wood block. He went even further and ended up with a 3-block combo of power supply, amp, and DAC:

    Here's how the mod began:
    [​IMG] [​IMG]

    So he ground out the wood to make room for a PIMETA PCB:
    [​IMG] [​IMG]

    Not content with that, he bought a couple more mahogany blocks and made a power supply and a DAC (Guzzler DAC, I believe):
    [​IMG] [​IMG]
    [​IMG] [​IMG]

    I thought all of this was singularly fascinating. I just had to find out more about this guy and what else he was up to.

    Eventually his knowledge and experience developed way beyond the instances described above. He built a ton-load of tube headphone amplifiers. As with his latest post referenced at top, his posts often became a wealth of information. On top of that, he seemed to be blazing his own trail against conventional norms of the day with respect to headphone amplifiers. Posts would catch my eye on Headwize, Head-Fi, and diyforums. Often, he'd be saying something like, "Tube amplifiers can have frequency responses as good as solid-state, as long as they're designed correctly." I'm paraphrasing and not quoting directly, but that's an example. He seemed to focus on tubes the most (at the time) and that's what kept my attention, for sure.

    His early website became a collection of his various tube and solid-state projects, along with other information that became invaluable. By the time Colin Tooles and I had developed the Millett Hybrid MAX and MiniMAX, there was very little left to do that would improve the basic Millett Hybrid circuit, except for capacitor selection. As a single-ended, positive bias design, the tubes sat with their peak positive swing at 27 volts above the ground reference. So, the MAX and MiniMAX used capacitors on the output. This meant the audio quality of the capacitors was very important. One of the earliest information goldmines that Doug posted was his "Some Notes on Coupling Capacitors." It became our top resource:
    http://diy.ecpaudio.com/p/some-notes-on-coupling-capacitors.html

    Humble Homemade HiFi has hosted a website giving detailed reviews on coupling capacitors for about as long as Doug, but they focus on speakers and the capacitors used in speaker crossovers. On the other hand, Doug's pages on capacitors were specific to headphone amplifiers. It quickly became my reference for choosing capacitors and bypasses to use on the MAX, MiniMAX, and elsewhere. We ended up standardizing on Muse ES electrolytics with Vitamin Q bypasses, then later with Sonicap Gen 2 bypasses - a specific combination that Doug's "Notes" recommended. "Some Notes on Coupling Capacitors" is still a useful reference today.

    Meanwhile in 2008, Pete Millett once again surprised the headphone DIY world with his introduction of the Starving Student Millett Hybrid:
    [​IMG]

    This was posted on his own website and on Head-Fi. Nate Maher followed up with his own second-ever construction of the Starving Student headphone amplifier:
    [​IMG]

    This was a point-to-point, very simple amplifier circuit based on the 19J6 tube, with a single MOSFET follower for a solid-state buffer: almost like a tube-based CMoy. Interestingly, the power supply was a surplus Voice-over-IP telephone power supply made by Cisco, available quite inexpensively through many listings on ebay. The MOSFET buffer was ingeniously biased by the tube heater supply itself. The final touch to an inexpensive, starving student budget was the 19J6 tube. At the time, it could be had for $2 or less. It's a testament to the effect Pete's design had on the worldwide tube market as the 19J6 went from plentiful and $2 to scarce and $10-$12.

    Even though the Starving Student was still somewhat low-voltage (48VDC), I was still reluctant to pursue the point-to-point construction needed. However, Dsavitsk soon posted a PCB design for the Starving Student in May of 2008:
    [​IMG]

    I can't remember how it came about exactly, but Nate and Pete got together and eventually blessed the idea of a PCB for the Starving Student. (They wanted to give opportunity for everyone to build the point-to-point version, first.) So, Doug and I started a conversation about selling the PCB through beezar.com. I guess that's how our collaboration started. We started communicating back and forth through e-mails on parts selection, PCB features and how to develop the casework. The result was the SSMH DIY kit (Starving Student Millett Hybrid), still available today. I keep collecting 19J6 tubes from time to time. Once I have enough to justify a manufacturing run of casework from Hammond (usually 30-50 cases), I offer the kits for sale on beezar.com. This has happened 3-4 times since 2009. They're all still based on Doug's original PCB design. There has even been a copycat PCB design since then - based on the 12AU7 - that sold for a while from references on Head-Fi.

    Needless to say, I built the prototypes for Doug's PCB and a couple of production versions that I still have today:
    [​IMG] [​IMG]

    After the experience with the Starving Student, Doug went on to post something on his website that became groundbreaking for DIY headphone amplifiers: the Less Pressivo. This was a true high-voltage tube amplifier with output transformers. Unlike the conventional wisdom of the day, Doug was recommending some of the most inexpensive output transformers possible. For years I had been reading about tube amplifiers and the use of output transformers. The ever-present probelm with output transformers was that they were very expensive. It's why so many OTL (output transformer-less) tube amplifier designs came about. Almost everything with tubes was either an OTL or a hybrid. Here was something with Doug's L'espressivo (the final name iteration) that recommended inexpensive output transformers that resulted in reasonable, high-quality sound for $100 (minus casework)!

    [​IMG] [​IMG]

    Not coincidentally (we both shared a fascination with Doug's creations), Colin Toole was one of the first to build one after Doug's:
    [​IMG]

    The L'espressivo was somewhat based on a design by Gary Dahl - the Espressivo. The Espressivo essentially used the tube-parafeed circuit with premium parts to construct a top-of-the-line headphone amplifier. Doug's initial experiments led to non-premium, inexpensive parts resulting in surprisingly good performance with the L'espressivo. However, he tried the premium parts route, too, with his own take on things. It resulted in the L-2. At the same time, he formed his own company to begin marketing and selling the L-2: ECP Audio.
    [​IMG] [​IMG]

    Nate gave it a sterling review on Tyl's InnerFidelity here:
    https://www.innerfidelity.com/content/ecp-audio-l-2-headphone-amplifier

    Sometime around this period, I began begging Doug to make a PCB version of the Less Pressivo. I was still wary of anything high-voltage. I thought if he could design a PCB-version of the L'espressivo, two outstanding things could be the result: 1) I'd personally be able to finally build a true, high-voltage tube amp, and 2) we could offer it to the masses as an easy-to-build DIY kit. As far as I knew at the time, the Cavalli Bijou was the only true high-voltage tube design available in PCB, DIY form. The problem was that it was modular (3 PCBs), had no case design, and the power transformer required 100% wiring and mounting (undefined). So, I was trying to talk Doug into a design similar to the Millett MAX/MiniMAX/StarvingStudent, only as a true, high-voltage tube amp: everything on a single PCB, with a case design to fit. This would include little to no wiring and no metalwork required for the casework: anyone who could solder could populate the PCB and assemble the casework.

    Doug answered the challenge. It resulted in the Torpedo headphone amplifier.
     
  6. TomB

    TomB MOT: Beezar

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    Before we got to the "Torpedo," it started as the "Less PCB." Doug's initial idea was to base the amplifier on an output-transformer equipped, classic parafeed design. It would be based around the 6J6 tube. This was a nod to the Starving Student. After all, the goal was an affordable, DIY project. As the 19J6 tubes for the original Starving Student became more scarce, almost every tube dealer began suggesting the 6J6 when I contacted them about the 19J6. It's the same dual triode tube, only with different options on heater voltage requirements. In fact, you will find that the tube data sheet encompasses the 6J6, 5J6, and 19J6 - all in the same tube sheet. The 19V heater voltage of the 19J6 happened to just fit with the Cisco power supply and MOSFET biasing scheme that Pete Millett used on the Starving Student. However, a 6V heater on the same tube meant 450ma of current, compared to just 150ma for the 19J6. Tube dealers didn't realize that 6J6 substitution into the Starving Student was impossible with that kind of current disparity.

    However, the 6J6 was 10 times more plentiful than the 19J6 and if Doug was designing from the ground up, the very high heater current could be taken into account. Most tube dealers had hundreds, if not thousands of 6J6 tubes. Some claim there are even tens of thousands available. Price, when purchased in volume (100 or more) was down to about 35 cents in some cases! (I still have several hundred of them.) So ... Doug's first attempts at a new tube amplifier design are usually air-wired with the pieces sitting on an old wooden door. This one appears to be some sort of thick, plywood paneling (or maybe it really is a bread board):
    [​IMG]

    Note thePCB-pinned power and output transformers from Edcor. Since Doug had already designed and built his "Less-Pressivo" and "L-2" designs, the primary focus in this air-wired prototype was to check the suitability and operation of the Edcor transformers, along with the power supply, tube circuits, etc. This was a great success according to Doug, but he noticed some hum interaction between the output transformers and the power transformer, depending on how close they got. Initially, the thought was to provide the amplifier in two parts, an amplifier section and a power supply box. This was how the L-2 was made. However, I was pretty adamant that it remain all on one PCB. (See my earlier post on opinions about modular PCB designs.)

    So Doug used his door test circuit to come up with a suitable distance of separation between the PT and the OPTs. If my memory is correct, it ended up being somewhere over a foot. Long story short, that's how the amplifier arrived at its very long layout. We first tried Hammond Mfg, a personal favorite of mine and their 1455 series cases had been used for several years in the DIY community: PIMETA, PPAV2, Millett Hybrid, etc., were all cased up in 1455 series cases at some point or other. Doug's PCB design fit the cross-section of one of the 1455 series cases, but he eventually ended up with a 14" long PCB after fitting the other needed components. This meant a custom extrusion length was needed. I contacted Hammond. I had a pretty good relationship with them from the Starving Student and PupDAC experience. They were quite helpful, but as is usual with these things, I had to order 6 of them to make it worth their while. Here's Doug's first prototype build using the custom-length Hammond case:
    [​IMG] [​IMG]

    Because we had the cases, we invited a number of users to build the design, too. Nate Maher built this one:
    [​IMG]

    Head-Fi/Head-Case user luvdunhill built this one in a gorgeous powder-coat blue, with impressive cooling slots:
    [​IMG]

    Somewhere along the line, I can't remember who - came up with the name "Torpedo." We were looking for a name around when the prototypes were being built, but I can't remember exactly how it transpired. Somebody suggested "Sausage," which we didn't like for obvious reasons, then someone else mentioned "Cruiser." I don't think we liked the explosive-sink-ships connection with "Torpedo," but there were other less violent uses for the word "Torpedo." So for some reason, the name stuck. I guess we've been trying to get away from that name for a while now, so we began calling the Torpedo III the TIII [T3] (we referred to the Torpedo II as the "TII" [T2] before that, but more on that later). Now, we've gone straight to "T4," no "Torpedo" involved, thanks. ;) However, the lineage is important and with this - you have the history.

    Also around about this time, CanJam 2010 occurred. Doug lived in Chicago, so it was a no-brainer for him. I flew up and we shared a table at that CanJam. I displayed the Torpedo prototype and some of my Millett MiniMAXes/MAXes. Doug's stuff featured the L-2 and I believe he had the DSHA at that time, too.

    This is a Head-Fi pic (linked) showing Doug on the right. The gentleman to the left is holding the Torpedo prototype.
    [​IMG]

    That's me on the far right in the medium blue shirt, sitting in the user position adjusting something or other. The other two guys are listening to Doug's stuff - L-2 and DSHA, I think.
    [​IMG]

    The event was notable for me, because the guys at the table right next to me (out of the pic) were a couple of individuals with a brand new headphone design. They were a new company called Audeze. ;) Alex Cavalli was on the other side of the room, out of the picture. Tyll was also there (not in that room per se) showing off his first headphone testing enclosure. He was testing headphones at the meet, many for the first time ever. I also got to meet Pete Millett, Nate Maher, and Colin Toole for the first time (many others, too).

    Anyway, the prototyping of the Torpedo was fairly successful, but the biggest thing to come out of those initial builds and tests was the problem with heat. The slim Hammond case did not leave much room for heat sinking and the amps got hot - very hot. (The high heater current from the 6J6, no doubt.) Doug re-designed the PCB and we started using taller heat sinks. Neither of which would fit in the Hammond case anymore. We went to Context Engineering for the next casework. One of their stock designs would fit the design in cross-section, but again - we needed that 14" custom extrusion length.

    I built one with the new casework when it came in, but was quickly concerned when it developed what I thought was ripple noise. Everyone knows about hum and its 60Hz sound. However, this was slightly higher, I assumed at 120 Hz. Very strangely, it was associated with the case lid. When the case lid was on, you could hear the ripple. When the case lid was off - nothing, quiet as can be.

    Here's my build with the first rendition of the Context casework:
    [​IMG] [​IMG]

    All that said, the noise was still minor in the scheme of things. Only a few very efficient headphones could detect it when the lid was on. Again, nothing could be heard with the lid off. However, operation with an open lid on a tube amplifier running close to 300V was not something we were going to recommend. As best I can remember, we never mentioned that the noise would go away without the lid - in deep concern for safety.

    Still, it was detectable with certain headphones (lid on). We were open about it, but it didn't help sales. Some tube experts on the forum chimed in with agreement for Doug that the noise was trivial and that many tube amplifiers had worse. That didn't make us feel any better, though, and Doug spent many hours trying to figure out what was going on. I sent him my prototype at one point and he tried many things, to no avail. He did discover that the actual frequency of the noise was at 180 Hz, not 120 Hz ripple. That sort of made the issue more puzzling than ever, though.

    Eventually Doug developed several tweaks, two of which finally solved it. His first tweak increased the Power Supply Rejection Ratio of the tube circuit, which enhanced the performance of the amplifier - once the primary noise source was fixed. He discussed the Torpedo issue with none other than Morgan Jones at one point. It was Kevin Gilmore, however, who suggested that the rectifiers were oscillating and the power transformer was picking it up and spreading it through the circuit. This also tied in with the case lid phenomenon, in that the case lid was reflecting the oscillation back to the PT. I have heard of oscillating rectifiers before, but never heard about it reflecting from case lid back to the power transformer.

    The last two tweaks solved it - 1) capacitor snubbers on the rectifiers and 2) slower-specified rectifiers. Both made the noise go away. We finally had a successful amplifier! Needless to say, I sent rectifiers and snubber capacitors for free to every existing Torpedo customer and included them on all new kits that were sold from that point going forward. Eventually, I increased the quality of the casework by having it black anodized and laser etched. Below is an example of the final iteration of the original Torpedo:

    [​IMG][​IMG]

    I went to a black knob eventually, but what you see above is the planform and appearance that formed the basis of the T3. We took a small detour for the T2 (explained in the next post), but the T3 was next.
     
    Last edited: Jan 10, 2019
  7. Walderstorn

    Walderstorn Friend

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    Really entertaining reading. I would only point out that i am unable to see 2 of the pics, don't if i'm alone on this.
     
  8. dsavitsk

    dsavitsk Friend

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    There is a slight revision to this - somewhere in there I built a DAC based on using 2x TDA1543* chips in a differential configuration. It was, and indeed remains, one of my favorite things I have ever built. But importantly, it contained a novel output stage that eventually grew into the DSHA circuit. It was the headphone amp based on that circuit, the DSHA1, that led to the creation of ecp audio. The L2 was a late add that I thought would be more marketable, but which is kind of a boring circuit. But who, after all, was going to buy a weird transformer coupled solid state amp? The answer was, not very many people :)

    Anyhow, while the T1 was a budget friendly derivative of the L'espressivo and L2, the T3 and T4 owe more to the DSHA.

    * the TDA1543 was all the rage in DIY circles for a while because it was cheap, easy to use, and it sounded better than theory would predict.
     
  9. purr1n

    purr1n Desire for betterer is endless.

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    I have in my temporary possession one of the finest solid-state headamps I have ever heard, made by Doug. It's definitely in my top 3 (#1 with Elex or Utopia) with everything else not even coming close. Yeah, no shit. More details later. I love teasing you guys.
     
  10. Jerry

    Jerry Friend

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    Hope it's available for sale and doesn't cost too much.
     
  11. bengo

    bengo Friend

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    I guess you mean top 3 solid-state, not including OTC or other tube designs which I think are your preference?
     
  12. Elnrik

    Elnrik Super Friendly

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    Damnit.
     
  13. Vtory

    Vtory Audiophile™

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    Sounds like DHSA-3.. damn we are teased!
     
  14. jexby

    jexby Posole Prince

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    glad to see confirmation that my old deaf dum dum ears didn’t deceive with this SS marvel.
    still trying to figure out why it also sounded great with Auteur.
     
  15. MisterRogers

    MisterRogers Ethernet Nervosa

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    Yea, but you’re still old mate
     
  16. 9suns

    9suns [insert unearned title here]

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    DHSA-3F?
     
  17. purr1n

    purr1n Desire for betterer is endless.

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    Top 3 solid-state, top 5 overall with one of them not being in production yet. Might be #2 overall with Elex or Utopia. It's not often solid-state designs impress me like this.
     
  18. brencho

    brencho Friend

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    Can attest to Marv's delirium. Sounds amazia.
     
  19. jexby

    jexby Posole Prince

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    I was initially in favor of this amp never going to kalifornia and being the exclusive, sole property of @MisterRogers and SBAF Colorado for another year. kindness and sharing wins out though. :D
    thanks @MisterRogers for sharing the wealth, and of course to @dsavitsk for genius work.
     
  20. MisterRogers

    MisterRogers Ethernet Nervosa

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    Yea, I probably gave Doug fits on this build; had something very specific in mind (thanks for putting up with me Doug) - but he really knocked it out of the park. Envisioned as the ultimate Utopia driver, it's been magical with many headphones, very good with most.
     

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