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audio:audio_by_van_alstine_work [2019/08/02 23:03]
mithat [The future]
audio:audio_by_van_alstine_work [2020/01/02 18:03] (current)
mithat [The present]
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 New vacuum tube line stage to replace AVA’s existing design originally derived from the Dyna PAS 3. New vacuum tube line stage to replace AVA’s existing design originally derived from the Dyna PAS 3.
  
-**Contribution:​** Concept origination,​ development,​ and implementation. ​ I’m pretty sure this was the first commercial application of my vacuum tube computer optimization methods based on my [[https://​www.birotechnology.com/​articles/​VTspice.html|SPICE model optimization work]] ​(i.e., there were two layers of computer-based optimization:​ one to model the tubes and the other to optimize the performance of the circuit).+**Contribution:​** Concept origination,​ development,​ and implementation. ​ I’m pretty sure this was the first commercial application of my vacuum tube computer optimization methods based on my [[https://​www.birotechnology.com/​articles/​VTspice.html|SPICE model optimization work]].
  
-**Discussion:​** I thought the time had come for AVA to have a new vacuum tube line-level stage to replace their aging 12AX7A-based design, and they agreed. I based the initial work around two stages of 12AT7A gain using heaps of the SPICE simulation ​to optimize the circuit behavior for audio reproduction. I originally wanted to apply my design optimization methods to a number of different tube triodes and subjectively evaluate the results, but after hearing the results with the 12AT7A, AVA decided to put the design into production immediately. A variant of this stage remains in production today in the form of AVA’s Fet Valve CFR and FetValve CF RB preamps.+**Discussion:​** I thought the time had come for AVA to have a new vacuum tube line-level stage to replace their aging 12AX7A-based design, and they agreed. I based the initial work around two stages of 12AT7A gain using heaps of SPICE modeling ​to optimize the circuit behavior for audio reproduction. I originally wanted to apply my design optimization methods to a number of different tube triodes and subjectively evaluate the results. But after hearing the results with the 12AT7A, AVA decided to put the design into production immediately. A variant of this stage remains in production today in the form of AVA’s Fet Valve CFR and FetValve CF RB preamps.
  
 ===== Transcendence Six ===== ===== Transcendence Six =====
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 **Contribution:​** Concept origination,​ development,​ and implementation. **Contribution:​** Concept origination,​ development,​ and implementation.
  
-**Discussion:​** This was a continuation of the work I started with the Transcendence Five. Historically,​ AVA had demonstrated some success with two different hybrid approaches. In the first, high-voltage MOSFET buffers were placed inside the main feedback loop of vacuum tube gain stages. In the second, a low-cost opamp stage was used to provide high impedance buffering of a conventional closed-loop tube preamp design. My idea centered around placing a high-speed solid-state buffer IC stage //inside// the global feedback loop. This would allow AVA to offer a preamp with performance that exceeded their tube/MOSFET hybrid at a considerable cost savings. ​This design ​was so good that it obsoleted their tube/MOSFET hybrid preamp until I was able to complete work on the Transcendence Seven.+**Discussion:​** This was a continuation of the work I started with the Transcendence Five. Historically,​ AVA had demonstrated some success with two different hybrid approaches. In the first, high-voltage MOSFET buffers were placed inside the main feedback loop of vacuum tube gain stages. In the second, a low-cost opamp stage was used to provide high impedance buffering of a conventional closed-loop tube preamp design. My idea centered around placing a high-speed solid-state buffer IC stage //inside// the global feedback loop. This would allow AVA to offer a preamp with performance that exceeded their tube/MOSFET hybrid at a considerable cost savings. ​AVA considered the design so good that it obsoleted their tube/MOSFET hybrid preamp until I was able to complete work on the Transcendence Seven.
  
 ===== Transcendence Seven ===== ===== Transcendence Seven =====
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 **Contribution:​** Development and implementation. This was a major rethink of the work covered by AVA's [[https://​patentimages.storage.googleapis.com/​3b/​ca/​c7/​daa969bad4f092/​US5017884.pdf|“Fet Valve” patent]] and embodied in their first-generation Fet Valve products. **Contribution:​** Development and implementation. This was a major rethink of the work covered by AVA's [[https://​patentimages.storage.googleapis.com/​3b/​ca/​c7/​daa969bad4f092/​US5017884.pdf|“Fet Valve” patent]] and embodied in their first-generation Fet Valve products.
  
-**Discussion:​** One of the reasons my Transcendence Six design outperformed AVA’s more costly discrete MOSFET hybrid approach was that it used the optimized 12AT7A-based gain stage core initially developed for the Transcendence Five. So a natural progression was to see whether using that gain stage in one of the discrete MOSFET output buffer architectures ​covered in their patent ​provided an advantage over the IC-based buffer I designed into the Transcendence Six. In the process of designing the new MOSFET stage, I revisited a number of assumptions made in the original ​AVA implementation and produced ​circuit ​optimized for this application ​that was vastly ​simpler than the one it replaced. AVA thought its performance warranted it being offering as a premium hybrid product.+**Discussion:​** One of the reasons my Transcendence Six design outperformed AVA’s more costly discrete MOSFET hybrid approach was that it used the optimized 12AT7A-based gain stage core initially developed for the Transcendence Five. So a natural progression was to see whether using that gain stage in one of their patented ​discrete MOSFET output buffer architectures provided an advantage over the IC-based buffer I designed into the Transcendence Six. In the process of designing the new MOSFET stage, I revisited a number of assumptions ​AVA made in the original implementation and produced ​an optimized ​circuit that was significantly ​simpler than the one it replaced. AVA thought its performance warranted it being offering as a premium hybrid product.
  
 ===== "T7 CF" ===== ===== "T7 CF" =====
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 **Contribution:​** Concept origination,​ development,​ and implementation. **Contribution:​** Concept origination,​ development,​ and implementation.
  
-**Discussion:​** I was aware that AVA was losing preamplifier sales because they didn’t support any kind of remote control and that AVA regarded even the simplest of remote control functionality ​an unsolvable problem ​given their manufacturing quantities and methods. So I decided to solve it. The solution hinged on working with a turnkey supplier of remote control transmitters and pre-programmed receiver ICs and sourcing a motorized potentiometer that was as good as the potentiometers they were using. The result involved minimal changes to the chassis design and a build that was easier than the non-remote approach they had been using.+**Discussion:​** I was aware that AVA was losing preamplifier sales because they didn’t support any kind of remote control and that AVA regarded even the simplest of remote control functionalitygiven their manufacturing quantities and methods, an unsolvable problem. So I decided to solve it. The solution hinged ​on sourcing a motorized potentiometer that was as good as the potentiometers they were using and on working with a turnkey supplier of remote control transmitters and pre-programmed receiver ICs. The result involved minimal changes to the chassis design and a build that was easier than the non-remote approach they had been using.
  
-My original ​expectation was that AVA would offer the remote as standard equipment on all “big body” preamplifiers. Instead it was offered as a relatively costly option, which they justified because the remote control transmitters were costly, which they were because of the small quantities they ordered them in, which was the case because remote control was offered only as an option.+My expectation was that AVA would offer the remote as standard equipment on all “big body” preamplifiers. Instead it was offered as a relatively costly option, which they justified because the remote control transmitters were costly, which they were because of the small quantities they ordered them in, which was the case because remote control was offered only as an option.
  
 ===== Ultimate 70 and Ultravalve power amplifiers ===== ===== Ultimate 70 and Ultravalve power amplifiers =====
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 **Contribution:​** Strategization and development. Changes centered on improving loop behavior and power supply regulation, producing a circuit design that has remained in the AVA catalog for over 13 years. **Contribution:​** Strategization and development. Changes centered on improving loop behavior and power supply regulation, producing a circuit design that has remained in the AVA catalog for over 13 years.
  
-**Discussion:​** AVA felt they needed to produce a revision of their Dyna 70 rebuild offering and asked me to design it. I was proscribed from changing the tube complement or making similar large changes. So I opted to apply some of the insights ​gleaned ​from the application of regulated power supplies in tube and hybrid applications ​to the existing circuit ​and to revisit ​some assumptions about pole and zero locations that the original Dyna engineers had made, likely based on the kinds of parts that were available in 1959 and definitely based on the slightly different tube complement. The revisions ​I developed ​resulted in the Ultimate 70, and the circuit continues today in different packaging as the AVA Ultravalve amplifier.+**Discussion:​** AVA felt they needed to produce a revision of their Dyna 70 rebuild offering and asked me to design it. I was proscribed from changing the tube complement or making similar large changes. So I opted to apply to the existing circuit ​some of the insights ​we gained ​from the applying ​regulated power supplies in tube and hybrid applications and to revisit ​the assumptions about pole and zero locations that the original Dyna engineers had made, likely based on the kinds of parts that were available in 1959 and definitely based on the slightly different tube complement. The revisions resulted in the Ultimate 70, and the circuit continues today in different packaging as the AVA Ultravalve amplifier.
  
 ===== DAC core for Vision and Vision Hybrid DACs ===== ===== DAC core for Vision and Vision Hybrid DACs =====
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 **Contribution:​** Design and implementation. **Contribution:​** Design and implementation.
  
-**Discussion:​** In the mid-1990s, I built AVA a prototype stand-alone DAC that demonstrated to them that producing such a product was within their manufacturing ​abilities. This ushered in an era of their being able to offer a product that they had previously considered impossible. So it was probably natural that they approached me to design the core circuits that would be used in their next-generation of stand-alone DACs. They had preselected the the Wolfson WM8740 as the DAC IC they wanted the design based around, but by the time the design was completed we had moved to the WM8742.+**Discussion:​** In the mid-1990s, I built AVA a prototype stand-alone DAC that demonstrated to them that producing such a product was within their abilities---something ​they had previously considered impossible. So it was probably natural that years later they approached me to design the core circuits that would be used in their next-generation of stand-alone DACs. They had preselected the the Wolfson WM8740 as the DAC IC they wanted the design based around, but by the time the design was completed we had moved to the WM8742.
  
-AVA originally wanted to support only 44.1kHz PCM formats ​and a single coaxial S/PDIF input. Additionally,​ their manufacturing capabilities precluded the use of microcontrollers,​ which would have allowed for advanced use of the receiver and converter ICs. In spite of these constraints,​ I designed in automatic support for up to 96kHz PCM streams, jumper-configurable support for 192kHz PCM, and support for multiple inputs. Because of this, AVA was able to use this design to meet subsequent customer demands for high-rate audio support and multiple inputs; this board was used unchanged for all AVA DAC production for seven years until it was replaced by my DAC MK5 design.+AVA originally wanted to support only 44.1kHz PCM formats ​with a single coaxial S/PDIF input. Additionally,​ their manufacturing capabilities precluded the use of microcontrollers,​ which would have allowed for advanced use of the receiver and converter ICs. In spite of these constraints,​ I designed in automatic support for up to 96kHz PCM streams, jumper-configurable support for 192kHz PCM, and support for multiple inputs. Because of this, AVA was able to use this same design to meet subsequent customer demands for high-rate audio support and multiple inputs; this board was used unchanged for all AVA DAC production for seven years until it was replaced by my DAC MK5 design.
  
-This would be the first time AVA would use predominantly SMD parts in a PCB design. The previous generation DAC had used a single hand-soldered ​SOIC package. This design used SMD components exclusively.+This would be the first time AVA would use predominantly SMD parts in a PCB design. The previous generation DAC had used a single hand-soldered ​SMD package. This design used SMD components exclusively.
  
 I was not involved in the development of the analog stages for the first DAC products using this board. However, I was responsible for the analog circuits found in the [[#​vision_dac_improved|2015 revision]]. I was not involved in the development of the analog stages for the first DAC products using this board. However, I was responsible for the analog circuits found in the [[#​vision_dac_improved|2015 revision]].
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 **Contribution:​** Development. **Contribution:​** Development.
  
-**Discussion:​** AVA decided to pursue a stronger presence in the growing phono market by developing a stand-alone phono preamp. I was consulted on the project near the end of its development to determine the best passive component values ​to be used to yield the best RIAA conformance. I provided some subjective evaluations of the unit while it was being developed as well. I had nothing to do with the preamp’s topology or other design decisions.+**Discussion:​** AVA decided to pursue a stronger presence in the growing phono market by developing a stand-alone phono preamp. I was consulted on the project near the end of its development to determine the best passive component values to yield the best RIAA conformance. I provided some subjective evaluations of the unit while it was being developed as well. I had nothing to do with the preamp’s topology or other design decisions.
  
 ===== Vision DAC improved ===== ===== Vision DAC improved =====
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 **Contribution:​** Concept origination,​ development,​ and implementation. **Contribution:​** Concept origination,​ development,​ and implementation.
  
-**Discussion:​** Given the availability of a less costly remote control transmitter that I secured for the SLR and CFR chassis as well as AVA's new ability to burn microcontrollers in-house, it was natural to apply these toward a limited-feature remote control ​design ​for their RB (Real Basic) preamplifer chassis ​to replace the existing design developed 14 years earlier. As was the case 14 years before, I expected AVA to adopt the remote control as standard equipment on the RB chassis, but again they decided to offer it as an option, albeit not as costly as the solution it replaced.+**Discussion:​** Given the availability of a less costly remote control transmitter that I secured for the SLR and CFR chassis as well as AVA's new ability to burn microcontrollers in-house, it was natural to apply these to replace the now 14 year old and more expensive ​design ​still being used in their RB (Real Basic) preamplifer chassis. As was the case 14 years before, I expected AVA to adopt the remote control as standard equipment on the RB chassis, but again they decided to offer it as an option, albeit not as costly as the solution it replaced.
  
 ===== The present ===== ===== The present =====
  
-I continue to provide ​ongoing ​consulting services to Audio by Van Alstine, particularly in the areas of digital audio, small-signal analog audio, low-power amplifier design, and user interface design. For reasons that should be obvious, I'm not at liberty to discuss projects under development.+I continue to provide consulting services to Audio by Van Alstine, particularly in the areas of digital audio, small-signal analog audio, low-power amplifier design, and user interface design. For reasons that should be obvious, I'm not at liberty to discuss projects under development.
  
 ===== The future ===== ===== The future =====
audio/audio_by_van_alstine_work.1564787000.txt.gz · Last modified: 2019/08/02 23:03 by mithat