I am intrigued Scott, could it be to do with the very small cells they are on about doing, almost one per a few homes. My guess would be high power, small package, high slew rate Rf amps or op-amps that are suitable for audio, so you could get a power amp almost on the back of a postage stamp.
For the headphone guys, check this device out:
TPA6141A2YFFR
Not saying its the ultimate in fidelity, but have a look at the size, amp supply a caps etc on 12x15mm board area.
Of course I still miss doing design by tape ups, life was much simpler then but Moores lay etc things move on
OK everybody, let's go through Esperado's power amp design:
First, the basic topology is relevant to a 1966-67 level of topology used by pro audio.
It is composed of an input transistor (BC204) that drives a second complementary transistor(2N1893) which drives the single transistor bias set (2N3403), that is loaded by a BOOTSTRAPPED split load resistor 220, 1.2K, 220uf. This allows the positive feedback of the bootstrap to MIMIC a real constant current load at audio frequencies, therefore lowering the distortion generation of the drive transistor and EVEN giving superior drive voltage (on one side) to the output stage.
Wow! And we did all this in 1968 in making a small monitor amp at the Ampex audio department, to replace an existing pp 6V6 amp that sounded pretty good.
Finally, the output is QUASI-COMPLEMENTARY. Do you know why? Because apparently, if I get Esperado's 'drift', the BDY24C was an exceptional, high F(t) power transistor.
This forced the output to be quasi comp, rather than dual Darlington full comp, because most complementary power parts with good safe area, at the time, were fairly slow, 4MHz f(t) or less, or very expensive. There was an exceptional set of devices made by Siemens or Thompsen (sp) at the time that had BOTH high f(t) and good safe area. These devices were good, and were used ultimately by NAIM AUDIO for their power amps, but because they had no complement, they had do be used in quasi-comp.
Am I right so far, Esperado. Please correct me where I am wrong. '-)
First, the basic topology is relevant to a 1966-67 level of topology used by pro audio.
It is composed of an input transistor (BC204) that drives a second complementary transistor(2N1893) which drives the single transistor bias set (2N3403), that is loaded by a BOOTSTRAPPED split load resistor 220, 1.2K, 220uf. This allows the positive feedback of the bootstrap to MIMIC a real constant current load at audio frequencies, therefore lowering the distortion generation of the drive transistor and EVEN giving superior drive voltage (on one side) to the output stage.
Wow! And we did all this in 1968 in making a small monitor amp at the Ampex audio department, to replace an existing pp 6V6 amp that sounded pretty good.
Finally, the output is QUASI-COMPLEMENTARY. Do you know why? Because apparently, if I get Esperado's 'drift', the BDY24C was an exceptional, high F(t) power transistor.
This forced the output to be quasi comp, rather than dual Darlington full comp, because most complementary power parts with good safe area, at the time, were fairly slow, 4MHz f(t) or less, or very expensive. There was an exceptional set of devices made by Siemens or Thompsen (sp) at the time that had BOTH high f(t) and good safe area. These devices were good, and were used ultimately by NAIM AUDIO for their power amps, but because they had no complement, they had do be used in quasi-comp.
Am I right so far, Esperado. Please correct me where I am wrong. '-)
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You just perfectly resume month of our work on each and every points. Including the power NPN/PNP devices problems at this time. I'm impressed.
Our goal was to provide the best sounding and reliable amp we could do with limited budget and as little parts we could for mass production.
Believe-me or not, and it is not because i was part of the design, but this amp has nothing to be shamed in comparison to many modern ones, sound side. (And, now, you know why
You have too to remember we where in France, and had no access (and no time to read)) to the US literature or other's topology. Just what all of us knew from schools, data-sheets and own experience.
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Your amp WOULD be faster than average, Esperado. Let me give you that credit.
MY amp at the time was slower, but it didn't matter, because it was a MOTOR DRIVE AMP.
However, my amp at home, only 15W, driving my K-horn, was also slower because I used 4MHz f(t) COMPLEMENTARY output devices.
MY amp at the time was slower, but it didn't matter, because it was a MOTOR DRIVE AMP.
However, my amp at home, only 15W, driving my K-horn, was also slower because I used 4MHz f(t) COMPLEMENTARY output devices.
The big thing now is envelope tracking on the RF amps to enhance efficiency so there is a need for 1A+ op-amps to drive the PS dynamically.
John, you know what is the daily work in an R&D department of a consumer audio manufacture. Dealing with hundred of stupid problems, fighting with our providers, suffering pressure from the marketing and financial department ("too expensive !"), working on several projects in the same time. (With a stupid boss
I had learned more about other's works and designs in few months reading this forum than in all my professional life. The manufacture was in the country, we had never concurrence's products to reverse engineer, and no time to read French (because English was a pain) electronic literature.
But it was a lot of fun, discovering, experiencing, listening to results, measuring our speakers in the field next to the cows. We where few in the R&D office (4 or 5) and worked on everything in the same time: Tuners, turntables, power amps, loudspeakers, in a very friendly atmosphere, full of laughter, learning from each others. We were so young, we knew so little, discovered so much. We made several patents.
Real fun !
I had learned more about other's works and designs in few months reading this forum than in all my professional life. The manufacture was in the country, we had never concurrence's products to reverse engineer, and no time to read French (because English was a pain) electronic literature.
But it was a lot of fun, discovering, experiencing, listening to results, measuring our speakers in the field next to the cows. We where few in the R&D office (4 or 5) and worked on everything in the same time: Tuners, turntables, power amps, loudspeakers, in a very friendly atmosphere, full of laughter, learning from each others. We were so young, we knew so little, discovered so much. We made several patents.
Real fun !
Lab Gruppen have been doing that for audio power amplifiers since the early 90's. These days we have 1 RU 10KW rated power amps.
Only problem is how to connect to the AC mains!
The 5 or 6 orders of magnitude in frequency difference is an issue. As far as we're concerned audio is DC.
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That was a fast response!
Didn't you follow the previous discussion there is no such thing as DC as far as applying Fourier theory is concerned!
RF?
Did I read "RF" on this site?
My background includes RF -- mostly High Energy Pulsed Power and Microwaves... secondary Standards Lab doing measurements at >500Mhz. Still have some MicroWave test equipment around me here (including HP network analyzers to 6Ghz at my home).
Any fall-out for audio would be interesting.
Thx-RNMarsh
Did I read "RF" on this site?
My background includes RF -- mostly High Energy Pulsed Power and Microwaves... secondary Standards Lab doing measurements at >500Mhz. Still have some MicroWave test equipment around me here (including HP network analyzers to 6Ghz at my home).
Any fall-out for audio would be interesting.
Thx-RNMarsh
My only interest is to *understand*. Specialty in audio, where the things can be so subtle or fugitive or misleading.
When i find something nice, i usually spend time to explore *why*, never i am satisfied by 'it works'.
By example, when this story of "sound of the cables" was new and hype on the market (Thanks Monster cables ?) i made a week of experiments to demonstrate that the same two set of cables can present opposite signatures, depending of the charge and source, and i can explain how this "sound signature" was due only to their lumped elements. Made the same experiments to ensure type of metal in wires has no signature (like silver is better for trebles) as long as resistance, inductance and capacity are the same. (Happy for us)
You have an incomparable experience on open loop designs, as an example, (and i will not take the risk to compete with you on this domain). Therefore, I believe that you have a lot to say about signature of components (if any) and various topologies. When you talk about this kind of things, i read your inputs carefully. May-be you can have benefit, on your side, to do the same from people who, because they had worked differently in other contexts (Rolls VS Ford), had explored other tracks. Like how to get good results with average components, integrated circuits etc...
By example, i recognize *only advantages* to SMD parts, despite i hate them, because my old eyes, my trembling hands and my lack of experience to weld or remove them.
I believe we all try our best with passion, despite different approaches. And even when we argue against each others we can learn more... at worst we can organize better our toughs, trying to explain our points of view. Never, never, it was, on my side, a matter to compare the size of our D...s.
Unlikely anyone here would know that Art Clokey creator of Gumby was an acolyte of Adi Da and fan of LSD. I was always a fan of the blockheads, unfortunately their most politically incorrect episodes will remain out of circulation.
I have worked on a product with a 25 year warranty, mixed through hole and SMD, as others have said warranty is dictated by market segment.
Wrinkle
Scott,
I always assumed that he was the inspiration for the English Wallace and Gromit series? Once watch a pair of guys hand wire a complete recording console while using the latter substance you sighted! They did know what they were doing but I don't think that they lived a long and prosperous life. I have no idea how they managed to function that way!
I always assumed that he was the inspiration for the English Wallace and Gromit series? Once watch a pair of guys hand wire a complete recording console while using the latter substance you sighted! They did know what they were doing but I don't think that they lived a long and prosperous life. I have no idea how they managed to function that way!
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