A few weeks ago I came across this forum and spend most of the evenings since then browsing the posts. This is really fun. How good that such a community exists. The feeling is coming back to play around with diy audio. I posted a few things already, so I feel obliged now to introduce myself to you.
I started building audio stuff allmost 30 years ago (I'm now 44); my fist project being the EKWA power amplifier from Elektor (Elektuur in the Netherlands) in the early seventies. Around 50W per channel and supposed to be high quality. I used it for a long time and ultimately gave it away. Later on I studied electronics and build a PA sound system for a band, I did the mixing for: speaker cabinets, amplifiers, active cross-overs, etc. I finished my study with designing (together with a friend) a high quality power amplifier with no overall feedback, based on the results of an evaluation of distortion sources. It uses an Hawksford error correction scheme around the output. That was really fun to do and the amplifier was amazingly good. At least that was what we thought and we got some support in that. That was in 1983 and we compared the amplifier with a Bryston 2B, a Hafler DH220 and a Stax DA-50M. The Stax and ours were regarded as the best, on Quad ESL63 speakers. Perhaps I will share more about this amplifier later in this forum. At this moment the report is just typed in Dutch and not so easy to share on the web. Part of the report was published in the Dutch magazine Audio & Techniek in the early years of that magazine (1984, '85). The magazine went bankrupt (I think) before the actual schematics were published. Later on they started again with the magazine, but did not continue the report.
Professionally I got involved in audio too, by working for Philips, developing PA amplifiers and as team member and later project leader for the first digital conference system in the world (DCN) with 16 audio channels on a single coax connecting thousands of conference units for large multilingual meetings. 'Our' part of Philips has recently been sold to Bosch and now I am working with Bosch as product manager, related to development, for the design of new Public Address and Voice Alarm systems. Also these systems make use of a multi-channel digital audio network, but now over POF (plastic optical fiber).
Being professionally involved with electronics and audio, the DIY part moved to the background and I did not do much with it. But now as a product manager I do not use a soldering iron anymore for my work, so maybe it is a good time to pick that up as a hobby again. This forum is a good stimulus, I think.
I hope to have nice discussions with you!
Steven
I started building audio stuff allmost 30 years ago (I'm now 44); my fist project being the EKWA power amplifier from Elektor (Elektuur in the Netherlands) in the early seventies. Around 50W per channel and supposed to be high quality. I used it for a long time and ultimately gave it away. Later on I studied electronics and build a PA sound system for a band, I did the mixing for: speaker cabinets, amplifiers, active cross-overs, etc. I finished my study with designing (together with a friend) a high quality power amplifier with no overall feedback, based on the results of an evaluation of distortion sources. It uses an Hawksford error correction scheme around the output. That was really fun to do and the amplifier was amazingly good. At least that was what we thought and we got some support in that. That was in 1983 and we compared the amplifier with a Bryston 2B, a Hafler DH220 and a Stax DA-50M. The Stax and ours were regarded as the best, on Quad ESL63 speakers. Perhaps I will share more about this amplifier later in this forum. At this moment the report is just typed in Dutch and not so easy to share on the web. Part of the report was published in the Dutch magazine Audio & Techniek in the early years of that magazine (1984, '85). The magazine went bankrupt (I think) before the actual schematics were published. Later on they started again with the magazine, but did not continue the report.
Professionally I got involved in audio too, by working for Philips, developing PA amplifiers and as team member and later project leader for the first digital conference system in the world (DCN) with 16 audio channels on a single coax connecting thousands of conference units for large multilingual meetings. 'Our' part of Philips has recently been sold to Bosch and now I am working with Bosch as product manager, related to development, for the design of new Public Address and Voice Alarm systems. Also these systems make use of a multi-channel digital audio network, but now over POF (plastic optical fiber).
Being professionally involved with electronics and audio, the DIY part moved to the background and I did not do much with it. But now as a product manager I do not use a soldering iron anymore for my work, so maybe it is a good time to pick that up as a hobby again. This forum is a good stimulus, I think.
I hope to have nice discussions with you!
Steven
Audio & Techniek
Hi Kees,
Thank you for your nice words
, and yes, I'm the person you think I am.
The series of amplifier articles in Audio & Techniek actually went on till part 12 in the combined July/August number of 1985. At that moment about 75% of our graduation report had been covered in the magazine, but not yet the actual amplifier implementation and especially not the power stage. In that period of time the issue date of each magazine issue slipped more and more in time, already an indication of things not going too well, and indeed it stopped after that July/August number.
In April 1986 John van der Sluis started over again with the magazine, but now called Audio & Muziek instead of Audio & Techniek. This became volume 1, number 1. I was not amused
when John appearantly had decided not to continue with our amplifier series, as it was not finished yet. But even worse : in that first issue John van der Sluis and Peter van Willenswaard published their own power amplifier design (the M30, no component values given, only available as a kit), with the same kind of output stage, with Hawksford error correction and no overall feedback, as our amplifier had. Hawksford's correction scheme has been described in the JAES, and as far as I know it has not been patented, so they had the right to use it. Also there exist more amplifiers without overall feedback, so that is not new either, but still the combination of these was new (I think) and they used it without even mentioning that a similar approach was in the amplifier they stopped the publication of.
Well, let's forget this, years have passed. There is more to do.
Steven
Hi Kees,
Thank you for your nice words
, and yes, I'm the person you think I am.The series of amplifier articles in Audio & Techniek actually went on till part 12 in the combined July/August number of 1985. At that moment about 75% of our graduation report had been covered in the magazine, but not yet the actual amplifier implementation and especially not the power stage. In that period of time the issue date of each magazine issue slipped more and more in time, already an indication of things not going too well, and indeed it stopped after that July/August number.
In April 1986 John van der Sluis started over again with the magazine, but now called Audio & Muziek instead of Audio & Techniek. This became volume 1, number 1. I was not amused
when John appearantly had decided not to continue with our amplifier series, as it was not finished yet. But even worse : in that first issue John van der Sluis and Peter van Willenswaard published their own power amplifier design (the M30, no component values given, only available as a kit), with the same kind of output stage, with Hawksford error correction and no overall feedback, as our amplifier had. Hawksford's correction scheme has been described in the JAES, and as far as I know it has not been patented, so they had the right to use it. Also there exist more amplifiers without overall feedback, so that is not new either, but still the combination of these was new (I think) and they used it without even mentioning that a similar approach was in the amplifier they stopped the publication of.Well, let's forget this, years have passed. There is more to do.
Steven
Thanks guys, for your frendly welcome. I feel already at home! 
It will take some time to prepare the old graduation report into something that I can publish now. I'm thinking of converting everything to HTML, or at least make it digital (by other means than just scanning) and put it on a website. And probably I will take the opportunity then to add some simulations and things that were not possible in 1983. But reading the old report I sometimes think: hey, did I understand all that math back then? I have forgotten a lot.
Steven
I feel already at home! It will take some time to prepare the old graduation report into something that I can publish now. I'm thinking of converting everything to HTML, or at least make it digital (by other means than just scanning) and put it on a website. And probably I will take the opportunity then to add some simulations and things that were not possible in 1983. But reading the old report I sometimes think: hey, did I understand all that math back then? I have forgotten a lot.
Steven
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