ETI System A pre amp by Stan Curtis. Full article.

[tiefbassuebertr]

Wjlamp
---Stan Curtis was, is, I don't know if he is living,a great designer,but a bad trader.---

He worked for a lot of companies and designed many products which were successful :
Stan Curtis, the hifi guru, introduction

I know his circuits from follow commercial available vintage amps:
1) Monrio MC25 (power amp) and PRIMUS (preamp)
Primus preamplifier :: Sonus HiFi
http://www.audio-kontakt.com/forum/nalozeno/AUIOOA-1237804927KIF_0915.JPG
2) Moth
Stan Curtis, Engineer, Moth amplifier downloads
3) Mission 777
Stan Curtis, Engineer, The Mission 777 power amplifier
4) Mission Cyrus (and Cyrus II)
Freie Ton- und Bildwerkstatt: Mission Cyrus II Variante 3 - ca. 1989
5) Cambridge Audio P25 (there are same integrated amps from AMC, Proton and Audio Pro (A7) - but this versions use a motor volume control for remote controlled volume adjust)
Cambridge Audio P25 integrált er?sít? - Oldal 2 - Er?sít?k - AVX Fórumok
http://www.audiopro.se/sites/audiopro.se/files/expired_product_folders/A.7_manual.pdf
HiFiForum.nu - Min musikanläggning/ lite nytt

There are probably many more products, where this approaches are in use.
Also this site is very interesting:
Stan Curtis, Engineer, The Lecson AP4 and ETI Class A amplifiers

 

[baez]

Well I guess I ought to reply. Yes I'm still alive but less active in the audio world.
Some of my designs have been listed earlier plus almost everything Rotel sold in the 1980s; Cambridge Audio from the 1970s to the 1990s and so on. I gave up counting when I reached 450 designs.
It is probably not too far from the truth to say I was a poor trader. Certainly in the late 1980s my accountant told me I had made a lot of money for a lot of people but less for myself. Anyway in 1994 I formed Wharfedale & Quad into IAG then added Mission & so on and built the turnover into hundreds of millions by the time I parted company with my Chinese partners.
That exercise made me some significant money & I semi-retired just doing designs for friends in the industry but eventually you say; how many more DACs or power amps do I want to design? Particularly as there haven't been any really original new concepts for a long time.

So today I spend most of my time in a second career designing very advanced sensors & instrumentation. I keep in touch with audio by writing for "HiFi Critic" and "Linera Audio" magazines. I like to think I can challenge conventional thinking now I don't have a commercial axe to grind

Finally I have come up with something pretty radical in audio which solves a problem everyone ignores. The change is very audible. However I'll say no more for now because Linear Audio are independently testing it to determine if I've lost my marbles in my old age;-)

Best wishes
Stan

 

[SUZTEK]

Nice to see that Stan Curtis is still contributing to the Audio world. Read with great interest the posts on the ETI 1985 Stan Curtis preamp. Have been building amps since i was an apprentice (1967) and this preamp, i rate, as one of DIY very best. I am still using it and at present,in fact, it is being used in conjunction with my newly completed Hiraga amp (check the gallery). I have removed the volume and the noisy wirewound balance control from their respective position and repositioned them at the output before C15. Replaced the wirewound with a carbon type.This eliminated the wiring and earthing at this sensitive point and the new potentiometers position resulted in a very smooth and quiet preamp.Highly recommended for those who would like a very good preamp.The moving coil preamp is also extremely quiet.

 

[forr]

I have come up with something pretty radical in audio which solves a problem everyone ignores. The change is very audible. However I'll say no more for now because Linear Audio are independently testing it to determine if I've lost my marbles in my old age;-)

Effects you described in Linear Audio volume #6 have been very rarely reported and even less investigated.
I remember Hiraga mentioning wiring without PCB as better sounding.
More significative was a french author called Brault reporting his experience with a very old amp using Ge transistors and sounding marvelously.
As the wiring was "awful", he dismantled it to keep the same components because of the lack of similar parts available and built a new version with a neat setup.
And then, it worked ok but gone was the magic sound !
I look forward comments about what you have written in volume #7.

Regards.