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SET Amp History in Japan

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I've seen at least a couple of SE schematics from Japan dating back to the early 1950s...1952 is the earliest I recall.
I've also seen a Japanese schematic for a plate-coupled PPP 2A3 OTL, designed to drive a 500 ohm Stephens system from 1956 (at least I *think* it was from '56).

The point is that tube DIY experimentation was definitely going on in Japan in the 1950s.

Jim
 
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Way back in 1970 many of my engineering mentors were in the US Army Signal Corps at Fort Monmouth NJ or worked at Bell Labs. I was 14 at the time and was lucky enough to live close to Fort Monmouth and Bell Labs (Holmdel NJ). Nearly all of them were ham radio operators or audiophiles, some both.

One of the Signal Corps engineers returned (in 1970) from a 2 or 3 year tour of Japan. He was thrilled with what Japanese audiophiles were doing with tubes and got me quite involved. By Christmas 1971 I replaced my Dynaco ST-80 power amp with a close copy of his Bi-amped system using PP amps for the low end and SE amps for the mid-high end. It was actually two stereo power amps. There was no active crossover, the amps were bandpass limited with a low pass filter in the bass amp and a high pass filter in the treble amp. I think the "crossover point" was 1 KC or 1.5 KC. The bass amp had no input level control, the treble amp did and we had no problem getting what we thought was a good balance.
I don't recall what the design of the bass amp was based on. My friend wanted to base it on the WE 92 but he couldn't find interstage transformers he liked. I do remember the treble amp was based on the WE 91 and included the same negative feedback the 91 used.
My friend was using Big JBL woofers and horns, I was using speakers from big 30's console radios that were pretty common curb finds at the time.
I wasn't, by any means the "brains" behind the amps we built, I just closely copied my friend's. He based his on an existing P-P design and on the WE 91. His system was based on what he had learned from ham radio/audiophiles while on tour in Japan. He was really impressed with the sound of the systems he'd heard in Japan and with the extremely low cost of building a similar system here. The only real $ he spent was on the P-P output xformers in his bass amps. They were Pearless and the only parts he bought new (other then a handful of resistors and caps). I bought nothing, and I mean nothing new. All of parts I used were free at the time, including the WE 166B P-P output xformers that I was given when I spent the summer at Bell Labs and the 6 300A's my friend gave me.
I do recall that some of the surplus outfits were selling good 300B pulls for $5.00 each at the time, but in 1970 that wasn't as good a deal as it sounds like today.
I wish I could remember what we used for output transformers on the treble amps. I do remember that they were P-P xformers, but sounded fine.

Sorry I've gotten so far off track here, I haven't thought about those amps in a long time. The actual point I had intended to make was that the Japanese were well involved in tubes for audio, including triodes and single ended power amps at least as far back as '66-67, based on what my friend learned when he was stationed in Japan during that period.
 
Well, here we are, more than 6 years later. I found that post last week searching information on Ikeda's system. Pictures of him are of high historic interest for me.

I also have the chance to own Jean Hiraga's book Initiation aux amplis à tubes. Plus, French is my first language, so it's a true pleasure to read and look at this book.

On page 56 of it, we have a schematic from 1936 made by Kinsuido. This was Lux amplifier, reference 661-A. It uses a triode 50 (UX-250) triode tube in the amplifier stage. Later, Lux became Luxman. A big part in SET history in Japan.

Sébastien
 
This subject interests me as well. I got this from another forum, posted by Angelo in 2008. While not directly about SET amps, I think it is worth sharing:

"Mr. Kei Ikeda has been an enthusiast audiophile since 1919 and his auditorium is a museum devoted to audio.
Look at the two giants horns WE 15 A used in the high bass and low medium range in the main 4 ways system!
The low bass is reproduced by the big woofer you see behind the left shoulder of Mr. Ikeda , another room close to the auditorium is used as a rear load for the woofer . This woofer, IK38 inspired from a RCA duocone loudspeaker, was designed by Kei Ikeda for JVC.
You'll also notice the famous WE 59 A (or WE 540) loudspeaker known as "chinese hat" intended to works with the first Western Electric amplifier, the WE 25A.
Compare the huge mouth of the WE 15A to the smaller WE 6368, half visible behind books and a desk lamp up to the chair in the left part of the view.

ikeda.jpg


Comment: Pictures "ikeda.jpg" and "takashir.jpg" were published in a paper with the title "On ne vit qu'une fois, de musique" in the No1. issue of "Stereoplay" (French edition) in October 1979 . That paper with some others in the same review and the famous papers of Jean Hiraga in "La Nouvelle Revue du Son" from the end of 70's and the beginning of the 80's , led to a deep change in the mind of the French audiophiles.


takashir.jpg


Shigemi Takashiri plays piano and 10 others instruments. His favorite leisure is to record and reproduce music in his auditorium.
Two Steinway pianos, some Japanese drums and percussion instruments are visible in the auditorium but the loudspeakers are difficult to locate through the collection of lamps and crockeries.
The Goto tweeters are at the same level as the ears of Mr Takashiri. Those tweeters are touching the high medium and low medium Goto horns, the throats of which go across the rear wall, the Goto compression loudspeakers situated in a small room behind.
But where are the bass loudspeakers? Look at the ceiling and you will see the two giant mouths of the concrete bass horns the cut-off of which is 20Hz.
Not visible are the turntable with 6 tonearms, the 6 tape recorders and the rest of the electronics.


There are two 5-way loudspeakers systems in the auditorium of Dr. Idemiya Yoshikatsu .
The two sytems share the concrete bass horns each of which works with two woofers, Goto SG 38 W.
The first system uses:
In the low midrange, MB-90II horn with an YL D-7500 (Yoshimura Laboratory) compression driver.
In the high midrange S-300A (Goto) horn with a SG-555PS (Goto) compression driver.
In the low part of the high frequency range the S-500 (Goto) horn works with the SG-370 Goto compression driver and in the upper part there is a tweeter SG-17T (Goto).

The second loudspeaker system uses:
-In the low mids the JBL PRO 2202.
-In the high mids the JBL PRO 2440 with a 2355 horn.
-In the highs the JBL 2420 with an home-made horn and.
-In the upper range the tweeter JBL 2405.

yoshikat.jpg



5-way loudspeaker of M. Tatsuo Kobayashi.
f < 150 Hz : 2 x 416 8A loaded by a concrete bass horn,
150 Hz < f < 650 Hz: compression driver Onken ES 255 Esprit with a concrete bass horn,
650 Hz < f < 2800 Hz: compression driver Onken 500MT with a wooden multicellular horn,
2800 Hz < f < 8000 Hz: compression driver Onken OM 455 with a multicellular horn SC 500 Wood, f > 8000Hz tweeter Onken 5000T.

kobayash.jpg


Comment: That system has inspired the French society: AII Ingenierie SA in building their reference sytem in their auditorium in Chatou (near Paris). AII Ingenierie SA designed the Eurythmie 33 and Eurythmie 11 (the last one is also sold under the label Jadis)."
who can upload this images ?
Photobucket host images only for short time.
 
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