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Antique Hi-Fi Archive Technical

Hi Fi Amplifier Schematics c. 1954

The Craftsmen C-500 power amplifier

Today we have some hi-fi amplifiers from the mid 1950s to look at.  Many of them use unusual output transformers with split primaries, so I am really not sure if it’s even possible to build these designs today.  The Craftsmen C-500 pictured above uses a standard PP-VC output transformer; it also uses readily available, robust 6SN7 and Kt66 (aka 6L6) tubes.  Check out the circuit in the output cathode bias; even though this is a cathode-biased amp, there is a provision for adjusting the overall bias, as well as a balance adjustment ( to allow the use of unmatched power tubes).  Here’s a few more…

Bogen DB15 schematic

General Electric A1-300 power amp.  This is a good simple design that will provide 12 watts.

The Leak TL-10 amplifier

The Quad II pre-amp and power amp.

A DIY hi fi preamp design from 1954.  Note the very sturdy parallel-cathode-follower output (the 12AU7 section).  This could probably drive a 10K load pretty easily.


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Antique Hi-Fi Archive History

1955: Japan Goes Hi-Fi

Download a three-page 1955 article entitled “Japan Goes Hi-Fi” as originally published in AUDIO magazine.

DOWNLOAD: Japan_Goes_hifi_1955

The article concerns an early Hi-Fi show in Tokyo.  Postwar Japan had sufficiently moved beyond the subsistence level to indulge in luxury-leisure pursuits; soon Japan would come to dominate the world in the electronics field.

The ‘hi-fi coffee shop’ pictured above may seem like a quirky anomaly, but you would be amazed at the sound systems on display in even modest Japanese bars and restaurants.  The last time I was in Japan, we stayed at a bed and breakfast in the mountains of Hokkaido; upon arrival at the inn, my jaw dropped when I saw that the sound system in the lounge consisted of a JBL Paragon speaker and huge McIntosh tube amplifiers.  It’s hard to say exactly why this trend developed, but if you spend any time in Japan, I think it’s clear that ‘excellence’ in general is an important concept in Japanese culture.

Above is a 1955 advert for The Panasonic.  Not ‘a Pansonic,’ but THE Panasonic.  The Panasonic was a single product introduced for the US market by the Matsushita corporation: an 8″ full-range hi-fi driver.  Panasonic would soon grow into an entire global electronics brand, second only to SONY as an ambassador of the Japanese electronics industry.

Here is a 1955 review of “The Panasonic:”

Previous Japanese audio culture coverage here and here.

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Concert Sound RCA

RCA Mixing setup at the Hollywood Bowl arena c.1955

You gotta wonder where this thing ended up.   Consider the history that passed through these faders.

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Altec Pro Audio Archive

Pro Audio hardware of the early 1950s

The General Electric (GE) BA-5-A Limiter

Continuing our review of the first two years of AUDIO magazine, today we will look at some of the more interesting bits of pro audio kit in evidence during 1954/1955.  AUDIO magazine had just made the transition to its new moniker in the wake of the introduction of the AES Journal (Audio Engineering Society), and for the moment, AUDIO sill covered a bit of the pro audio equipment that would soon largely leave its pages.

The GE BA-5 pictured above is, AFAIK, the largest and most complicated analog audio compressor ever made.  Although it has much less tubes, it’s kinda even more sophisticated than the Fairchild 660/670.    Here’s the schematic if you are interested.  From what i recall,  the BA-5 works by creating an ultra high frequency sidechain to obtain the control voltage value for the compression; I can’t recall the details at the moment but the basic concept was to allow the unit to have huge amounts of compression with very fast timings, but without any pumping or dipping artifacts.  Which was also the intent of the 660/670 design.  If anyone out there has a better explanation of this monster, please chime in.

The General Electric BA-6-B remote amplifer/mixer

The General Electric BA-9-A compressor, a much more basic pro audio compressor.  Circuit is essentially the same as the Gates Sta-Level.  The BA-9 is also known as the the uni-level; schematics are readily available online.

The General Electric BA-1-F plug-in preamp and BA-12-C plug-in power amp

The Hycor 4201 equalizer.  Similar to a Pultec program EQ but without the makeup gain amp; the Hycor is a fully passive device.

Langevin 5116 modular preamp

The full Langevin modular line of 1954: 5116 preamp, 5117 power amp, and 5206, 5208 power supplies

Another remote amp from 1954 – the Magnasync G-924.  Looks very cool.  Magnasync would soon be merged with the Moviola corporation and become a brand name for sound-for-film equipment.  See this previous post for an experiment with the Magnsync URS device.

An early ad (1955) for the Altec 604 duplex loudspeaker.  The 604 would remain a studio-standard recording/mixing monitor speaker well into the 1970s.

Okay this is getting pretty tech-y but here’s an advert announcing some new-ish tubes you might want to consider: the Tung-sol 12AX7 and the 5881 (AKA ruggedized 6L6).   Transistors were on the market at this point (1955) but were a ways off from reaching the performance and reliability that these great tubes offered.

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Microphones

Studio Microphones of 1955

The Altec 639, 633, 670A, 660, 671A, 632C, M-20, and M-11 microphones

From the pages of AUDIO magazine in 1954/55: new and new-ish studio microphones at the dawn of the transistor age.  Check em out…

The Shure 530.  This was Shure’s mid-range ‘pencil’ mic in the 1950s.  At the top end was the 525; lower in the line was the 535.  See this link for some audio tests including the 535.

Reslo and Bang & Olufsen ribbon microphones were marketed and distributed in the USA under the ‘Fentone’ banner in the 1950s.  Fentone continued as a brand-name for microphone marketing into the 1960s, but later Fentone product was not of this quality.

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Above is the two-page advertising spread that introduced the Electrovoice 666 to the world.  The 666 is the grandfather of the much-beloved Electrovoice Re20, which has been a favorite of recording and live-sound engineers for decades.  Like the Sennhesier 421, the RE-20 is somewhat proof that dynamic microphone technology hasn’t really advanced much in the past three decades.

 

 

 

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Above, a 1955 advert for the 666 along with a review of the 666 from AUDIO magazine.

Above is a 1955 ad for the Electrovoice 664.  The 664 was the ‘public address’ aka ‘cheaper’ version of the 666; the 664 was immensely popular and thousands remain today.  If you come across one of these, there is a good chance it will still work fine.  In terms of visual recognition,  I would argue the 664 has an iconic appeal exceeded only by the Shure 55 series and the RCA 77 and 44 series.  The 664 is not a terrible sounding microphone, although i don’t recommend actually using it in a modern high-decibel PA system.

Wrapping up, here’s an ad for all the microphones that Electrovoice considered its ‘professional quality’ in 1955: the 666, lesser-variant 665, 655, its lesser variant 654, 646 lavalier, 650 and 535.    Hear my pair of ancient 655s in-action here…

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Magnecord Pro Audio Archive

Magnecord Complete Line Catalog Circa 1953

From the personal archive of John Boyers, founding partner of Magnecord INC, we present the complete circa 1953 Magnecord INC catalog. Click the link below to download the eight-page PDF:

DOWNLOAD: Magnecord_Catalog_Circa1953

Products covered, with text and photos, include: Magnecord PT6-A Recorder Mechanism, PT6-R line-level input amplifier and PT6-J Mic-level input/output amplifier; PT63-A three-head recorder and companion PT63-J amplifier; the full line of PT6-series accessories, including the PT6-HT ‘turnover’ panel, PT6-IM3 and PT6-IM4 microphone-level input mixers, PT6-M ten-inch reel adapter mechanism, PT6-EL continuous loop panel (really confused as to how on earth this thing works).  Also includes the Magnecord PT7-A, PT7-M, PT7-C series of recorders/amplifiers, which offered slightly improved audio specs relative to the PT-6 series.

Click the ‘Magnecord’ link in the right-hand ‘Categories’ column of the homepage to see much more Magnecord coverage on PS dot com.

 

Categories
Microphones Pro Audio Archive

Studio Microphones of 1954

AKG D36 advert from 1954

Continuing our survey of AUDIO magazine’s early years: over the next couple of weeks we will look at some of the more relevant content from the first two years that this venerable publication ran under the title ‘Audio,’ the prior title having been ‘Audio Engineering.’ (full backstory here and here).  We’ll start today with the crop of studio microphones on the market in 1954.  One thing becomes pretty clear: the Austrians were really ahead of their time.AKG C-12 advert 1954

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Telefunken U-47 and 201-M adverts 1954

Capps CM 2001, 2030, 2250, and DM 2050 microphones c. 1954.

Anyone have any experience with these mics?  Look interesting.  Let us know…

The Reeves S-T Condenser Microphone; another early American Condenser mic. Very rare.

The Shure 333 ribbon mic.  This was their cardiod ribbon.  I’ve never used one of these, but i would love to get my hands on one.  Stephen Sank recently re-ribboned my circa 1954 Shure 300 (the 300 was Shure’s high-end figure-8 ribbon of the same period) and wow did he do a great job.  It sounds incredible now.    I had thought it was a P.O.S. until he re-did it.  If you own a vintage Shure ribbon mic and you are underwhelmed by it. give Sank a call and see what he can do for you.

…and here is some period analysis of the then-new Shure 333.

Follow the link below to READ-ON….  more studio mics of ’54 follow….

Continue reading “Studio Microphones of 1954”

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Guitar Equipment Pro Audio Archive

Vintage Marshall Archive Material Part 2: 1974

Download the complete sixteen-page 1974 Marshall Amplification catalog:

DOWNLOAD: Marshall_1974_Cat

Products covered, with text, specs, and photos, include: Marshall 1959, 1987, 1989, 1992, 2048, 2068, and 1986 tube heads; 1960, 1982, 1990, 2049, 2045, 2069, and 1935 speaker cabinets; Marshall 2064, 2065, and 2052 ‘powercel’ cabinets; Marshall 2040, 2078, and 2077 combo amps; Marshall Disco Unit (yup…) 1993 ‘turntable control unit’; Marshall 2071, 2050, and 2070 mixers; plus a slew of additional P.A. equipment.

I spent yesterday doing the final wiring and installation of my newly-restored Wheatstone SP-6 console into the control room at Gold Coast Recorders.  Took the opportunity to listen to a pile of records that I had not gotten around to.  “The Welsh Connection” by Man really caught my ear, and got me into a real UK Rock circa ’75 kinda mood.  Hence today’s post.

The most interesting bits to the ’74 Marshall Catalog are the 2050 and 2070 mixers, neither of which seem to have survived the 1970s. I cannot find a single reference to them on the web, other than in a book about Marshall.

The much smaller # 2071 mini-mixer remains in evidence; here’s a link to one for sale for a few bucks in Ireland.   A unit cosmetically similar to the 2050 is also available in England right now; price is quite good IMO…

And of course, let’s not forget the Marshall Disco Unit.

Jim Marshall offers some sage advice here as well:

This really is true.  Do not try to Disco alone.  Sad at best.

Finally, we meet the face of Marshall:

Oh that’s the wrong pic.

Here he is:

Follow this link for previous vintage Marshall coverage on PS dot com.

 

 

Categories
Uncategorized

British Broadcast Tape Recorder Circa 1935: The Marconi-Stille

The development of magnetic tape recording is generally credited to German scientists.  It is their Magnetophone that provided the inspiration for the Ampex recorder, which was the first truly high-fidelity tape machine.  From Wikipedia:

Early magnetic tape recorders were created by replacing the steel wire of a wire recorder with a thin steel tape. The first of these modified wire recorders was the Blattnerphone, created in 1929 or 1930 by the Ludwig Blattner Picture Corporation. The first practical tape recorder from AEG was the Magnetophon K1, demonstrated in Germany in 1935.

Although lesser-known,  the British Broadcast industry had a similar machine in use in that same decade.  The following account is given in the May 1954 issue of “Audio.”

Categories
Magnecord

Magnecord, INC, company history from John Boyers, Founding Partner

D. Boyers, son of Magnecord, INC founding engineer John Boyers, has once again presented Preservation Sound with an incredible collection of rare documents from this seminal pro audio manufacturer.  (click here to read the previous installment)

Over the next few weeks I will work on getting all the material online.  To start things off, here’s a written history of the Magnecord organization as related by J. Boyers in 1980.  Boyers discussed the company’s early products leading up to the introduction of the PT-6 tape machine and the PT-63 binaural (aka Stereo) tape machine.  Fascinating to learn how much trial and error was involved in these pioneering efforts.  Enjoy –

Click the link below to READ ON….

Continue reading “Magnecord, INC, company history from John Boyers, Founding Partner”