Monthly Archives: May 2011

Building an (almost) RCA OP6 Mic Preamp

Posted on 05/31/2011 by chris

(image source) The RCA OP-6 ‘Portable Amplifier’ is one of a handful of truly visually-iconic vintage mic preamps.   The OP-6 was designed as a “remote,” as-in, ‘on-location’ single-channel mic preamp for radio station broadcasts.  It uses three 1620 (6J7) tubes  … Continue reading →

Posted in RCA, Technical | Tagged , , , | 10 Comments

A Few Interesting DIY Audio Projects c. 1955

Posted on 05/28/2011 by chris

Circuit for a simple bass/treble parametric equalizer that uses no inductors.  Could be  a useful piece.  Not sure if 250k/500k dual pots are still available?  Since I have still not finished building the last tube EQ project that I described, … Continue reading →

Posted in Technical | Tagged , , , | 5 Comments

A DIY tube mixing console; plans, schematics, methods

Posted on 05/27/2011 by chris

Some more interesting bits from AUDIO magazine c 1955:  plans and schematics for a radio station mixing console.   Very little in terms of equalization devices, and no compressors discussed, but a wealth of ideas for low-level and line-line level amplifiers … Continue reading →

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Altec 436 Compressor: Taming the output level: part 2

Posted on 05/26/2011 by chris

In a previous post, we looked at the Altec 436 vari-mu tube compressor.  I built one of these a few years ago, and it never really got used all that much because the output level is so hot.  The 436 … Continue reading →

Posted in Altec, Custom Fabrication, Technical | Tagged , , , | 14 Comments

Hi-Fi in Mexico 1955

Posted on 05/25/2011 by chris

A two page article from AUDIO magazine circa 1955.  Consider this article in comparison to “Japan Goes Hi Fi.“  How differently these two countries have developed since these pieces were written.   Both certainly became manufacturing powerhouses, but Mexico has … Continue reading →

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Hi Fi Amplifier Schematics c. 1954

Posted on 05/24/2011 by chris

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 … Continue reading →

Posted in Antique Hi-Fi Archive, Technical | Tagged , | 8 Comments

1955: Japan Goes Hi-Fi

Posted on 05/23/2011 by chris

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; … Continue reading →

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RCA Mixing setup at the Hollywood Bowl arena c.1955

Posted on 05/18/2011 by chris

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

Posted in Concert Sound, RCA | Tagged , , | 2 Comments

Pro Audio hardware of the early 1950s

Posted on 05/18/2011 by chris

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 … Continue reading →

Posted in Altec, Pro Audio Archive | Tagged , , , , , , , , , | 2 Comments

Studio Microphones of 1955

Posted on 05/17/2011 by chris

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 … Continue reading →

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