Tag: mixers

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Technical

A DIY tube mixing console; plans, schematics, methods

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 and mixing circuits.  Download the entire piece as a 4-page PDF:

DOWNLOAD: DIY_Console_1955

There is little of real interest here in terms of a complete system, as the system discussed is a mono mixer; but if you are interested in some simple, novel mic preamp and line driver plans, you might find this worthwhile.  Personally I am drawn to the OD-3 regulator tubes; i know zero about voltage regulation tubes; I have always used Zener diodes in the past when i needed regulated voltage; but the very simple way that these tubes are used here leads me to believe that they are pretty easy to work with.. Might wanna try them out.  They are just $5.15 at AES.

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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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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
Western Electric

Western Electric in the late 40s: Audio Engineering Mag pt. 5

The Western Electric 755A speaker

In a previous post, we looked at some early Western Electric cinema-sound equipment and the cult that surrounds this early kit.  Here’s a series of print ads from 1948 that describe some of the last-ever pro audio offerings from Western Electric.  WE was soon to be broken up by the government, and many of these products would then re-surface as Altec-branded components.

The Western Electric 756A speaker


The Western Electric 25B mixing console

The Western Electric 141, 142, and 143 audio amplifiers

The Western Electric speaker line up, featuring the 757A

 

Categories
Altec Pro Audio Archive

Altec Sound Equipment 1968

Download the sixteen-page 1968 Altec Sound And Communication catalog:

DOWNLOAD:AltecFullLine1968

Products covered, with text photos, and limited specs, include the full range of microphones, horn speakers, Duplex coaxial speakers, full range drivers, voice-of-the-theatre systems, tube and solid-state power amps, pre-amps, compressors, and mixers; the full range of plug-in transformers, 9200 console and attendant components; a page devoted o the ‘Giant Voice’ public warning system (see earlier post); plus the range of telephone audio equipment and intercom systems for industry and hospitals.

If you are not familiar with Altec’s classic pieces, this brief catalog is a great place to start.    Altec’s market-leadership would soon be supplanted by a range of innovations introduced by smaller companies in the 1970s, but at the time, this was still top-end gear.  Much of this equipment is still used today; if not in recording studios, then by audiophiles.  Dig in.

Categories
Connecticut Audio History

LOFT recording consoles circa mid 1970’s: UPDATE

Pictured above is the very first recording/mixing console made by LOFT (Loft Modular Devices, Inc.).  It is a model 440.  LOFT was a manufacturer of Pro Audio equipment in Manchester Connecticut active in the 1970s.  In 1980 LOFT became Phoenix Audio.

Here’s a close up shot of a Loft model 440 console.  From the first picture, the Tascam 80-8 mounted in the desk to the right tells us that these were boards aimed at the professional project studio/demo studio market.

Another close-up image of a 440, this time a series 2.  These images, and all that follow in this post, come courtesy of LOFT founder Peter Nimirowski.  Peter got in touch with PS after we ran this earlier post which mentioned some of the LOFT outboard gear.  Peter has this to say about LOFT’s consoles:

“Loft … made two series of mixing desks.  The 440 Series  used a Microtran Transformer in the mic pre-amp. This console was probably one of the first low cost professional desks. My understanding is one is in use in CT another in Calif.    (Regarding) the 800 Series: we only made a handful of these boards. This was at the crossover point from Loft Modular Devices to Phoenix Audio.  (We) tried to make the leap into the pro studios. The first console used Allison’s Trans-Amp in the pre-amp circuit. Consoles after that used our own transformerless pre-amp design.  John Roberts was responsible for all Loft and later Phoenix Audio circuit designs. A truly brilliant designer. The consoles were manufactured mid to late 70’s. By 1980 LMD had become Phoenix Audio which did not manufacturer any consoles. When I together with Richard Federman started LMD it was a result of wanting to build a recording studio, not a manufacturing company. At that time except for API, Quad 8 and Maybe Neve, there really wasn’t much of a choice in affordable mixing desks. As far as technology, the first IC op-amp the 709 had just been developed. PC boards where just coming into existence. LMD manufactured all PCB in house. I designed and built the etching system. Everything was done in house.

Thanks for getting in touch Peter.  Here are some images of the later 800 series console, again from Peter’s archive.

Categories
Technical

Gately EM-7 Mixer and EQ-7 4-channel Equalizer Unit

In a previous post, I included the scan at left from a 1969 issue of the AES journal.  It’s an ad for the Gately Electronics EM-7 4×2 mixer and EM-7 4-channel equalizer.  At the time I had hoped to find one of these little setups, and sure enough,  one of the EM-7 mixers came along on eBay.  I checked the sellers ‘completed listings’ and saw that he had sold the companion EQ-7 equalizer unit earlier.  I contacted that buyer through eBay, indicating that I was interested in the EQ-7 should he decide to part with it.  Sure enough, he did.  So I was able to get an EQ7 as well.

All in all it turned out to be a great deal.  It was a bit of a pain in the ass to get these things working, but at the end of the day I ended up with 4 fully discrete mic preamps with discrete EQs, all running on 48v, and all with UTC input and output transformers.

This post will get a bit technical, so follow the link below to read on…  CLICK TO CONTINUE….

Continue reading “Gately EM-7 Mixer and EQ-7 4-channel Equalizer Unit”
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Altec Pro Audio Archive

Altec Professional Audio Controls Paper Circa 1960’s

Around the time that ALTEC introduced their 947X series of solid-state plug-in amplifiers, ALTEC staff engineers Arthur Davis and Don Davis published the following paper in AUDIO magazine (see my previous post on AUDIO mag).  ALTEC then reproduced and re-printed the paper as promotional material. I have scanned and uploaded the fill 12-page document.

DOWNLOAD: Altec_Professional_Audio_Controls

Covered in this document: the 9200 modular console, the 9704A transmission measurement set, and the various ALTEC passive equalizer units of the period: graphic, shelving, and pass filters.

Check out the publication.  It is a good quick primer on early impedance-matched mixing systems.  In the future, I will post more extensive documentation on these ALTEC consoles and filters.