Assorted Stuff


Decoders using ambiance recovery, such as early Dynacos, worked best on live recordings where the large area of the concert hall allowed natural reverberations and reflected sound waves to be recorded.

Radio-Electronics magazine in its March 1971 edition says the DynaQuad ambiance recovery unit first appeared in the spring of 1970. This product may have led the 70’s ‘quad craze.’

Remember folks, ambient recovery extracts naturally occurring audio info, it is not designed to retrieve specifically encoded quad info placed on a record; though the passive ambient recovery systems will extract some of the encoded quad info. However, passive decoders only detect part of the encoding on matrixed-type quad records (SQ, QS, EV-4, etc). On CD-4 records, passive decoders can only extract info from the front stereo info; the rear channels are encoded in frequencies the passive decoder can’t detect.

Two tracks on the Beach Boy’s Sunflower LP were recorded to increase their out-of-phase info to increase a passive decoder’s ability to extract rear channel info. These tracks are: Got to Know the Woman and Cool Cool Water.

The Electro-Voice EVX-4 decoder and the Heathkit Stereo-4 decoder use the same circuitry; just different names. I wonder how many other quad products are like this???

The Electro-Voice EV-4 system was the first encoded quad available on vinyl records. There are a few LPs floating around with the EV-4 designator on them. Since it is a matrix-type quad system, SQ and QS will decode them.

The April 1971 Stereo Review magazine shows how to hook up rear speakers to extract out-of-phase info. Since it involves connecting the left/right positive speaker terminals to the rear speaker(s), care must be taken (though I’ve never heard of any harm coming to the receiver/amp). In a blind test by an audio magazine, high-end full logic decoders produced a quad sound that most listeners could not differentiate from a true discrete quad source.

On Matrix-Encoded Records:

Vectored modulations in the records’ groove carry front channel information. Helical modulations carry rear channel info. Wheeeeew !!! Shake yer booty !!!! That needle must be rockin’ and rollin’. Guess a high-quality cartridge/stylus would help capture the quad info on a record. And, maybe, perhaps, and I’m just guessing…….. a little extra weight (not much) on the tonearm (if yours is adjustable) may improve the quad sound being scraped off the vinyl.

As with any cartridge/stylus, a better-quality one will help preserve your records. Cleanliness of the record and the stylus is also important. Some reports indicate that the rear-channel grooves on a matrix-encoded record can be worn down after repeated playing, just like stereo and mono recordings!!! So……. perhaps it’s a good idea to record those quad records onto tape.

Another tip from the pros is to not play a record twice without giving the vinyl a little time to cool off. The pressure of the stylus against the vinyl creates heat which slightly softens it. Playing the same record twice in a row is supposed to allow a higher rate of wear.

For REALLY cheap quad, you could have bought Radio Shacks’ Quartette ambiance recovery unit for $6 in 1973.

Electro-Voices’ EV-4 matrix system was the only encoded quad vinyl and matrix decoder format available as of September 1971

Attempts at creating a quad cassette deck led to the JVC 4CO-1680, which never made it to market, for various reasons. To see a pic of it, check out the Apr 1974 Popular Mechanics magazine.

The May 1988 Stereo Review magazine says (while retrospecting on the quad years) that

“. . .one of the joys . . .” of using quad equipment was finding the hidden ambient aspects of music recorded in stereo (Another way of saying that synthesized quad from a stereo source sounds neato).

More Assorted Thingys

CDs and matrix decoders are a nifty combination. My Sansui Vario-Matrix decoder slurps up CD stereo output and synthesizes some ultra funky quad tunes. The Barenaked Ladies Rock Spectacle CD sounds sooooooooo darn good in synthesized quad.

Perhaps it’s the excellent separation between left/right channels. Or, it may be the lack of audio compression in CD’s that other audio formats have that allow such excellent stereo to quad synthesization. Maybe it’s just good Karma!!! Whatever the reason, CDs and quad decoders go together like M&Ms and peanuts, potatoes and gravy, Sonny & Cher; you get the idea.

The Marantz 4400 has an onboard oscilloscope that showed output per channel. Other receivers by various manufacturers had similar looking devices but were not true O’scopes. Also, the 4400 was the ‘top dog’ of Marantz quad units, but it too used optional plug-in modules for SQ, QS, and CD-4 as many other Marantz receivers did.

Yamaha is considered by some to be a high-end manufacturer. I’ve found only one quad goodie by them: the CS70R receiver. Discrete or matrix. 4 X 12watts. 1974. $370. Ever see one??

Buying Tip

Several Marantz receivers were ‘quad’ types. They had 4 channels of output, etc. BUT, many models required an extra-cost add-on module to allow quad decoding. The module plugged into a receptacle on the bottom of the unit. If you buy a Marantz, check to see if it requires a module and if so, ensure it is included with the unit. These modules are VERY hard to find.

Marantz SQ Decoder Modules

SQA-1 has “Front/Rear” Logic, SQA-2 Full-Logic unit, SQA-2B a later Full-Logic module. These are the optional extra-cost plug-in modules that fit into the bottom of many Marantz receivers. Very hard to find. There was a CD-4 module, also.

There it is, sitting on the thrift store shelf; a quad 8-track home unit. Neato. Something to remember is that most of ’em only played back in quad. The majority of home 8-track quad units did NOT record in quad. If you’re looking for a quad recorder, reel-to-reel units are easier to find. If you must have a quad 8-track recorder, look at the faceplate carefully to determine (hopefully) if it is a recording type. Some units do not explicitly indicate if they are quad recording units or not. Some would record in stereo but not quad; even though the unit plays stereo AND quad. Sometimes you have to make an educated guess by the controls and faceplate markings if the unit actually records in quad.

In 1988 the Fosgate company built a series of audio surround sound processors.

The Pro Plus series was designed by Jim Fosgate and Pete Scheiber. Scheiber was a key figure during quads’ prime years. He helped Electro-Voice design the EV-4 matrix system and was instrumental in the process which allowed quad to be encoded onto vinyl records.

The Pro Plus units have “360 Degree Space Matrix” written on their faceplates. Having never heard these units perform and unable to find a review of their output, their effectiveness in creating a quad-like surround sound field is unknown to me. Has anybody out there in World Wide Webland heard these things??? If so, send in a review and share it with others interested in quad and/or surround sound.

Two sets of quad headphones were reviewed in the July 1972 Popular Science magazine. The writer stated that on quad recordings where the rear channel output was mostly ambient sound, the phones weren’t that great. When the output in the rear channels was a more “direct” sound, the writer says that the phones worked better.

A few quad headphones had built in decoders, most of which were passive, ambiance recovery types. Most quad headphones simply used the quad source fed to the headphones via the receiver headphone jacks.

A large selection of quad headphones were available, though every review I read stated that the quad effects were inferior to the quad from 4 speakers.

Some super cheap quad components are not actually quad. A few cheapo units had a circuit to send front left/right sound to the rear speakers after a few millisecond delay. Somewhat akin to a reverb unit. Another gimmick was to use the passive ambiance recovery method and call it true quad.


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