AR Music Room Amplifiers

[charger3834]

Does anyone know what Preamps and power amps were used in the AR music rooms, Dynaco mark 3s ? I assume the AR amplifier would have been used after 1967. How was it all wired up to facilitate the switching from speaker system to speaker system ?

[tysontom]

>Does anyone know what Preamps and power amps were used in the

>AR music rooms, Dynaco mark 3s ? I assume the AR amplifier

>would have been used after 1967. How was it all wired up to

>facilitate the switching from speaker system to speaker system

>?

Brad,

Prior to the AR Amplifier, the Dynaco PAS-series preamps were used with Dynaco Mark III power amps; later the Stereo 70 was used. AR Turntables and a Tanberg 64 were frequently in use. Dynaco and AR were the only amplifiers used in the Music Rooms, to my knowledge.

The switch setup used a custom-designed switch box with red lights, adjacent to each speaker, that would illuminate for the speakers being used at that time. There was no equalization or loudness compensation utilized, as the efficiency of each of the AR speakers is within a dB or two across the board; furthermore, this was simply a switching setup rather than an A/B comparitor circuit.

http://www.classicspeakerpages.net/dc/user_files/2410.jpg

Fig. 1 AR Music Room, GCT. Note AR-3s, on the now-rare AR speaker stand, atop the building used to provide Christmas Music throughout Grand Central Terminal.

http://www.classicspeakerpages.net/dc/user_files/2411.jpg

Fig. 2 AR Music Room, GCT. Switching between AR speakers for GCT travelers and New Yorkers.

http://www.classicspeakerpages.net/dc/user_files/2412.jpg

Fig. 3 AR Music Room, GCT. This image shows clipping from newpapers covering AR's live-vs.-recorded concerts. Also shown are some original pieces of art along with reproductions.

--Tom Tyson

[charger3834]

Interesting indeed. I presume they used two Stereo 70's as monoblocks. AR and Dynaco must have had a healthy, informal working relationship in the early years. How well did those big tube amps like the Marantz 9,Dynaco 70 and the MC275 handle the AR-3 1-2 ohm loads ?

[tysontom]

>Interesting indeed. I presume they used two Stereo 70's as

>monoblocks. AR and Dynaco must have had a healthy, informal

>working relationship in the early years. How well did those

>big tube amps like the Marantz 9,Dynaco 70 and the MC275

>handle the AR-3 1-2 ohm loads ?

Brad,

Ed Villchur always believed in good performance, and he knew that the Dynaco amplifiers and preamps were excellent, but they were not prohibatively expensive. The Marantz 8B, the 9 and McIntosh MC60s, MC75s, Fisher tube amps, Fairchild 60- and 75-watt monoblocs, etc., could handle the AR-3 load satisfactorily, as most had transformer taps for low impedances. The Macs had 2-ohm taps on some models. The AR-3 was nominally 4 ohms, but dipped well below that impedance at certain frequencies, depending on the setting of the level controls. However, the AR-3's low sensitivity, along with its very low impedance at certain frequencies, caused many lesser amps to overload and some to self-destruct. The Stereo 70s was used in their normal stereo configuration, which provided plenty of power for most circumstances. The standard ST-70s (used in the Music Rooms), rated at 35-watts-per-channel, came closer to 40 or 45 watts, and had enough headroom to provide 70-80-watt peaks, enough for most circumstances in the Music Rooms. The Mark IIIs were used for the live-vs.-recorded demonstrations, and each amp could produce 60-70 watts continuous and about 120 watts peak.

David Hafler of Dynaco and Ed Villchur were professional associates, and Dynaco (along with Concertapes and to some extent Ampex and Sony) partnered with AR to produce the 75+ live-vs.-recorded concerts. These concerts were very expensive to produce, but as we know, were extremely successful and important to the legacy of Acoustic Research and Dynaco. AR always used Dynaco for public demonstrations, and some AR ads included Dynaco equipment as recommended electronics. This was stop-gap, of course, until the introduction of the AR Amplifier and Receiver.

--Tom Tyson

[Guest matty g]

Tom -

Thanks for that post. My father worked at an engineering firm in NYC in the 50's and 60's, and when he decided to bite the bullet and put together an audio system in '63, he spent alot of time at the Grand Central AR listening room. He finally decided to go with the AR2a system, unfinished pine. Quite a bang for the buck! I'll bet that listening room was the highpoint of his day in the city - until he got home to us in Long Island (he probalbly couldn't wait to get back to Grand Central Station!)

The Dynaco instruction manual for the Stereo 70 actually recommends the AR3 system (it says "a high quality system such as the AR3 should be connected" or something to that effect) so there is a strong connection between Dynaco and AR.

Had many AR turntables and love 'em all. Had many Tandberg 64's and 64X's... nuthin' but trouble!

Matt