Re: Marantz Recording Technology
By Wayne Stahnke
Mark Fontana wrote me a note requesting information regarding the Marantz recording technology. I thought my response might be of interest to a larger group than just Mark himself, so I am posting my response through Foxtail.
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As it turns out, I have a good deal of knowledge relating to the Marantz recordings and recording equipment. I was not directly involved in the design and construction of the mechanisms, but I knew the engineers well and I followed the progress with interest. The Marantz facility was about 20 miles from my home, so visiting did not pose any difficulties for me.
Your statement that you have heard that the Marantz recording piano used mercury to sense dynamics is disheartening. I am shocked and dismayed to learn that we have yet more myth masquerading as fact. I have no idea how it happens that mercury has taken on such a particularly important place in people's thinking; after all, it is not gold or platinum, and it has no place in the list of precious metals. Nevertheless, each and every discussion of recording technonology seems to center around a discussion of a "mercury trough" and "prongs" that "dip" into the mercury. Mercury has become the Holy Grail of reproducing piano technology, and it seems that no narrative of recording technology is possible without it. How all this came to be is a mystery, although there are some clues.
Let me assure you that there was no mercury in the Marantz recording piano, not in a "trough" and not anywhere else. There were not even any mercury switches of the type one finds in German vorsetzers. I examined the instrument on several occasions. I made test recordings myself at the keyboard, and I had lengthy discussions with the designers and engineers. I know from direct experience what was in the recording piano and what was not. Here is a brief description:
The keyboard activity was sensed by a set of optical switches (that is, light-emitting diodes and phototransistors), one for each note. These optical switches were placed above the hammer shanks in such a way that a shutter, attached to the shanks, would interrupt the light beam when the key was depressed. This idea was originally mine, and the fundamental patent on it bears my name. The patent is now assigned to the Yamaha Corporation, and modern Disklavier instruments use this scheme. (Yamaha later acquired what was then the Pianocorder Division of Marantz. ) There were no sensors under the keys. Pedal activity was sensed in a simple on-off fashion.
The computer used to process and store the keyboard data was an Intel MDS-800. The sample rate was in the vicinity of 35 hertz. The storage medium was 8-1/2 inch floppy disks conforming to the Intel "double density" standard, with 128 bytes per sector and 52 sectors per track. (Single density disks had 26 sectors per track.) There were 77 tracks per disk. The data was stored in raw, open frames, without data compression of any kind. As you might expect, this limited the playing time that could be stored on a single floppy disk.
The original roll transfers were made using a Welte-Mignon vorsetzer modified for the purpose. There was a drum attached to each of the two expression pneumatics. Each drum was equipped with 32 silver wire contacts and a common buss bar in such a way that as the expression pneumatic closed the individual contacts were connected to the buss bar in sequence. A separate circuit converted this "walking code" into the 5-bit binary (32 level) code used for the bass and treble halves of the Pianocorder solenoid stack. In addition, there were two switch boards attached to the primary valve chest in place of the ordinary secondary valves used to play the vorsetzer. The bass switch board had 43 contacts, and the treble switch board had 37 contacts. These were connected to auxiliary circuit boards that provided the necessary interface.
The positions of the 32 silver wires on each of the expression drums were adjustable, and were adjusted by ear for optimum results. As you would expect, the wires were closer together at the position corresponding to softest play than they were at the position corresponding to loudest play.
At a later time, this original mechanism was replaced with a number of roll "readers" built primarily by Joe Gaide of Cee-Jay Machine in Sun Valley, California. Joe later retired, and the word on the street is that he subsequently went into the pornographic film business. He has since dropped out of sight.
I hope this description clears up a few points for you. On an entirely different subject, I am happy that you are taking a close look at View. Please let me know your response and suggestions.
With best regards, I remain
(Message sent Tue 25 Jun 1996, 06:41:22 GMT, from time zone GMT-0400.)