The Ampex MM1200 Studio Recorder

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This page is dedicated to vintage Ampex MM1200 multi-track analog recorders and keeping these wonderful sounding machines alive! During the 70's and 80's, countless hits were recorded on these machines in many major studios. Many of your favorite songs from this period were likely recorded on these machines along with countless other classic hits.

During the late 90's and into 2000 and beyond, RTZ® manufactured upgrade reproduce and record electronics for these machines. The cards were also used in the smaller AG440 machines and were a popular upgrade for two track machines. The RTZ upgrade electronics significantly improved the audio quality of these machines and raised the bar on some of the best sounding analog tape recorders ever produced.

We produced and sold these cards in limited quantities during this period and these cards are still sought after for their outstanding audio peformance even today. Unfortunately, these cards are fairly rare and it's unlikely you'll run across many of these in the field. None the less, our upgrade electronics achieved significant praise in the short period these were produced.

We still maintain and use a 24-track MM1200 in our private personal studio. Our machine has received numerous upgrades and modifications over the years, and we still continue to upgrade this machine and design new electronics as a labor of love. The RTZ machine has received all new repro and record electronics over the years through several revisions. We have the custom roller upgrade kit for our machine originally made by Mike Spitz of ATR Services. Over the years we experiemented with several diffent digital transport controller designs to provide a true constant tension servo loop transport controller using modern digital microcontrollers.

DTC-1200 Digital Transport Controller

DTC-1200 Card

The DTC-1200 digital transport controller completely replaces the original Ampex transport controller and provides full servo loop control of the transport reel motors as well as real-time constant tension control. A few wiring modifications are required in the MM1200 control card bay to use this new controller, but the original Ampex transport control card can still be used afterward if ever needed for some reason.

The DTC-1200 is designed around a Texas Instruments 32-Bit Tiva ARM M4 microcontroller especially designed for motion control systems and applications. TI-RTOS was selected as the real-time operating system. The real-time kernel is scalable and is designed to be used by applications that require real-time scheduling and synchronization or real-time instrumentation. It provides preemptive multi-threading, hardware abstraction, real-time analysis, and configuration tools.

Reel Motor Encoder

The Ampex reel motors require modifications to add quadrature encoders to both motors. We provide a kit with bolt on magnetic quadrature encoders that is easily installed with common hand tools. These new magnetic quadrature encoders provide high resolution tachometer and direction information to the DTC-1200 servo controller. Please see the DTC-1200 Owners Manual for complete installation and modfications details.

STC-1200 Search/Timer/Cue Controller

STC-1200 Card

The STC-1200 replaces the original Ampex search-to-cue/timer-counter card and greatly expands the functionality of the machine completely via software. This card uses an even more powerful Tiva TM4C1294NCPD ARM M4 processor that supports a number of communication interfaces as well as providing the tape counter and auto-locate functions.

The STC-1200 provides RS-232, RS-422, Ethernet, BlueTooth and MIDI communication interfaces. It also supports a SD memory card for logging and hosting other files. Support for web page hosting may be added in the future, or other Ethernet based control interfaces. Support for MIDI Machine Control (MMC) is also planned. MIDI MMC support allows MIDI controllers and other DAW software to remotely control the transport functions via MIDI.

The STC-1200 also serves as a host communications interface for the DRC-1200 remote control over high speed RS-422. The remote will provide access to transport control and multi-point auto-locate functions. Future sofware updates will greatly enhance the functionality of the STC-1200 and DRC-1200 features.

DRC-1200 Remote Control

DTC-1200 Remote

The DRC-1200 is designed to be a robust remote control that provide basic transport functions and serves as a full featured multi-point auto locater. The STC-1200 serves as the host for the DRC-1200 remote control and the two units communicate via 1Mbs high-speed RS-422.

The DRC-1200 remote is basically a dumb display device with buttons and a jog wheel that communicates to the STC-1200 host. The balanced RS-422 communctions bus provides robust industrial strength high speed communications over long cable runs with standard twisted pair eight conductor wire.

4840356 Capstan Servo Card

Capstan Servo Card

The RTZ capstan servo card is a direct replacement for the Ampex 4840356 servo card that includes several enhancements. It includes the added buffered output signals required by machines fitted with the original Ampex constant tension kit. No modifications or hacked on daughter cards are required for use with machines that have the Ampex constant tension kit. A linear regulator was also added to provide true 5V regulation and replaces the crude zener regulator circuit used by the original Ampex capstan servo cards.

We've also thrown in the SPARS capstan flutter indictor LED circuit. This is a very sensitive circuit that gives visual indication of any flutter in the PWM servo data stream. This circuit is sensitive enough to give visual indication of motor bearings with a small tick or that are starting to fail.

Phase Comparator Module

The RTZ capstan card requires the CoolTone Audio Phase Comparator Module. This daughter card module contains an FPGA based phase comparator module that replaces the 9750 logic chips used in the original Ampex design which are no longer in production and extremely difficult to find. Our friends at CoolTone have developed this precision FPGA based module to perform the critical phase comparator functions necessary for servo loop control.

Lastly, the RTZ capstan card supports the AG440 and MM1100 machines and is jumper configurable to support any speeds offered on the AG440, MM1100 and MM1200.

Ordering and Availability

Ampex upgrade products are not sold through dealers and are only available direct from RTZ. Please contact us directly to confirm pricing and availability information. Generally these items are not stocked and most of our Ampex upgrade products are built to order. Items with the price shown as N/A are currently not available.

DCT-1200 N/A DTC-1200 Digital transport controller PCB (Rev-C). Requires the DTC-QEI-KIT encoder kit below.
DTC-QEI-KIT N/A DTC-1200 reel motor quadrature encoder kit for supply and takeup reel motors.
STC-1200 N/A STC-1200 Timer/Counter/Locator I/O PCB. Requires the DTC-1200 Controller.
DRC-1200 N/A DRC-1200 Remote Control / Locator unit. Requires the STC-1200 Controller.
4840393 N/A Motor Drive Amplifier PCB for MM-1200. Precision components for stable motor drive.
4840356 N/A Capstan Servo PCB for MM-1200. Requires CoolTone FPGA phase comparator module sold separately.