hifi engine

Manual Library / Eico

Eico MX-99

Multiplex Autodaptor (1961-63)

add a review add a review

Eico MX-99


The new EICO MX-99 Multiplex Autodaptor employs an original method of zero phase shift, filterless detection of multiplexed signals.

The unit automatically delivers stereo on a stereo broadcast signal, and mono from a mono signal without spurious signals in either case.

The stereo signal is automatically gain-balanced and the mono signal is automatically equal from both outputs without adjustment. An indicator lamp turns on when the station selected is broadcasting multiplex stereo.

The design features freedom from phase distorting filters in either the main or sub channel paths which cause loss of separation.

Nevertheless this design provides the required, or better-than-required, suppression of all spurious signals including SCA (67kc) background music carrier, reinserted 38kc sub-carrier, 19kc pilot carrier, and all harmonics thereof.

This is achieved partly through an original technique for deriving the left and right signals, and partly by sharp ultrasonic filters after the signals are derived.

All of the foregoing is very important for high quality tape recording, where spurious signals can beat against the tape recorder bias oscillator and result in audible spurious tones in a recording.

This adaptor will synchronize with any usable output from the FM tuner and will demodulate without significant distortion tuner (composite signal) as high as 5 volts peak-to-peak.

The MX-99 is self powered, and includes low impedance cathode follower outputs. External controls include an oscillator turn-off switch to permit interference-free listening to mono stations having low sub-carrier frequency SCA store-casting and a separation control.

A separation of 30db between channels is typical and an overall gain of unity is provided from input to output on both stereo and mono.

The MX-99 is designed for all EICO FM equipment (HFT9O, H FT92, ST96), and any other component quality, wide band FM tuner provided with a multiplex output.


Tube complement: 2 x 12AU7, 1 x 12AT7, 1 x 6AU6, 1 x 6D10, 1 x 6X4, 6 x diodes

Dimensions: 3-7/8 x 9-1/8 x 6-3/8 inches

Weight: 7 lbs


Related Catalogues

Kits and Wired

If you have any problems opening files please read the download FAQ. All files are provided under strict licence and reproduction without prior permission or for financial gain is strictly prohibited.

If you have additional documentation please consider donating a copy to our free archive.


This website is not affiliated with or sponsored by Eico. To purchase MX-99 spares or accessories, please contact the company via their website or visit an authorised retailer.