Myryad MT 100 FM stereo tuner
Myryad's designer and technical director, Chris Evans, highlighted the MT 100 stereo FM tuner during a press conference at the 1999 International Consumer Electronic Show. After reading Michael Fremer's recent report (Stereophile, June '99) on the high quality of 1999 FM broadcasts in the New York area when he used a rotor-operated, outdoor Channel Master FM antenna and a refurbished McIntosh MR67 stereo tuner, I decided to review the MT 100.
On first seeing the MT 100 emerge from its shipping carton, I had to admit that I rather liked its back-to-basics approach. Its sleek, snazzy, art deco design and functional and elegant construction were stunning. No bulky tuning knob or flashy displays here. Instead, the unit's appearance is dominated by its recessed, anodized black tuning knob, which is conical, and smoothexcept for a circular cutout (as on a Movado watch) for your tuning finger. This is placed centrally in the silver-gray, ¼"-thick aluminum front panel. To the right, arrayed in an arc, three pushbuttons handle the Preset, Manual, and Search functions. The tuned frequency, preset, and signal-strength indicators are mounted behind a black plastic screen. These use a blue vacuum display, while the Stereo and Tuning indicators are backlit red.
The back panel contains (from left to right) line outputs, antenna inputs, and a rocker power switch. As in other M-series Myryad components, the My-Link connectors on the back panel allow the user to power on and off from the remote control a single M-series component or an entire Myryad stereo system.
As I began to use the MT 100, I noticed its smooth integration with the hand-held Myryad System remote control. Replete with myriad functions and a central numerical keypad, this remote duplicates the MT 100's front-panel Dim, Standby, Store, Mono, Preset, Search, and Tune Up/Down functions, though the Dim and Standby buttons on my remote didn't work. Even so, the remote worked over a wide range of angles; I could operate it from my listening chair 12' away.
The MT 100 is built in a rigid steel chassis with the display, control processor, and operating keys on a single printed circuit board sandwiched between the front plate and the steel subchassis. This ensures that noise from the digital circuitry cannot affect the tuner's performance. When not in use, the MT 100 is normally switched to Standby, which keeps the power supplies and key circuits active but isolates the audio outputs with a high-quality relay. If the Myryad MT 100 is used with the Myryad ML 120, amplifier, the two can be coupled via the My-Link; each unit can be switched in or out of Standby by pressing the appropriate front-panel or remote button.
Opening the MT 100's top cover, I discovered an extraordinarily neat, well-designed circuit board, only 8" by 8.25", which is well laid out, has a minimum of point-to-point wiring, and uses a mixture of proprietary IC chips and individual components. The PCB's designator identifies each functional section of the tuner's circuitry, such as IF amplifier, MPX filter, AGC detector, and stereo decoder. Other than this compact board and a large toroidal transformer, the MT 100's innards are completely empty!
Like other British tuners I've reviewedincluding the Quad FM-4, Naim NAT 01, and Meridian 204 (Vol.15 No.9)the Myryad MT 100 emphasizes the functional basics: Let the owner tune in the station, and automate the rest. Therefore, it does not include controls for IF bandwidth selection, stereo/mono switching, or muting defeat. Rather, the tuner automatically applies partial muting in stereo mode to allow for quiet tuning between stations.
The MT 100 employs an OEM RF front end from Mitsumi with a low-noise dual-gate MOSFET input amplifier, three tuned RF stages, and a buffered local oscillator. The local oscillator is tuned by a crystal-locked digital frequency synthesizer. Unlike other high-performance FM tuners, which use an analog signal, the Myryad uses a digital synthesized signal for tuning. The resulting Intermediate Frequency (IF) signal is fed to a three-stage, low-noise discrete IF amplifier with linear-phase ceramic IF filters. This amplifier is designed to handle strong signals, and is further enhanced by an automatic gain control (AGC) circuit.
From the IF amplifier the signal is demodulated using a low-distortion, double-tuned quadrature detector. The demodulated composite stereo signal next is passed through a phase-compensated "birdie" filter to remove interfering signals before passing on to a phase-locked loop (PLL) stereo multiplex decoder IC. After being decoded into stereo, multiplex pilot tones are removed with a double-notch filter. This is followed by a discrete class-A push-pull output buffer amplifier, which provides low output impedance and high drive capability. The MT 100 has eight separate power supplies.
The signal-strength meter combines the signal-strength output from the IF amplifier IC and a second signal detector. This combination allows the meter to cover a wide range of signal strengths to provide useful information.
External finish, appearance, shielding, internal circuitry, and component quality are very good to excellent. This FM tuner should provide years of trouble-free reception.
Setting up the MT 100 went smoothly. Connecting it to my antenna feed was easy, MT 100s shipped to North America being fitted with an "F" coaxial antenna connector.
Setting the MT 100's presets with my preferred station frequencies was another matter. No matter how many times I program a VCR or FM tuner, I have to laboriously read the instruction manual with every new product. If I try to wing it and not read the manual, I regret it. Same with the MT 100after several minutes of pressing the Store, Manual, and Preset buttons on the tuner and its remote, I had gotten nowhere. Just read the manual. With minutes of reading the instructions at the bottom of p.5, I had successfully programmed 10 of the MT 100's 29 available presets.
As my first test, I followed Don Scott's recommendations (published in the August 1997 Stereophile, pp.2123). I disconnected the antenna and listening to the MT 100 playing interstation static. As Don described, "It should sound full-spectrum, deep, and also crisp with a muted smoothness at the same time. No squeals or birdies (oscillations) should be heard, as this indicates distortion being generated in either the front-end or IF amplification stages, which will give a tuner a nasty, gritty quality."
To test a tuner, I usually set up and run a closed-circuit FM broadcast (described in Vol.14 No.12). This procedure allows the repeated playing of specific musical selections, broadcast locally in the listening room. This time, unfortunately, the equipment for this test was not available. Instead, I listened to the Myryad and a comparison tunerthe analog-tuned, $5800 Magnum Dynalab MD 108 (May 1997, Vol.20 No.5, p.145), using its single-ended outputs. A single Mini-Circuits ZFSC-2-1 precision signal splitter took the feed from the rooftop antenna and split the resulting signal to two 8' lengths of RG-59U coaxial cable attached to the antenna inputs of the two tuners. The signal splitter has an insertion loss of 3dB, and the cable connectors reduce the level by another 2dB, for a total loss of 5dB. Because this results in fewer stations being received, the actual number of stations received by any one tuner cited here is a very conservative underestimate. However, each tuner receives the same attenuated signal, so comparisons using the outside antenna are still meaningful.
Care was taken to tune both tuners to the same frequency; if one tuner was left tuned to one frequency, it was very easy to "pick up" that tuner's oscillator when the two units were exactly 10.7MHz apart (10.7MHz being the IF frequency). The audio outputs of the two tuners were matched by attaching a precision stereo potentiometer between one tuner's stereo outputs and the line-level input of the Mark Levinson ML-7A preamplifier. Then it was possible to switch between tuners with no gain change. The end result: It was possible to move the main selection knob on the Mark Levinson ML-7 between Tuner and Auxiliary (from Myryad FM tuner to comparison tuner) with no change in level!