Magnum Dynalab FT 101 Tuner Review

The Canadian-made Magnum Dynalab FT 101, which covers only the fm band (88 to 108 MHz), is perhaps the last of the analog tuners—and the only new one to come our way in some years. Its tuning knob, a vanishing feature on today’s digital tuners, varies the setting of a potentiometer whose output voltage controls the frequency of a voltage-controlled oscillator. A heavy flywheel provides the silky, freewheeling action that used to be a hallmark of a good tuning mechanism.

The only other controls on the handsome pale-gold panel are five lever switches for power, mono/ stereo mode, wide/narrow IF bandwidth, AFC, and muting. Three fairly large illuminated meters are the most visible front-panel features. In the middle is a zero-center tuning meter whose pointer indicates the correct tuning setting. To its right is the RF input meter, which reads relative signal strength, and to its left is a multipath indicator.

The FT 101’s only obvious concession to digital technology is a large green frequency readout below the tuning meter. An internal frequency counter measures the frequency of the local oscillator and subtracts the 10.7-MHz IF frequency, so that the readout shows the actual frequency (to the nearest 0.1 MHz) to which the tuner is set.

The rear apron of the tuner contains an F-type coaxial connector for a 75-ohm fm antenna and two pairs of gold-plated audio output jacks. Marked HI and LO, these jacks carry the audio signal at two different fixed levels for compatibility with preamplifiers (such as a few British models) whose line-level inputs are designed to operate with low-level input signals. A transformer is supplied for use with 300-ohm fm antennas, and its screw terminals allow it to function as an adaptor for connecting feeder wires or lugs to the coaxial connector.

A Magnum Silver Ribbon FM Power Sleuth adjustable dipole antenna is supplied with the tuner. The Silver Ribbon’s base can be placed on any horizontal surface, and the length and orientation of its elements can be adjusted for best reception.

The front panel of the FT 101, which is slotted for rack mounting, is 19 inches wide and 3-5/8 inches high. It weighs 12 pounds. Price: $629.

Lab Tests

For our measurements we used a distortion analyzer to tune the FT 101 for minimum measured distortion at low signal levels, and we did not change the setting for measurements made at higher input levels. Tuner parameters that are usually dependent on if bandwidth were measured in both the wide and narrow modes.

The channel separation of the tuner was unusually uniform across its full frequency range of 30 to 15.000 Hz and was not affected appreciably by the bandwidth setting. The audio output level from a 100-percent modulated signal was 1.1 volts from the Hijacks, 0.35 volt from the LO jacks.

The frequency response was quite flat, measuring +1,-0 dB from 30 to 15,000 Hz. The 19-kHz pilot-car-rier leakage was a respectable —70 dB, and hum was —62 dB. Stereo channel separation (wideband) was a maximum of 35 dB at 100 and 1.000 Hz, dropping to 34 dB at 10.000 Hz. Capture ratio and am rejection were good.

Comments

Unlike digital-synthesis tuners, which can be set only to precise frequencies (such as 104.3 MHz) and generally do not allow vernier adjustment of the frequency, an analog tuner can be set to any frequency in its tuning range. This means that, also unlike a digital tuner, it is not subject to inherent (and generally unknowable and uncorrectible) frequency errors. We often find in our test of digital tuners that the calibration is in error by a number of kilohertz (as many as 30 or 40 in some cases). As a result, the distortion is often increased. This pan degrade the usable-sensitivity measurement, although it has little effect at higher signal levels.

An analog tuner treats the radio band as a continuum and thus, ideally, can be set to the exact frequency of the signal source, realizing its minimum distortion and optimum sensitivity performance. This ideal assumes, however, that the tuning indicator, if any, is both sensitive and accurate enough to identify the correct frequency or that the user can hear the difference as the tuning is adjusted. In practice, these conditions are rarely realized.

Since it is usually impossible to hear even the several percent of distortion that can result from moderate mistuning, the user of an analog tuner must depend on the accuracy and sensitivity of the tuning meter, often with the aid of an AFC (automatic frequency control) system. The meter on the Magnum Dynalab FT 101 was accurate, with correct tuning always corresponding to a center pointer position, but it was not sufficiently sensitive to insure minimum distortion.

Although the various sensitivity, noise, and distortion readings we obtained did not coincide exactly with the measurements made by the manufacturer on our test sample (a common occurrence with fm tuners), the errors were not serious. In some cases our readings were better than those from the manufacturer.

We were disappointed in the inadequate indicator sensitivity, however. The meters gave evidence of working well, and if the tuning and multipath meters were several times more sensitive, they could be truly useful. We also would prefer to see a 300-ohm antenna input in addition to the 75-ohm coaxial connector. The omission is especially odd since the Silver Ribbon antenna, an excellent dipole, has only spade-lug outputs for 300-ohm receiver inputs and must be used with the FT 101’s 300- to 75-ohm transformer.

The FT 101 is the only home fm tuner we can recall that has nonde-featable automatic signal-controlled channel blending. This is a common feature of car stereo tuners, where its function is to minimize rapid background-noise fluctuations during the wide signal strength variations that occur while the car is in motion. The rationale is that the noise will remain at a nearly constant, and acceptable, level over a wide range of signal strengths, although the channel separation is reduced at lower signal levels. In practice, this usually means that only fairly strong signals are heard in stereo, while weaker ones are essentially heard in mono.

It is not clear why Magnum Dynalab has chosen to build this system into a high-quality home tuner, but the result is basically mono operation at inputs under about 20 dBf and only partial stereo until the level reaches about 50 dBf (a fairly strong signal). The benefit, in this case, is a signal-to-noise ratio (S/N) of about 50 to 55 dB at weak signal levels (where blending takes place), increasing to approximately 70 dB for strong signals.

The FT 101’s AFC circuit had a very mild action. It was virtually impossible to tell—either from listening, the meter readings, or the tuning “feel”—whether or not the AFC was turned on.

The instruction booklet for the Magnum Dynalab FT 101 is quite complete and informative, although it makes only passing mention of the multipath meter that is one of the tuner’s most prominent front-panel features. Presumably movement of this meter’s pointer indicates multipath distortion. Of all the stations we received in suburban New York using the Silver Ribbon antenna, only one produced a multipath-meter movement greater than the width of the pointer.

Our impression of the Magnum Dynalab FT 101 was of an elegant-appearing, easy-to-use fm tuner whose overall sound quality was impeccable. Anyone with a trace of nostalgia for the “good old days” of analog tuning (and we confess to sharing that feeling on occasion) will find the delightfully smooth, easy tuning of the FT 101 a refreshing contrast to the myriad buttons, plates, and levers that have virtually eliminated knobs from our tuners.

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