Marantz 2100 Tuner

Some of the technical features of the Model 2100

DUAL GATE MOSFET FRONT END

One very important area of any tuner is its "front end". This is the first section of the tuner through which the radio frequency signals are amplified. The design of the front end greatly influences the sensitivity, noise, and selectivity characteristics of the tuner. Most tuners being built today use MOSFETS (Metal Oxide Semi-conducting Field Effect Transistors). MOSFETS are used for three basic reasons:

(1) IMPROVED LINEARITY

MOSFETS have the ability to amplify over a wide dynamic range of signal levels while maintaining the correct linear relationships between input and output. This gives them a higher overload capability.

(2) LOWER INHERENT NOISE

These devices contribute to a better quieting slope (see next section).

(3) HIGH INPUT IMPEDANCE

MOSFETS have very high input impedances, which reduce loading effects on tuned circuits and result in better tuner selectivity.

QUIETING SLOPE

The quieting slope specification measures a tuner's ability to provide good signal-to-noise performance under actual operating conditions. It is a far more reliable indication of performance quality than the IMF (Institute of High Fidelity) sensitivity figure often quoted as the prime specification to consider when evaluating an FM tuner.

The IHF figure gives only the number of microvolts necessary for minimum quality reception: A signal with 3% distortion and noise (30 dB quieting) hardly qualifies as high fidelity.

A signal-to-noise ratio in excess of 50 dB (the revised 1975 IHF specification) is generally recognized to be necessary for high quality listening. It is most important then, to examine a tuner's ability to quiet quickly beyond the 30 dB quieting point.

Quieting slope sensitivity figures measure the signal-to-noise ratio in the crucial five-to-500 microvolt range, where the majority of usable broadcast signals fall. The steeper the slope, the quieter, and therefore the more listenable, the station.

LINEAR PHASE IF SECTION

The performance of the FM tuner is also influenced to a great extent by the performance of its Intermediate Frequency (IF) amplifier. The ideal IF amplifier should accept the desired band of frequencies with minimum phase distortion, while rejecting all undesired signals.

The IF amplifier used in the Model 2100 includes an integrated circuit designed expressly for FM reception, and three dual-element ceramic filters.

Use of this 1C provides excellent capture ratio and AM suppression. The ceramic filters are ideal in that the 200 kHz passband is phase linear with sharp cutoff slopes. This eliminates a major source of high frequency distortion and loss of stereo separation. The sharp cutoff slopes improve the tuner's rejection and selectivity characteristics, permitting a clear reception even when stations are closely spaced.

PARAMETRIC MUTING CIRCUIT

FM tuning is made completely noise-free by a special parametric-type muting circuit. The circuit responds to two characteristics of the FM signal: RF signal strength and DC offset at the ratio detector, thus assuring positive muting of the audio signal even under the most adverse conditions.

PHASE LOCKED LOOP FM STEREO DEMODULATOR

The Phase Locked Loop (PLL) design was developed originally to provide a state-of-the-art. communication system for the space industry. Today the same technology is used in the Model 2100 to assure low distortion, excellent stereo separation, and superior noise rejection.

PLL circuitry positively locks to the stereo pilot signal broadcast by an FM station. This precise "phase lock" is absolutely necessary for high performance in the stereo demodulation process: It enables the multiplex demodulator to separate the stereo channel information from the FM multiplex signal with more accuracy and less distortion than multiplex demodulators using other designs.

In addition, PLL is dependent on pilot phase rather than pilot amplitude, making it less susceptible to false triggering from various types of noise interference.

Specifications

FM Tuner Section:

Sensitivity IHF Usable:  10.3 dBf (1.8 µV)

Sensitivity IHF 50 dB Quieting :

Mono : 13.2 dBf (2.5 µV)

Stereo :  37.3 dBf (40 µV)

Quieting Slope (Mono)

RF Input for 30 dB Quieting  9.3 dBf (1.6 µV)

Quieting at:

20 dBf ( 5.5 µV) :  58 dB

25 dBf ( 10 µV) :  62 dB

40 dBf ( 55 µV) :  70 dB

65 dBf (1000 µV) :  74 dB

Quieting Slope (Stereo)

Quieting at:

30 dBf ( 17 µV) :  42 dB

40 dBf ( 55 µV) :  53 dB

50 dBf ( 173 µV) :  58 dB

65 dBf (1000 µV) :  65 dB

Distortion (Mono) at 65 dBf (1000 µV)

100 Hz :  0.25%

1000 Hz :  0.15%

6000 Hz :  0.3%

Distortion (Stereo) at 65 dBf (1000 µV)

100 Hz :  0.35%

1000 Hz :  0.3%

6000 Hz :  0.5%

Distortion (Mono and Stereo) at 50 dB Quieting, 1000 Hz :  0.6%

Hum and Noise at 65 dBf (1000 µV)

Mono :  72 dB

Frequency Response 30 Hz to 15kHz :

Mono :  +0.2 dB, -1.5 dB

Stereo :   +0.2 dB, -1.5dB

Capture Ratio

at 45 dBf (100 µV) :  1.5dB

at 65 dBf (1000 µV) :  1.0 dB

Alternate Channel Selectivity:  70 dB

Spurious Response Rejection:  90 dB

Image Response Rejection:  60 dB

I.F. Rejection (Balanced):  80 dB

A.M. Suppression:  50 dB

Stereo Separation

100 Hz :  40 dB

1000 Hz :  45 dB

10kHz :  40 dB

Subcarrier Rejection:  60 dB

AM Tuner Section:

IH F Usable Sensitivity :  15 µV

Distortion (THD), 30% Modulation:  0.5%

Signal-to-Noise Ratio:  50 dB

Alternate Channel Selectivity:  46 dB

Image Rejection:  45 dB

Spurious Response Rejection:  60 dB

I.F. Rejection:  40 dB

General:

Power Requirements 120 V AC, 60 Hz

Power Consumption 23 W

Dimensions (W x H x D):  416 x 146 x 239 mm  (16-3/8" x 5-3/4" x 9-3/8")

Weight:

Unit alone :  6 kg (13.2 Ibs)

Packed for Shipment :  7 kg (15.4 Ibs)