Marantz 2250B

 Quasi-complementary circuitry tends to generage high order harmonic distortion and is particularly susceptible to crossover distortion. To reduce theses types of distortion, manufactures increase the amount of feedback within the amplifier. Under actual dynamic conditions, however, the amplifier with exessive feedback is prone to higher transient distortion and also lower stability.

In contrast, full complementary symmetry output circuitry requires less feedback by incorporating positive and negative amplifiers which are balanced to mirror-image each other's characteristics. This design produces exceptional linearity, lower total harmonic distortion and  intermodulation distortion.

Early transistorized power amplifiers featured one of two types of output design. A transformer or a capacitor was incorporated between the power output stage and the speaker system. However necessary this was for proper output-to-speaker coupling, it tended to limit low frequency power response or to cause degrading phase shift, and thus impair sound accuracy.

Today's more advanced technology has eliminated the need for coupling transformers and capacitors and the sound inaccuracies they can cause.

A massive power transformer forms the heart of a dual-balanced positive and negative power supply that symmetrically powers the amplifier stages. large capacity electrolitic capacitors assure high energy power reserves, while massive heat sink promote highly reliable, long-term operation even under full power output conditions.

The more flexible the tone controls, the more accurately you can adjust for non-linearities in frequency response caused by speakers, speaker placement, room acoustics of the program source itself.

the tone control system in Marantz Models  2250B features a sophisticated five-position tone turner/mode switch for versatile bass, midrange and treble control. This eliminates a major shortcoming of conventional tone controls - their tendency to affect too wide a band of frequencies. Optional frequency turnover points limit the effect of the bass and treble controls to just the desired range.

The three-stage, 40 dB gain amplifier built into Marantz receivers utilizes feedback-equalized circuitry to maintain extremely low distortion the use of close tolerance, stable components, such as tantalum input coupling capacitors, low noise carbon film resistors, Mylar output coupling and polystyrene-type equalization capacitors assures superior performance.

RIAA equalization is precise - within +/-0,5 dB, from 20 Hz to 20 kHz -  and under test in the 2325, the equivalent noise input to the phono section measures a low 0,8 microvolts. The phono overload point occurs at over 100 millivolts in the 2250B. These figures result in a dynamic range capability of greater than 96 dB.

 Superior selectivity is assured by a four-gang tuning capacitor in the Marantz  2250B, and a dual-tuned RF interstage on Model 2250B provide excellent image and spurious response rejection.

Marantz FET RF amplifiers and mixer stages provide excellent spurious signal rejection and extremely low noise operation that results in excellent quieting sensitivity.

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

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 all Marantz tuners and receivers to assure you of low distortion,excellent stereo separation and superior noise rejection.

PLL circuitry positively locks to the stereo pilot signal broadcast by a 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.

SPECIFICATIONS   2250B

Rated Power Output:  50 Watts (Minimum Continuous Watts per Channel, Both Channels Driven)

Power Band:  20 Hz to 20 kHz

Total Harmonic Distortion:  0,25%

Load Impedance:  8 ohms

I M Distortion (IHF Method, 60 Hz and 7 kHz mixed 4:1 at Rated Power Output):  0,25%

Damping Factor (at 1 kHz):  55

Main Inputs Sensitivity/Impedance:  1,5 V/33 kΩ

Frequency Response (at 1W Output, 20 Hz to 20 kHz): ±20 dB

Pre-Amplifier Section

Phono

Dynamic Range (Ratio of Input Overload to Equivalent Input Noise):  96 dB

Equivalent Input Noise (RMS, 20 Hz to 20 kHz):  1,5 μV

Input Sensitivity and Impedance:  1,8 mV/47 kΩ

Frequency Response (re. RIAA, 20 Hz to 20 kHz):  ±1.0 dB

High Level Inputs (Aux and Tape)

Input Sensitivity and Impedance:  180 mV/100 kΩ

Output Impedance

Tape record:  200

Pre-Out:  900

Tone Controls

Bass:  ±12 dB (50 Hz)

Mid:  ±6 dB (700 Hz)

Treble:  ±12 dB (15 kHz)

AM/FM SPECIFICATIONS

Quieting Slope (Mono) 30 dB Quieting:  1,9 μV (10,8 dBf)

5 μV (19,2 dBf) : 55 dB

10 μV (25,2 dBf) : 60 dB

50 μV (39,2 dBf) : 70 dB

1000 μV (65,2 dBf) : 72 dB

Distortion at 1000 μV (65 ,2 dBf, Mono)

100 Hz : 0,3%

1000 Hz : 0,3%

6000 Hz : 0,35%

Distortion at 1000 μV 965,2 dBF, Stereo)

100 Hz : 0,45%

1000 Hz : 0,4%

6000 Hz : 0,55%

Distortion at 50 dB Quieting (Mono and Stereo)

1000 hz : 0,6%

Hum and Ni=oise at 1000 μV (65,2 dBf)

Mono : 70 dB

Stereo : 60 dB

Frequency Response 30 Hz to 15 kHz

Mono : ±1,0 dB

Stereo : ±1,5 dB

Capture Ratio

at 100 μV (45,2 dBf) : 2,0 dB

at 1000 μV (65,2 dBf) :  1,5 dB

Alternate Channel  Selectivity:  65 dB

Spurious Response Rejection:  95 dB

Image Response Rejection:  70 dB

IF Rejection (Balanced):  100 dB

AM Suppression at 100 μV (45,2 dBf):  60 dB

Stereo Separation

100 Hz : 38 dB

1000 hz : 40 dB

10 kHz : 30 dB

Pilot (19 kHz) Rejection:  60 dB

AM usable Sensitivity:  20 μV