Technics SU-7300 Amplifier Review

The Technics SU-7300 amplifier has the basic inputs required for a simple system comprising a single phono input, a tuner and a couple of tape systems. Switching between the tuner and phono cartridge inputs is by means of two pushbuttons which provided excellent isolation with effectively non-existent crosstalk.

With the exception of the single DIN compatible tape connector, all the signal inputs are rear panel phono sockets with terminals being used for the two sets of loudspeakers and a front panel jack socket for the headphones. An unusual feature is that the loudspeaker switching is such that either the local or the remote loudspeakers can be used, but not both sets. Similarly the use of headphones cuts off the loudspeakers. So far as loudspeaker impedance is concerned, the amplifier was quite happy to work into 4 or 8 ohm loudspeakers.

Further front panel controls include a low pass filter which is sensibly aimed in frequency and attenuation such that it does not ruin the reproduction of music, whilst providing a reasonable noise and scratch attenuation, plus three position toggle switches for tape monitoring and for tape dubbing in either direction between tape units.

Two front panel meters are provided and are calibrated in dB and in Watts, there being a meter sensitivity switch which increases the meter sensitivity by a factor of 10 when depressed. Calibration of the meters was sufficiently accurate, and it was pleasing to note that these meters were very considerably faster in attack than the meters fitted to most amplifiers. However, the meters did not respond fully to transients in music, and were not therefore a particularly reliable indicator of overload conditions.

Treble and bass controls are in the form of eleven-position rotary knobs, but as a result of the wide tone control range available and a poor law of the control, the extreme steps of both the treble and the bass controls were excessive and extended to 4dB in one instance.

So far as the measured performance is concerned, the power bandwidth was excellent as was the harmonic distortion. Furthermore, intermodulation distortion at half power was also unusually good, and even better at 1W.

Noise from the phono input was outstandingly good, with the high level inputs offering a good performance. However, the output noise associated with the worst case volume setting was noticeably disturbing when using headphones, and none too good with loudspeakers.

Inputs had adequate sensitivity and the phono input had a reasonable but not outstanding overload margin; it was however felt that the input capacitance of the tuner input at 430pF was decidedly on the high side and that input resistance variations were rather large.

Subjectively, the amplifier gave no cause for concern in normal use, but the overload distortion was rough if the amplifier was overdriven. Also, the loudness control was rather unusual, because whilst it boosted the bass by an enormous 8dB at 100Hz it at the same time cut the treble by 1.5dB at 10kHz.

From the points of view of finish and overall construction, Technics SU-7300 was first class, with a tidy external appearance and the internal parts being mounted on printed circuit boards which had a clean layout and proper components identification for servicing.

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