Technics SU-7700 Amplifier Review

In many ways, the SU-7700 amplifier, the bigger brother of the Technics SU-7300, may well be of particular interest because of its overall performance and the facilities which it offers, although outside the lower price bracket.

The three basic inputs for a magnetic phono cartridge, tuner and auxiliary are selected by neat push-button switches, whilst the two tape connections are controlled by three position toggle switches. These permit monitoring either tape unit, and also tape dubbing in either direction.

All the inputs had a practical sensitivity and good overload margins, but the input impedance variations of the high level inputs were rather large and also it is felt that the capacitive component of the high level input impedances is on the high side at over 300pF.

Input signal connections are, with the exception of one tape connection which also has a DIN compatible connector, phono sockets; the two sets of loudspeakers outputs are terminals, either or both sets of loudspeakers being selected by push-button switches. Examination of the power output capability of the amplifier shows that it is quite happy with single 4 ohm loudspeakers and the manufacturer wisely recommends the use of 8 ohm loudspeakers where two sets are to be used simultaneously.

Further facilities include a sensible low pass filter, which is subjectively useful for reducing noise without having a drastic effect upon music, the usual loudness control which has an 8dB bass boost at 100Hz and peculiarly, a 1dB treble cut at 10kHz, and a mono/stereo switch. In addition, there is what has been termed a ‘subsonic equalizer’ associated with the phono input. This is in fact a very sensible addition of a high pass filter for reducing turntable rumble, the filter having a well chosen â€" 3dB point at 30Hz and a rate of attenuation of 12dB per octave.

The treble and bass controls are of the eleven position switched type providing ±10dB range at 100Hzz and at 10kHz, and with the exception of the extreme positions, the increments between steps are reasonable, but the extreme steps are too large.

The remaining front panel controls consist of the balance control which was found to have excellent performance whilst providing a full range, so that either loudspeaker could be muted, and the volume control which was well suited to both loudspeaker and headphone listening. However, it was found that the high noise at the worst case volume setting was particularly objectionable with headphones, and none too good with loudspeakers.

In other respects the noise performance was good, with the noise associated with the phono input being outstandingly good. Also the crosstalk between input source and across the tape monitor switch was unusually good.

The power bandwidth and both harmonic and intermodulation distortion were excellent at both half power and at 1W output with the intermodulation distortion at 100kHz being outstandingly low.

The amplifier includes two front panel meters which are calibrated in Watts with respect to 8 ohms and in decibels in relation to full power output, and whilst these meters do not read fast transients it is pleasing to say that they are much faster than meters fitted to many amplifiers. In addition, the meter sensitivity is controlled by a switch which provides an X10 sensitivity, and this completes the list of facilities.

The standard of construction of the Technics SU-7700 was very good both internally and externally.

Read all