Audio Database

SQ78
Commentary

The pre-main amplifier introduced in the copy "This is SQ78, not SQ38 or SQ77".
While inheriting the design philosophy of SQ38, it adopted a design similar to SQ77 SQ77, and was developed as an amplifier with conditions for beginners.

The main section uses an improved circuit based on the Altec circuit using 6AN8.
DC feedback is used to improve the stability of the direct-coupled stage, so that even if an arbitrary vacuum tube is replaced, it is always kept within the optimum operating point automatically.
In addition, measures are taken against the negative effect that the high-frequency characteristics deteriorate as the volume changes.

The newly developed COH type output transformer is used, and a stable amplifier with 14 dB NFB is used.

Included circuits include a headphone jack, low - and high-cut filters, a tape monitor, a left and right channel mixing circuit, a tone control, and a balancer.
In addition, a low-pass reinforcement circuit is mounted.

Model Rating
Type Tube type pre-main amplifier
Output 10W+10W(50Hz)
Distortion factor 1% or less
Frequency characteristic 20 Hz to 40,000 Hz 1.5 dB or less
Input Sensitivity / Impedance Phono : 27mV/50k Ω
Tape Head : 2.7mV/100k Ω
AUX1, 2 : 260mV/100k Ω
Monitor : 400 mv (1 khz) / 90k Ω
Signal-to-noise ratio Phono:57dB
Tape Head:55dB
AUX1, 2 : 70 dB
Monitor:76dB
Tone control LUX method
Attachment Tape monitor
Headphone jack
Low boost switch
Scratch filter switch
Used vacuum tubes, etc.
Vacuum Tubes (9 pcs) 6RA8 : 4
6AN8 : 2
12AX7 : 3
Silicon Diode : 4 pieces
Power consumption No signal : 110W
Maximum output : 120W
External dimensions Width 348x Height 130x Depth 215 mm
Weight 8.3kg