Audio Database

Technics 20A
Commentary

High power stereo power amplifier with OTL circuit.

An OTL circuit is used for the circuit configuration. By wiring five new type 50HB26 beam tubes in parallel to the output tube, ordinary speakers can be directly connected.
We have also succeeded in reducing the distortion by minimizing the pre-NF distortion and limiting the amount of NF in the main loop to 30 dB or less. Moreover, by making the load resistance of each stage extremely small, the high-frequency characteristics are stable up to 200 kHz or more even without NF.

A 5-pole tube with excellent high-frequency characteristics is adopted in each stage, and large output can be taken out without strain up to high frequency.

The plates and screen power supply for the upper and lower stages of the SEPP are independent from each other, and the bridge method with small ripple voltage is adopted for the rectification of each plate stage, thereby suppressing hum during small output.

Equipped with a 2-stage switching mechanism that can switch between high output and low output.

Model Rating
Type Tube type main amplifier
Music Power (1 kHz)
High Power: 100Wx2 (32 Ω, Distortion Factor 0.04% or Less)
80Wx2 (16 Ω, Distortion Factor 0.06% or Less)
40Wx2 (8 Ω, Distortion Factor 0.15% or Less)
Low Power: 35Wx2 (32 Ω, Distortion Factor 0.06% or Less)
18Wx2 (16 Ω, Distortion Factor 0.1% or Less)
12Wx2 (8 Ω, Distortion Factor 0.5% or Less)
Rated Output (1 kHz)
High Power: 80Wx2 (32 Ω, Distortion Factor 0.04% or Less)
60Wx2 (16 Ω, Distortion Factor 0.1% or Less)
30Wx2 (8 Ω, Distortion Factor 0.2% or Less)
Low Power: 30Wx2 (32 Ω, Distortion Factor 0.06% or Less)
14Wx2 (16 Ω, Distortion Factor 0.2% or Less)
10Wx2 (8 Ω, Distortion Factor 1.0% or Less)
Frequency Response (16 Ω Load) 5 Hz ~ 100 kHz + 0 -0.5 dB
S/N ratio (IHEM standard, ASA standard, A-curve)
Input Short (1 hfm) High Power :

Low Power:
100 dB (16 Ω)
105 dB (32 Ω)
97 db (16 Ω)
103 dB (32 Ω)
Input Open High Power :

Low Power:
92 dB (16 Ω)
97 db (32 Ω)
90 dB (16 Ω)
96 dB (32 Ω)
Input sensitivity (at rated output)
High Power: 0.4 v (8 Ω)
1.0 V (16 Ω)
1.6 V (32 Ω)
Low Power: 0.3 V (8 Ω)
0.6 v (16 Ω)
1.2 V (32 Ω)
Input attenuator 3 dB step, -21dB decay
Input impedance 100k Ω
Damping factor High Power : 50 (16 Ω)
Low Power : 30 (16 Ω)
Semiconductor used
Vacuum Tubes (28 pcs) : 6267 : 2 pieces
12AU7 : 2 Pieces
6BQ5 : 4
50HB26 : 20 pieces
Diode (30 pcs) : SM-150A : 2
SM-150C : 4
SW-05B : 24
Pwer 100 VAC, 50/60Hz
Power consumption No signal : 500 VA
Maximum power : 900 VA
External dimensions Width 380x Height 185x Depth 370 mm
Weight 23.5kg