Counterpoint SA-6 tube headamp

Counterpoint SA-6 Moving-Coil TUBE Headamp at AllegroSound.com
SA-6 is a precision-engineered, highly accurate Moving-Coil cart step-up device.
Several new pre-preamplifier circuit improvements have been developed for SA-6:
- Mute/Operate switch to eliminate pops and thumps during warm-up.
- Bias Level control to compensate for tube aging and matching to cartridge.
- Regulated filament voltage for long tube life and consistant sonic performance.
The SA-6 uses the best components available for each application.
The audio & power supply circuitry use German Roderstein "Resista" resistors.
Capacitors are metalized Polypropylene with Styrene bypasses.
Resistive loading of Moving-Coil cartridges is accomplished on the circuit board
with Micro-Jacks, allowing you to use the value and type of component you desire.
Reference-quality amplification of Moving-Coil cartridges is assured by the SA-6.
Once you have enjoyed the outstanding performance of the SA-6, you will
understand why Counterpoint has earned the replutation of continually striving
for sonic perfection. Your Counterpoint SA-6 will give you decades of fine
music reproduction, and will be a valued part of your home stereo system.
The Audio Circuit of the SA-6 uses one 12AX7 Dual Triode per channel.
Both triode sections are operated in parallel with a fixed bias source,
thereby allowing a wide dynamic range and excellent signal-to-noise ratio.
Negative Bias voltage is applied to the grids of the tubes through a high
impedance network de-coupled to prevent crosstalk. The absolute BIAS
LEVEL and hence the idle current of the tubes is adjustable means of the
BIAS LEVEL TRIM potentiometer. The input of this stage is capacitorcoupled to prevent D.C. Bias voltage from entering the phono cartridge.
Using fixed bias permits the cathodes of the tubes to be tied to groundpotential resulting in maximum gain with a minimum of noise, and eliminates
the need for sonically-unacceptable electrolytic cathode resistor bypass caps.
The power supply utilizes solid-state rectification & regulation. The rectified
and filtered B+ voltage is regulated using a 2N3440 as the pass device.
This pass element is contrilled by a zener voltage reference fed by a constantcurrent diode to assume immunity of the SA-6's output to line-voltage variations.
Each channel is then individually de-coupled to prevent crosstalk. Solid-state
regulation of tube filaments is accomplished with an adjustable voltage regulator.
Gain: 26dB (20X).
Bandwidth (uncompensated, 47k Ohm, 180pf load): -3 db at 1Hz & 30kHz.
Signal to Noise ("A" Weighted, RIAA equalization de-emphasis): -90dB with 10mv
reference.
Distortion (1kHz, 1Volt out, varies with bias setting: 0.06%.
Input Impedance: 47k Ohm, user adjustable.
Output Impedance: 16k Ohms.
Absolute Phase: Inverting (reverse leads at pickup).
Crosstalk at 10kHz: -80dB right-to-left, left-to-right.
Max Output: 30 Volts p/p.
Power Draw: 20 Watts, 100~130 VAC, 50/60 Hz.
Tube and Semiconductor complement:
2-12AX7 audio amplification V1 & V2.
1-2N3440 transistor series pass device.
4-1N4007 diodes high voltage rectifier.
1-FW100 diode bridgefilament rectifier.
1-LM317 integrated circuit filament regulator.
3-1N5378 zener diode regulator voltage reference.
1-1N5368B zener diode regulator voltage reference.
1-CR160 constant current diode, current source for voltage reference.
AllegroSound (Est.1973)
htp://www.AllegroSound.com
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