STAX CA-Y

Commentary

Control amplifier that uses newly developed super shunt regulator.

A super shunt regulator is installed in the power supply part.
The signal circuit of the amplifier operates by DC voltage. A power supply with high stability of DC supplied from the power supply, which can always supply a constant voltage even for dynamic sound changes, is excellent. In addition, various noise characteristics generated by the power supply itself must be taken into consideration. With these considerations in mind, the Super Shunt Regulator was developed aiming at a power supply with characteristics superior to battery power supply.
The power supply mounted on the CA-Y has features and specifications such as an output impedance of less than 1m Ω from DC to 100 kHz, a power noise reduction ratio of less than -106dB up to 100 kHz, an earth potential that is not affected by load fluctuations, and extremely low internal noise of less than 0.2 μ V (IHF-A).

Multiple feedback circuit is used for the amplifier circuit.
Even after the introduction of DC amplifiers, a coupling capacitor is needed in the preamplifier to eliminate DC drift. However, this coupling capacitor has a large effect on sound quality because all of the signal amplified in the previous stage passes through. The CA-Y uses a multiple feedback circuit to eliminate the coupling capacitor, literally connects the MM input to the pre-out directly, and lowers the cutoff frequency in the lower range without using a large-capacity coupling capacitor.
The basic circuit consists of a class A SEPP buffer amplifier added to two differential stages for both equalizer amplifier and flat amplifier. A low-noise one chip dual FET is used for the first stage, and in-phase feedback is applied from the second stage to the first stage to improve DC stability.

All circuits such as tone control, mode switch, and loudness are excluded in consideration of sound quality degradation.
In addition, the recorder is equipped with a recording out ON/OFF switch to prevent a capacitive load on the preamplifier caused by the shield line between the recorder and the tape deck when recording is not performed, which adversely affects sound quality.

There are two types of MAG input. MAG1 has fixed impedance and MAG2 has variable impedance.

The balance control uses a new circuit and is designed so that the signal does not pass through the resistor at the center position.
The variable range of this balance control is 0 to -6dB.

The internal parts are also considered.
We use air condensers (shaved brass plated with silver), styrol / polypropylene / Meiler condensers, low impedance electrolytic condensers for audio equipment, and metallic film resistors.
In addition, low-noise and low-distortion CP volume with good sound is adopted for the volume and balance control, and parts selected for detailed measurement and hearing are used for the substrate, such as glass-epoxy 300 μ - thick oxygen-free copper foils and wiring of gold-plated jumpers.

In consideration of operability and internal layout, the signal is designed to flow from right to left, and the position, size and shape of each switch and knob are determined.
We have also installed an indicator that shows the position of the push switch during operation in green text.

There was a head amplifier unit as an option sold separately for users who use MC cartridges.
The circuit of this unit has a two stage amplification configuration in which four pairs of high Gm FETs with PNP low-noise active load are connected in parallel at the first stage and received by an inverted Darlington circuit. In addition, a current balance circuit is provided to keep the current supplied from the power supply constant by canceling the current change in the amplifier section with the reverse phase current so as to prevent the influence of the large current change in order to reduce noise on the very small output voltage of the MC cartridge.
Since this option is self-contained, power is supplied from the super-shunt regulator. If this head amplifier is built-in, MAG1 becomes the MC input, and the word MC appears on the indicator.

Model Rating

Type	Preamplifier
Circuit configuration	First stage : Nch Dual FET Differential 2-stage 2-Stage : Emitter Grounded Current Mirror Load Final stage : 3-stage direct connection of push-pull emitter follower
Input Sensitivity / Impedance	Mag Pu1 : 2mV/47k Ω (MC head amplifier 70 μ V/100 Ω) Mag Pu2 : 2mV/30k Ω ~ 80k Ω (continuously variable) Cond Pu/Tuner/Aux/Tape play1, 2 : 143mV/42k Ω
Maximum allowable input	Mag Pu1, 2 : 180 mV (1 kHz) rms (THD0.03% or less) MC Head Amplifier : 30 mv (20 Hz ~ 20 khz) rms (THD0.03% or less) Cond Pu/Tuner/Aux/Tape play1, 2 : 2 v (20 Hz to 20 kHz) rms (THD0.01% or less)
Output Level / Impedance	Output1 : 1V/60 Ω (1 kHz) Output2 : 1V/160 Ω (1 kHz) Rec out1, 2 : 143mV/220 Ω (1 kHz)
Frequency characteristic	Mag Pu1, 2 : 20 Hz to 20 kHz ± 0.3 dB or less MC Head Amplifier : 2.5 Hz ~ 1 MHz + 0 -3dB Cond Pu/Tuner/Aux/Tape play1, 2 : 0.33 hz to 1.5 mhz + 0 -3dB
SN ratio (IHF-A network, input short)	Mag Pu1, 2 : 78 dB (at 2 mV rated input) MC Head Amplifier : 68 db (at 70 μ V rated input) Cond Pu/Tuner/Aux/Tape play1, 2 : 110 dB at 143 mV rated input
Distortion factor	Mag Pu1, 2 : 0.003% or less (at Volume max, 3 v output) MC Head Amplifier : 0.03% (at 100 mv output) Cond Pu/Tuner/Aux/Tape play1, 2 : 0.0015% or less at Volume max and 3 v output
Crosstalk	-70dB (10 khz, Volume -6dB, between MAG and Output)
Amplification factor	Mag Pu1, 2 → Output1, 2 : 54 dB MC Head Amplifier : 29 dB Cond Pu/Tuner/Aux/Tape play1, 2 → Output1, 2 : 17 db
Pwer	Supershunt system (constant current + shunt regulated circuit)
Constant voltage power supply input noise rejection factor	-100dB (DC to 100 kHz)
Power Supply Output Impedance	1m Ω or Less (DC ~ 100 kHz)
Residual noise	0.2 μ V or Less (IHF-A)
Power Supply Voltage / Frequency	100 VAC, 117 V, 220 V, 240V/50 ~ 60 Hz, ± 10% Each
Rated power consumption	28W
External dimensions	Width 435x Height 88x Depth 381 mm
Weight	6.0kg
Sold Separately	Built-in CA-Y MC Head Amplifier Unit IHA-Y (¥ 30,000)