Minute Passive Pre-Amplifier
with Silk Transformer Volume Attenuator STA-522A

SACThailand proudly presents our own 100% handmade Supermalloy Transformer Attenuator in our new Passive Pre-Amplifier chassis.



Fully passive to fully realize the most clearest and purest line stage of all, at the heart of the new Minute Passive Pre-amplifier lies SILK STA-522A, the most sophisticated small signal transformer that attains extraordinary performance from its Supermalloy core material & SILK winding technique on highest purity OFC wire. This new edition of passive pre-amp is offered in a new package to match all our "Minute" range of Audio Amplifier. The unit contains 3 set of RCA inputs (selectable), 1 set of RCA output, 0dB/+6dB switch.


Resistive type of passive attenuator

In a typical resistive type of passive attenuator (using discrete resistors, or using just a potentiometer) there is always an addition of at least 10K, 20K or 50K ohm (depending on the version you installed) of added resistance to your source output impedance, thus making your source apparent output impedance goes much higher resulting in adding noise, lower damping factor and reducing frequency bandwidth. (Imagine connecting high resistance speaker cable in between your amplifier and your loudspeaker, several bad effects would certainly happen from such act) Also 10K ohm resistive element type passive attenuator forms very tough load to your source output. At 2Vrms signal, 10K ohm load will draw 0.2mA of current.  

Minute Passive Pre-Amplifier circumvents the above issues by utilizing transformer attenuation method that offers much higher impedance at +1 Megaohm range at 1KHz so at 2Vrms signal, the transformer will draw much less than 2uA of current (<0.002mA). +100 times less current drawn than resistor attenuator type. Another benefit of using transformer attenuation is its low DC resistance device at both input and output coils (in range of much less than 1 Kilo ohm). This low DCR characteristic forms easy path for noise or ghost voltage to bypass to signal ground. The figure is +10 times more effective than typical resistive element type passive attenuator. (dilemma to resistor attenuator is that it can't be chosen too low value since it will load the source and create unacceptable distortion & poor bandwidth, can't be chosen too high value since it will be inefficient to suppress induced noise)

Last but not least SILK STA-522A can amplify signal by doubling its output (+6dB function) to drive low sensitivity Power Amplifier which the resistor passive type could not do. Should there be a need to make phase correction in the out-of-phase audio systems, special arragement could be had for the phase inversion of signal modification since transformer can invert signal phase by just switching the coil arrangement (resistor could not do this).


SILK STA-522A Transformer attenuator (info Click)
SILK STA-522A continues to be the best alternative over resistive type passive pre-amplifier as well as other active line stages in many audiophile systems owing to its low signal resistant whilst processing unprecedented high impedance from input to output section which causing the elimination of almost all signal impurity. By completely winding our own STA-522A transformer in house for more than 8 years of its production, we can absolutely maintain the secret ingredient and develop special techniques to ensure that the quality and performance of STA-522A is always at the highest level to any other brands on the market.  
  New Minute Passive Pre-Amplifier internal parts are point to point hand wiring with silver solder and silver plated/
Teflon insulated wiring. The switches are highest quality 23 steps 2 decks gain selector is from SEIDEN (Japan)
that has gold plated contacts which offers very smooth rotation feel with very accurate tracking and very pure signal connection.
Dimension ( W x D x H ): 16 x 24 x 9 cm.
Weight: 2.2 Kg.