AMT Electronics Tube Guitar Series SS-20 Guitar Preamp
The SS-20 Guitar Preamp from AMT Electronics has incredible Clean, Overdrive, Distortion, and Lead tones in a compact tube valve driven pedal. AMT is raising the bar in guitar pedal design and offers affordable high end tone pedals. This one is going to be finding its way onto lots of pedalboards. AMT's principle and motto for this device is it is the VALVE that sounds and sings, however, the transistors do their best to help it sound in all its beauty and originality.

In order to achieve the full opening of input valve cascades working in the "hottest" conditions the giant amplitude of one hundred and more volts is necessary. The dynamic properties characteristic to valve—based preamps are implemented in the SS-20 preamp due to the elimination of signal limiting OA (feed level of 20-25V) in the part of preliminary amplification and using special cascades capable of reaching 250V amplitude with nonlinearity similar to a 12AX7 triode. Thus, AMT has managed to achieve full dynamic characteristics of guitar signal without usual hybrid "squeeze" as well as assign special sound character to SS-20.

Special attention was also paid to to the SS-20's clean channel—in this section AMT has also followed the way of preserving the dynamics of guitar signal with simultaneous formation of soft "nonlinearity" inherent in the cascades on vacuum triodes. It also allowed us to escape both the "squeeze" and "refinement" peculiar to many clean-channels of hybrid devices.

The basis of the inner preamp structure is the principle of maximum use of amplification and nonlinear transformation of the valve part of the device. Thus, the semi-conductor part of the hybrid practically does not participate in the sound limitation (except for the use of preamp in LEAD mode at Gain LEAD level of higher than 7) and the entire spectrum is formed by the valve preamp part. In the preamp stage the quantity of semi-conductor cascades is not used in the sound processing, and in the absence of jacks in SEND and RETURN the signal is forwarded to OUTPUT through compensating circuits directly from the output triode cascade. Therefore it is advised to use high quality minimum length cables for connecting the preamp output with guitar amplifier input.

The SS-20 guitar preamp uses the original cabinet emulator, however, ONLY in direct out mode. It models the amplitude-frequency characteristics of guitar amplification systems for the most accurate reproduction and ease of recording direct. Secondly, it simulates own nonlinearity of dynamic head peculiar to instrumental loudspeakers, that in its turn colors the output signal with short-range harmonics making it live and closer to real. AMT's unique speaker emulator circuitry supplements the signal with 2nd and 3rd harmonic with smooth increase in their level at signal level growth (it actually is similar to instrumental head in the closed cabinet), not found on other manufacturers pedals.