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The Stax SRM-T1 is a high-voltage amplifier and bias source for Stax' electrostatic headphones.

The SRM-T1 has two Professional and one Standard outputs, so any Stax earspeaker ever made since 1959, from the original SR-1 to today's SR-009, works perfectly. Stax calls its headphones "earspeakers".

The SRM-T1 is a tube-output, pure class-A, DC-coupled amplifier. It has no capacitors or transformers in the audio path. It's housed in a completely non-magnetic case to ensure no pevent any inadvertent electromagnetic coupling. It uses two 6FQ7/6CG7 vacuum tubes in its output stage.

It has enough output to deafen us with any of Stax' headphones, without any distortion.

It is fed from any device with 1/4" RCA jacks, or even directly from iPods and iPads The SRM-T1S is the same as this SRM-T1, except for a switchable input selector.

Frequency Response

DC-20 kHz ± 1dB at 100 V RMS driving an SR-Λ Signature 1.

Appreciate how no other amplifier rates its performance actually driving a real, reactive load as Stax has rated this amplifier.

Distortion

0.02% at 100 V RMS driving an SR-Λ Signature 1.

Again, this is real performance driving a real, reactive load.

Line Voltage: Rear-panel selectable 100 V, 117 V, 220 V or 240 V.

Frequency: 50 - 60 Hz.

Power Consumption: Rated 45 Watts. With the main amplifier off (red pilot light) but the pre-heater left on (green pilot light only), it's rated 12W.

 

The SRM-T1 is built internally more like a piece of military or industrial hardware than almost anything from what passes for professional audio gear today.

The big volume control knob just glides. In fact, the Alps potentiometer is so smooth and the knob so big that you can spin it and it keeps going by inertia.

The amp is built on a heavy inner aluminum chassis with nonmagnetic top and bottom covers, and a solid aluminum front panel.

Stax deliberately made everything nonmagnetic to eliminate unintended audio interactions.

The nonmetallic metal covers are held in place by machine screws screwed into solid metal inserts. Stax never got lazy and tried to use self-tapping bung screws; they took this very seriously.

Now for the best part:  my friend, a well-known recording engineer, apparently could still hear some vestiges of noise (which I could not hear as it was at some unmeasurable levels).  He has added a whole lot of the ultra-high grade, ultra expensive Rel-Caps and some $$$ resistors.  He kept at it until he was satisfied.  This cost me over $1200!  But let me tell you, it was well worth it.  Altough I did not hear it as noise, when he was done, the amp and the headphones simply vanished, and all I could hear was music, as if I was right there!  The tubes are the famous RCA clear tops, the best tubes for these amps (pix show Sylvanias, which I liked less). I probably have spares, and I will include them if I have them.

 Cosmetically, the amp is in excellent condition.  The were a few tiny scrapes on the top cover which I touched-up with a marker.  You can see these in one photo.  Front and rear pictures show some dust.

Sorry, I do not accept returns.