Solid state tube replacements

[Axtman]

I think I vaguely remember these….but then I vaguely remember what I had for breakfast this morning.

I am not sure when they were introduced. They came in 3 flavors: red (high), amber (medium) and blue (low) gain. They probably did not take off because we already had a big supply of preamp tubes readily available. Maybe production will start back up?

https://www.youtube.com/watch?v=3YdrNjipRgo&t=5s

[glebert]

I have one of those that I use as a "golden tube" for diagnostics. I figure it won't go microphonic or be sensitive to heater noise (although I've never investigated if it does anything with heater voltage). I think it sounds fine, I would consider using it in some bass amps but the glow from the LED is silly bright.

[stokes]

Mesa was using these for a very short time in their MKII series amps.They only used it in a small number and got away from them for some reason.They are called fetrons and I believe they can still be found.They use different voltages than typical 12AX7 voltages and Mesa had a switch to lower the voltage when using the fetron.You could also flip the switch back to use the 12AX7 in its place.

[Mick Bailey]

Does anyone remember the Carlsbro amps fitted with solid state 'tubes' (Valves as we call them over here). They had embedded red LEDs to give an unconvincing glow. I've never played through one, but they were advertised in the music press in I think the early 80s.

[g1]

It seems that the Jet City Retrovalves are no longer in production. I was going to suggest the AMT 'warm stone' solid-state tube replacement, but AMT is a Russian company, so I don't think they will be exporting until Russian tubes are once again available.