Electra-Print 5687 single ended prototype tube amplifier.

This prototype was built in 2021. The very large cathodes of this dual triode, the 5687, made me curious.

The power is 6+ watts per channel, and very clean, no NFB needed.

This is operating in class A2 or A3 depending on the tube used, and into 15K output transformers to 8 ohm load. A2-3 is a voltage/current shift of A1 operation. This tube can take and develop much more power and input sensitivity. Most other tubes like this one cannot go to A2 etc.

The results are very good. No distortion and full music bandwidth and exceptional staging and detail.

Best to be used on near 100+db speakers and with a powered subwoofer on the right channel for these lower power tube amps.

This has balanced pots on the rear to center and set playing levels of music perfectly.

Operational papers (do’s and don’ts) are supplied for proper placement/operation and two extra output tubes.