NOCTURNE JR BARNYARD OD
Back in 1935 the days of the first Jazz Electric guitar what few amp makers came and went were the first to use the new 8 pin, 11/16" RCA 'octal tubes'. Octal was the name they gave the base of the tube. It soon became an industry standard word wide and today it is a rare amp that does not use them. The earliest tubes sounded different as you may expect many makers refined or specialized designs for different functions. To get to the point Nocturne has attempted to capture the tone of these early amps in a pedal. The Nocturne sets out to simply capture that sound. In fact they provided a circuit for Bass and even a microphone.
CONCLUSION
It is an interesting but not an overly practical idea. The effect is all about a subtle even if pleasant sound.
Many amps own sound are going to not blend with it let alone they will take over with their own sound. I think it might even sound best thru a very neutral sounding clean channel of a transistor amp. Ideally the cleanest sounding Fender tube amps might benefit from at least the blend.
TRIVIA
Why do vintage amps often use a 'Tweed' cloth?
Early amp makers had a very small niche market. They were much like the gourmet amp or pedal makers today. Nearly all were too small to have a carpentry shop to make cabinets. In those days industry was regional. Every state would have at least one small company that made luggage. You guessed it. Early amps were built into what is just really a suitcase. The covering, the handles etc. were nothing more than what were on the suitcases of the day. Often just small openings were cut out to let the sound of the speaker thru as there was very little else than the thin side of a suitcase to hold them up.