Hi,
Received two 6N7G tubes - one Arcturus and one Sylvania.
There is no identifying information except what you see here. Arcturus was founded around 1927 and went out of business in the 1940's. The name continued being used for rebranded tubes until the 60's. The tube looks old so I am guessing that it was made around 1940, but only a guess.
Interesting innards:
Here is the Sylvania 6N7G: It's name is engraved on the base the same as the Arcturus, but it has a date code of 8 D R and the symbols 7 D on each side of the name (no silk printing on the glass of either tube).
Another guess - the tube was made in April 1948 (1938?) in factory R. 7 D? Oskari - what do you think?
A couple of pictures of the internal construction:
At the bottom of this picture the newly discovered display stand can barely be seen - a roll of 3/4 inch scotch tape with the tube resting in the inside circle. (A little scary; after all it's glass, but what don't you have to do for the sake of furthering the understanding of antique and presumably rare radio tubes.)
In a post yesterday I described the wonderfully wide and holographic sound stage and sweet mid range of these tubes. BUT, do they sound better than than my beloved C3g tubes?
I decided to A/B the C3g and the 6N7G while listening to a high quality mono recording and moving the balance control right and left on my integrated amp with the Elise doing the preamp function.
https://www.youtube.com/watch?v=tftUXJ_uBPA
This tune was recorded in 1929 and is aptly called "Nervous Tension." Has plenty of detail and percussion and fits into the Arcturus time period.
Disclaimer : This method only highlights the differences between two tubes, but it does NOT describe the differences between the two sets of tubes since the synergy is missing - the sum total is greater than the sum of the parts. You just get two different halves of the recording with this method with the Elise.
Ok, I got it off my chest... The C3g goes lower, has more slam and impact and a more chiseled treble. The 6N7G is overall warmer, sweeter and more musical with a beautiful mid range and tonality. The C3g tubes do not match the holographic presentation and the wide and deep sound stage of a pair of 6N7G tubes.
Will finish with a true story to describe how I feel about which tube is the best: A lady comes into a shoe store and tries on winter boots. Finally she narrows it down to two different pairs. The salesperson asks which pair she wants to buy, and the lady answers: I can't make up my mind, I'll take both!
