The 1578 that I got was made in 1980.
The 1578 that I got was made in 1983 not 70's.
8n6s Nos tube was made in 12/78.
Even without 1578 notation, some tubes are still pretty good for the price.
QUAD FOUR Matched Balanced Russian 6N8S 6SN7 double triode TUBE NEW NOS | eBay
After listening to 1578 Melz, I am back to Nos 6n8s tube made in 1978 that I got quad at 46$.
By the way i got my first serious audio system on 1978.
What a coincidence.
This is a steal.
It sound musical with good balance of full bass and sweet treble.
Jump at it before they run out of this batch.
After listening to 6n8s tube made in 1978 for several hours, I am back to Kenrad vt 231.
KR also has nice bass with sweet and refined atmostphere.
Definitely KR vt231 is at least half notch or even one notch above 6n8s .
Now I have 16 different variants of 6sn7 tubess.
After changing tube, sound also change as if new pre is being used.
It is like tasting various wines or coffees.
But if you do lot of tube rolling, be sure to use socket saver.