Cornet - 12AX7 tubes

Laudanum · « **on:** 4 Aug 2004, 11:42 pm »

Wondering if the 12AX7 filaments are connected in series or parallel in the cornet?

Thx

GRD · « **Reply #1 on:** 5 Aug 2004, 01:27 am »

I would think they are parallel (6.3V source, pins 4 and 5 to 9). But I tried a 7058 in place of the 12AX7 and it seemed to work. Got the 7058 in a bunch of used tubes which were 12AX7 or equilavent. Later read up on the tube and learned it was wired for 12V only. I was left wondering if the 7058 was mislabeled.

Laudanum · « **Reply #2 on:** 5 Aug 2004, 01:52 am »

Had to be mislabeled or filaments are series because I believe the 7058 would not operate otherwise. But that was why I was asking

GRD · « **Reply #3 on:** 5 Aug 2004, 02:07 am »

O.K. I just looked at the tube. It's an RCA (printing clearly visible) and very clearly labeled "7058". And it works. You might be on to something as the 7058 is a sleeper so I hear.

Grant