CurtZHP
Well-known member
Building a tube preamp that uses both stages of a single 12AX7 tube. Fairly simple circuit, and so far it works great.
I'm running into an odd issue that affects the filament supply. By the way, I'm using Jakob's power supply PCB that he threw in with the G9 layouts to power this thing.
Anyway...
I was fooling with an idea that involved adding a second tube to the circuit, but when I tested it, I found that the circuit would pass audio for maybe less than 30 seconds and then suddenly lose power. The audio would fade out. At some point, I nixed the extra tube and moved on. (Decided to keep it simple...)
Now I'm in the process of powering the two small lamps inside the VU meter. I'm powering them from the filament supply. Same exact issue! It runs for several seconds, then craps out. The lamps go very dim, then the audio starts to fade until it's gone.
Plate supply still looks good.
I can unplug the unit, wait a little while, plug it back in, and it'll work fine, until it craps out again.
Thoughts?
I'm running into an odd issue that affects the filament supply. By the way, I'm using Jakob's power supply PCB that he threw in with the G9 layouts to power this thing.
Anyway...
I was fooling with an idea that involved adding a second tube to the circuit, but when I tested it, I found that the circuit would pass audio for maybe less than 30 seconds and then suddenly lose power. The audio would fade out. At some point, I nixed the extra tube and moved on. (Decided to keep it simple...)
Now I'm in the process of powering the two small lamps inside the VU meter. I'm powering them from the filament supply. Same exact issue! It runs for several seconds, then craps out. The lamps go very dim, then the audio starts to fade until it's gone.
Plate supply still looks good.
I can unplug the unit, wait a little while, plug it back in, and it'll work fine, until it craps out again.
Thoughts?
