I'm Getting 156VDC on the secondary before a bridge rectifier using the 260V tap using antek AS-05T280.
http://www.antekinc.com/as-05t280-50va-280v-transformer/
and 4 HER208G diodes here:
https://www.mouser.com/datasheet/2/258/HER201G-HER208G(DO-15)-479248.pdf
I think this is causing the 12.6V winding to have rectifier induced heater hum described in Merlin B's book "Designing Power Supplies for Tube amplifiers" page 194.
The Scope image below doesn't appear as extreme as the one in Merlin's book. but I am having a hell of a time getting AC Heaters quiet. Elevating them to 68V via the CT got me to -60-55 dBu. He says bridge rectifiers are more prone to this rather than the "2-phase" 2 diode with CT traditional tube supplies. before elevating the Hum Buzz and general HF hash was horrible. I tried Humdinger and balance resistors to pin 9 on the input valve. But Elevation seemed the best. The noise his highest at 60 Hz with some funky HF hash and buzz below 80-90 dBu.
The B+ is going from 47R to 68uF to 1K1 to 68uF to 1K1 to 44uF and feeding a McCurdy AU300 type PP preamp PCB. The ripple seems tame and pulling around 16 mA going to 12u7 at 285-290 VDC via a Cinemag 9600T.
Anyone have any thought's? Merlin? Is this particular to Toroids?
Scope of 12.6 VAC
http://www.antekinc.com/as-05t280-50va-280v-transformer/
and 4 HER208G diodes here:
https://www.mouser.com/datasheet/2/258/HER201G-HER208G(DO-15)-479248.pdf
I think this is causing the 12.6V winding to have rectifier induced heater hum described in Merlin B's book "Designing Power Supplies for Tube amplifiers" page 194.
The Scope image below doesn't appear as extreme as the one in Merlin's book. but I am having a hell of a time getting AC Heaters quiet. Elevating them to 68V via the CT got me to -60-55 dBu. He says bridge rectifiers are more prone to this rather than the "2-phase" 2 diode with CT traditional tube supplies. before elevating the Hum Buzz and general HF hash was horrible. I tried Humdinger and balance resistors to pin 9 on the input valve. But Elevation seemed the best. The noise his highest at 60 Hz with some funky HF hash and buzz below 80-90 dBu.
The B+ is going from 47R to 68uF to 1K1 to 68uF to 1K1 to 44uF and feeding a McCurdy AU300 type PP preamp PCB. The ripple seems tame and pulling around 16 mA going to 12u7 at 285-290 VDC via a Cinemag 9600T.
Anyone have any thought's? Merlin? Is this particular to Toroids?
Scope of 12.6 VAC
![Heaters%205.8.18.JPG](https://proxy.imagearchive.com/f3f/f3f5c51313a68563bce8f891cfced7fe.jpg)