I just finished a tube DAC with 10 tubes, and I'm using a Pete Millett DC filament supply. The DAC calls for 6.3VAC at 3 amps, but can be replaced with DC supply. I'm feeding the Pete Millett supply with 7.5VAC 80VA, and the diodes are getting too hot for my liking. My thermapen, which isn't really meant for hard surfaces, shows about 180-190 F. Within the operating range, but they are heating up the caps nearby.
Are there any other recommended 6.3V supplies? I looked at the TentLabs, but ordering is kinda weird with them.
Are there any other recommended 6.3V supplies? I looked at the TentLabs, but ordering is kinda weird with them.
https://www.mouser.com/ProductDetail/Hammond-Manufacturing/166N6?qs=dhCoiiGcT1IAXD2gHZeluA%3D%3D
Do you have schematic of the tube DAC?
Do you have schematic of the tube DAC?
Here is the relevant portion of the schematic. The original design called for using the 6.3VAC tap of a transformer with at least 3 amps. That does the heaters, then goes to R137 and R138.
I followed what other builders of this DAC have done and instead of using a 6.3VAC transformer tap, I used a 6.3VDC regulated supply. In this case, the Pete Millet one.
I have the regulator sufficiently cooled, but the diodes get too hot. I have it set to 6.3v under load. It was 6.3v unloaded but dropped to about 5.6v under load before adjustment.
I followed what other builders of this DAC have done and instead of using a 6.3VAC transformer tap, I used a 6.3VDC regulated supply. In this case, the Pete Millet one.
I have the regulator sufficiently cooled, but the diodes get too hot. I have it set to 6.3v under load. It was 6.3v unloaded but dropped to about 5.6v under load before adjustment.
Attachments
Does Pete Millet circuit going 7.5 ac to 5 dc for 300B? Look like you are underload that got overheat. You can do 8.5 ac to 6.3 dc. Since you have 7.5 ac, you may look for AC / DC to DC Buck Step Down
The output voltage of your transformer is too low. You need at least 8.5V / 6A /51va. output. Hang a scope on the output, would not be surprised if there is ripple on the DC.
You can use the Duncan power supply simulator to model the circuit up to the LDO regulator.
Surplus Supply of Nebraska has a 8.5V / 6A transformer that will work.
Dan
You can use the Duncan power supply simulator to model the circuit up to the LDO regulator.
Surplus Supply of Nebraska has a 8.5V / 6A transformer that will work.
Dan
What is the regulator chip? A LD1084 would be an option. I have an existing board with L200 but that only supplies 2.5A max, it could however be reworked for LM338/LD1084/LT1084 if you are serious.
Cheers,
V4lve.
Edit, had some spare time, this is the board i came up with.
Cheers,
V4lve.
Edit, had some spare time, this is the board i came up with.
Attachments
Last edited:
