This has been covered before, but I'll offer it up:
If you have a spare 5.0 VAC winding (or add a small transformer for five or six volts ac at an amp or so), build a simple voltage doubler, then regulate it back down to 6.0 VDC using a 7806 or similar chip, and you can enjoy the near silence DC filaments can offer. Hope we're not over the OP's head here.
FUCHSAUDIO wrote:This has been covered before, but I'll offer it up:
If you have a spare 5.0 VAC winding (or add a small transformer for five or six volts ac at an amp or so), build a simple voltage doubler, then regulate it back down to 6.0 VDC using a 7806 or similar chip, and you can enjoy the near silence DC filaments can offer. Hope we're not over the OP's head here.
If you have the current sure that works fine, you'll need double the current as well as much bigger caps.
I still say for $20 a switcher and you are done, or use a 25VCT and use 12V heaters
I'm running dual 6800 UF's per cap section, and it gives me plenty of overage from a 5.0 VAC winding. About ten volts DC, into a 7806, gives you plenty of overage to stay clean and hum free, and to not lose regulation if the line drops. One 7806 can handle a pair of 6.0 V 12AX7's, and you can mount on the chassis for "free" heat sinking...
Switchers are another option, although I prefer to stay analogue...
I have bridge-rectified a 12.6V Radio Shack 1.2A transformer (seal off the center tap), regulated that down with a 7812 to 12V, and powered 3 12AX7s with it. 2 1000uF caps get the job done. I also use the chassis as a heat sink. Works just fine. Helped my Express be just a little bit quieter. At 12V I'm only using 0.45A for the 3 tubes, so the 1A capacity of the 7812 is not in jeopardy, nor is the 1.2A capacity of the transformer. As a bonus, the wiring is simpler - don't have to connect anything to pin 9. If I wanted, I could connect either pin 4 or pin 5 directly to ground and just run one 12V wire to all tubes.
Wife: How many amps do you need?
Me: Just one more...
mlp-mx6 wrote:I have bridge-rectified a 12.6V Radio Shack 1.2A transformer (seal off the center tap), regulated that down with a 7812 to 12V, and powered 3 12AX7s with it. 2 1000uF caps get the job done. I also use the chassis as a heat sink. Works just fine. Helped my Express be just a little bit quieter. At 12V I'm only using 0.45A for the 3 tubes, so the 1A capacity of the 7812 is not in jeopardy, nor is the 1.2A capacity of the transformer. As a bonus, the wiring is simpler - don't have to connect anything to pin 9. If I wanted, I could connect either pin 4 or pin 5 directly to ground and just run one 12V wire to all tubes.
I would use a LDO regulator since otherwise you could be the edge with punch through on a 7812, especially if the wall voltage dips a bit.
