Vreg or Ireg for Phono heaters

[fred76]

Hi,

Please bare with me, I'm not that knowledgable when it comes to the inner workings of circuits and the math involved, especially with sand in power supplies...

I have this phonostage build and it currently uses a single chip (fixed reg) that regulates voltage down to 6VDC for 4 Triodes, pulling ~1.3A.

I have no chassis space left for more sophisticated regulated heater circuits, like seperate regs for each tube etc., and it wasn't meant to be an 'ultimate' build anyway...

Now I want to replace the chassis heatsinked 1A fixed reg chip with an adjustable LM1806 (1.5A). It might run cooler with the higher spec. So now I have the option of doing Current Mode operation for the heaters... When reading forums (archives), subjectively most seem to like the sound of current mode better, but I don't know if it would be a wise implementation running it that way for 4 triode sections, with the overvoltage issues it might entail and all... What do you guys think? Should I just stick to Vreg? BTW, I have the B+ and Heaters in a separate PSU Box, with the reg chip in there.

I think the supply lacks some more capacitance..It has 8,800uF in total right now, that includes the input and output cap for the chip, with two more RC cells after the output cap.. I could still increase capacitance up to 17,600uF max (same value for each cell) if it helps lower ripple. And if I go with Vreg I coud make use of Cadj to lower ripple further.

I could also ditch any regulation altogther and just go Passive DC.. Even some of the more sophisticated phonostages I've seen have passive supplies. But those have large choke/s and other more elaborate 'tricks' etc. Most likely carefuly designed not to have any choke resonances along with the high value caps.

Thank you.

fred

[Steerpike]

If you do current regulation, you'll need to wire the heaters in series (or use 4 regulators). Seried's heaters gives a progressive voltage drop along the heater chain; is that bad? I'm not sure.

The heat generated by the regulator is dependent on (1) the voltage drop across the regulator and (2) the current flowing. Changing the regulator to a higher current spec chip doesn't change the heat output. If heat in the regulator is a problem, series-wired heater will help at lot.

Best plan: build a prototype series reg on strip-board & see what it sounds like.