OLD TRANSFORMER SPECS…

[HappyHourStudio]

The total heater current for the "new build" should be easy to calculate; just add up the current from each of the tubes. The B+ is trickier....does the Heath have a current meter?

Regardless, for the B+ download the FREE PSU Designer app offered by Duncan Amps. You can "what if" a ton of variables to arrive at a good solution.

Bri

PS, if doing a new build, don't overlook the toroidal transformers from Antek....excellent value.

Any idea if there are mac/ipad compatible PSU design apps? Actually, is there a good all around design app that I can test preamp schematics, etc.

Even if it costs a little. That’s fine.

 

[amplexus]

That 6.3 V is biased up to +34V which an SMPS may not be happy with.
Read the docs.

There's no need to elevate the heater string with DC if you're already using DC heaters....

 

[Brian Roth]

Any idea if there are mac/ipad compatible PSU design apps? Actually, is there a good all around design app that I can test preamp schematics, etc.

Even if it costs a little. That’s fine.

I'm a PC user and many engineering apps are Windows only. Perhaps a Mac user here will have some suggestions.

Bri

PS, if you get "stuck" on your design, I'll take a shot at with PSU Designer if I had some general specs for your project.

 

[HappyHourStudio]

I'm a PC user and many engineering apps are Windows only. Perhaps a Mac user here will have some suggestions.

Bri

PS, if you get "stuck" on your design, I'll take a shot at with PSU Designer if I had some general specs for your project.

Was thinking of getting one of these guys, but would need to knock that 20A down to exactly (or roughly?) 10.2A.

Is that realistic? I’m semi new to this. Currently reading Merlin’s “Designing Power Supplies for Tube Amplifiers” book…

 

[Brian Roth]

That 20 Amps rating describes the current the transformer can supply at 6.3 VAC output. You don't "knock it down" as you mentioned when using it to supply power at a lower current. However, when "lightly loaded" with 1/2 the rated current, that rated 6.3 V winding voltage will increase by an unknown amount.

In addition, I also see the primary voltage spec is at 115 VAC. In most places in the USA, the voltage from the power utility is 120 VAC or higher. That, combined with the "light loading" of the secondary will result in the voltage to be a (unknown) voltage greater than 6.3 VAC. Maybe not enough to be worried about Do you have that transformer in your inventory?

Bri

 

[Cqwet Dbdfte]

The DC bias of filaments are needed to keep the cathode to heater potential within spec, normally used for cathode followers. It is unrelated to DC or AC heating.
LTspice is a free circuit simulator and has a very large user community. Mac OS? Did not check, but Linux Wine is OK.
With that voltage doubler circuit and low current requirement a common isolation transfomer is an option.
Heating does not require tight tolerances but a little lower will promote longer tubelife.
Regulated DC is most common these days for heating, unrealistic in the past.

 

[Cqwet Dbdfte]

LTspice has native MacOS support.

 

[gilmorneau]

Any idea if there are mac/ipad compatible PSU design apps?

If you're still working on this, PSUD2 has always worked well for me. It's here:
https://www.duncanamps.com/psud2/
But it looks like it's only for Windows.

 

[CJ]

Note hat if you use a 20 amp fil xfmr for a 10 amp load, the voltage might be a but high as regulation is going to depend on the DCR of the heater winding and the current flowing through that wind.

Ex: a wind with 0.1 ohm resistance will drop 2 volts at 20 amps and 1 volt at 10 amps.

So you could end up at 7.3 instead of 6.3 if underloading the xfmr.