How low can you go?

[Andy Le Blanc]

That stuff used a chopper.... A switching device to make pulsating dc (ac)
then stepped up...

A "non-synchronous vibrator and rectifier circuit" the old Buick had a 250v B+.

Power scaling, vvr is for more attenuation, with a better tone.

[David Root]

'50s car radios ran off 90V batteries. These are now made from unobtainium.

[martin manning]

The battery works, dont know how long it'll last with the heater.

About an hour and ten minutes based on an Energizer's stated capacity of 350 mA-h @ 300mA. Nice job, Andy, now that's what I call point-to-point!

[Andy Le Blanc]

Ahhhh...... that's the number, the practical was much less.
The first turn on with a battery was good, the second not so much.
I was thinking of trying a 12av7, I vaguely remember a purpose for the type
???? any way..... I found a 500ma 12v dc wall wort to try, and a 1000ma 9v ac..
It really can be fun to noodle, especially with a relatively safe voltage.
I've always liked the simplicity of zero bias, I think the gain pot. might be better
with a much lower value taper, 5k, 1k, you can really hear how the bias
changes the response, but it's a very tight little range.
That style build reminds me of a basic transistor project, there was never much to
even many of the early EH products, mojo-a-rific cheese.

I think you can still source 45v batteries, choppers used to be very common.
its an early inverter, put the dc into a convertible form, even the cheap
inverters that plug into the old lighter socket
put out a choppy sine form, some electronics do ok, some don't like it

[Andy Le Blanc]

I've got all these random old wal-worts from when I used to bother with pedals.

Now the biggest issue besides V was the ac hash making it to the effect,
and the random 9v battery eliminator was making 16 v, jezzz.....

I put a 50 ohm rheostat between two high value caps, 50v 4700uf, and
dialed in the voltage from 2v to 14 v like any dc filament supply.
good way to control the V and kill the buzz. This should work ok for a pedal
supply, if the pt your using has a large enough current rating for the load
you intend, it is nice to dial in the voltage for the load and not guess about
voltage conditions affecting tone.

That little tube dirt circuit seems to work best as a light on lights off effect.
just the color of circuit is enough distortion, its doesn't get like a ss pedal
its soft, another tinker toy, It makes a paraphase tone pretty good.

A 9V tube circuit, just enough to get the 12v heater going.

[Aurora]

Old choppers are too inefficient.....
there's plenty of modern DC-DC converters on the market...ain't cheap, though.....

[selloutrr]

I built a valvecaster a year ago that runs on a boss 9V 400ma wall wart happy as can be.

It's voiced entirely by the tube you use. With a ***** ge it's very stoner rock QOTSA. Kinda neat but still not a vt40 of course.

The tone control left room for improvement it could be more responsive.
I had more fun painting And baking the housing in a toaster oven then the building or playing with it.

IMHO yes. It works. Yes it's worth a listen. Try to make friends with someone who has built one cause it'll prob collect dust like mine does.

[tubeswell]

How long does the battery last running the fil.?

Probably about 5 minutes of decent sound