anyone tried this mojotone product?

[Milkmansound]

It takes the 6.3V heater supply and dumps it down to 5-13VDC

http://www.mojotone.com/amp-parts/Pedal ... srf0KUVVmj

think this might be juts the ticket for getting DC onto sensitive preamp tubes, but I have no idea what the output current is. I have an email into them and will post more when I hear more.

[Colossal]

Looks like a run-of-the-mill voltage doubler circuit with an LM317 or equivalent regulator chip and adjustable output. I would question whether that circuit has sufficient capacitance and filtering to make for truly quiet DC filament work. Depends on how big those caps are.

[roberto]

Take care that an inceease in voltage means a decrease in current, so your heater's winding could be not enough for the whole amp.

[mhartman]

On my latest build, I just used a bridge rectifier and a big cap (10,000uf) on the 5VAC taps for the DC heaters on the preamp tubes. It works out to about 5.5VDC, which seems to work fine (see pic - the square rectifier and cap near the power section is for the preamp heaters).


https://tubeamparchive.com/viewtopic.php?t=23439

[Milkmansound]

Looks like a run-of-the-mill voltage doubler circuit with an LM317 or equivalent regulator chip and adjustable output. I would question whether that circuit has sufficient capacitance and filtering to make for truly quiet DC filament work. Depends on how big those caps are.

thats a good point - but the caps can always be upgraded to a higher value. I ordered one up so we'll see what it is in a week

I would just want to run 1 or 2 preamp tubes off DC. Reverb driver and PI can stay with AC - so a 1A supply should be ok if the filtering is ok

[Colossal]

Looks like a run-of-the-mill voltage doubler circuit with an LM317 or equivalent regulator chip and adjustable output. I would question whether that circuit has sufficient capacitance and filtering to make for truly quiet DC filament work. Depends on how big those caps are.

thats a good point - but the caps can always be upgraded to a higher value. I ordered one up so we'll see what it is in a week

Yeah, it's hard to tell what those caps are on the board, so maybe they are 4,700uF 25VDC caps so may be sufficient.

[Milkmansound]

heard back from mojo - they said not to use the board for this, so I removed them from my order

supposedly hoffman makes something like this that will work

[mhartman]

heard back from mojo - they said not to use the board for this, so I removed them from my order

supposedly hoffman makes something like this that will work

If you have an extra 5VAC tap available, use my setup from above -- it works great for this and is cheap.