Baja mini tube driver power supply

[spoontex]

Hello,

I can use 15vdc instead of 9vac? Maybe changing heaters resistor to 30R?

https://www.....org/viewtopic.php?f=13&t=9943&hilit=baja+mini+tube+overdrive

Any other change?

Thanks.

[Marcos - Munky]

With the circuit as is, no. It calls for an AC power supply, then it rectificates it to have a bipolar DC supply.

[spoontex]

Ups, yes...

So I need something like this:

http://tagboardeffects.blogspot.com/2014/01/bipolar-voltage-converter.html

Thanks.

[Marcos - Munky]

That will work, but you'll have to modify the layout and attach the + and - voltages to the correct places.

It's something easy to do. But you'll have to make that converter board and use more parts. It's way easier (and probably cheaper) to just use an AC power supply, which is basically just a transformer.

[vigilante397]

That will not work. The LT1054 has a very low output current, so it wouldn't be anywhere near enough for a tube, and even if it did that's nowhere near the best idea. If you really don't want to buy an AC supply then leave out the rectifier. Leaving out the rectifier and just dumping 15VDC into it would work if you modified the drop resistor for the heaters, but you're dumping close to 4W of heat into it, so you'll need a BIG resistor and it will still get very hot.

[Marcos - Munky]

The LT1054 have current output up to 100mA. If you use it to power only the plates (and the ic), it'll work. There are just two triodes, each one requires 1.2mA (12AX7) to work. The heater should be powered directly from the power supply (with the resistor), if you try to power it with the positive voltage from the LT1054 it'll surely not work since they requires more current than the LT1054 can output.

That said, the LT1054 can be powered by a max voltage of 16V. A 15V power supply is so close to this maximum, and a not well regulated power supply will have more than this voltage, so it's a big risk of blowing it up. Not a great idea to use a 15V power supply with this one.

Btw, I just opened the link again and that is a voltage doubler + bipolar power supply. You just need the bipolar part, not the voltage doubler part.

Leaving out the rectifier and just dumping 15VDC into it would work

I was gonna suggest this, but it won't work. This pedal is basically the BK Tube Driver (http://www.generalguitargadgets.com/wp-content/uploads/tube_driver_sc.gif), and it rectifies the AC supply to a bipolar DC supply. It's possible to use a DC power supply to power it, but the entire power supply should be modded. Keep V+ as V+, use a voltage divider to create a Vref and connect all ground points to Vref, and finally connect all V- points to ground. By doing this, the layout will need to be modded. Not worth all the trouble.

If your 15V DC power supply isn't a switching one, and if you're gonna use it just to power this OD, then you can just mod it to give an AC output. Just check if it have 500mA or more. And, as pointed out by Nathan, the heater resistor need to handle almost 4W of heat, so it'll be hot. The best idea is to just buy a 9V 500mA transformer.

[spoontex]

The reason that I doesn't  buy a transformer, is because I don't want more transformers, cables etc to my pedalboard. So, I'm searching for alternatives. I can get two outputs of my power supply ( switching ) in series.

Removing the rectifier and changing the drop resistor.

It's an option no?

But I think it's better a voltage divider from 18Vdc source, instead a serial two 9Vdc ( +18 -18 ).

[Marcos - Munky]

Removing the rectifier and changing the drop resistor.

It's an option no?

Yes, you can, if you rework the power supply part of of this effect, as I described on the reply before this one.

But I think it's better a voltage divider from 18Vdc source, instead a serial two 9Vdc ( +18 -18 ).

Yes, it's better to power it from a 18V DC with a voltage divider to create the virtual ground for the power supply reworking. A serial two 9V DC won't even work in some cases.

[Ben N]

Is there a schematic somewhere for this beast? Surely this whole discussion isn't based just on the layout?

[Marcos - Munky]

It's a BK Tube Driver using a submini tube instead of a 12AX7.

[Ben N]

Yeah, I made the connection, looking at the layout and a BKTD schematic.

And no cathode biasing.