Some newbie questions regarding submini's

[Ripthorn]

Hi everyone, I am new here and to building tube projects. I have done the stompbox and guitar building thing, so amps is the next logical step. That said, I wanted to start with something not quite so "scary" in terms of electricity (the wife is 7 months pregnant and wants the baby to have a living father).

So what I am thinking is doing a submini amp with 6111's and 5902's (similar to Dana's lil devil), but I have several different things I want to do with it. My main question is regarding the power supply. I know I need 6.3V to the heaters, but I would like to run the tubes at about 100V. I was hoping I could get a single 115 primary/6.3 secondary transformer and run the tubes using just rectified mains voltage. But then I ran some quick numbers and after rectification, my 115V turns into about 160V which is about the max my tubes can handle and I would like to be safe and run them a little lower. My question is if there is a way to drop either my mains AC or my rectified voltage to an acceptable level without a transformer. I also considered using a charge pump on a rectified portion of my 6.3V, but the charge pumps I have looked at can't supply enough current for all the tubes. Any ideas? If there is a thread regarding this, I would be thrilled to read it, I just didn't find anything in all my searches regarding this topic. Thanks.

[DHHZ]

Hi,
I am planning something similar, and I think you can run the transformer backwards, from a 6v supply, to get the B+. The 6v supply powers the heaters. Here is a link: http://www.jjs.at/electronic/class_ab_subminiature.html
Look at the power supply section. If you want a lower B+, then use a transformer with a higher voltage secondary (which you will be using as the primary), e.g. if you put 6v into a 115v-9v transformer, you will get approximately 75v before rectification, and 105v after.
Hope this helps, and good luck!
Daniel

[Wayne]

Two back to back transformers works well as described above, as long as the current demand isn't excessive - should work fine for sub-minis.

In the interest of ensuring that your offspring grow up in a two-parent family, do not under any circumstances use directly rectified wall voltage to obtain your HT!!!

W

[Ripthorn]

Thanks for the responses. After doing some more poking around, I think I can get away with a single 115/6.3 transformer and use a nixie power supply for the high voltage. If you aren't familiar with it, it basically uses a 555 timer, bc547 and an inductor and some caps to take a reasonable input voltage (9V ish) and converts it up to anywhere between 100V and 200V depending on a trimpot. I think this should work well. If not, then the two and half bucks for the parts won't kill me.