Ebay: Semi Nano Head Clone

[Regan]

I think there is great potential here with the sub 1w amps- traditional high voltage isn't really necessary- I think you can get by with not much over 100v, much below that and you may have a tradeoff of lack of dynamics etc.
I have seen at the surplus sites small power transformers that have 12v and 50v secondaries. I think these may be perfect with a voltage multiplier.  Actually the size of box I'm working with right now are those old parallel port switch boxes- I think they are maybe 6"x4"x2.5" its still a tight fit but still workable.
Josh,
I don't even know if I will produce the amps other than for a few friends-I'm still trying different ideas, and have to source reliable parts.
Ansil's amps look great, sound awesome, and look to be a great bargain for the money. I hope he sells lots.
Regan

[Ansil]

so has anyone had any good luck with the ehx things  peter weren't you working with one.??

Are you talking abour reverb transformers?

I've built a series of circuits based on Fender reverb transformers and I do like single ended tones, but I also like push-pull since you get so much more out of it.

I tried designs with from 1 to 4 preamp stages in front of a 12AU7, 12AT7, or 5814 with either one plate or both plates in parallel driving a standard Fender replacement transformer and there are some lovely tones in there! Some of the 4 stage stuff is just insane.  :twisted:

actually i meant voltage trannys.  i was using the hammond 269 somehing or other. and it drops down to 90V when i put it to the tubes.  i was going to go with the ehx torrodial transformer.  in the sticky thread.  and was wanting to know if anyone had tried it yet.

[mlabbee]

In respomse to Regan's post, I'm really curious to know how you can do a voltage multiplier without an additional transformer - I'm starting to design a low wattage amp using sub-mini tubes (like the zvex tubes), but the transfomers are pretty pricey for a 6.3/150 volt unit - if I could use something cheaper (and lighter) that would be nice.

I'm planning on building mine in and old Philco wood radio box - very retro looking with a small speaker (5") built in and, of course, jacks to plug into a cab.

[Peter Snowberg]

actually i meant voltage trannys.  i was using the hammond 269 somehing or other. and it drops down to 90V when i put it to the tubes.  i was going to go with the ehx torrodial transformer.  in the sticky thread.  and was wanting to know if anyone had tried it yet.

Ah yes.... that was a duhhhh on my part.

Thanks to Aron, I have one of the Puretube torroidals here. You can pull 6mA from it without it melting but the big question is how far that can get pushed. The plan is to bias a single section of a 12AU7 for a driver to consume 6mA and do the preamp by other means. That setup should all fit nicely in a 1590BB with the torroid and the input jack at opposite corners. One big advantage of that is that you don't need regulatory approvals since the hardware all sits after a pre-approved wall adapter. It also disconnects the mains voltage from the amp. I'll post results as soon as I have them.

[Ansil]

thanks i appreciate the info. i am using a hammond 269ex.  its supposed to deliver a 25ma @ 230V thats the loaded specs.. but when it hits the tubes man it drops down to 90v or so.

not quite sure i thought it was just maybe the way i had it wired but i tried it on another amp that i know doesn't use that much juice and it still did the same thing. i think its a bad tranny.. however if someone wanted to look at this privately [no offense i just dont' want to publicly post schematics yet.] i would be grateful, cause i dont' get it. lol unless i am just looking at it too hard for too long and missing the obvious.

[Regan]

Ansil,
Sounds like the transformer to me. Maybe loading the transformer down outside of the amp and see how the voltage is dropping.
Mlabbee, most basic electronic books have voltage multiplier circuits, or check epanorama.net . I wouldn't do a multiplier from 6.3v- maybe double but not much more-they can be noisy.
Regan