Using Aron's transformers

[TryingToDo613]

Hi guys. Is there a way to use the 12v/220v transformer that Aron sells to go from 12v DC to tube voltages? I can't find any way to do this in the books I have but it must  be possible because there are inverters that go in your car. I have a couple of these trannies and I'd like to find a use for them. -ph

[puretube]

just take a 12V/2W/50 or 60Hz sinewave generator/amp
that can drive inductive loads...

[TryingToDo613]

Can you get one at walmart?  I don't even know what that is or what I'd use it for. I'd like to make a firefly that can run off a car starter hit pack. -ph

[transient]

You also can use two of those transformers back to back to get high AC voltage, then convert it to DC. Take a look at the power supply section of Fred Nachbaur's "Real McTube II" to see how it's done.

...
emre

[puretube]

[aron]

You need to feed the transformer AC. So at the very least you would need to convert 12V DC to AC first to use the transformer.

[transient]

Sorry, i thought the transformers were 12V AC.

.
e

EDIT: Nevermind my posts, i totally misunderstood the question

[puretube]

to make the confusion perfect: they are both: 12V AC and 220V AC...

ooops

[TryingToDo613]

That is actually my question Aron. How do I do that?  I'm actually buidling a real mctube right now but I'm using radio shack transformers already.  A firfly needs about 40ma@200v or so, which you jack up with recto. I want to run the whole banana off of 12vdc. You know those hit packs?? They usually have a cigarette lighter jack in them. Perfect for playing my mandobird at the beach. I can of course just use an inverter from the hitpack and plug the firefly into that but I'm sure there are losses. I know I"ve read that transistors can be used as ossilators and I figured one of you smart guys already has a treatise on the web somewhere. I can't even spell ossilator. -ph

[Paul Marossy]

I can't even spell ossilator[\quote]

oscillator 

[R.G.]

If I could put in a bit of advice...

You're wanting to use 120Vac to 12Vac transformers to power a small tube amp, but you want to start from a 12Vdc battery. That's relatively hard to do.

The problem is that what you have is DC and the transformers run on AC. It is at least as complicated to make AC from the available DC to run the transformers as it is to build the rest of your amp that you're working on. Assuming you're successful, then you have an amp that only works from 12Vdc, and sooner or later,  you're going to buy or build a 120Vac to 12Vdc power supply to use it away from your car.

I would highly recommend just buying a smallish (100W  to 500W ) power inverter. These things are designed to make 120Vac from 12Vdc, and they're relatively cheap and reliable right now. Then lavish your time and skill on making an amp that makes beautiful sounds when running on 120Vac.

I don't say this as criticism, just a comment on the amount of sheer work involved.

If I were desiging an amp to run from a car battery, I would go high frequency switching directly from the 12V to B+, DC heatersupply and negative bias supply directly. It' s entirely possible, but it would use ferrite transformers to get there at frequencies over audio so that the noise would be inaudible.

Just my two bits. It's worth what it cost you.

[TryingToDo613]

As always R.G. it's worth what I should have paid for it, not what I paid. Thanks. I'll stick to the inverters. -ph

[Penguin]

hey RG.  while i am thinking about it.. i got a few of the ehx ones.  thats the same ones arons got right.  lend me your wisdom please.

i hooked up everyhting just like GGG said to do.. this as well is what the datasheet i got with them from ehx. says too.  doulbe checked.  and although i get good high voltage. for the love of me when its hooked up to a 12ax7. [any 12ax7 i have about 200 different ones] it drops to around 50vs onthe plate..?

i have three of the transformers and all three do the same thing.

any suggestions.

[puretube]

Hi Ansil,
welcome back again!!!
you made it thru the jungle? WOW!


the plate-voltage is being deminished by the plate-resistor...

calculate ~70k as the tube-resistance for a 12ax7...

if the plate-resistor is 180k with a B+ of 250V,
there`s ~70V left on the plate...

[Penguin]

thanks pure tube i was was wondering about that. so i am guessing that i will need a bit more voltage then.. lol.. 

funny thing i was using this cool transformer[same one i still use but now they dont' give as much power]  its rated 190-0-190 and when i rectified it i was getting nearly 500vdc.[480 aprox]  after applying it to the tubes i was getting around 330v on the plates.  which i liked the sound alot of that voltage.  much better than waht i get now.  same transformer.  same wiring.  gets now  250v on the plates wiht an idle of 410 or so.   not sure why i lost that much voltage unless the control specs of the transformer were just whacked on that batch i got.

it was that hammond 229dx series. i belive.