Tube Build and DC?

[Zben3129]

Hi guys,

Just wanted to ask a couple questions.

First off, I got a 12ax7 off of ebay for 3 bucks, and 4 sockets for 6 bucks, so I now know....it is time to venture into the world of tubes.

So, I have decided on the Shaka Tube, to start

My question is, is it possible to power this circuit off of DC? If so, what voltage/current would i need.

Also, if the above is not possible, what AC would I need to power it? All I have is an "Output:9v AC 700mA 6.3VA"

I am trying to get this project up and running without buying a new wall wart, I want to make do with what I have. Thanks.


Zach B

[petemoore]

  I have a big one..lol, because I housed 2 transformers in a box to supply the heater and the DC circuit supply.
  IIRC the one adapter is from a printer and does 36vdc, and the other is...able to make the heaters light up [I forget how I wired the heater].
  Also the tube's data sheet will tell the heater current supply requirements...I forget, haven't had to do that in a while, it should be pretty easy to find a WW with current supply ability > what the tube requires for filament.
  The circuit DC is low current, pretty sure 500Ma. is more than enough, less than what a printer draws @@Rate. the 30v-36v WW's are large.
  I diddled with the 9v supply, then 'roundabouted' and hooked it up to 2 DC WW's.
 
 

[Zben3129]

Thanks for the info,

But I am still a little confused. If theres one part of the pedal design proccess with tubes i don't understand, It is the power.

Would that specific wallwart work directly plugged into the pedal, no transformers or ic's?

[RonaldB]

You can use your AC power suppley. But convert it to DC.

So when you put a rectifier after the AC power that will make 9volt x 1.4 = 12.6 volts DC
Search the internet for a schematic to do this.

So then you can make the Tube driver of Jack Orman site http://www.muzique.com/schem/tubedrvr.gif
And power it up with the 12.6 volts DC.

Hope it helps.

Ronald

[the_random_hero]

You're pretty unlikely to be getting 9VAC from that transformer if it's not loaded up (you're looking at something like 150mA current draw plus a bit more), so your heater voltage will be off. If you can work out approximately what the voltage will be (use some high power resistors to simulate the heaters), you can work out what resistor you'll need to include in series with the heaters to be getting approximately 12.6V.
Otherwise, just buy a 12VAC transformer, rectify it and bump a 7812 regulator up to 12.6V by using a silicon diode forward biased from the ground pin.

[Zben3129]

Thanks guys

Random - If its not too much trouble could you provide a schem of what you are saying? If not, thats ok too and ill try to figure it out


Zach

[MartyMart]

These will be useful to you :

http://www.kpsec.freeuk.com/powersup.htm

http://sound.westhost.com/psu-wiring.htm

http://mysite.du.edu/~jcalvert/tech/transfor.htm

[Zben3129]

Thanks much guys!

And also, I pulled a 14vac 1125mA off a phone at the dump today, will this work?


Cheers

[petemoore]

And also, I pulled a 14vac 1125mA off a phone at the dump today, will this work?
  You can get it to do something...
  First measure the unloaded WW to get the actual voltage.
  Actual voltage will be a little higher than when current is being drawn by the circuit, loading it down.
  I'd say put that right to a Diode rectifier/filter cap and run the valve at about 20VDC.
  Running the heaters on a different supply disconnects it from the signal circuit, coils convert the primary voltage to a floating AC [using another WW for heater filament V]. If you start with like 6v or a little better you 'can string 1n4007 diodes in series of PS V+ to drop to ~6.3v.
  Not as compact, but worked and I had the WW selections available.
   

[Zben3129]

thanks guys will try some of these

[Zben3129]

Ripped a transformer out of a dead amp

Figured it might be close

Plugged it in and here are results:

Probes on ends = +/-26V~
Probe - one middle one outside = +/- 14V~

Would this transformer be suitable?

[the_random_hero]

Sure, you'll have to drop some voltage with a high power resistor before you hit the regulator though.