tube driver

[peterg]

I dug this schematic up while looking for a circuit to use a spare 12au7 tube. What do I need to do to use a 3pdt throw switch? http://www.muzique.com/schem/tubedrvr.gif

[MaxPower]

Sorry, can't help you with switch wiring.

What the hell part of that circuit merits a patent? That's what I'd like to know.

[italianguy63]

It says "from patent"  It might have been lifted in part from a bigger patented product?  MC

[GibsonGM]

Maybe one registered about 1923?  ;o)

[italianguy63]

The answer to your question is in my opinion.. (nothing)?

It has a LED built in.  So, the DPDT will be OK as is.

If you just HAVE TO use a 3PDT, you can leave one bank unused, or you could improve on the "bypass" wiring some, and incorporate the LED to the switch.

But, not needed really.

[duck_arse]

like italian says, nothing, unless you want to true-bypass it. then you'd have to split the bottom 3 connections into the standard dpdt configuration, with a shorting loop across the lower left 2 connections, input and output wires to the 2 lower middle lugs, and the input to board and output from board on the lower right lugs. that's at least one way to "do" it.

the top row grounds the first stage output when the circuit is bypassed.

[peterg]

Thanks All

I should have asked "What needs to be done to wire true bypass"? Just remove the connection from between the OpAmp sections and the switch and wire a 3PDT switch normally as per duck arse's comment.

[teemuk]

What the hell part of that circuit merits a patent? That's what I'd like to know.

Positive "pull-up" grid biasing scheme, which (in comparison to usual method of referencing the grid to common) results into higher input impedance and headroom of the stage when the tubes are powered from such low B+ voltage supply.

I assume starved plate voltage designs weren't exactly something everyone "skilled in art" were familiar with when Brent Butler designed the initial versions of the Tube Driver and applied for its patents. ...Or its just the usual issue of everything being super easy to patent if you just happen to have too much cash in your pockets.

Anyway, Merlin Blencowe has written an excellent tutorial about starved plate design. I guess you could say the article addresses the issues of what "merited the patent".
http://www.valvewizard.co.uk/Triodes_at_low_voltages_Blencowe.pdf

[mth5044]

Just get rid of the switching in that schematic, including the trace from the input to the switch. Treat the input as the circuit input and lug 2 of the volume pot as the output then wire it up as whatever true-bypass situation you prefer.

[peterg]

Got it. Thanks Matt.

[electrichammer]

Hi guys

I'm a total noob when it comes to electronics.
I want to start by making this pedal but i can't figure out how to wire the tube.
The schematic shows 3 connections that go off it, but what do I do with the other 6 pins


Thanks for your help in advance 

[defaced]

Look at the inside of the diagram you posted.  You'll notice that the plate, grid and cathode are shaped differently.  Those shapes match what is in the schematic above.  This might help too: http://www.diystompboxes.com/wpress/?page_id=10

[peterg]

electric hammer - the scheme shows the tube connections in three different locations. Pins 4 and 5 are show at the top left and are labeled "TUBE FIL(iment). HEATER" for the power supply and ground (pins 5 and 4 respectively). Pins 1, 2 and 3 are shown on the left round tube symbol and pins 6, 7 and 8 are shown on the right symbol.  The tube driver circuit tube section is very similar to the Valve Caster circuit but has an additional front end (don't know what it's called) stage. Pin 9 is not connected.

http://www.diystompboxes.com/smfforum/index.php?topic=63479.0

[MaxPower]

Just to beat a dead horse (I'm sadistic that way): that schematic appears to be the entire circuit of the patent and it was filed in 1989, assuming the site I saw it on was accurate. In any case, it brings to mind something Mark Cuban said about "...dumb-ass patents..."

Sorry. Just made me laugh when Cuban went on a rant about the patent system.