Tube boost + overdrive running off a 9 volt battery

[Ripthorn]

Your question is all about headroom and amplification.  When it comes to tubes, that translates directly into plate voltage (for the most part).  So the answer to your question is "maybe."  It really depends on your plate voltage.  If you go 9V plate voltage, I highly doubt that it will work any better than any other pedal you have tried.  If you put, say, 150V or higher on it, it could probably match your output level pretty well and give enough headroom that the clipping range is wide enough for good use.  Of course, you will really need to play with the voltage to see what you need for your particular situation. I think a 12au7 can handle something like 300V or so on the plates, so try different plate voltages up to that range to see if you can get enough output.  Just as a side note, on one project I did, I found that the difference in output level between 24V and 100V was ridiculous, it was so much louder it was hard to believe.

[T-200]

OK, Brian,

I think that with my skills I have to keep away from those high voltages and try to figure out something with transistors...

Thanks for the info,
Juha

[Ripthorn]

Depending on what you want to do, you could use a high voltage opamp (by high voltage, I mean something like +/-24 or 30V) which could be done using a charge pump to get the right voltage from a +9V supply.  Of course, those opamps start at 3 or 4 USD and go up to over 100 depending on what you want.  The thing there is that the voltage swings can be huge, making line level inputs plus gain no problem.  The only thing is that if you want overdrive, you will have to find a way to do natural clipping.  Of course, you could always look at RG's adjusticator over at geofex.

[bassmannate]

So, I finally got a 12v supply for my Valvecaster yesterday. I was just playing through 9v batteries occasionally to play with it. This is a filtered and regulated power supply. It's a 12v 1Spot with a capacity of 1500ma.

Got it all set up and turned it on. I'm getting a hiss from the circuit now. I've tried putting a 22uf cap in to filter the power (it was the only one I had laying around) and it helped but i still enough hiss that it's annoying.

Also, the hiss is louder when I turn the gain pot down. Probably has something to do with the fact that the gain shorts to ground. I really can't turn the volume pot up more than half way without the hiss being unbearable.

Is there anything else simple I can do to filter the power? The power is the only thing I can think of that it would be since I haven't changed anything else.

[Ripthorn]

Are your components rated high enough?  I am guessing that they are.  The only other way to really filter out a power supply is to either add caps to ground or inductors (or sometimes a resistor) in series.  If the supply is already filtered and regulated, I don't suspect that it would need too much external filtering, if any.  Have you audio probed with both 12 and 9V to see what the differences are at each stage in the circuit?

[bassmannate]

I took a look at my voltages and it looks like they may be off a bit judging by earlier posts. Also, it looks like the voltage on pin 6 is almost identical on both supplies. My output cap is a tantalum because it was the only one I could find around here in that value. Not sure if that could cause any problems. I'm 99.99% sure that I put it in with the correct polarity. I may swap it out for something else.
12v:
1: 5.82
2: -0.15
3: 0
4: 0
5: 12.13
6: 6.86
7: -0.16
8: 0
9: 6.11

9v:
1: 6.31
2: 0
3: 0
4: 0
5: 8.46
6: 6.85
7: 0
8: 0
9: 4.2

[frequencycentral]

Lookiing at your 12v voltages, pin 1 is too high and pin 6 too low - check for dry joints or resistor values that are out?

[bassmannate]

Resistor values are good. Going to try resoldering those joints here after a while. My soldering skills leave a bit to be desired and it may be the problem.

[Renegadrian]

maybe you swapped the two resistors (pin1 220k - pin6 100k) ??
As the first plate res. has an higher value, it should receive less voltage than the second plate...If I am right?!

Edit: I didn't read you already checked them...mmm...

[bassmannate]

Update:
Re did the joints. the voltages went down a bit but not much. pin 1 is now 5.76 and pin 2 is 6.82

[cab42]

Well, the thread has dropped to page 5, so its time to get it back on the front page...

After more than a year i have have finally made the Valve Caster work. I started when 2008 was fairly new, but I couldn't make it work. I even rebuild it from scratch (twice) and tried three different  tubes and and two power supplies in all combinations. In disgust and dispair I threw it in my box with abandoned circuits where it has been for more than a year.

Last week I pulled it out from the box, plugged it in, and it worked!!!!! I have heard about self-healing circuits, but I really don't have a clue why it suddenly worked.

One thing puzzles me, however: The voltages on the pins are pretty close to the ones frequencycentral posted on the last page, except for pin 1, which is almost twice the size. I have measured R2 and it is 220K as it should. Should I change the value of R2 in order to lower the voltage on pin 1?

Here's my voltages (FC's voltages in paranthesis for reference). I used Renegadrians no-tone vero-layout: http://www.aronnelson.com/gallery/main.php/v/Renegadrian/Valvecaster-no-tone.gif.html

Supply Voltage 12.03 regulated
Pin 1: 5.4v      (3.02v)
Pin 2: -0.75v   (-0.518v)
Pin 3: 0.00v    (0.00v)
Pin 4: 0.00v    (0.00v)
Pin 5: 12.03v   (11.97v)
Pin 6: 7.46v     (8.21v)
Pin 7: -1.20v    (-1.285v)
Pin 8: 0.00v     (0.00v)
Pin 9: 6.21v     (5.91v)

Regards

Carsten

[frequencycentral]

How was your Gain control set when you took your voltages? Mine was maxed, ie the cathode was grounded. IIR the voltage at the plate (anode, pin 1) reduces as you put more resistance between ground and the cathode.

[cab42]

How was your Gain control set when you took your voltages? Mine was maxed, ie the cathode was grounded. IIR the voltage at the plate (anode, pin 1) reduces as you put more resistance between ground and the cathode.

It was turned almost all the way up, I had read your note about that in an earlier post. However changing the tube did the trick. With another tube the voltage of pin 1 came below 4V.

The first tube (a Mazda, bought on ebay.uk for 19p) does not sound bad at all but distorts more (in a nice way), while the second (RCA) is much more mellow.

Thanks for your help

Regards

Carsten

[tipetu]

Hi, as a new member here I`m glad I found this page cause the tube pedal looks awesome! I bought everything I needed to build it, but unfortunately it does not work!

My question is; on page 1 on this thread there is a handy schematic of the pedal. I used this one when I built it. I get no glow on the heaters, and how come pin 9 is not connected?? it runs the heaters right?? pin 9, 4 and 5?? I assume this pedal is for a standard 12AU7??

I really would appreciate if someone would answer me on this one, thanks Frank

[tipetu]

OH, I noticed the hot tip on the input jack was touching ground! and I read up on the 12AU tube and it says you can connect pin 4 and 5 in series and leave pin 9 blank! interresting!  I`ll try it out tomorrow!!

[tipetu]

It did not work! damn!... anyone got any suggestions?

A new question, on the handy schematic on page 1, are the pots wieved from the back or front? kinda makes big difference either way look at it.

[Renegadrian]

Hi there - the pots are always drawn as you see their back. It should work anyway I believe, even if you wire them au contraire...
The tube heaters receive the 12 V they need with the pins 4 and 5. 9 is left unconnected.
Can you post some pics?!

[tipetu]

I wired them as they were wieved from the back. But I thought it was meant to run on 9V?? I`ll post some pics a littlebit later! Thanks for the reply!

[tipetu]

As promised here are the pics! The box was i littlebit tiny but I managed to get it all in there!

I must add that I tested it now and there is glow in the fils! Haha they were so small I didn`t notice it earlier! but now I hear this powerful hum! Does anyone see an error in the pics?

It had to be carbon comp resistors and orange dips!





there is a tube socket in there somewhere..





As you can see I left pin 9 blank and no the resistor is not touching it




Here you see the result! It`s nice and shiny!





And again, I appreciate any response! thanks!

[tipetu]

INFO! Looking from underneath inside; the pot on the right hand is the tone control, and on the right hand is the gain control. The big one is the volume