Tube boost + overdrive running off a 9 volt battery

[tranceracer]

Thanks for the link Renegadrian!  The sound clips sound good! This is definitely one that I want to build also.

Just a quick question, is there a connections next the 68K resistor and the 150K variable resistor (where the red circles are)?

[frequencycentral]

Just a quick question, is there a connections next the 68K resistor and the 150K variable resistor (where the red circles are)?

I would say no there are not. Also consider making the 50K screen resistor a higher value, and having a cap to ground from the screen.

[biggy boy]

Just a quick question, is there a connections next the 68K resistor and the 150K variable resistor (where the red circles are)?

I would say no there are not. Also consider making the 50K screen resistor a higher value, and having a cap to ground from the screen.

The Screen cap to ground where does it go? on the left side of the resistor ( between the screen and resistor ) or the right side of the resistor?

Also can I use a EL84?


Glen

[frequencycentral]

Just a quick question, is there a connections next the 68K resistor and the 150K variable resistor (where the red circles are)?

I would say no there are not. Also consider making the 50K screen resistor a higher value, and having a cap to ground from the screen.

The Screen cap to ground where does it go? on the left side of the resistor ( between the screen and resistor ) or the right side of the resistor?

Also can I use a EL84?


Glen

Left side, have a look at my Pentaboost, which is similar: http://www.diystompboxes.com/smfforum/index.php?topic=70524.0

[tranceracer]

Thanks Rick!   

Updated schemo:

[Renegadrian]

Yeah, that's it, the suppressor and the cathode go togheter - the input goes to the grid and the output has no connection with the screen.

Basically pentodes share the same schematic (I studied some in the last days, like mark lavelle's you can see at his site http://www.harmonicappliances.com/index.html) and every schem I saw has that screen cap.
I tried to put one in, but it's not so mandatory, you can just try but it sounds good without, so I wouldn't bother...
You can have a 220k instead of that strange 150k (a 150k pot?!) and you can surely play around raising that screen res.
If you want more gain, put an electro cap at the cathode, say 33µF, maybe tied to a small value pot, 1k-10k.

[1878]

Just finished building this and I only get a clean boost when the effect is engaged ?? There's no overdrive sound whatsoever. I used this layout:

http://www.aronnelson.com/gallery/main.php/v/Schematics-etc/Valvecaster-no-tone.jpg.html

I can hear a 'difference' if you know what I mean. The signal is definately passing through the tube.

Any ideas ??

[Renegadrian]

Don't know, man, that layout is verified by myself and other people too...Check the voltages and compare them to the ones posted by Rick a couple of pages ago...Also, check back every connection on every pin, and maybe the res. values, maybe you got one wrong?!

[1878]

I'm running this off 9v. Would that affect the effect ??

[frequencycentral]

I'm running this off 9v. Would that affect the effect ??

Sorry 1878, I can't help you until you change your avatar! Why would anyone come from Liverpool and support 'the other team' as they are referred to in my house?

Seriously though, you should be getting some nice dirt at 9 volts, but as Adriano says, post your voltages, check your resistor values and solder connections.

Rick

[1878]

Q: How many 'Liverpool' supporters does it take to change a lightbulb ??
A: 5... 4 to change the lightbulb and one to make sure they all get back to Bristol safely.

You should have more respect for your parent.

I'll check and post the voltages tomorrow. All componant values are correct, the valve heats up/glows but no overdrive. I bought a JJ Tesla ECC82 which I'm hoping will do the job. Volume control works as does the gain, it's just there's no gain to control

[Renegadrian]

Maybe you inverted the tube pins?!
http://www.dogstar.dantimax.dk/tubestuf/pinout.htm

[1878]

Luckily for me, the pins are numbered on my socket. Made my first foray into tubes a bit easier !! Here's my voltages using a well filtered 9v power supply:

1: 7.03
2: -0.15
3: 0.01
4: 0.00
5: 9.20
6: 8.05
7: -0.15
8: 0.00
9: 4.61

Hmmm.....

Thanks again.

[Renegadrian]

Those are the voltages Rick posted of his Valvy some pages ago - As you can he runs it at 12V so some values are to be a little higher.

Pin 1: 3.02v
Pin 2: -0.518v
Pin 3: 0.00v
Pin 4: 0.00v
Pin 5: 11.97v
Pin 6: 8.21v
Pin 7: -1.285v
Pin 8: 0.00v
Pin 9: 5.91v

What it differs too much is the voltage you get at pin 1 - post the value of the res. wired to the plate.

[1878]

The resistor is 220k and the capacitor is 0.047uf (47nf) which are correct to the layout. Just checked all the other values and they're also correct. I've double checked the wiring/soldering also. Everything seems fine.

I'm getting a nice sparkly valve boost but no overdrive.

[frequencycentral]

Yup, your pin 1 should be 25% of the power supply voltage - about 2.3v in your case.
Your pin 6 should be 66% of the power supply voltage - about 6 volts in your case.

This seems to be a common debug problem with Valvecasters - the plates being too high.

Those voltage of mine that Adriano posted were taken with the gain set to maximum (ie first stage cathode grounded) by the way.

If you are sure everything is correct (though it can't be if your voltages are off), you could replace the 220K resistor with a 1M pot (use the pot's lugs 1 and 2) and tweak it until you read about 2.3v at pin one. Then measure the resistance between lugs 1 and 2 of the pot. Do the same with the 100K at pin 6, though I think pin 6 will come into line when you sort out pin 1.

[frequencycentral]

For those of you who want to try (or have tried with poor results) a 12AX7 in your Valvecaster, I have some ideas.........

12AU7 is a medium mu dual triode
6111 (Subcaster) is also a medium mu dual triode

12AX7 is a high mu dual triode
6112 is also a high mu dual triode

I just breadboarded a Subcaster using a 6112 in place of a 6111 - blarty due to too much gain, so I experimented with a couple of resistor values and would recommend:

For a 12AX7 Valvecaster: change R2 to 100k, change R4 to 100k.

For a 6112 Subcaster: change R5 to 100k, change R6 to 100k.

I haven't got any 12AX7 to try this with, but I'm assuming that a 12AU7 is roughly equal to a 6111, and a 12AX7 is roughly equal to a 6112, based on mu.

I've got an idea for a new very dirty high gain tube pedal based on my little experiments with 6112 (should work well with 12AX7 too), it's working title is "Promiscuous Girlfriend" - watch out for the thread!

[Renegadrian]

ok Rick, I'll try that one tomorrow! 
Altough my tries with the Tube Star went nowhere with the AX...

[panterica]

here comes mine valvecaster:



works really nice.

big thanks goes to Adriano for his help.

Hey dcd666. I like that enclosure you used. Where did you get it?

[dcd666]

i'm glad that you like it.
enclosure was an old amp switch made by polish manufacturer KODA.
now it's called EXAR but i think they don't produce these enclosures anymore.