Tube boost + overdrive running off a 9 volt battery

[frequencycentral]

The heater does not glow at all.

Try just powering the heater from a battery, +ve to pin 5, -ve to pin 4, with the tube out of the circuit. Turn your room lights out. The warm up time of the heater is 11 seconds. If it hasn't lit up within 30 seconds its dead.

supply is 300mA...is that enough..what does your draw? Earlier in the thread someone said 500mA is the minimmum.

Using pins 4 and 5, the current draw is 150ma.

EDIT: Although pin 9 is not connected in this circuit, it will show a voltage of approximately half the voltage going into pin 5. Make sure pin 9 (or its socket tab) isnt touching anything else,

12AU7 datasheet: http://www.guitaramplifierblueprinting.com/files/GE-12AU7.pdf

[Renegadrian]

The heater does not glow at all.

My power supply is 300mA...is that enough..what does your draw? Earlier in the thread someone said 500mA is the minimmum.

http://www.nj7p.org/Tube4.php?tube=12AU7

It seems a heater issue...check back all the connections, either build my verified vero layout and remove that extra cap (you can install it back when it's workin')

[kurtlives]

Threw in a battery and it works... yeah!

There was a lot of gum though...it stopped when I touched a ground point thouhg, so I gotta figure that one out.

Did this not work because the power supply could supply enough current?

[frequencycentral]

Threw in a battery and it works... yeah!

Excellent!

There was a lot of gum though...it stopped when I touched a ground point thouhg, so I gotta figure that one out.

Gum I can live with, it's hum I hate. Bad earthing somewhere.

Did this not work because the power supply could supply enough current?

I don't think tubes like unregulated, unfiltered power supplies. You need a really good supply for this one.

[kurtlives]

I was using a LM317...

I tried another 300mA 12V DC power supply and got low voltages again...

I guess I gotta buy a third power supply... (this will be the 3rd one in 2 days )

Can you measure how much the effect is drawing for me?

[frequencycentral]

I was using a LM317...

That should keep the voltage stable - just don't give the heater more than 12.6 volts.

Can you measure how much the effect is drawing for me?

Tell me how and i will - not sure how to do this - I'm going from the datasheet on curent draw.

FYI, I am able to run two 12AU or two 6111 from my 12 volt / 500ma wallwart with ease.

Going to bed now - it's 1am her in the UK!

[danielzink]

I'm in a bit of a quandry here.....

I really want to build this pedal (as well I probably will) - my problem is this:

My pedalboard is run by 2 Voodoo Labs Pedal Power II's - I have the option of 9v or 18v....if I want 12v I'll have to add a wall wart to the operation somewhere - not my best option.
Is there a way to run 18v into the circuit but "resistor" it down so it only sees 12v input ?

Thanks, Dan

[kurtlives]

I was using a LM317...

That should keep the voltage stable - just don't give the heater more than 12.6 volts.

Can you measure how much the effect is drawing for me?

Tell me how and i will - not sure how to do this - I'm going from the datasheet on curent draw.

FYI, I am able to run two 12AU or two 6111 from my 12 volt / 500ma wallwart with ease.

Going to bed now - it's 1am her in the UK!

You set your meter to measure current and put it in series with the B+.

I measure the current draw with a battery and it was only 0.12A... My power supply should work fine, 

Thanks for the help btw

[kurtlives]

I'm in a bit of a quandry here.....

I really want to build this pedal (as well I probably will) - my problem is this:

My pedalboard is run by 2 Voodoo Labs Pedal Power II's - I have the option of 9v or 18v....if I want 12v I'll have to add a wall wart to the operation somewhere - not my best option.
Is there a way to run 18v into the circuit but "resistor" it down so it only sees 12v input ?

Thanks, Dan

You can use the 18V supply and add a LM7812 regulator inside the pedal so it only sees 12V.

[Renegadrian]

I'm in a bit of a quandry here.....

I really want to build this pedal (as well I probably will) - my problem is this:

My pedalboard is run by 2 Voodoo Labs Pedal Power II's - I have the option of 9v or 18v....if I want 12v I'll have to add a wall wart to the operation somewhere - not my best option.
Is there a way to run 18v into the circuit but "resistor" it down so it only sees 12v input ?

Thanks, Dan

Dan, you can also build  one running at 9v - 12au7 seem to work good even at 9v at the heaters, else I'd suggest you to get a 9au7, which is the same tube accepting 9v as heater...You can get one dirt cheap thru the bay (as usual...)
I got one at €4 shipping included, go figure...I'd suggest you also to put a regulator, in that case it'llbe a 7809.

[Renegadrian]

FYI, I am able to run two 12AU or two 6111 from my 12 volt / 500ma wallwart with ease.

Going to bed now - it's 1am her in the UK!

Me too, no problem with 500mA
Going to bed now - it's almost 3 am here in the Italy!

[danielzink]

I'm in a bit of a quandry here.....

I really want to build this pedal (as well I probably will) - my problem is this:

My pedalboard is run by 2 Voodoo Labs Pedal Power II's - I have the option of 9v or 18v....if I want 12v I'll have to add a wall wart to the operation somewhere - not my best option.
Is there a way to run 18v into the circuit but "resistor" it down so it only sees 12v input ?

Thanks, Dan

Dan, you can also build  one running at 9v - 12au7 seem to work good even at 9v at the heaters, else I'd suggest you to get a 9au7, which is the same tube accepting 9v as heater...You can get one dirt cheap thru the bay (as usual...)
I got one at €4 shipping included, go figure...I'd suggest you also to put a regulator, in that case it'llbe a 7809.

well....yeah.....I already bought my 6111's 

Dan

[danielzink]

I haven't utilized a 7812 yet - but - from doing a quick search - it looks pretty easy.

Get a 7812 with proper output voltage. 7812's have 3 legs 'eh ? 18v into one leg, gnd into the other and 12v out of the other ?

Dan

[kurtlives]

Yep, and ground one leg.

Make sure you get the right "legs" though.

[liddokun]

I tried going through all the posts and such, but there's a little bit of confusion on my part, so please excuse if I'm asking something already answered.  So this pedal acts like a booster, and not like a distortion?  I understand there won't be a lot of gain, but will it add some colour to my tone and just a bit of crunch?
And also, if I build it stock will it sound decent? 
Thanks a lot!

[andrew_k]

And also, if I build it stock will it sound decent? 

Yes. Perhaps a little dark.

It's not an entirely clean boost, even with the gain turned right down. The gain control increases dirt and volume.

[Jimmy-H]

Threw in a battery and it works... yeah!

There was a lot of gum though...it stopped when I touched a ground point though, so I gotta figure that one out.

Did this not work because the power supply could supply enough current?

I don't know If you have solved your problem.
But it seems to me, that there is something wrong with your wiring.
Because there is no supply at all on your measurements.
Just try to connect the supply again and measure the incoming power on the power connector.
If this is good, then measure one side of 220K and so on.
I Hope you will find the problem

[frequencycentral]

I tried going through all the posts and such, but there's a little bit of confusion on my part, so please excuse if I'm asking something already answered.  So this pedal acts like a booster, and not like a distortion?  I understand there won't be a lot of gain, but will it add some colour to my tone and just a bit of crunch?
And also, if I build it stock will it sound decent? 
Thanks a lot!

I would say this circuit is definately an overdrive/distortion - and yes, a very decent sound.

As for cleaner boost, I have found the more resistance between you put between V1A pin 3 (the cathode) and earth, the cleaner the sound. I use a 100K gain pot instead of 50K for VR1, cleans up nicely.

There are a number of other mods people have suggested to clean up the sound and brighten it a little - andrew_k is right, it is a little dark. I trawled this thread a while ago and got together all the mods. I've posted them before, but here they are again:


Possible improvement, depending on context:


"I note that the original schematic and layout specify that the triode at pins 1-3 be used for the voltage gain stage, and 6-8 for the follower.

This isn't usually the best way to do it with a 12A*7.  With battery power or regulated DC going through the heaters, it doesn't matter which triode you use in which position, but if you're using AC or less-than-pristine DC, the triode at pins 6-8 will be quieter, due to the location of the heater pins on the tube.  (You can find mention of this in the data sheets on many 12A*7 series tubes.)"



"I lower the coupling cap between stages for less bass."



"For lowering bass, you could try lowering the value of either the input cap, or the coupling cap between the two tube stages."



"I am bypassing the Valvecaster gain pot with a 2.2nf cap. This helps maintain some brightness when the VC gain is turned down. For the input cap on the Valvecaster I am using a combination of caps to give me 2.7nf. This helps tighten up the bottom end."



"To tame the gain I would lower R2 and R3. 220k and 100k seem pretty high for a low voltage circuit. Even in a regular high voltage amp the normal value is just 100k. So maybe cut them in half."



"if you bring down that 220k to 100k it will def lower the gain a bit.  I built mine with both plate r's at 100k."



"A 1M gain pot allows massive, saturated gain. A little mushy in the bass frequencies, but pretty cool. I'm considering putting a "more" switch in, whereby it adds a resistor in series to the regular gain pot."



"Adding resistance to the plate resistors(R1 and R2) will increase gain. Adding resisitance to VR1, in series with the gain pot, will decrease gain."



"guitarx: replace the 100k resistor with 47k. Replace the 220k resistor with 100k. Beautiful cleans."

   

"To fellow Valvecaster experimenters -- I've currently got this circuit on a breadboard, switching out everything and I have some items of interest to report, especially for those looking for more gain.

The nicest clean sound I've found so far, is with the following mods:
R2 = 100k
R3 = 47k
C1 = 0.1uf
Remove C4 and VR2"



"Finally received that 7812 - mounted with the 100uF filter cap on the dc jack - hiss is just a memory... 
put a 100uF cap across the DC jack (positive leg to positive rail, neg. leg to neg. rail), then, instead of connecting the positive rail directly to the circuit, connect it to the regulator's pin1, ground to pin2, and the circuit to pin3. Then screw it on the enclosure. It is a 7812."

[kurtlives]

Tried my Valvecaster with a LM7812 and now it works with a power supply!

It dosent seem regulated at all though...not sure if its working (I think this because the voltage is not 12V and there is a bit of added hum).

Also my gain knob did seem be to functioning....now it does nothing.

[Renegadrian]

Dismantle it - build it again, even with the vero layout someone made...