Tube boost + overdrive running off a 9 volt battery

[newfish]

OK, a new 'JJ' 12AU7 arrived this morning, and I duly put it into my Valvecaster.

With everything at '10', the signal with the pedal engaged is only at Unity.

Swapping out for my original 12AT7 yields more grit and boost, as you would expect given the increase in Mu.

Here are my voltages - does anything look out of place here?

Pin     Volts DC

1        6.38
2        0.23
3        0.0
4        0.0
5        9.38
6        7.17
7        0.37
8        0.0
9        4.5 (no connection).

I've checked the valus of all resistors with my DMM, and they all read as 'correct' (i.e. 220K, 470K, 1M etc...).

The only 'sub' I've made is to increase R3 (Pin 6) to 220K for a little more 'push'.

I realise a 100v tube will not boost the same at 9v, but other posters here have commented on the gain available from a 12AU7.

Would anyone be kind enough to suggest how to get more than Unity from a 12AU7 tube in this circuit?

Many thanks,

Ian.

[wizbey]

Well I thought id have a crack at this Valvecaster stuff and i have gotta say, I am damned impressed!!!

Here is my tweaked version of one with a JJ.

http://soundcloud.com/bmcguitar/bmc-guitar-effects-tweaked

Definitely going to build one of these and add it to the pedal board for sure.

Recorded using a Alesis Multimix + condenser mic in front of Kustom KCA10 SS Combo attached to a 2x12 Marshall MC212 Cab and 1991 Ibanez RG560

[MichelP]

"OK, a new 'JJ' 12AU7 arrived this morning, and I duly put it into my Valvecaster."

The bad news first : I had the same issue with the JJ 12AU7/ECC82.  I found out through a discussion in a German forum that the JJ´s just don´t work well at low voltages 12 V. 

Indeed on my valvecaster and vanilla overdrive unity with the JJ was at max, the EH 12AU7 adn China 12AU7 don´t have this problem and work well.

Now the good news : set the anode voltage somewhat higher (36 V) and gone is the issue (unity at 9 H !!!).

[iccaros]

OK, a new 'JJ' 12AU7 arrived this morning, and I duly put it into my Valvecaster.

With everything at '10', the signal with the pedal engaged is only at Unity.

Swapping out for my original 12AT7 yields more grit and boost, as you would expect given the increase in Mu.

Here are my voltages - does anything look out of place here?

Pin     Volts DC

1        6.38
2        0.23
3        0.0
4        0.0
5        9.38
6        7.17
7        0.37
8        0.0
9        4.5 (no connection).

I've checked the valus of all resistors with my DMM, and they all read as 'correct' (i.e. 220K, 470K, 1M etc...).

The only 'sub' I've made is to increase R3 (Pin 6) to 220K for a little more 'push'.

I realise a 100v tube will not boost the same at 9v, but other posters here have commented on the gain available from a 12AU7.

Would anyone be kind enough to suggest how to get more than Unity from a 12AU7 tube in this circuit?

Many thanks,

Ian.

as others have stated IT my be the JJ (been told that long plate tube have issues with lover voltages, but have not tested it), In fact the 12u7 should give you more boost than the higher MU tubes at 12 volts due to its history with the 12u7 and the way it handles current.  In my Linear Tube project --> http://www.diystompboxes.com/smfforum/index.php?topic=91745.0
I posted this write up --> http://www.freewebs.com/valvewizard2/Triodes_at_low_voltages_Blencowe.pdf

[newfish]

OK.  Thanks.

Found some 12U7s on the internet last night.  Have orderd a couple to play with, since this box is intended to run with my existing 9v / 12v split supply.  30v isn;t really an option - unless I employ *another* power supply.

Cheers!

[iccaros]

where did you find 12u7? I have been looking for at least 2 more for the 24volt amp I setup... 12au7's work but the 12u7's have more gain.
you may have to bias a little different for the 12u7, changing to a 100K pot instead of the 50 and it stays about 2/3 of the way.

[newfish]

where did you find 12u7? I have been looking for at least 2 more for the 24volt amp I setup... 12au7's work but the 12u7's have more gain.
you may have to bias a little different for the 12u7, changing to a 100K pot instead of the 50 and it stays about 2/3 of the way.

I thought I'd found some at 'tubedepot', but it turns out that they're on back order.   
'thetubestore' appears to have them for $15 or so, with an availability of 'usually ships within 24 hours'.
No mention of 'waiting for stock'.

Hope this helps.

[akkor68]

Hi,
Finally my Valvecaster works!!!!
The problem was the power supply as always.
The fun thing is that a Boss adapter in my country is about 30-35$, but I used my brother's 8 port switch's adapter and it is perfect, and he bought the switch and the adapter for about 10$...so I think I will also buy a switch like this
I only have a little noise with it, but I think I will solve this with the transistor mentioned above.

Oh and the gain and the volume pots work reverse, any ideas why?

I found a tube named PCC189 I tried it, it has less gain and less volume, but I like what I heard, I'm thinking of building another valvecaster soon with this. But it also was very hot when I played. First I want to finish this project, a nice housing, maybe a 3PDT switch for true bypass.

Thanks for the help!!!

[iccaros]

Oh and the gain and the volume pots work reverse, any ideas why?

you wired them backwards.... swap the the outer wires

http://sound.westhost.com/pots.htm

I found a tube named PCC189 I tried it, it has less gain and less volume, but I like what I heard, I'm thinking of building another valvecaster soon with this. But it also was very hot when I played. First I want to finish this project, a nice housing, maybe a 3PDT switch for true bypass.

Thanks for the help!!!

That is a weird tube, already not linear, want 7.6 volts on heaters and draws 300ma just for heaters.. I would not expect much "Boost" from the load line at these voltages.
http://tubedata.tubes.se/sheets/030/p/PCC189.pdf

[blackcorvo]

That is a weird tube, already not linear, want 7.6 volts on heaters and draws 300ma just for heaters.. I would not expect much "Boost" from the load line at these voltages.
http://tubedata.tubes.se/sheets/030/p/PCC189.pdf

In this kind of situation, you can always use a regulator to get the right voltage... a 7806 with some 1N4007 will do the trick.
_____
[   O    ]
|_____|       
[ 7806 ]
|_____|
  |  |  |
  |  |  |_______7.4v
12v |
      |
    _\/_
      |     2x 1N4007
    _\/_
       |
  ___|___
  |_GND_|

Whenever you need an "odd" voltage, like 7v or 13v, you just need to get a regulator for the closest voltage (7806 for 7v, 7812 for 13v, etc) and add diodes to it's "GND" pin.
Each diode adds 0.7v to the output voltage. Just check the difference between your regulator's output voltage to the voltage you need, and divide this difference to 0.7 so you get the number of diodes you'll need.
If you wanna be more precise, you can use schottky rectifiers. These add just 0.1v to 0.2v .

[tuckster]

Ok now it works. I don't know why... I put in a new Pot for R2 becaus ethe last one was realy burned after all these resoldering adventures.
I still got the same pin values for 9V and it also works for 12V but then I obviously have different values.
I tinkered around with R2 and R3 to get a nice sounding pedal. I'm going to post the pictures in the pitures thread.

Yes it worked but it was not very loud. I swaped the JJ tube with a tube-town one and it's much better.

[atelier musiques lourdes]

my own valvecaster, & first attempt with tube as well...

[newfish]

^ ^ ^

What Lies Beneath...

Good idea to have a kick-plate over your Tube.

[iccaros]

^ ^ ^

What Lies Beneath...

Good idea to have a kick-plate over your Tube.

Yes, playing this weekend, made me want to add a shield to mine.. I use mine to boost my amps distortion for leads.. So after the 4th or 5th song I noticed I was kicking the tube..

[newfish]

Well, a 12U7 arrived yesterday, courtesy of eBay - in its original 'CBS' box...

...and it works *so* well!  Plenty of boost available, decent amount of grit in there too.

Thanks once again to all the splendid folks on this forum for the ideas, advice, and intellectual generosity, without which, my pedal board would be really bare.

Cheers!

[ayayay!]

Okay so I'm finally gonna take a crack at this too.  Got a couple GE 5814a's that should do the trick.

I'm seeing conflicting reports on boost.  Does thing have enough?  If this was my one only pedal, would it do the trick or would I need some kind of booster after it? 

Well I thought id have a crack at this Valvecaster stuff and i have gotta say, I am damned impressed!!!

Here is my tweaked version of one with a JJ.

http://soundcloud.com/bmcguitar/bmc-guitar-effects-tweaked

Definitely going to build one of these and add it to the pedal board for sure.

Recorded using a Alesis Multimix + condenser mic in front of Kustom KCA10 SS Combo attached to a 2x12 Marshall MC212 Cab and 1991 Ibanez RG560

Sounds good man!  What I would expect to hear, which is a good thing.  I hear some underlying fizz I'm not so crazy about, but it still is great for what it is. 

[zambo]

this thing has enough boost to raise the level of your guitar for a lead. You can add more gain and it will add some "wool" to the tone of a clean guitar or you can use a semi dirty amp and it will drive an amp into serious distortion. I hope that answers you question.

[ayayay!]

this thing has enough boost to raise the level of your guitar for a lead. You can add more gain and it will add some "wool" to the tone of a clean guitar or you can use a semi dirty amp and it will drive an amp into serious distortion. I hope that answers you question.

It does!  Thanks Zambo.  I'm hoping I can get to this one this week. 

[Bill Mountain]

Ok.  So, I finally broke down and built a Valvecaster.  I have been on the search for a bass overdrive and I think my search is over.  I followed the original schematic except I used a 10uF output cap, I did not include the tone control, and I skipped on the master volume control (for now).

I am running it on 9v but I plan on trying higher voltages in the future.  After I built it, it was a little "farty" for my taste.  I kept trying smaller and smaller input caps and I finally settled on a 1nF cap.  This was not the best sounding cap (I lose a little too much bass) but it was the least "farty" sounding one.  I checked Jack Orman's RC calculator and it is telling me that a 1nF cap and a 1M resistor will create a high pass filter at 160 Hz.  This of course is pretty high but I can add some bass later on in the circuit if I need it.

My question is related to a statement on the RC calculator page, "This calculator assumes a low source impedance, which usually is small enough that it does not change the corner frequency."  Since this is right after my bass which is a high impedance source, how do I actually figure out what frequency the high pass filter is?

Edit:  I just remembered that I used a 12AT7 (It's all I had).  I'm pretty sure that higher voltages and lower gain tubes will allow me to raise the input cap but I gotta work with what I have for now.

[zambo]

to tame farts try and lower the value of the cap from pin 1 to pin 6 and drop your output cap back to 1 uf. .022uf sound great on a lot of stuff for bass. The master volum is nice too. if you are running it wide open its not as good as it could be imho. I like the three knob version for the versatility.