Tube boost + overdrive running off a 9 volt battery

[glenn.b]

And yes, tube is a 12au7.

[frequencycentral]

1:9.24                                                                         
2:8.51                     
3:000
4:9.33
5:9.34
6:9.34
7:8.93
8:000
9:9.33

Check out your voltages and connections at pins 4, 5 and 9 first, that's the heater. Pin 9 should be half your supply, so about 4.5v. Pin 4 should be 0v and pin 5 should be 9v. Once you get the heater voltages sorted out we can look at the rest of you voltages, which will change once the heater is correct, so repost them. There should of course be no connection to pin 9, as it's the heater's centre tap and is unused in this circuit. Good luck, it will work eventually!

[glenn.b]

Thank you again for the push and the encouragement!  When I get up tomorrow I will unsolder the whole works and then restart, working towards those numbers you gave me.  I will let you know what I come up with just as soon as I get it together.  gotta get the gremlin out...

[adynata]

i have a fender champ 600, a newer one, that i hack on. it sounds really nice with this tube-booster in front of it. thanks, guys, for making these things tangible.

goodluck debugging glen.b

[Renegadrian]

Welcome to both of you - 

[dano12]

Man this thread keeps going and going...

Has anyone come up with simple mods to the valvecaster to make it function as a simple buffer. Maybe with just a little gain?

[frequencycentral]

Man this thread keeps going and going...

Has anyone come up with simple mods to the valvecaster to make it function as a simple buffer. Maybe with just a little gain?

Yes it does Dano - it's been quite an inspiration. Though I think it's now offically too long to read!

Using just a single triode stage, a 100K plate resistor and a 100K cathode resistor, taking the output directly from the cathode through a cap value of your choice, will give you a non-inverting unity gain buffer.

[dano12]

Man this thread keeps going and going...

Has anyone come up with simple mods to the valvecaster to make it function as a simple buffer. Maybe with just a little gain?

Yes it does Dano - it's been quite an inspiration. Though I think it's now offically too long to read!

Using just a single triode stage, a 100K plate resistor and a 100K cathode resistor, taking the output directly from the cathode through a cap value of your choice, will give you a non-inverting unity gain buffer.

thanks buddy, I'll give that a try.

[Ripthorn]

If I recall, setting it up like that will actually give you slightly less than unity gain, but like .99 or something, just a technicality, but I remember reading somewhere that that is why some people prefer to not use a cathodyne phase inverter.

[lazerphea]

Hello everyone!
I read almost all the replies in this thread and I built my valvecaster and then the twincaster; it's nice, but not really my favourite kind of sound.
Anyway, I still didn't get one thing: I tried to use an AD/DC transformer to power the circuit, and I get a quite loud constant hum, still I can hear the output of the pedal.
Why's that? Maybe a crappy transformer? If I use a 9V battery everything's fine, but I'd like to try to feed it with 12V.
The transformer has a trim that lets me choose the output voltage, and I tried 9V and 12V: the quite strange thing is that if I measure its output, I measure ~12.5V instead of 9V, and ~17V instead of 12V (if I recall correctly... I'm @ work right now ). Can someone kindly shed some light on this?

[frequencycentral]

Hello everyone!
I read almost all the replies in this thread and I built my valvecaster and then the twincaster; it's nice, but not really my favourite kind of sound.
Anyway, I still didn't get one thing: I tried to use an AD/DC transformer to power the circuit, and I get a quite loud constant hum, still I can hear the output of the pedal.
Why's that? Maybe a crappy transformer? If I use a 9V battery everything's fine, but I'd like to try to feed it with 12V.
The transformer has a trim that lets me choose the output voltage, and I tried 9V and 12V: the quite strange thing is that if I measure its output, I measure ~12.5V instead of 9V, and ~17V instead of 12V (if I recall correctly... I'm @ work right now ). Can someone kindly shed some light on this?

Sounds like your power supply is an unregulated one. What you need to do is get a 7812 voltage regulator and use that to regulate down the ~17v to a stable 12v. Also, add a 100uf electro cap across the power rails from +ve to ground. That wil get rid of your hum issues and give you a nice stable 12v. This method is mentioned elsewhere in this thread, a lot of people have used it.

[Ripthorn]

The reason why you measured higher voltage on your transformer is 1) it is unregulated and 2) they design wallwarts to deliver a MINIMUM of 9V at the rated current, so if you are drawing less current, then the voltage will be higher.

[biggy boy]

Yes transformers can be real noisy sometimes.
My ValveCaster is housed in the same enclosure as a VooDoo lab OD, the valvecaster is powered by a transformer and is relatively quite.
The vooDoo is powered by a 9 volt battery.
The two circuits are totally separate from one and other, two channels in, two channels out of the enclsure.
Yet if I use the Voodoo while the valvecaster is powered up I get all kind of noise bleeding into the surrounding wires of the voodoo circuit.

I think I need to isolate the voodoo wires going to the pots away from the 120 volt wires that feed the transformer for the valvecaster!!
For now I just use one or the other.



left side ValveCaser in, right side Voodoo in. The outputs are on the back.

[Renegadrian]

I went to the reharsal yesterday, First time with this band, playing QUEENSRYCHE songs - me on the bass - I took my Valvy with me...Man, it's so good on bass...It just rounds up the sound to achieve the Eddie Jackson (bass god for me...) sound...
Just wanted to share this experience...

[biggy boy]

  it's so good on bass...It just rounds up the sound to achieve the Eddie Jackson (bass god for me...) sound...
Just wanted to share this experience...

+1 about running a bass through it, sounds so good with a double musicman pickup.

Glen

[lazerphea]

frequencycentral, Ripthorn, thanks for the advices!
I bought today my 7812 and a small dissipator, and if I unterstood correctly what I have to do is:
- wire the transformer's output to the 7812's input
- take the output of the 7812 and feed the + pin of the electrolytic cap, while the - pin goes to ground
- take the +12V from the + pin of the cap
Right?

[Ripthorn]

That is exactly right.  Don't forget to ground the regulator, it uses that for a reference.  Probably what I would do, though, is put an electrolytic cap before and another after the regulator, since the smoother the input voltage, the smoother the output voltage will be.  An extra few cents is worth it.

[terminalgs]

If using 12.6v heater supply:  pin 9 is not used,  pin 4 and pin 5  are used.  give one 12v+ and ground the other. @12v the heater draw is 150ma.
If using 6.3v heater supply:  pin 4 and 5 are jumpered together and get 6v+ and pin 9 is grounded.  @ 6v the heater draw is 300ma.

9v is not enough for a 12.6v heater.  the current draw from the heater would kill a battery quick, so you ought to be using a transformer of some sort.  might as well be 12v instead of 9v.  better yet,  get a 120-200v transformer and give a 12ax7 high plate voltage.  everything becomes easy once you do this.


without a load, a power supply's voltage may be higher than the required 12..,  like 15-17,,  once you put the load across it ,, (the filament) it should drop to 12v (or just below).  are you getting a 17v reading with the filament as a load? or without the tube installed, across pins 4 & 5?

[lazerphea]

Guys, I tried the 7812 ant it outputs a nice 11.40V supply, but now, instead of a constant hum I get a constant buzz!
Terminalgs, I don't get it... do I have to modify the tube's wiring? 

[lazerphea]

Update: I rebuilt the valvecaster and the buzz disappeared, but... It has a crappy sound! No sustain and a farty distortion...
Ok, I'll try to debug it--- just a question: is it normal for the tube to be quite hot (sorry for the n00bish question)?