Vibracaster - or "How to turn your Valvecaster into a Tremolo"

[Renegadrian]

Check this out...




EDIT
Forgot to write that both Speed 1 and 2 go to ground
Corrected

[kurtlives]

Looks good! Thats one hell of a ground jumper though.

[kurtlives]

Check this out...




EDIT
Forgot to write that both Speed 1 and 2 go to ground
Corrected

Did a careful look over and cant find any errors. I am going to building this in the next few weeks. I am building it so the osicallor can be switched on and off for a "distorsion" pedal with switchable tremolo. Should be pretty easy this way to tell if we made an error with the oscialltor layout.

You going to build one?

[Renegadrian]

As I wrote in the page before,I am lacking some components, so I cannot build that before a couple of weeks...
But yeah that's my will...

[Br4d13y]

pardon me asking, but i am kinda new to building stompboxes and am having lots of trouble with power supplies.
would you just run this at 12v to the v+? or would you have to run the heaters and the v+ seperate, i just really need help as this is my biggest setback with building anything

[Renegadrian]

Br4d13y, if you look closely the vero layout or the schem, you see that the 12V goes to the heaters too, as the tube used is a 12AU7 - so yes it runs on 12V! 
So pin 5 is wired to the +V and pin 4 to ground. No need for separate power supplies here...Easy, uh?

[kurtlives]

Could run the pedal at 18V (Maybe higher I imagine) as long as the heaters get 12.6V DC.


My Caster is almost all drilled. Just need to finish it then wire it up.

[Br4d13y]

Br4d13y, if you look closely the vero layout or the schem, you see that the 12V goes to the heaters too, as the tube used is a 12AU7 - so yes it runs on 12V! 
So pin 5 is wired to the +V and pin 4 to ground. No need for separate power supplies here...Easy, uh?

but what if i am using the 6111? do i just have to put a resistor inbetween pin 5 and the v+?

[frequencycentral]

Br4d13y, if you look closely the vero layout or the schem, you see that the 12V goes to the heaters too, as the tube used is a 12AU7 - so yes it runs on 12V! 
So pin 5 is wired to the +V and pin 4 to ground. No need for separate power supplies here...Easy, uh?

but what if i am using the 6111? do i just have to put a resistor inbetween pin 5 and the v+?

I used a 6111 in my build. My power supply is 12 volts. The 19 ohm / 3 watt resistor in the 6111 Vibracaster schematic drops the voltage to 6.3 volts. It should be placed in series with the heater.

Note that the heater for the 6111 is pin 3 (+ve) and pin 6 (earth).

[Br4d13y]

thanks, i have come to understand most aspects of schematics, but power supplies always get me when it comes to tubes. also, kinda off topic, if you want to put two pedals in one enclosure, would you just wire the power in series? i really wanna make a two stage valve caster, but don't know how to connect the power

[kurtlives]

Youd want to power the effects in parallel. That way if one fails the other can keep chuggin.

Also if they were in series there would be a voltage drop across the first load and your second effect wouldnt be getting as much "juice".

[frequencycentral]

thanks, i have come to understand most aspects of schematics, but power supplies always get me when it comes to tubes. also, kinda off topic, if you want to put two pedals in one enclosure, would you just wire the power in series? i really wanna make a two stage valve caster, but don't know how to connect the power

Have a look at the Twincaster schematic on the 'Tube boost + overdrive running off a 9 volt battery' thread, there's also a layout for it in Renegadrian's gallery. You would be wiring the power in parallel. Except if your'e using two 6111 tubes to make it, then you would run the two heaters in series (see diagam above), but everything else in parallel.

[SirElwood]

Ok, even I got interested about this one. So, I build it. I used 6111 submini tube (man that's great little lamp!). First, I build a "standard" subcaster with ~20V B+. It's really good sounding preamp/clean booster. Then I add that oscillator and did changes according to frequencycentrals schematic. It works just like tremolo in my Fender vibro champ. And that's not all good thing. First of all, depth (intensity like big F calls it) sucks out alot of tone (highs) and gain. In vibro champ, you can compensate it little with treble pot. But in this case, you can't (in fact, subcaster lacks highs to begin with). And 100k reverse audio pot might work better as a depth. I also have some ticking (just like vibro champ), but I think this can be solved by good grounding. I also did that rate led modification, but it (led) was really dim, and useless. But I don't care those things anyway.

I don't have BC547C transistors, but it works fine with BC547B, BC548C, 2N5088 etc. I also run it with 9, 12 and 20 volts. No big difference. Anyway, speed range is good. Slow enough, but at max. even too fast (for me). It also has a kind of strong feeling in it (depth almost full). I like it alot! Only really annoying thing is that "tone sucking", because I know I have a good sounding preamp somewhere under there. Need to solve this one. It would be so cool to have tremolo and clean boost/preamp in same box. In fact, EA tremolo does this... But I'm a tube brain.

So, there's my 0.02$. Great work mr. frequencycentral!

[frequencycentral]

Hey SirElwood,

Thanks for the build report. Glad you like it. And excellent that you tried different transistors too. I haven't noticed any loss of highs with my build, or on the breadboard. I agree with you about a slight loss of gain though - but I compensated for that in my build by increasing the second triodes plate resistor to 220K. I built mine as a tremolo only though - no gain or volume controls, so the increase in that resistor gave me unity between effected and bypassed. Ticking is always an issue with this type of circuit - I found that the 1N4148 got it down to a level where it was almost imperceptible though.

It's possible to play about with the cap values in the oscillator to alter the range. They don't all have to be the same value. If they were all 1uf the range would be slower. I think it would be possible to have a broader range by experimenting with a few different value caps in different positions - but the PSO is a balancing act between resistor and cap values. As R.G. said "The only thing that the circuit really cares about is that the total phase shift from the collector back to the base is 180 degrees. Any combinations that do that will work. "not working" usually results when the resistor gets too big to make up enough phase shift or so small that it pulls the feedback signal too low to sustain oscillation. Making caps non-identical works, and might offset non-identicalities in the resistors."

As for the rate LED, I didn't use that in the end either. That mod was the only way I could get around the rate LED causing ticking as it turned on and off, and I guess it's still not the perfect solution. But as I said in page 1 of this thread - "You also have to bear in mind that I'm really a complete idiot masquerading as an elecronics engineer." I take this stuff as far as my knowledge allows - it's up to others to impove on it!

[SirElwood]

More tweaking done. I'm too tired to draw my own schematic, so I edited frequency's original (it's past 1.00AM here...). I will draw my own eventually.

Shortly:

I added 2µF NP cap on dwell pot, that seems to work with that gain loss. I'm not sure it's good fix, but at least it's a first step towards right direction. Then I need to bypass tremolo without true bypass. Schematic shows where I put that switch (jumper wire). I'm not sure about this either, but it seems to stop oscillator with no defects. But all this might have been on this thread earlier.

I also put a simple jfet booster in front of this. And as a gain pot a dual 100kB controls jfet boost and first cathode of 6111. I must say I think this was (is) a clever trick. Volume difference is quite big when gain is turned, but this indeed gives sweet clean tremolo and (with oscillator stopped) some nice overdrive tones. 3PDT switch to bypass this whole thing, and another 3PDT to change from tremolo to booster/overdriver. And because tremolo switch is just single on/off, I have two switchs free for something... This is not over yet!

Anyway... schem looks like this:

"You also have to bear in mind that I'm really a complete idiot masquerading as an elecronics engineer."

Same here! Random tinkering is the path to success.

[frequencycentral]

Hi SirElwood,

Glad your tinkering! I'll have to try that 2uf NP cap idea.

Probably the easiest way to bypass the tremolo function would be to have a switch to short pin 5 to earth.

[SirElwood]

Probably the easiest way to bypass the tremolo function would be to have a switch to short pin 5 to earth.

Yes, but this way there is no change in sound. If you short pin 5. to ground, it would make some change in sound, because of that depth pot affects it. And if I remember correctly (from yesterday), that little ticking noise remained if I didin't stop the whole oscillator.

[frequencycentral]

Quote from: SirElwood on September 21, 2008, 10:21:19 AM<blockquote>

Quote from: frequencycentral on September 21, 2008, 09:54:25 AM<blockquote>Probably the easiest way to bypass the tremolo function would be to have a switch to short pin 5 to earth.
</blockquote>


<removed by request></blockquote>


Ok, then switch between the oscillator and earth. If you're still getting ticking without the oscillator connected to the cathode it's a decoupling issue. Put a 10uf cap across the supply rails

[kurtlives]

Wouldn't breaking the connection from pin 5 to the oscillator be the easiest way? That's how I was going to go about it.

[Br4d13y]

could someone post a schematic with all the valvecaster controls, and a boost/tremolo switch?