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

[Franky]

Wow, this project rocks!! I think i'm gonna have to design a 12V power supply for all those nice tube projects..   

[frequencycentral]

Here's mine:

[kurtlives]

Nice!

What did you build it on? Perf, vero?

[frequencycentral]

Nice!

What did you build it on? Perf, vero?

Tripad - three holes per pad. I really like it a lot!

[Franky]

It looks great! Good work man!

[col]

I need to try that oscillator in a tremelo circuit I've been messing with to see if it cuts out the thump I was getting, not even a tick. What we really need for true vintage mojo is a Ge transistor oscillator. I have tried a few but they have produced ticking, I wonder if this could be adapted to remove it?

Col

[Franky]

I was just about to talk about that oscillator.. In a different way, using an opamp to get more waveshapes (tri or square, or even a mix)...

[frequencycentral]

I need to try that oscillator in a tremelo circuit I've been messing with to see if it cuts out the thump I was getting, not even a tick. What we really need for true vintage mojo is a Ge transistor oscillator. I have tried a few but they have produced ticking, I wonder if this could be adapted to remove it?

Col

Most of the ticking I had to fix was caused by the rate LED turning on and off, only a little from the LFO itself. I found the diode between the wiper of the depth pot and the cathode sorted that out, together with playing about with the values for the voltage divider at the LFO output.

As for Ge - they're really low gain as far as I know (I'm no expert), I think the BC547C I used has a gain of 800. I tried this oscillator with BC107's - it wouldn't oscillate.

I was just about to talk about that oscillator.. In a different way, using an opamp to get more waveshapes (tri or square, or even a mix)...

You could use a transistor or (opamp) comparator to turn the LFO's sine output into a square wave - but you may then experience ticking. Triangle is so similar to sine (for this purpose) that's it's not worth the extra hassle! And triangle would also probably have ticking problems. The LFO in my other tube tremolo 'Bipolar Disorder' was based on a triangle, I had to work hard to stop thumping/ticking. The nice thing about a sine is it's smooth turnaround.

What I like about the Vibracaster is it's 'vintageness' - old school tremolos used similar sine wave phase shift oscillators - this one just uses transistors instead of tubes. Tubes won't oscillate at 12 volts........

[frequencycentral]

Finished:

[Jimmy-H]

OOOoops you did it again!
Nice piece of work Rick
Does it sound different compared to the Bipolar disorder?

And you couldn't help yourself to build the Vibracaster!

[Renegadrian]

[frequencycentral]

OOOoops you did it again!
Nice piece of work Rick
Does it sound different compared to the Bipolar disorder?

And you couldn't help yourself to build the Vibracaster!

Thanks Jimmy! I haven't done an A/B test with the Bipolar Disorder yet - I'll get around to it and post some more clips.

No - I had to build it really to get 'closure' - now I can move on to #3 in my submini tube series: "Doppelganger".

And...........if I hadn't built it I wouldn't have sorted out the bugs!

Hehehe - where you get those icons from I just don't know!

[liddokun]

I can use the 6111 version 2 schematic, but just build it using a 12AU7 right?  The pinout's are just different, but all the resistor values and everything is ok staying the same?

[frequencycentral]

Here's the 12AU7 version, just the tube pinouts change. The rate LED circuit is optional.

[liddokun]

Alright, thanks a lot Rick.

[liddokun]

The circuit can also be run at 9VDC, correct?  If I'm running it at 12V using a wallwart, what should the current specs be for it? 300mA?
And those two big resistors..if I'm building with 12AU7, then I can just use 1/4 watt resistors throughout?

[frequencycentral]

The circuit can also be run at 9VDC, correct? 

Correct - but it would have to be the 12AU7 version.

If I'm running it at 12V using a wallwart, what should the current specs be for it? 300mA?

12AU7 version should draw about 150ma.

6111 version should draw about 300ma.

Make sure your power supply is regulated. Maybe you should get a 500ma (or more) so you can power future tube projects.

And those two big resistors..if I'm building with 12AU7, then I can just use 1/4 watt resistors throughout?

You only need the big resistor(s) for the 6111 version. To run the 6111 heater from 12 volts you need to reduce it to 6.3 volts. That's what the 19 ohm / 3 watt resistor does. I used two 10 ohm in series - they were 5% tolerance,  I measured them at 19 ohms - perfect!

Alternatively you could use a 7806 voltage regulator (6 volts is at the lower end of the heater tolerance, but it should be fine). Or you could use a LM317 and trimmer (like the Subcaster) and dial it in to 6.3 volts.

Don't forget you could also add all the original Valvecaster controls with a bit of tweaking: Gain, Tone, Volume. I will add a schematic of that version to this thread eventually - but it's pretty easy to work out if you compare the schematics.

[liddokun]

Hey, thanks for the help.  I saw a few tweaks in the valvecaster forum, specifically using the 7812 on the dc jack with 100uf filtering cap.  Should I add this on the vibracaster?  I'm planning on doing it 9vdc, with a 12AU7 so that I can power it off my daisy chain.  The 7812 is a 12v regulator, so I suppose I wouldn't use it here for my 9v circuit. 

[Johnny Halo]

Can someone post the PCB layout for this in the 12au7 version?

Thanks.

[frequencycentral]

Hey, thanks for the help.  I saw a few tweaks in the valvecaster forum, specifically using the 7812 on the dc jack with 100uf filtering cap.  Should I add this on the vibracaster?  I'm planning on doing it 9vdc, with a 12AU7 so that I can power it off my daisy chain.  The 7812 is a 12v regulator, so I suppose I wouldn't use it here for my 9v circuit. 

Don't bother with a 7812 if your'e running on 9 volts. Maybe you could consider a 7809 instead, but build it without first - you may not need it. Use the 100uf cap though.

Can someone post the PCB layout for this in the 12au7 version?

Thanks.

Sorry, i don't do PCB - I'm a Tripad guy (see above). Someone else is welcome to come up with a vero layout or a PCB though...............