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

[kurtlives]

I guess I have to put the switch just after the diode from the cathode...!?So if it's on it lets the connection to the depth pot.
Is that so?!

Before the diode I think.
I forget, I know I did it though  . If you look back a few pages you'll see mine. Drive and trem in one box.

[frequencycentral]

BTW, on the Vibratone amp I built, I added a 0.47uF cap to ground from the cathode which smoothed out the loss of volume of the depth pot.

I'd still say after the diode, as the diode is biasing. But try both ways!

[markeebee]

Oh ok, I'll go public.

I love the Vibracaster.  It's great, I love the old-schoolness.  I've made four so far, and I'm just starting another.  But.......

Has anybody come up with a way of switching off the trem without popping?  I've tried, but no matter what I do there's always at least a faint pop.  Best results so far came by switching the emitter of Q2 to ground.....totally noiseless when switching the trem off, but a lttle pop when switching on. 

Any ideas?

[frequencycentral]

Hey Markee, I think you should be able to use a switch to select what the cathode sees, either the depth pot, or a low value resistor to ground. I'd suggest trying 1K and see what happens - play about with the value until the static volume is equal to the modulated volume. I wouldn't advise directly switching the cathode to ground, as there's your pop.

[markeebee]

Thanks Rick.  TBH I had already tried that, though.  Less pop, but still some pop. 

I reckon I should probably just live with it, but it really niggles me when I make something for a friend and they say "Yeah, I really like it, but if only.......". 

[~arph]

How about quickly fading in the tremolo when switching on, so you go from zero depth to the depth set.  I'm thinking in terms of the anti-lockup on the PT2399.. Something with a cap charging up and a transistor slowly turning on.. Can do the same for switching off then too.. slowly discharge cap.

[jimipop]

Hi there !

first, thanks for all this information we could find there !!! so cool

I'm a newbie with diy (and english, i'm french ...) but could anyone check at my layout ?
i made it with ressource on this topic but if you could verify it ... 

I think i'll have a pop with the tremolo switch (pin 8 to ground etc).



A great thanks !

[jimipop]

 

there ...



sorry !

[neurino]

First of all thanks Rick for this nice tremolo.

I just breadborded this version



it sounds good but in my circuit the volume is not constant while turning the Depth pot.

With pot at about 25% I have no tremolo (depth = 0) and unity gain while under that value signal gets significantly boosted.

Above 25%  volume keeps almost constant, maybe with a little perceived loss, than it raises again reaching 100%.

Did you experience the same behavior?

I could live with it but it sounds weird to me having part of the pot acting as a boost, part as tremolo depth.

Any advice is welcome.

[frequencycentral]

The last time I built a Vibracaster was in this: http://www.diystompboxes.com/smfforum/index.php?topic=83831.0 ...which included a 0.47uF cap from between the cathode and the diode. That solved the volume issue for me.

[neurino]

Thanks Rick, I saw your Vibratone and the cap, I will try it.

Did you experience the boost too with Depth pot to min? Just to understand if I may had done something wrong...

Another question, about the Vibratone tremolo part: you changed the res near depth pot from 47k to 8k2.

I tried some values but could not get what was changing in the overall sound, as depth changes.

[frequencycentral]

No, the depth was smooth with that cap in place.

The two resistors before the depth pot form a voltage divider. As the Vibratone was running on 80v it needed more voltage from the LFO to generate tremolo, hence the 8.2k instead of 47k.

[neurino]

Ok, thank you 

[HeimBrent]

Breadboarded it a while ago, loved it, and finally got my self to put it together in a box, but... I seem to have built a Valvecaster. :/ I did the first design due to practicality, and now the tremolo-part won't work. Maybe if I tried building a Valvecaster I would end up with a functioning Vibracaster? Hehe.

[frequencycentral]

What transistors are you using?

[HeimBrent]

That is a mighty good question. I've put the pieces so tightly together that I can't read it. It is howeverthe same ones that I used when I breadboarded it, and it worked fine there. But that's a while ago. You think they might be shoot?

[frequencycentral]

I only ask because BC547C work, but BC547B don't - not enough juice.

[blown240]

I am getting ready to build one of these in an enclosure with a regular Valvecaster and a Little gem.  Its basically going to be something that I can use as a practice amp, or bypass the little gem for an effects pedal.

Is there a Radio Shack number for the transistors?

[peterg]

http://www.aronnelson.com/gallery/main.php/v/frequencycentral/Vibracaster+Stock+12AU7+V2.JPG.html

i'm planning on making a two tube vibracaster using the attached single tube version as a starting point. I'll cascade the second tube. My questions are regarding the gain and vibra controls. Can I join the number 3 pins and send them to a pot for the gain and can I join number 8 pins together and send the signal to the diode at the start of the vibra section? Will I need stacked pots for this?

[peterg]

Anyone?....