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

[savvy]

Hi folks, is anyone still reading this post? I have a problem with my build,I built the valvecaster prior to seeing this and decided to add the trem'. Valvy works good with a 386 pwr amp section into my spkr cab but I cannot get the trem working with it!
I connect pin 8 to the 1n4148 and ground to the jack socket/amp ground.all I get is nothing until I turn the pot fully c/w and then that connects the 12au7 to grnd and the valvy powers up :icon_question:I have put an led from grnd to Q1c and that flashes and the rate changes as the pot is turned.
Voltages using a 9v battery are:    Q1 c=5.54  b=0.657  e= 0.032        Q2  c=9.0  b= 3.7   e=3.16 they seem in the ballpark 
To connect the trem part I am removing the pin 8 connection to grnd and inserting this circuit between pin8 and grnd, is pin 8 to grnd meant to stay connected?
Can someone help please?
 Thanks

[frequencycentral]

What transistors are you using? Pin 8 should no longer be grounded.

[savvy]

Thanks for replying, I am using 547c BUT I made a big boo boo! the led flashes when I connect to ground and Q1c not V+ 
I have tried and tried with this but no luck, I have just got some more 547c's and am going to rebuild it
I was certain in my mind that pin8 grounds through the trem circuit but I thought I would ask the question to make sure.
Thanks again, any ideas?Barrie   ps if it don't work this time I will try the EA trem and build it in to the valvecaster as a pre'

[savvy]

  well it works finally, I popped in a couple of new tranny's and presto, Just one thing tho' it seems the led works as I noted, by connecting to earth and 'c' of Q2, thats the leg with the connection to the Q1,3M3 and 10k junctions in case I have Q1/2 reversed.Is this correct?
Any way I now have a working trem and will start modding now
Thanks for a really good unit, need to get a nice panel to fit the controls onto and build it into my speaker cab I made.I now have my Vibracaster into a 386 chip amp and then my speaker cab,lovely for a battery setup Works great off a 12v motorcycle battery/cigar lighter socket or power pack.

[DiamondDog]

Rick-

I know I've been away for a while- good to see you're still going strong with the tubes! 

Is there a definitive VibraCaster schem out there? I've 12AU7/U7 Version 3 (and 2 and 1) dated 180808; is there an "official" release after the V3?

Have you (or anyone else) tried stations and isildur100's mods from the previous page?

Cheers

DD.

(FWIW the "clean" Valvecaster @ 12v has put up with touring for about year now- congrats to all involved.    )

[frequencycentral]

That's the latest version. I did build a Vibracaster oscillator into a submini amp recently: http://www.diystompboxes.com/smfforum/index.php?topic=83831.0

I changed a resistor value (from 47k to 8.2k), largely because I was getting only very subtle tremolo, due to the running at higher voltage - probably not a good idea on a 12v build. One thing I did find useful was hooking a 0.47uF cap from the cathode to ground, thing got rid of the slight volume drop between 'no trem' and 'some trem'. A 100R resistor between lug 1 of the depth pot and ground (instead of directly grounding lug 1) is also probably a good idea, as it should cut out that slight 'thunk' when you turn the depth to minimum. I really should breadboard the Vibracaster again _ I've learned a lot since I first did it!

[sundgist]

After building my valvecaster, liking it, and realising I don't have a tremolo. I went ahead and made this stripboard layout for the vibracaster LFO taken from Rick's vibratone schematic. Pot connections may need reversing.



Verified and working well.

I'm running it off the regulated 12.6v heater supply. My valvecaster uses a 12at7 and runs on 21v, it also worked well wired to this. Had a bit of ticking which was removed by putting a 220uf cap across the + and gnd. The 8k2 resistor may need changing if yours runs on other voltages. 27k gives me a nice range from subtle wobble to chopping. 47k is stock for 12v.

Added a flashing rate LED. Based on Taylor's rather artistic post here.
http://www.diystompboxes.com/smfforum/index.php?topic=79078.msg657184#msg657184

...and added to the vibracaster schem like so.


I've put the LED on the emitter as the non inverted signal makes it flash clearer. Flashes on rather than flashing off.
I'd be interested to know if there should be any reason not to do it this way.
I tested it with various gain settings and checked with a scope. Works well and doesn't affect the sound or LFO waveform, not a tick or bump to be seen.

[El Heisenberg]

Is there nothing else I can use but the BC547? I've never had these transistors.

I tried it with a 2n5088 and a 2n4011 cos all I had left were one of each and it don't work.

[El Heisenberg]

Well I got it working. The depth control doesn't sound good with the volume turned low. Just kinda, mushes it up.The .47 uf cap after the diode really worked wonders. I had to use two .22 caps for every .47 caps cos I can't find .47 anywhere I can drive to. I also changed the 47k resistor to 27k. Way to choppy at 8k2. Nothing at 47k. I'm running it at 17.5v right now, but I plan to use 21v.

Anyway, I was thinkin if the depth control problem isn't cos of the transitors I used, then why have the depth control set up this way? Why not just jigger with the 47k resistor?


Also, I just replaced the 10k resistor to a 6k8 followed by an LED. Why not do this?? It's working.

The gain control is useless to me. It only sounds good when it's open. Whenever I put any resistance there, I get buzzing noise. This could just be the bad tube. I know for a fact it makes noise....It's too bad, I wanted to put a switch so I could just switch out a 100k resistor or a shunt to ground. But the fixed resistor gives me noise too!

[El Heisenberg]

BTW i'm using a 12AU7 tube. Heaters are AC 6.3v

Stuck a .1 uf cap in parallel with the 100k resistor from pin 3 to ground and it's fine now. I don't have room for more than one more volume/gain control in the amp I'm adding this to though. I think I will use a DPDT switch to engage the tremolo, but  it'd be cool to have the overdriven valvecaster tremolo with it also. Choices choices.

I don't get any problem with using the 6k8/LED instead of the 10k in the tremolo circuit. I'm not getting ticking.


I still hate the depth control

[El Heisenberg]

Well I was using a bad pot for the depth control. All is well now. Works great. Don't even need a switch to engage it. I could just wire it like this cos the depth control goes down to no audible tremolo. I hope that's what it's sposed to do.

 since I will be running the tube plates at 21v (right now I'm using a different transformer to test this and I'm running the plates and LFO circuit on 18v) should I also run the transistors at 21v?? I was gunna run them on regulated 12v I have in the amp already for the reverb but I dunno if that'll mess with the tube stage when I engage the tremolo.

[El Heisenberg]

datasheet says the transistors can do 30v max. Guess I'm in the clear? wonder if it'll add noise....

I don't wanna power this thing with all DC. I could run it all off the 12 regulator, but I'd like 21v on the plates and heaters on AC.

[El Heisenberg]

I wanted to run this vibracaster before my digital reverb which is before my 12au7 preamp. But I think the tubes output is way too much for the digital reverbs input. The reverb circuit is the General guitar gadgets belton circuit. Im running that on regulated 12v and there's a LM7805 giving 5v to the belton reverb brick.

I still dunno how all this works really. Is the tube about running at 18 or 21v too much for inputs of TL072s running at 12v?? With much distortion the reverb starts to fart. Ugly distortion. Goes away after the initial attack.

I'm still gunna put the vibracaster before the reverb. I can't have tremolo after reverb.

[kaalaraab]

Found my problem! DC current getting into the oscillator. The problem was obvious and the fix was simple

This weekend was a tube weekend. Finished my 18W (waiting on tubes to test it) and I finished this...





It sits beside it's twin the Valve Caster and looks awesome!

For comparison...


Great pedal! Thanks Rick.

Ok, I was to build a simple valvecaster, buy I stumble upon this and the design by GeorgeM2. I hope you guys, GoergeM2 and Kurtlive could help me to make my mind. I just need to know if GeorgeM2 design is booster/overdrive too, and how exactly Kurtlives wire the DPDT and 3PDT switches. Could you, please, tell me?

[kaalaraab]

I was thinking of using a DPDT.

One side selects normal trem circuit the other shunts the second triode's cathode to ground.

The other side of the switch for LED.

This is the part I just don't get. 

[kaalaraab]

I just need to know if GeorgeM2 design is booster/overdrive too, and how exactly Kurtlives wire the DPDT and 3PDT switches. Could you, please, tell me?

Sorry, one month ago I didn't even knew that there were something call "capacitor". But I'm a fast learner, hope that will help. I just realize that GeorgeM2's built is a booster/overdrive too, and I realize that the above image shows the circuit where kurtlives put the 7812 and it's companion capacitor, but I see too another two capacitors and I'm still  wondering how to wire the DPDT and the 3PDT, could you post a layout? Or just a simple explanation could be enough.

I was trying to decide: GeorgeM2 or kurtlives built and finally that little voice inside me speak up: "What the hell, build both". So I'm starting right know with George's, since I have figured it out completely, (or so I think).

[kaalaraab]

...3) without partlist, best view wire



...Best regards, George (Anatoliy Martynenko).

I came up with a PCB layout for Anatoliy design, could please somebody check if it is right? I have doubts between in parts with poor visibility like volume 2, tone 3, pin 9, diode, etc.



Note that I added a trail to connect tone 1 and volume 3 trying to avoid the wiring, is that right?

Hope somebody check this out. Thanks.

[kaalaraab]

Note that I added a trail to connect tone 1 and volume 3 trying to avoid the wiring, is that right?

Hope somebody check this out. Thanks.

I just realize why that can't be done, so here is the layout fixed.



EDIT: Volume 2 goes to output, not to ground, it's fixed.

[kaalaraab]

Ok, sorry again, the layout had the pin 9 connected to tone 2, now that is fixed.

[glenn.b]

I think your making progress on this!  I will try this!