Ok, so I built it. 4 valvecasters in series @ 12v. I'm not quite done tweaking, but here's some pics and a video demo (on bass and guitar) so you can hear it.
Basically I used the stock valvecaster circuit with just a few mods:
1. Instead of the pots to ground on the cathodes I used a voltage divider after the first gain stage as a gain control. The pedal doesn't have the DC noise the valvecaster has when adjusting the gain.
2. I stuck with stock plate resistor values, but did play with the coupling cap values, mostly because I'm using it on bass. I started with the stock 47nF but slowly increased at each stage to 1uF by stages 7+8.
3. I used 100k trimpots on the the cathodes (pin 3) of all 4 tubes. I can adjust the gain of each tube independently to set the overall gain of the pedal. Maxing them all out tends to make the pedal sag with hard string hits, something I'm still dealing with ATM.
4. I did not use a tone control. It honestly doesn't need one!
5. V2-4 are 12AU7s while V1 is a 12AT7. I used JJ tubes. I like the added boost and distortion from it, and it doesn't change the warm character of the pedal.
6. I went with 12vdc on the pedal from a 2A regulated laptop supply.
The sound on the video is somewhat dark due to the mic on my iPhone and the amp. On a more modern setup there is more high end. It feeds back really nicely.
I will post the schematic I used once I sort out the last few bugs. My gain control is really only effective in about 1/4 of the sweep so I'm going to try an audio taper. Also, as i mentioned before there is some sag with hard string hits and a gating effect right after you stop playing. I'm pretty sure it's related to V2 since I don't have a trimpot on pin 3 (it's straight to ground, ran out of trimpots!) and can't adjust the gain.
I REALLY like the sound of this. It sounds like a JCM 800 driven really hard. Very good sound. If you're looking for a high gain pedal I suggest trying this. If you back off the trim pots and gain control it will get more touch sensitive but still retain that sweet, fat valvecaster tone.
I will post a schematic soon... promise! Until then, here's pics and a video. NOTE: I haven't labelled the pedal yet.
Fantastic looking powdercoated enclosure from Small Bear :)
(http://i33.photobucket.com/albums/d88/smellymonkeybutt/IMG_0789.jpg)
(http://i33.photobucket.com/albums/d88/smellymonkeybutt/IMG_0791.jpg)
(http://i33.photobucket.com/albums/d88/smellymonkeybutt/IMG_0790.jpg)
It looks like a rat's nest but it's really quite organized:
(http://i33.photobucket.com/albums/d88/smellymonkeybutt/IMG_0788.jpg)
Sounds sweet. Share this over at Talkbass and your inbox will be flooded with preorders!
I was afraid with this many tubes it would be all distortion with no dynamics. Could you maybe post a video show some of the touch sensitivity?
Hey Bill,
I'm still working on it a bit, but once I get the pedal fine tuned I will def post another video with some dynamics! As for TB, I'll prob post something once I get a clip on a real bass amp, those guys would eat me alive playing bass through that guitar amp! lol.
Quote from: runmikeyrun on December 27, 2011, 08:30:15 AM
Hey Bill,
I'm still working on it a bit, but once I get the pedal fine tuned I will def post another video with some dynamics! As for TB, I'll prob post something once I get a clip on a real bass amp, those guys would eat me alive playing bass through that guitar amp! lol.
You must not spend much time over in the Doom/Stoner thread then!
Also, what is the buzzing noise at the beginning? Is that the power supply?
Looks like a nice tight build! :o
Don't be apologetic about the wiring. Remember... the important part is IT WORKS! :P
How were you able to cut/mill the holes for the tube sockets? Hole saw??
I am in the process of uploading a much better video with a SS amp that gives a much quieter and accurate representation of the pedal. I'll post it when it's done.
I used a Unibit for the tube holes. They came out a bit crooked because I marked and drilled the mounting tabs first. Next time i'll drill the tube hole first then mark/drill the tabs.
Quote from: runmikeyrun on December 27, 2011, 11:58:34 AM
I am in the process of uploading a much better video with a SS amp that gives a much quieter and accurate representation of the pedal. I'll post it when it's done.
I used a Unibit for the tube holes. They came out a bit crooked because I marked and drilled the mounting tabs first. Next time i'll drill the tube hole first then mark/drill the tabs.
But , oh well . :D
Much, much better video here:
Nice, like the knobs on the side.. good look..
I like the 12AT7 as the first, is this still at 12V? or did you use a 9 volts?
Quote from: iccaros on December 28, 2011, 02:01:56 PM
Nice, like the knobs on the side.. good look..
I like the 12AT7 as the first, is this still at 12V? or did you use a 9 volts?
He used 12v :D
Nice build. A few more Canadian Moose Droppings and you'll be wiring up an OctalCaster. :icon_lol:
(http://i206.photobucket.com/albums/bb54/seedlings/IMG_0788.jpg)
CHAD
lol... how else am I going to get the brown sound? :)
Looking forward to the schematic!!
schem: (also posting in Aron's gallery)
(http://i33.photobucket.com/albums/d88/smellymonkeybutt/quadcasterschematic.jpg)
Could you make the schem a bit bigger ?
Tia, Alf
I second the schematic work. I am having a lot of trouble reading a lot of the values and notes. It is probably just a matter of me making a simple adjustment to read it, and if so, please forgive me...
Can you post a stripboard layout for this? I have some really rare Telefunken tubes I would love to toss in one of these things. 3 ECC802S and a ECC801S would be pretty amazing sounding I think.
the last interstage cap (unspecified on schematic) is 1uF, i presume? the one before and after are 1 uF. nice job! this goes on the 'new project' list. -larry
Sounds like......
DOOM. :icon_evil: :icon_twisted: :icon_evil: :icon_twisted:
pretty sure the schematic has an incorrect connection between the second and third triode sections and again between 6 and 7.
Either that or i didn't read all 137 pages of the valvecaster thread. But in there somewhere Merlinb says:
That schem has an error. (Someone really should have removed it from wherever you found it!)
The 2nd and 3rd stages are not connected together properly, which is causing your delayed hiss problem. It should look more like this (you can ignore the switch and extra tone/vol pots if you want):
(http://i386.photobucket.com/albums/oo302/Smiler/TSschem-1_switchable.jpg)
hey guys,
Sorry about the schem... I made it in paint and i'm not sure what's up with it. If you PM me your email i'll email you one.
The stripboard layout I used is the same one for the Twincaster, I just doubled it up and changed the values where specified.
As for the last cap, yes, 1uF. I'm not the best with schems! lol
Mrmoo, I'm not sure what you're getting at... there's no switch in mine between stages...? Not too sure, I didn't read all 137 pages either!! ;D
The schemo shows stage two's anode (pin 6) connected to stage three's anode (pin1) when it should go to the grid of stage three (pin 2). You'll also need a grid leak resistor from pin 2 to ground.
it's also that way between stage 6 to stage 7...
Gah, I suck at this!! Jesus. I'll fix and modify the original post. Sorry guys.
here's the fixed schematic... sorry it's still small, photobucket is resizing it.
Gallery image (larger!) http://www.aronnelson.com/gallery/main.php/v/diyuser/quadcaster+schematic.jpg.html?g2_imageViewsIndex=1
Smaller original schem:
(http://i33.photobucket.com/albums/d88/smellymonkeybutt/quadcasterschematic.jpg)
F'in awesome.
:)
Sounds Ef'n great! :o Ever try more than one 12AT7? Ive got two AU7's and two AT7's that need a doomy home. :icon_twisted:
Ha ha, that RAWKS! :o
Well I just built this beast and its sounds freaking great, but I think I have some issues to iron out. If anyone can offer some advice to a newb, it would be greatly appreciated!
1.) First and foremost is noise. It just screams high pitched noise when not playing. Even with the trimpots at like 40% or less. It's even very noisy with the trimpots all the way down.
2.) If the trimpots are over 50% it squeals and shrieks like crazy. Something has to be screwy.
3.) When the pedal is off, the volume knob produces a low amplitude high pitched squeal when turned nearly all the way up.
4.) If the gain knob is past 85-90% the pedal goes quiet.
I used a 1.8A laptop power supply that puts out 12.6v. I thought it might be the issue, so I tried a known good 9v supply with the same outcome.
I swapped tubes around a little with no difference. I'm using a Tung Sol 12at7, two Tung Sol 12au7's, and one EH 12au7.
As far as I can tell, everything is grounded well. Poking around produces no changes in sound which would suggest bad connections.
Any idea where I should look first? I will upload any pics or sound clips if requested. THANKS!
You have a very large amount of gain in this circuit. If there is any feedback from the plate of one stage to the grid of the previous stage, you have an astable multivibrator and the relatively small amount of capacitance required would make it scream at a high (but audible) frequency. Shielding between all stages may be necessary.
The electrolytic across the B+ to ground may need additional help in the form of a film capacitor across it. At high frequencies, it may act inductive and make matters worse.
Quote from: amptramp on March 11, 2012, 04:57:54 PM
You have a very large amount of gain in this circuit. If there is any feedback from the plate of one stage to the grid of the previous stage, you have an astable multivibrator and the relatively small amount of capacitance required would make it scream at a high (but audible) frequency. Shielding between all stages may be necessary.
The electrolytic across the B+ to ground may need additional help in the form of a film capacitor across it. At high frequencies, it may act inductive and make matters worse.
Oi. That sounds unpleasant. I suppose it wouldn't help that I built this all on the backs of the sockets rather than on a pcb. Of course, maybe not, since all the leads are technically shorter than running wires to a pcb. Would pics of the guts be of any use? Would sound clips help diagnosis at all?
I'll try a film cap across the 'lytic as you mentioned. Thanks a lot for helping!
Alright, I went through and reflowed each solder joint and popped in a .047uF film cap across the main lytic. It may have helped a bit, but it's still pretty noisy.
Here's some gut shots. Let me know if anything seems amiss or if you have any ideas on how I could improve the high noise issues. I'd appreciate it.
The orange drops are 600v pieces, hence the huge size. Just what was available. I assume the high voltage rating isn't causing any issues right?
(http://farm8.staticflickr.com/7184/6836138842_0dc812563b_b.jpg)
(http://farm8.staticflickr.com/7063/6836138786_66bf047b63.jpg)
Here's a sound clip I recorded showing the noise floor. It's just a single string plucked and then muted to show how the noise floor fades in after muting. Thought it may be a clue. You can see the fade in on the waveform.
http://soundcloud.com/jerry-mcdougal/quadcaster-noise
Just audio probed the gain stages. No single stage seems to be the issue. The idle noise starts right after the first stage and gets progressively louder through the stages. I'm assuming this means my issue is most likely that I need to use shielded wire between stages/tubes?