hi everybody
i build the dual valvecaster using this unverified schematic
http://www.beavisaudio.com/Projects/ValveCaster/twincaster.gif
it work great but the gain control of the second tube has no effect .
does anyone have the same problem ?
thanks
Loïc
I have only built single tube versions. But try unhooking the two stages and see if the second stage gain works as a standalone maybe???
Or maybe the second stage is just so saturated by the first???
Quote from: frequencycentral on June 18, 2008, 12:59:59 PM
Or maybe the second stage is just so saturated by the first???
thanks for helping
i was actually asking myself the same question .
i've read a good part of the 29 pages valvecaster thread and i didn't notice anyone talking about it
Yes, I still haven't build a two-valver myself...So... ???
hmm, i think dano made a mistake
shouldnt the 1 uf cap on v2a (called v1a on the schematic) go the grid not the plate?
try that, disconnect the 1uf cap on v12 and connect it to the grid
might be why its not working
Yes, looking at the schematic, Alex is right, that cap should go to pin 2. I think the schemo misses out the third triode altogether.
The 100K above the second triode should be connected to 9v too.
like this
(http://img398.imageshack.us/img398/2199/twincasterbt1.gif)
you should probably power it on 12v dc too
thanks a million guys it's working now
good to hear that
btw
how's the twin?
it has a lot of gain?
i don't know what you define has a "lot of gain" but to me that's a lot of gain !!!
it's actually a cool sounding distortion when both tube are engaged but it really kill the sustain (high notes fade away in about 2sec)
maybe my second tube is dead ! i used some crappy ehx tubes btw
Sounds like a bias problem maybe?
it sucks
2 sec?
change the R3's and R2's to trimmer and try to bias the tube
i tried that but with no results .
this is really strange i have a 3pdt to switch the second tube ; when the second tube is engaged i have a cool sounding disto but if strum hard on my guitar all the hiss disappaer and the disto become gated and farty
then i switch off then on and it works again
Can I ask what power you are supplying to the circuit? The power requirement of two tubes would be 300ma plus, assuming your not using the centre tap of the heater, which I think would double this to 600ma.
Personally , I would run what you have built from a 12 volt 500ma regulated wallwart, using the two tube heaters at 12 volt (paralleled) and ignoring the centre taps (pin 9).
try this
see on the first tube stage, the 1M resistor to ground after the input cap at the grid
well, do the same with the second stage, add a 1M resistor to ground after the 1uf cap
Isn't that just a pull down R?
It is called different, but in deed pulls down the grid to ground DC-wise, and also references the gridside of C3 to a fixed potential so it can`t float around wherever the electrons send the floating gate beyond control.
It is absolutely neccessary there.
Quote from: Renegadrian on June 21, 2008, 02:52:13 AM
Isn't that just a pull down R?
also, its not because pull down resistors (pop removal ones) are always before the input cap and after the output cap, when needed, usually the volume pot acts as a pull down resistor.
'K, learnt something more...So do you think it's mandatory to duplicate that R1 on the second part of the circuit?
Is it meant to be right after C3?
Quote from: snap on June 21, 2008, 03:36:01 AM
It is called different, but in deed pulls down the grid to ground DC-wise, and also references the gridside of C3 to a fixed potential so it can`t float around wherever the electrons send the floating gate beyond control.
It is absolutely necessary there.
Yeah you are right about that.
If you look at the pepper shredder schemo, they use 220K resistor right after the capacitor : http://www.tube-town.net/diy/lov/lov02-peppershredder.jpg
And C3(1) doesn't have to be 1uF, it can be a smaller one just like the C1.
I added a new VERO version with that correction - it should work - Please check it out!!!
In the LAYOUT GALLERY search for TWINCASTER.
PS actually it's 2 layout, with and without the R1 at the beginning at the second stage.
hi everybody thanks for all the answers
yeah it's much better with the second r1
frequencycentral thank you ! you made me realise the wallwart i was using was only 200 ma !!!
i always use my fx with different sources (bass guitar synth sampler etc ) so i have already put two switch for mods ! if anyone has a suggestion
anyway thanks a lot everybody
Quote from: alcoloic on June 23, 2008, 04:18:08 PM
yeah it's much better with the second r1
So did you try with and without R1b having the right wall wart???
Quote from: alcoloic on June 23, 2008, 04:18:08 PM
frequencycentral thank you ! you made me realise the wallwart i was using was only 200 ma !!!
:) :) :) :) :)
Quote from: alcoloic on June 23, 2008, 04:18:08 PM
i always use my fx with different sources (bass guitar synth sampler etc ) so i have already put two switch for mods ! if anyone has a suggestion
anyway thanks a lot everybody
Try an R1 value of 100k for synths, and perhaps 5M to 10M for microphones, depending on the type. Try it and tell me your results!
hi, just wondering if anyone else built this thing.
I just built single one and love it! but i wanna more gain. i wanna try this.
if you have pics or layout would be much appreciated to guide through and double check.
thanks bunch.
ps im so addicted to building pedal. i spent too much money on parts last three weeks :icon_wink:
Quote from: mitzrecords on November 19, 2008, 01:15:06 AM
if you have pics or layout would be much appreciated to guide through and double check.
As I wrote above,
In the LAYOUT GALLERY search for TWINCASTER.
Quote from: Renegadrian on November 19, 2008, 07:22:19 AM
Quote from: mitzrecords on November 19, 2008, 01:15:06 AM
if you have pics or layout would be much appreciated to guide through and double check.
As I wrote above, In the LAYOUT GALLERY search for TWINCASTER.
oops, sorry. got it!
thank you! :icon_redface:
Ive been playing with a design similar to this for the last two nights on the bread board. Getting great results...
Ditch the pots on the cathodes, no idea why you would want them on a cascading circuit like this. Instead I replaced them with 16K resistors, you could use lower values for more gain. I am also using a DIP switch to add a cathode bypass cap in parallel to those resistors, gain boost switch!
Anyways to add the gain control I am just adding a variable voltage divider between the two stages, essentially a volume control. Also between the two stages I added a tone stack.
Also with all these stages cascaded I needed to adjust the coupling networks. Cut most cap values in half. Also reduced the plate resistors value, more so in the first stage.
Also I have the heaters running at 12V regulated and the rest at 30V regulated. Sounds amazing, a good step up from 12V. Lots of tone, I dig.