hey guys I need your help!
I just finished my distortion valve but I can’t get it to work normally, in fact I feel like it doesn’t work if the input level is too low, so I tried to amplify my input signal which is just an oscillator connected to a sequencer. It gives me sound but:
-the switch on/off doesn’t make any difference. But sometimes it works when I switch from off to on but in a few seconds nothing more… I think the tube is saturated but it’s still strange!
-I have to set the valve volume to max as well as the gain and tune volume to get sound. It doesn’t make any difference since I can’t adjust anything at the risk of not hearing anything anymore.
-It’s a kind of oscillation but with the oscilloscope it gives me something shapeless …
1: are the tube’s heating filaments glowing?
2: can you post a picture of the oscilloscope showing the oscillation?
3: when applying an input signal, what signal do you measure with the scope on the grid of the tube and what on the cathode? And what are their DC values?
Well I can’t put a video…so I’m going to try with photos but I’m not sure if it will work.
I tried to see if there was a difference with or without the tube… No difference !!!
I removed the tube and it does exactly the same thing to me T_T.
Another thing I want to talk about is the fact that when I bring my hand near the module strange things happen. It makes strange sounds to me. When I touch the potentiometer screw too. It’s like when I touch the end of a jack that would be connected to an amp.
Check everything that should go to ground actually is. From your initial description that’s where I’d start. I also found that valve sockets can be hard to solder to reliably so I’ve always filed or sanded the points before soldering.
1: check that the voltages on the anodes (pin 4 and 8) of the tube halves are higher than the voltages on their respective grids (pin 2 and 7) and that those are higher than the voltages on their respective cathodes (pin 1 and 6)
2: check that there is only a capacitor connecting V1A to V1B.
If you connect a signal to C1, check where you loose it in the circuit. I’m using the Valve Caster schematic by Matsumin here:
So after checking the gnd I found that my jacks were poorly connected.
After fixing this I have the impression that it works but I’m still going to do the tests that you give me because I’m not sure to really understand the impact of distortion (so the gain rate and the tune rate) on a wave🙄. Is distortion only supposed to change the shape of the wave?
Ha, which is similar to asking: define ‘distortion’.
In the valve caster the amplitude is changed (possibly limited / clipped) and because of non linear gain by the tube, the signal is changed in shape as well. All depending on the settings of the pots of course. The limiting capabilities can be heard when you crank up the gain of the valve caster and then change the volume of the input signal. You will notice that the volume change of the input signal is not proportional to the volume change on the output of the valve caster anymore.
ok thanks I don’t understand everything but it’s still better to know what you’re trying to achieve with what you’re doing!
stupid question but why “the safety valve” and not the distortion valve?
I have the impression that the pot “tone” and “volume” change the same parameter?!?
I do the tests you gave me right away and send them to you…
The original name the circuit was published as was ‘valve caster’ and is well known to people playing electric guitar. Sam wanted to make one suitable for use with a synthesizer and added an op-amp to its output and came up with a new name afaik.
When active the effect of the valve caster should be clearly audible. The tone knob is a simple filter, the effect of this should be clearly audible although it will not dampen the high frequencies a lot.
Well, the filament has to glow for a tube to work at all. So you need to fix that first.
The low level output that you have may be cross talk (or a wiring problem).
