remember the tube tremolo project exposed below ?
I got ride of the phase oscillator which doesn’t give a good range of speed and I replaced it with a standard op-amp based oscillator . Actually it is not new , it’s the oscillator that I used in my motherphaser . I love the ramp effect and it offers a really good range of speed settings. Finding good oscillators which offer a large speed range is pretty hard , it often has a switch “hi/low” or ‘slow/fast” to expand the possibilities. This one doesn’t .
On the (crappy) picture there are the tube audio path (one triode used at the moment) in the metal chassis and the oscillator circuit (breadboard) . Both connected together by the patch cable. Then the audio path is connected to the power amp of my tube amp. Connecting the tremolo into the preamp input will quickly give overdrive , even if it’s a nice thing and the overdrive sound of the EF86 is great , it is not the goal for now.
No need to say that the workbench presented here is pretty dangerous if you’re not aware of the risk of getting chocked . So please if you do something that way be really carefull and shut the power off evertime you manipulate the circuit. And don’t forget the fuses ! Messing with Electronic is a really fun thing to do but dying of a heart attack or burnt like a chiken aren’t (but to honest I’ve never tried and I won’t …..)
In this project we’re only manipulating the grid voltage (or the cathode voltage) and there’s no High voltage in here so it can make in that way but attention still remains.
So what next ? Actually the project will turn into a tube version of a tremolo circuit that I’ve made with solid-state (LM13700) . The solid state version gave good results and could be really cool with tubes as well . Now that the oscillator part and the audio path are valided I have to use the second triode for creating the other effect, designing the path for the 2 next triodes (input stage and output buffer) , tweaking the oscillator to find final values of pots and caps , making a proper switching relay system , find a good box and a small power transformer to have the +12V for the solid state oscillator.
Note that even in this simple version , just a tremolo circuit, it works really well ! maybe reducing the plate resistor or making a resistor divider with the volume pot to reduce the output volume will be helpful to make it work better with input preamp. The second triode can be used for adding another gain stage after and creating a tube distortion/tremolo or making a buffer (but a mosfet can be used in this place). But all these stuff can be done with the following modifications that I’ll do .
to be continued…
04/29 : the additional circuit has been experimented with encouraging results. This second effect is nothing more than the “harmonic tremolo” form the old fender amps. I just moved the frequency crossover higher in the spectrum.
One drawback remains , the LFO produces click noise and thump noise (which seems to be unrare with tube tremolo) . LRD/LED combo (even if not really fun to do) could also be placed to avoid these problems (at least reduce them).