Hi
I having trouble with low output gain. I’ve speed read trough the tread and found that some people have reported “subtle” effect but no one low volume when engaged. Besides the volume drop it works perfectly as in my sound sample in my earlier post.
When I first made my Tri vibe and tested it I did as I usually do, that is connect the leads from the unboxed circuit to a test box that supplies power and In/Out jacks. That box is then connected directly to the amp so there will be nothing in between to interfere with the signal. At this stage the effect is always on so there is no bypass switch there. If the circuit behaves like it suppose to do I then solder in the stomp switch to the PCB as I always do. Then I box the thing. (I don’t want to de solder a stomp switch from the PCB from a bad circuit)
It was not until after I had boxed the Tri Vibe that I discovered that it had quite a large drop in volume when engaged. I have checked my layout and all the components on the build (not so easy after boxed up in those small boxes) without finding any errors.
I then discovered a thing by chance. The first thing the guitar signal hits in my setup is a switchbox. Beside switching and rerouting it also contains an On/Off switchable line buffer to eliminate the loss of tone trough all of my true by pass pedals witch sloppy cables between them. (It’s the first Op-amp buffers showed in the link below.)
http://www.muzique.com/lab/buffers.htmI discovered that when the line buffer was ON directly after the Tri Vibe the volume loss was gone and the engaged effect had unity gain. This goes for the rest of my pedals as well though a bit harder to tell because they add distortion or other effects to the tone. The common factor in all those cases was that the signal immediately after the Tri Vibe would hit a high impedance source. This will not be the fact connected directly to the Amp with a volume drop as a result.
My conclusion is that a low impedance source directly after the Tri Vibe will load down the output buffer stage U2b and the result will be a volume drop. A high impedance after the Tri Vibe will make U2b buffer the signal and will retain unity gain.
What do you think about suggestion to add the 2:nd JFET buffer type in the link above after U2b to let the signal always meet a high impedance?.
Am I way out here.....
(used TL062 for LFO and TL072 for audio and LM13600)
BTW here is the Tri Vibe in a small costume
