more design thoughts...

So as I continue to wait for the replacement of this digital oscilloscope to arrive (maybe by this Saturday, they're now saying), I'm running through thoughts and ideas in my mind about how to make the circuit work better.

I've decided not to do any further work on the actual physical prototype, until I have a scope and can thus see what I'm doing.  This is something I've learned, in my experience of designing new circuits: it's very important to manage my own energy and emotions, and not let myself get overwhelmed by too much disappointment or failure at any one time.  Building circuits designed by someone else is a totally different endeavour.  In that case, there's a known standard of performance that I'm seeking to replicate.  If it doesn't work at first, it's always possible to keep trying and searching for the mistakes, and with enough effort, it's guaranteed to work eventually.  With a novel design, there are no guarantees, and so one can never be sure whether more effort is worth it or whether it's hopeless to continue.  Yet, nothing but monumental effort and dedication will ever produce good results.  So one never knows whether one is engaged in a fool's errand or not.  And having to give up and set a project aside as a dead end is terribly painful.  In truth, it almost never happens, but only because I have learned these techniques of pacing myself and carefully applying *smart* effort after plenty of reflection and consideration, rather than galloping in with my heart on my sleeve and collapsing in frustration at the first difficulty!

So anyway, I've been reflecting thus on my first results, and on what I do and don't like about how the circuit is behaving.  Basically, it's just a pale shadow or a suggestion of "that fuzz tone", about 5% of something I want 100% of.  It's also harsh in tone and noisy and unstable in operation, but these things I think I know how to mitigate.  But I want to hear more of that magical fuzz behaviour out of it, in the first place; otherwise I'm just building a tube distortion unit -- which is a good thing in its own right, but not what I'm seeking, and I'd go about things differently if that were the aim (such circuits will be the heart of my basic "model 1" guitar preamp, whereas the fuzz unit is considered to be an "effect").

Right now, I'm using the two tubes in a simple cascade of identical one-tube fuzz circuits.  And there's a good amount of gain, but very little fuzz.  These things are different: that's my whole premise here.  So, what if I allocate the tube sections differently.  I'm picturing a single fuzz circuit, i.e., that self-biasing feedback loop, but with additional sections of gain in the middle.  Feedback from section 4 to section 1, with sections 2 and 3 in the middle, upping the gain.  The trick is, I want to preserve the overall DC nature of the loop, so sections 2 and 3 cannot be "normal" capacitively-coupled tube gain stages.  I guess they'll have to be just like stage 1, i.e., DC-coupled stages with roughly equivalent plate and cathode resistors, and big cathode-bypass capacitors to increase the AC gain.  Will this help?  Or do I really need to be increasing the DC gain of the loop to get more of the magical fuzz behaviour, which this won't do?  Maybe I can shift the operating point of the intermediate stages enough away from the exact center voltage, so as to get a small amount of DC gain.  Is the relative lack of DC gain the whole reason for the lackluster amount of fuzz I'm getting?  The transistors have plenty of DC gain, of course.

Hmmm, well, stuff to try...