Digitally Controlled Analog Dynamic/Harmonic Engine

[manticoreisthebastard]

Greetings to all from a lurker of many years who finally decided to start profile!

I've played with a few builds before, rarely mustering the energy to get them off of the bread board but AMZ's articles of clipping diode gave me a very ambitious idea that is almost approaching pipe dream territory. So in absence of practical knowledge, I'd like to see what the board thinks of the ideas. I believe describing the controls available in the design the best starting point so here goes.

First Stage::Filter-Splitter: The input signal is buffered and run to three active filters in order to convert the signal into three distinct channels (HI, MID, LOW) which is controlled by two potentiometers (we are choosing crossover points here), whose resistances are read by an ADC in order to allow software to calculate the necessary RC network. This stage is definitely in it's infancy and I have a lot to learn about active filter design. *Any tips on digitally controlling capacitance?* I haven't had much luck locating digital capacitors that serve the purpose. ***Everything here on out will focus on one of the three channels created here***

Second Stage::Booster: Three boost circuits to choose from (BPT, FET or IC), all of which have "n" possible choices of component (I'm thinking four). As far as the transistors go, I almost have this matrix solved as far as the multiplexing goes. Like components will use the same virtual socket, so I plan on using the same digital logic chain which chooses the component to re-bias the circuit with digital potentiometers. Obviously, the IC is a little more tricky (more pins, multiple pin-outs) but I think I can figure a solution out over time. For the BPT section, the ideas of the AMZ reverse power booster will be implemented thanks to a nifty phase-reversal chip!

Third Stage::Diode Array: This is probably the most developed section of the schematic so far as I immediately saw it being the most complex as far as the multiplexing problem goes. This takes everything AMZ has done with clipping diodes and the accompanying saturation control and allows it all to be done on one or two boards using only one up/down selector to select diode, one button to choose which diode is being changed, a potentiometer for saturation control and a rotary encoder to choose one of 16 possible saturation setups. Additionally, a switch is tied to a phase reversal IC, which will the flip flop the two diodes which go to ground (this will have no effect on some settings but on others such as a setting which introduces some crossover distortion, it will modify the harmonic content). **Though I've solved this matrix with multiplexers I would be very interested in finding a crosspoint switch suitable for analog audio!** I haven't done the exact math on number of possibilities, given some settings will have the equal effect of another but the number of combinations lies in the 2000 area.

Fourth Stage::Output: Here, all three signals are reintroduced, mixed and then fed through a Pup Simulator (or not if you press yet another button!). Piece of cake as long as I get the active filter section right and don't have phase issues.

Bonus Stage::Compressor: This idea may not survive in a state as complex as I have it now. I would like to run four circuits, three of which are dedicated to each channel respectively and capable tapping into the input of stage 2 or 3 for input and tapping into the output of stage 2 or three for it's output. The final compressor would effect the dry guitar signal and be a parallel compressor. I don't know if it's feasible as far as parts count goes.

I'm definitely interested in some input, suggestions of practical issues I haven't foreseen and IDEAS! I don't think this is too far-fetched but I will definitely need some guidance as far as the computing and storage of settings goes. I fully anticipate this project to take some time and end up taking up a 2U unit.

Probably a few schematics soon! I have most of the third stage done, but with all of the parts I'm far from a clean and easily understandable schematic.

[glasspak]

Just wanted to ask if you made any progress on this idea/circuit? I would like to help if possible?

[iainpunk]

i highly doubt it went further than an idea, seing that there are no other posts in the thread of from that user.

welcome to the forum by the way,

cheers, Iain

[mozz]

Opps, 8 years old, i was gonna answer varactors.