All articles from the Bad Screamer series
This one is very similar to the Bad Screamer: adding a mid-boost version, the difference being the gain stage has a Darlington pair, increasing maximum available gain (by a lot). I made this modification thinking ahead about using the same schematic but with germanium transistors. These having much less Beta available, only one transistor may struggle achieving good distortion. So two may be required.
This is untested at this stage of course, we’ll see how it all translated to an actual circuit soon.
Worked today to create a layout for a perf board, old way pencil on paper 🙂 Will use this layout to tune up the values – a simulator can only go this far and generally the sims aren’t good enough to model the transistor circuit behavior outside of the normal operating range. And the distortion is happening outside of the normal operating range.
The schematics with the Darlington pair instead of a single transistor:
Perfboard layout:
And while I’m at it, done the pnp version with germanium transistors too! Had to change some resistor values here to account for lower gain transistors (hfe is only 40) The power supply and the ground is upside down of course because pnp 🙂
The sim is showing the distortion as expected: red graphs are is showing the gain changed from zero to 90%, can see how the output is going up first cleanly and then distorting more and more progressively.
And this is the prototype with germaniums soldered but not plugged in yet. Will it work? Who knows…
