DanElectro “Green Ringer” unleashed // jcm(c)2020
The DanElectro “Green Ringer” was designed to have just enough gain to turn “over” the rectifying section, but not enough to produce an output higher than unity when converted to octave – a clever balancing act !!
Since the DanElectro design philosophy was to avoid knobs in general, the consequence of this choice results in a significant loss of performance potential in this particular case
begging to be released …
BACKGROUND
Several schematics are lying about on the internet, I don’t know which one is authentic … not that it really matters to me
Here’s one of the early ones to surface, drawn way back in the 90’s by Justin Philpott … btw, I felt inclined to clean it up a little and make annotations to explain what’s going on as far as overall structure goes …
Note, a common approach to cloning the “Green Ringer” involves using diodes instead of a transistor for the FW rectification … common knowledge
here’s one with my MODS from 2003, another edit job, this time on JD Sleep‘s schematic … the idea is to balance the driving point impedance leading into each leg of the FW rectifier // no point matching diodes, caps and resistors if those Zo’s aren’t the same … it’s just an easy way to achieve that goal
We can thus include diodes in Justin’s rendition …
Well, it doesn’t matter anyway. Because, with the availability of complimentary devices we could draw up six different circuits in total, by using functionally equivalent inverted SE stages. All we have to do is remember to reverse the diodes in the appropriate cases …
Ok, you get the idea …
MINIMIZING THE RELATIVE THRESHOLD
To help release the circuit’s potential for Octaving we can introduce a continuously variable (44db) gain boost circuit in the front-end, allowing for more mid-band signal to be produced internally, which in turn drives the Full-wave (FW) rectifier harder to then produce a more “idealized” waveform at the output.
That is, until clipping mechanisms kick in …
At the same time this will require a VOLUME control at the output, to tame things back down to instrument level.
Again, this can be made to work in any of the six possible ways of implementing the circuit … but the ones that make better use of grounding are the all-NPN and all-PNP versions, powered by respective voltage polarities …
VARIABLE-GAIN MOD TO THE ORIGINAL (Justin Philpott’s) VERSION
Converting the original circuit is pretty straightforward, all we do in the front-end is replace the 6k2 emitter bias resistor by a 5k pot and the 18k collector load by 15k, with the sweeper on the 5k pot going to a large cap (22u) to ground – as done similarly in a FuzzFace.
These changes are shown below on the simulator, at lowest DRIVE settings with an input source 200mVpp sine wave driving the works …
With extreme amounts of DRIVE (100% rotation) we get a nice and dirty double-frequency waveform …
VARIABLE-GAIN MOD TO AN ALL-NPN VERSION
We can implement the all-NPN (2n3904, 2n2222, 2n5210, …) version of the Green Ringer, which happens to have a little more gain built-in. The same Variable Gain mod can be used here of course with a 5k DRIVE pot and 27k Collector load, both on Q1. Here shown at Minimum drive settings …
And at Maximum drive settings …
Conclusion, both the PNP-NPN-PNP (Philpott/DanElectro) and NPN-NPN-NPN (my preferred version) versions seem to have very good potential for going dirty at full drive, with the NPN version giving a stronger Octave at minimum drive … in actual fact, all six versions should able to do pretty much the same
ADJUSTING DC BIAS
If for whatever reason the circuit doesn’t sound right, maybe you used a different type of transistor or something but resistors are the same, the first thing to check is the voltage at the resistor biasing the emitter of the Phase Inverter. On a 9volt battery you want to see close to 3 volts across that 10k resistor. If this is off, the best thing is to remedy the situation by altering the collector load on the first amplifier stage.
Another thing to note here, the DC bias will also indirectly affect the shape of the waveform when the circuit is clipping heavily – this should be noted, as it may help explain why the hard-clipping waveforms are different in the two sims shown here above …
FRONT-END TREBLE-CUT MOD
Another MOD we can do to the front-end is incorporating a variable TREBLE-CUT circuit; generally considered useful by some players. The option allows for a dialing in rather than an all-or-nothing type of thing …
In these sims notice the input capacitor in increased to 1uF and the bypass cap upped to 100uF … values worth exploring here
If DC bias is off, you should consider adding resistance (higher valued trimpot) in parallel with the the TREBLE-CUT pot and see if bias in the Phase inverter can be balanced this way. If not, then a higher valued TREBLE-CUT pot will be needed with steps repeated.
BALANCING THE FW-RECTIFIER STAGE
See if the following tweaks give you a more focused Octaver response …
FINAL BUILD // PARTING WORDS
All the MODS described here, under one roof // except for my Balancing one … you SHOULD try it of course, I didn’t think it would make the schematic elegant looking … so I left it out :)~
