Emulating a Germanium PNP Transistor in Synthmaker or Flowst

[granta1969]

I had this great idea (at least it's great in my mind) that it would be pretty cool to create a Ruby module in Flowstone that emulated a PNP germanium transistor for the purpose of creating vintage guitar effect pedals like the Fuzz Face. It uses two of them, a few resistors and a couple of ceramic capacitors. It's really a simple design.

Once a module has been created it would be fairly easy to re-create a lof of vintage effects. Most of the effects of the 60's and 70's used germanium pnp transistors. All the old vintage synths had germanium transistors. So no matter how much you replicate the physics of a synth it won't sound the same as an actual synth because the germanium transistors added in colour and character which transcends the limits of the physics. The germanium transistor went out of production because it cost too much to produce and couldn't compete with the economical silicon transistor which used less energy and didn't produce any heat. But everyone knows, these just didn't sound as natural or as organic as germanium transistors. Germanium is actually a crystal that they grow in a laboratory. That's probably what gives it it's mojo.

Just think of the possibilities for endless sound tweaking. If you created a synth, you could warm up the tone and give it an organic colour by adding in the sound of real germanium transistors. If you created a basic digital delay or chorus effect, you could output the sound through a transistor pre-amp to give it that undefinable most loveable fat fuzzy warm tone. Plus the endless uses that people could come up with that's far beyond my imagination. Someone could even create highly advanced fuzz guitar effects that have never been heard before. Perhaps a combination analog delay/chorus fuzz effect?

A germanium transistor would be an amazing addition to Synthmaker or Flowstone. Don't you think?

On a side note:

You know it's possible to emulate the sound of a germanium transistor in the real world by using two ordinary silicon transistors? You cut off one of the collectors, tie the centre bases together and then put a 3k to 10k resistor between the emitter's of both transistors. You have to fine tune the resistance to find the sweet spot which is relative to the particular transistors you're using. Both transistors should be the same. This works really well. I tried this on an old DOD Overdrive pedal that lacked something. So just imagine that if you could experiment with a transistor like this that it would open up a lot of tonal possibilities. Perhaps you could have a switch between silicon and germanium? You could have a switch to control the input voltage.. that sort of thing. How someone would go about mimicking a germanium transistor is beyond my abilities. Someone like Trogluddite could probably do it. I wouldn't know where to begin.

Anyone out there with advanced Ruby skills able to tackle creating/emulating a PNP transistor? I think that the proof that it works properly would be to create the simple Fuzz Face pedal.

One last exciting idea to give you before I go. Any design that someone created in synthmaker or flowstone using a germanium or even a silicon transistor could be realistically produced in real life with a few hours of work with the soldering iron and a handful of parts purchased of the internet. This could result in some really great effect pedals.

cheers,

Grant

[VPDannyMan]

Grant, depending on just how distorted the signal is to be, If it is really distorted, then I am not sure that one would even much notice whether its a Germanium or not emulation. What will make a huge difference however, is the filters and how the signal is treated going into the non linear processing.

If it is to be a slight variation, in other words, not distorted beyond belief, then maybe, just maybe you would notice the difference between a germanium model and a 12ax7 for example. In any case, I would concentrate more on the filter design than anything else. A bad/inappropriate filter design will cause a user to dismiss your work before the distortion will..

If you want to create a fuzz box, you can start here with this idea.

fuzzsmall.jpg (17.34 KiB) Viewed 13204 times

To do:
Add some type of EQ after the overdrive component
Experiment with the cutoff values and filter types.
Add a master volume control
Open the overdrive knob and change it's max from 1 to 1000. This is what will give you enough distortion, but just make sure you add a master volume control or get ready to blow your speakers...

Thats a Fuzz Box type distortion.

[strangeChild]

I think the Ge mojo is mostly proported to be in the mushiness of it's saturation... a very soft-knee in the wave shaping as singals approach/reach the clipping region. That together with low gain and likely some effect from their leakiness means they don't behave like Si.

That said I've never even seen a Spice model for one so maybe there's more to it.

As for emulation... you normaly don't emulate a discrete component but an you might an analog circuit like the fuzz face... but if you did I don't think you'd bother with the details of what specifically each of the two transitors are doing on a sample-by-sample basis. You'd be looking at the harmonic distortion and the implicit filtering.

Electronics simultators, like all the Spice flavours out there, do use a component-by-component approach but they're not designed to put audio rate data through. (Maybe it's possible... I really don't know!)

[VPDannyMan]

Electronics simultators, like all the Spice flavours out there, do use a component-by-component approach but they're not designed to put audio rate data through. (Maybe it's possible... I really don't know!)

I am by no means a spice expert, but having said that..
Spice as far as I know works on only one frequency at a time. So you can see what a circuit will do at 80hz, then 80.000001 hz, then 80.000002 hz, etc. That may only be the particular flavor of spice I was working with at the time, but as far as I know for spice to even be looked at for real time emulation we would need 5000000000000000000000000 ghz processors capable of infinite sample rate with billions of gigs of ram. Huge, seemingly unrealistic specs for our day and age.

This is also why so many believe real time emulations of analog audio equipment is BS.