[sdiy] [OT] Tube Screamer in depth modelling

[Andrew Simper]

Hi Guys,

I know this is a little off topic since strictly speaking it's not a
synth that is being modelled, but I know lots of people on this list
do various DSP analog modelling from time to time, and use SPICE (etc)
to model stuff.

I'm just finishing off a VST/AU/AAX plugin that is a full discrete
component model, and modified Boyle op-macro model, of an Ibanez Tube
Screamer TS-808. One of the interesting things is that when I was
matching the various resistor / capacitor / diode model parameters I
added a list view of every "constant" to the model so I could more
easily edit them and fine tune the model to match the units I have
used as a reference. I found this to be quite a lot of fun, so I
decided (possibly to my peril) to allow everyone access to this list.

I added a few extra resistors and capacitors to the model so that you
can also model all the modes on a TS9DX, and also the Boss SD-1. You
can alter the op-amp's slew rate, unity bandwidth, and dc open loop
gain, and swap different diodes and roughly change how many diodes are
in series in the main clipping section. I also added a battery voltage
pot and series resistor, and pot to adjust the bias. You can also add
your own diode .model statements to add them to the dropdown list of
available diodes. Supported diode model parameters are: IS, N, ISR,
NR, RS, CP, TT, CJ0, VJ, FC, M, IMAX, anything else will be ignored.

It's loads of fun to play with, especially on synths, here are some
audio examples of distorting a 303. First is the riff through an
actual TS808, then through the plugin, then through a "modded" version
with op-amp slew and and different caps to distort more of the signal:

www.cytomic.com/files/scream-acidvoice-saw02-ts808.mp3
www.cytomic.com/files/scream-acidvoice-saw02-scream.mp3
www.cytomic.com/files/scream-acidvoice-saw02-scream-mod.mp3

If any of the usual suspects here at synth-diy want a free copy I
would love to give you one, just email me directly with your name and
email in the form (I'm lazy and this makes it easy for me to copy and
paste to assign the free copy to you):

Firstname Lastname <your at email.address.com>

I've learnt so much from this list, and really appreciate everyone's
time and effort in their posts on such a wonderful variety of topics,
it's not much of a thank you, and it's partly me being proud and
wanting to show off all my hard work, but it is a pretty cool little
plugin and hopefully some of you may find it useful for your music.

If anyone wants to know about some of the details of the modelling
then please ask away, I'm open to chat about anything.

Cheers,

Andy