ridiculously simple cab sim : /

[deadastronaut]

hi guys



last night i was messing around with a distortion  with a 'passive', just 3 caps/3 resistors
HP..LP...LP..ultra ridiculously simple cab sim...into my DI box/mixer
and it sounded pretty cool.......well promising anyway..
it took the harsh top end off, and fattened the bottom quite nicely....
         
        220n
in.......//........2.2k......2.2k.......out
               /              /            /
               /              _           _
               / 4.7k       _ 100n  _  22n
               /               /           /

i was tweaking it , swapping resistors for pots etc...

this was ok for dirt....for clean i tapped off the 220n/4.7k junction...

needs a buffer...but quite promising...thoughts?

[Kipper4]

I'll bread it later Mate. Oh so simple pimple too.

[deadastronaut]

yeah worth a bread up...

i'll tack a buffer on it later..see how it goes.

[Bill Mountain]

Looks cool.  I'll have to sim it up later.

I have no ASCII art skills but my go as of late has been two LPF's in series like on many other projects but scaled 10x apart to lessen their effect on each other and give a slightly sharper slope.

Ex. 4k7 & 4n7 followed by 47k & 470p.  Works great with a bass fuzz I'm building.  You could scale the R values down further if you're using an opamp but I've only been doing this with MOSFETs and CMOS as of late so I wanted the values high enough so the output impedance from the dirt stages wouldn't skew my math too much.

EDIT: OK I just copied yours with different values:

      10u
in.......//........4.7k......47k.......................buffer
                              /            /                /
                              _           _                /
                              _ 4.7n   _  470p       /1M
                               /           /                /

On mine the output is buffered as well.

[deadastronaut]

cheers bill,

i'll give that a go too...(my ASCII skills are very lame too as you can see..)

what in/out buffer you using?

i was going to go with an opamp....hmmm...

[Bill Mountain]

I used an opamp cause I had a spare but anything will work.  I always use a Rat buffer when breadboarding.  It usually sound just fine after a dirt stage.  I don't like them as clean buffers though for lack of headroom.

[Bill Mountain]

I attached a schematic for a project I'm building.  I also zoomed in on the passive "cab sim" circuit for clarity.  This cab sim also introduces a heavy emphasis on the low end because the preceding circuit has a emphasis on the mids and highs.  Plus it's designed for bass after all.

[deadastronaut]

cool, nice one bill...

[garcho]

needs a buffer...but quite promising...thoughts?

you can buffer BETWEEN the stages too

scaled 10x apart

that's the usual practice, multiply the resistor by ten, divide the capacitor by ten, for each pole

[Bill Mountain]

needs a buffer...but quite promising...thoughts?

you can buffer BETWEEN the stages too

scaled 10x apart

that's the usual practice, multiply the resistor by ten, divide the capacitor by ten, for each pole

True.  I read it in a book or something many moons ago but I don't see it used often enough in pedals.

[deadastronaut]

heres a clip of how the (ASCII) at the top sounds....just to give an idea..

first clip...straight dist into di /mixer....harsh as hell..

second clip...through the sim..(as top of thread)...no buffers..so had to lift level quite a bit..

https://dl.dropboxusercontent.com/u/7464107/dist%2Bsim.wav

[Bill Mountain]

Sounds great!

What were you using for dirt?

[deadastronaut]

hi bill, its a new version of the spitfire that i'm still working on after months on  breadboards..

with active tonestack...

i was inspired to tinker with cab sims by my poor old multifx korg ax1500g..

if i turn the cab sims off it sounds utter pants, harsh and nasty (DI)...put the cab sim on, sounds cool..
good enough to record with...(i turn the cabs off in an amp obviously)

but i prefer my own dirt..hence the quest to add a relatively simple sim to it...

[vigilante397]

heres a clip of how the (ASCII) at the top sounds....just to give an idea..

first clip...straight dist into di /mixer....harsh as hell..

second clip...through the sim..(as top of thread)...no buffers..so had to lift level quite a bit..

https://dl.dropboxusercontent.com/u/7464107/dist%2Bsim.wav

I didn't read the explanation of the clip before I listened, so when you first started without the filters I was like "What the hell Rob, this sounds awful!" Then you kicked it on and I was like

[garcho]

sounds good!

[vigilante397]

And if it's not too late to weigh in on the buffer issue, if it were me I would put an opamp at the end with a small trimpot in the feedback loop (maybe 1k input resistance and 2k trimpot? I would have to breadboard it) so you can get a little more gain behind the signal if you need it.

[Kipper4]

Yep thats some sweet sounds.
Awesome chops. Thanks Rob
Now whens this OD gonna make an apperance?

[anotherjim]

A very good read on speaker tone...
http://www.soundonsound.com/sos/feb12/articles/speakers.htm
IMO, a filter based sim is well worth having, especially for the high cut, despite that it's not doing even half of things a real cab does to the signal. Maybe if your sound is complex enough, you don't notice the missing colouration of a real cab so much?

[dschwartz]

If you're going thru the problem of buffering the output, you should use a sallen key filter instead and have a better 2pole filter with low output impedance..and for the hpf use the other side of the opamp as an onput buffer

[Hatredman]

A side note:
- Library with ASCII Art components to copy+paste:
   http://www.retrojunkie.com/asciiart/electron/circuits.htm

- A program to draw ASCII Art circuits. Site is in german, but software is in english:
  http://www.tech-chat.de/download.html