# [PD] Vanilla replacement for tanh~

Alexandre Torres Porres porres at gmail.com
Fri Jul 3 17:14:26 CEST 2015

```> The tanh~.pd is working swell.

Are you using mine? why not just use [expr~ tanh(\$v1)]?

for the cheby filter, you'd need to know where are all the poles and zeros,
then you could do it with vanilla raw filters or maybe even a few biquad~

2015-07-03 11:55 GMT-03:00 Pagano, Patrick <pat at digitalworlds.ufl.edu>:

>  The tanh~.pd is working swell.
> Would you all be able to suggest a replacement for the lp8_cheb~? I needed
> to replace three non-vanilla items
> 1.) tanh~
> 2.) make symbol [zexy]
> 3.) lp8_cheb~
>
>  I am trying to convert an algorithmic patch by a gentleman named Scott
> Norlund and these are the only problems from a rather couple patch.
>
>  Also, is there a work-around for "inits"?
> Thank you all very much for the wonderful help
>
> Sent from my iPhone
>
> On Jul 3, 2015, at 2:44 AM, i go bananas <hard.off at gmail.com> wrote:
>
>   yes, you need to use a [clip~ -3 3] to restrict the input.  But the
> function converges to +0.999999 and -0.999999 or whatever by then anyway,
> so for all practical purposes it is fine.
>
> On Fri, Jul 3, 2015 at 2:26 PM, Miller Puckette <msp at ucsd.edu> wrote:
>
>> I've never seen that approximation before but there must be some
>> restriction on the allowable values of X since the expression diverges
>> for large positive or negative values of x, while tanh(x) converges to
>>
>> cheers
>> Miller
>>  On Fri, Jul 03, 2015 at 01:23:29PM +0900, i go bananas wrote:
>> > there's a good approximation for tanh that can be made using just a
>> couple
>> > of simple arithmetic objects:
>> >
>> > formula is:  tanh(x) ~= x*(27+x*x) / (27+9*x*x)
>> >
>> > it's close enough for every application i've ever come across, it's
>> cheap
>> > cos it only uses simple arithmetic, and it doesn't degrade the
>> resolution
>> > of your signal like a table lookup does.
>> >
>> >
>> >
>> > On Fri, Jul 3, 2015 at 12:56 PM, Chris McCormick <chris at mccormick.cx>
>> wrote:
>> >
>> > > On 03/07/15 03:06, Pagano, Patrick wrote:
>> > > > Is there a way i can replace something for tanh~
>> > > > and inits in Vanilla 46?
>> > >
>> > > Using a pre-computed table for speed:
>> > >
>> > >
>> > > Or install "blockhead" using deken. :)
>> > >
>> > > Cheers,
>> > >
>> > > Chris.
>> > >
>> > > --
>> > > http://mccormick.cx/
>> > >
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