AnsweredAssumed Answered

Tubescreamer guitar effect on Aida DSP

Question asked by MaxAudioDSP on Mar 10, 2016
Latest reply on Mar 23, 2016 by MaxAudioDSP

Hi,

 

I'm trying to emulate the sound of this analog processor with Aida DSP, but I'm facing some problems,

so I ask the community

 

The full schematic is available on the net, for simplicity I will post only the problematic part.

Tubescreamer2.bmp

Remove 1u-10k network, Cc on the feedback and the diodes. Also consider D is varying from 0.0 to 1.0.

This is a non inverting amplifier with an high pass characteristic (shelving). More precisely this is a first order

transfer function, and can be discretized in the following way

 

R2 = 51000 + 500000*D;

a1 = (R1 + R2) * Cz * 2 * Fs;

a2 = R1 * Cz * 2 * Fs;

B0 = (1 + a1) / (1 + a2)

B1 = (1 - a1) / (1 + a2)

A1 = (1 - a2) / (1 + a2)

 

tf1z = (B0+B1*(z^-1))/(1+(A1*(z^-1)));


with Fs=48kHz


TS9OpampFilter.bmp

My problem is that this filter has a tremendous gain and coefficients rapidly overflow 5.23 fixed point dynamic.

For example with D=0 you have

B0 = 11.3624;

B1 = -11.2724;

A1 = -0.9099;

but just with D=0.25

B0 = 36.7605

B1 = -36.6704

A1 = -0.9099


Any idea?


Thanks

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