Disabling Amiga Internal Filter

I have an a600 can anybody here explain to me how i go about disabling the internal low pass filter?

That depends on what software you are using. There is no native Amiga shell command to switch the filter on/off, but such commands can most likely be found on AmiNET.

In Protracker it is the E00/E01 effects.

If you need a hardware solution you might find some help here: http://eab.abime.net/showthread.php?t=57073 ?

Thanks for the reply,yeah i have been on that site an awful lot and cant get my head round it.I use gvp soundstudio as it came with my dss8+ The dss8+ has an option when sampling to turn on or off the anti aliasing filter,im not sure if this is the internal amiga one or if it is the samplers own filter.I have heard people say the the a600 sounds much duller compared to the a1200 as well do you think there is any truth to this?

Ok just found out they are not the same filter.Which would explain why i am still getting low passed samples.

This isn’t probably going to help you, but I had Amiga back in the day dreamsigh and have a vague memory of a short program I got somewhere that you could execute in shell and turn off the filter. So yeah, AmiNet is probably a good place to start. It was pretty easy to do in Assembler, but I don’t remember how anymore.

If you want to do it in assembler, it is easy. Set the bit number 1 in $BFE001 register to get the led off and filter off - bright sound. Clear the bit to get opposite - led on and filter on - filtered sound.

Filter off:

BSET.B #1,$bfe001

Filter on:

BCLR.B #1,$bfe001

Drop it to assembler, assemble, save executable in command directory and you got DOS commands switching leds on and off.

Alternatively use this Amiga executables in zip pack, what I made some time ago:


Interesting read here:

The Amiga contains an analog low-pass filter (reconstruction filter) which is external to Paula. The filter is a 12 dB/oct Butterworth low-pass filter at approximately 3.3 kHz. The filter can only be applied globally to all four channels. In models after the Amiga 1000, the brightness of the power LED is used to indicate the status of the filter. The filter is active when the LED is at normal brightness, and deactivated when dimmed (on early Amiga 500 models the LED went completely off). Models released before Amiga 1200 also have a static “tone knob” type low-pass filter that is enabled regardless of the optional “LED filter”. This filter is a 6 dB/oct low-pass filter with cutoff frequency at 4.5 or 5 kHz.

Plug-in based on research Milkytracker co-authors (Christopher O’Neill & Antti S. Lankila) except blep-tables. Simplified looks:

   -----------------+- Rolloff ---+- Cutoff -------------
   Amiga 500        | 6 dB/oct    | 4900 Hz , RC-filter
   Amiga 500 (LED)  | 12 dB/oct   | 3275 Hz , Butterworth
   Amiga 1200       | 6 dB/oct    | 28867 Hz , As is
   Amiga 1200 (LED) | 2x12 dB/oct | 3275 Hz , Butterworth

    | 2nd-order Butterworth s-domain coefficients are: |
    |                                                  |
    | b0 = 1.0  b1 = 0        b2 = 0                   |
    | a0 = 1    a1 = sqrt(2)  a2 = 1                   |
    |                                                  |

       Copyright (c) 2013, Eugene aGGreSSor Sobolev
                   All rights reserved.
        (from RUSSIA, Saint-Petersburg with L0ve!)
     Released under terms of the BSD Simplified license

So I used the old “filter2” in Renoise… Not sure if that is accurate.
crystalhammer.xrns (47.0 KB)
crystalhammer split.xrns (53.0 KB)
amegas.xrns (53.0 KB)

Did the Amiga use linear sample interpolation?
How can I create a 12dB butterworth filter?