English Amiga Board - View Single Post - Hardware recreation of Amiga audio sound / tone

GavinG · 23 December 2022, 01:42

Hi everyone,

I’m a big fan of the ‘crunchy’ Amiga sound - I think the heart of it is the aliasing bluntly filtered. I love especially the aliasing effect on soft string and wind samples, such as:
[ Show youtube player ]

I am trying to think how to create a hardware Amiga sound 'pass through' as a standalone hardware device. I can (and already do) pass audio through my Amiga to do this. But creating a hardware device would enable some enhancements - separately controlling and modifying the aliasing, filter and other characteristic elements of the Amiga sound.

Dr. Venom, in another post...
http://eab.abime.net/showpost.php?p=...0&postcount=11
...suggests breadboarding the Amiga DAC + analogue filter. I am not much use with a circuit diagram, but am trying to get close using Eurorack format synth modules. Here is my proposal:

1. Audio in to a Doepfer A189-1 VC Bit Modifier
(video of one in action: [ Show youtube player ] )
This has separate controls for bit depth and sample rate.
- set to 8bit depth, and with sample rate between 8-16 khz.

2. Then an ALM MUM M8 filter:
https://busycircuits.com/alm018/
This is a 6pole Butterworth, not the Amiga's 2pole (a 4pole filter option, the WMD AAF, was as close as I can find, but it has less fun modulation options).

Maybe before the filter you’d want to add some low level 50hz hum noise as well.

The fun thing here would be being able to accentuate or modify things separately, to make something sound more 'Amiga' than an Amiga, if you like. For example, if I added an LFO controlling the sample rate, the sample rate frequency could be dynamically synchronised in relation with the frequency of the audio note being played in, so you could always create the 'right' (wrong!) mismatch with the Nyquist rate to create 'tuned' or at least more controlled aliasing-per-note. Or, raising the filter cutoff dynamically to open up more aliasing across the duration of a note etc.

I’d really appreciate thoughts from those of you more technical than myself, especially on this second very achievable option. Are there any ingredients missing here before I splash some cash to try it out?

23 December 2022, 01:42	#1
GavinG Registered User Join Date: Dec 2019 Location: London Posts: 13	Hardware recreation of Amiga audio sound / tone Hi everyone, I’m a big fan of the ‘crunchy’ Amiga sound - I think the heart of it is the aliasing bluntly filtered. I love especially the aliasing effect on soft string and wind samples, such as: [ Show youtube player ] I am trying to think how to create a hardware Amiga sound 'pass through' as a standalone hardware device. I can (and already do) pass audio through my Amiga to do this. But creating a hardware device would enable some enhancements - separately controlling and modifying the aliasing, filter and other characteristic elements of the Amiga sound. Dr. Venom, in another post... http://eab.abime.net/showpost.php?p=...0&postcount=11 ...suggests breadboarding the Amiga DAC + analogue filter. I am not much use with a circuit diagram, but am trying to get close using Eurorack format synth modules. Here is my proposal: 1. Audio in to a Doepfer A189-1 VC Bit Modifier (video of one in action: [ Show youtube player ] ) This has separate controls for bit depth and sample rate. - set to 8bit depth, and with sample rate between 8-16 khz. 2. Then an ALM MUM M8 filter: https://busycircuits.com/alm018/ This is a 6pole Butterworth, not the Amiga's 2pole (a 4pole filter option, the WMD AAF, was as close as I can find, but it has less fun modulation options). Maybe before the filter you’d want to add some low level 50hz hum noise as well. The fun thing here would be being able to accentuate or modify things separately, to make something sound more 'Amiga' than an Amiga, if you like. For example, if I added an LFO controlling the sample rate, the sample rate frequency could be dynamically synchronised in relation with the frequency of the audio note being played in, so you could always create the 'right' (wrong!) mismatch with the Nyquist rate to create 'tuned' or at least more controlled aliasing-per-note. Or, raising the filter cutoff dynamically to open up more aliasing across the duration of a note etc. I’d really appreciate thoughts from those of you more technical than myself, especially on this second very achievable option. Are there any ingredients missing here before I splash some cash to try it out? Last edited by GavinG; 23 December 2022 at 02:11.