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

8bitbubsy · 27 December 2022, 20:37

Well, the Amiga has three analog audio filters, not just the "LED" filter.

Here they are, in correct order:
1) 1-pole (6dB/oct) RC low-pass (cutoff=4420.97Hz)
2) 2-pole (12dB/oct) RC low-pass (cutoff=3090.53Hz, Q=0.660) (aka. the "LED" filter, turned off/on in software)
3) 1-pole (6dB/oct) RC high-pass (cutoff=5.128Hz) (for centering / DC blocking)

On Amiga 1200, the cutoff is 34419.32Hz for 1). This is why A1200 sounds much sharper than other Amigas.

Note: Some of the schematics that are found online are wrong when it comes to the resistor/capacitor values for these filters.

27 December 2022, 20:37	#2
8bitbubsy Registered User Join Date: Sep 2009 Location: Norway Posts: 1,715	Well, the Amiga has three analog audio filters, not just the "LED" filter. Here they are, in correct order: 1) 1-pole (6dB/oct) RC low-pass (cutoff=4420.97Hz) 2) 2-pole (12dB/oct) RC low-pass (cutoff=3090.53Hz, Q=0.660) (aka. the "LED" filter, turned off/on in software) 3) 1-pole (6dB/oct) RC high-pass (cutoff=5.128Hz) (for centering / DC blocking) On Amiga 1200, the cutoff is 34419.32Hz for 1). This is why A1200 sounds much sharper than other Amigas. Note: Some of the schematics that are found online are wrong when it comes to the resistor/capacitor values for these filters. Last edited by 8bitbubsy; 27 December 2022 at 21:35.