blgardne@esunix.UUCP (Blaine Gardner) (09/18/87)
A couple of weeks ago I got a program called LED that toggles the
low-pass audio filter on the new Amigas (and the power LED on all
Amigas). The documentation for the program said that Commodore has
information on modifying the A1000 so that it's low-pass filter can be
switched just like the A500 & A1000.
George, could you be persuaded to divulge this little secret for us
hardware hackers?
--
Blaine Gardner @ Evans & Sutherland 540 Arapeen Drive, SLC, Utah 84108
UUCP Address: {ihnp4,ucbvax,decvax,allegra}!decwrl!esunix!blgardne
Alternates: {ihnp4,seismo}!utah-cs!utah-gr!uplherc!esunix!blgardne
seismo!usna!esunix!blgardnegrr@cbmvax.UUCP (George Robbins) (09/29/87)
In article <483@esunix.UUCP> blgardne@esunix.UUCP (Blaine Gardner) writes: > A couple of weeks ago I got a program called LED that toggles the > low-pass audio filter on the new Amigas (and the power LED on all > Amigas). The documentation for the program said that Commodore has > information on modifying the A1000 so that it's low-pass filter can be > switched just like the A500 & A2000. > > George, could you be persuaded to divulge this little secret for us > hardware hackers? The circuitry is basically simple, but defies my attempts to display a schematic diagram using the printable ascii characters. Basically the power on LED signal is used to control a JFET transistor that shorts out some of the resistors in the filter network when the LED is off. The same technique can be applied to the A1000 filters although the details might differ a little. The circuit shows up on the schematics contained in the A500/A2000 Technical Reference Manual. The schematics in the user's manual are not neccessarily up to date... -- George Robbins - now working for, uucp: {ihnp4|rutgers|allegra}!cbmvax!grr but no way officially representing arpa: out to lunch... Commodore, Engineering Department fone: 215-431-9255 (only by moonlite)