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From: dvljhg@cs.umu.se (J|rgen Holmberg)
Newsgroups: comp.sys.amiga.audio
Subject: Re: Disable low-pass filter on Amiga 500?
Message-ID: <1991Mar15.224308.9670@cs.umu.se>
Date: 15 Mar 91 22:43:08 GMT
References: <1391@ssp18.idca.tds.philips.nl> <1991Mar14.104334.15725@cc.tut.fi>
Sender: news@cs.umu.se (News Administrator)
Organization: Dep. of Info.Proc, Umea Univ., Sweden
Lines: 37

In article <1991Mar14.104334.15725@cc.tut.fi> s117986@lehtori.tut.fi (Salmij{rvi Janne) writes:
>
>From article <1391@ssp18.idca.tds.philips.nl>, by fwvo@idca.tds.PHILIPS.nl (Ferdinand van Ommen):
>> 
>> How can I disable the low-pass filter on my Amiga 500?  (workbench 1.2)
>> Audimaster II has this option, but when I use it I can not hear any
>> sound improvement, although the red power light turns off.
>> The soundsamples I use are made with samplingrates higher then 30khz, and
>> the Amiga is connected to my hifi-equipment. But I can not hear any 
>> differences in soundoutput using audiofilter enabled or disabled, 
>> the soundoutput still has no high-frequencies.
>> 
>> Do I need to open my Amiga for soldering?
>> 
>> Thank you very much for any help.
>> 
>> Ferdinand van Ommen.
>> -- 
>> -- Ferdinand van Ommen -- fwvo@idca.tds.philips.nl -- ..!mcvax!philapd!fwvo --
>
>I think you have an ancient A500 on which the filter just doesn't exist.
>Otherwise just set 2nd bit on $bfe001.
> 

Aaarrgghh! There are no A500 without lowpass filters, no matter how ancient!
From your description it seems that you have an old machine where it was not
possible to turn off the lowpass filter in software. You will need to bypass
the filter in hardware. I don't have the circuitry around so I can't tell you
exactly how to do that but the circuit display in the manual shows the filter
in detail. When you do solder, make that a switchable bypass. That way you
can avoid some nasty overtones if you want to :-)

/Jorgen
-- 
email dvljhg@cs.umu.se | DUMII: Sentinel of the scales
Everything I say is always true, just apply it to the right reality.
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