Re: ALF AMII Clone

[Michael J. Mahon <mjmahon@aol.com>]

Phil Tubb <googleplus@w127.com> wrote:
> On Sunday, March 10, 2013 5:28:23 PM UTC-7, Steve Nickolas wrote:
>> On Sun, 10 Mar 2013, Phil Tubb wrote:
>> 
>> 
>> 
>>> The Mockingboard used the AY-3-8910 chips, which have an error in the 
>> 
>>> waveform they produce, resulting in anything from popping noises (with 
>> 
>>> slow volume changes) to inappropriate low frequencies (with fast volume 
>> 
>>> changes, as is typical for "envelope" control).  If you download the 
>> 
>>> Sept 1981 issue of Creative Computing from archive.org
>> 
>> 
>> 
>> I wonder if the YM-2149 fixes that.
>> 
>> 
>> 
>> -uso.
> 
> Hard to tell from the Yamaha data sheet. From the first waveform
> screenprint, it appears to not be fixed.  The second waveform screenprint is illegible.

Changing to a bipolar output would require bipolar power, and would be
intrinsically incompatible with the GI chip. 

Changing to a +2.5v "zero" reference, so that the DC component of the
output would be independent of the volume would have been possible, but
also incompatible with the GI specs. 

-michael - NadaNet 3.1 and AppleCrate II: http://home.comcast.net/~mjmahon