Viewing Issue Advanced Details
ID Category [?] Severity [?] Reproducibility Date Submitted Last Update
03726 Sound Minor Always Feb 10, 2010, 11:36 Feb 4, 2014, 12:12
Tester Oliver_A View Status Public Platform
Assigned To AWJ Resolution Fixed OS
Status [?] Resolved Driver
Version 0.136u2 Fixed in Version 0.153 Build
Fixed in Git Commit Github Pull Request #
Summary 03726: popeye: Discrete sound filter for AY-3-8910 voice A not emulated
Description On the original Popeye board, sound channel A from AY-3-8910 is run through a discrete filter, producing a smoothed wave form. On MAME, the channel is reproduced without filtering, resulting in a harsher square wave sound.

Note: this only affects sound channel A.
Steps To Reproduce Turn on your original Popeye machine, and listen to the title melody. You'll notice that the 2 channels playing the leading melody sound sharp, but the channel playing the backgound beat is much more smooth and not a square wave.

Start the game, hear the introduction music, same pattern: leading melody is a sharp square wave, background beat is smooth.

Now play the game. All sound effects are sharp square waves. The background melody however is smooth.

See also Popeye schematics sheet 2, upper right corner. When I am taking the sound directly at resistor R52, bypassing the whole circuit, voice A is sounding as sharp as wrongly emulated in MAME.

Probable cause for filtered sound: capacitor C4, 0.047uF, resistor R51, 20KOhm

Circuit has been verified with original board.

See picture for circuit.
Additional Information I am going to provide some sound samples during the day.

EDIT: Sample has been uploaded.
EDIT: Part of schematic has been uploaded.
Github Commit
Flags Verified with Original
Regression Version
Affected Sets / Systems popeye
Attached Files
mp3 file icon popeye_sound.mp3 (1,125,982 bytes) Feb 10, 2010, 12:46
jpg file icon popeye_sound.jpg (76,187 bytes) Feb 10, 2010, 13:21
Relationships
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Notes
5
User avatar
No.05686
Tafoid
Administrator
Feb 10, 2010, 12:31
Suffice it to say, there are probably hundreds of games that have yet to get such filtering involving the ay8910/ym2149. It's been a slow process of adding them. I can acknowledge this for now, but not sure when those who deal with discrete issues can apply any fix. Reference recordings and examples are good, however, and will facilitate the process.
User avatar
No.05687
Oliver_A
Tester
Feb 10, 2010, 12:48
edited on: Feb 10, 2010, 13:24
I have now uploaded a whole sound section. If someone wants to implement it, he/she can listen to this sound file and look at the schematics. The filtering seems to be caused by capacitor C4.
User avatar
No.05688
Fujix
Administrator
Feb 10, 2010, 13:06
Thanks for uploading the original sound. I set the report status Confirmed.
User avatar
No.06055
couriersud
Developer
May 7, 2010, 21:30
The schematics could be emulated using 3 RC filters and a discrete mixer in MAME.
User avatar
No.10235
AWJ
Developer
Feb 4, 2014, 12:12
I've hooked up an RC filter matching the schematic to the first AY channel. The caps on the other two channels are only 330pF; the amount of lowpass filtering they provide is probably outside the range of human hearing and certainly outside the precision of the old integer-based flt_rc device.