It is currently Thu Jul 19, 2018 12:46 am

All times are UTC - 7 hours





Post new topic Reply to topic  [ 10 posts ] 
Author Message
PostPosted: Sat Jan 06, 2018 10:58 am 
Offline

Joined: Thu May 19, 2005 11:30 am
Posts: 560
I have finished my first "hot-plugging" program. It displays a white screen and beeps, expecting the user to exchange the RAM/Flash cartridge with an original Namco 163 Audio-equipped cartridge, then press A. It will play three 440 Hz tones: NES APU (gray screen), Namco 163 one channel (dark blue screen), Namco 163 eight channels (bright blue screen). I intend to acquire all ten of the games that use N163 Expansion Audio and record each one's output using the same hardware (Sharp Twin Famicom AN-505BK with clean audio mod; has nice APU vs. Expansion balance). That will provide a more precise measurement, using the exact same test tone rather than each game playing different music, of the relative volumes of the several games that use this expansion sound chip. This information then may help to update the Submapper proposal to reflect the relative expansion audio level of each game. Emulators can then let the user choose between original Famicom and GPM/AV Famicom APU vs. expansion sound levels.

The ROM has been successfully tested on real hardware, first by using an Everdrive N8 to upload the program to RAM, then exchanging the Everdrive with a Megami Tensei II cartridge and pressing A.
It sort-of works in most emulators, although most fail to honor the Sound Disable bit ($E000 bit 6), so they produce hanging notes when the screen goes black. Also, given the volume register value that I use, the one-channel and eight-channel test tone are just as loud; on emulators, the eight-channel tone is louder. Also on real hardware, the single-channel test tone sounds clean, while the eight-channel tone sounds "dirty", as expected.


Attachments:
N163TEST.7z [1.06 KiB]
Downloaded 26 times
Top
 Profile  
 
PostPosted: Sat Jan 06, 2018 4:37 pm 
Offline
User avatar

Joined: Sun Jan 22, 2012 12:03 pm
Posts: 6409
Location: Canada
Thanks for doing this. I'll give it a try later, though I only have 2 N163 carts. I think ideally we want to try a lot of N163 carts on the same hardware, since the relative mix across games is the most important information here.

I've been thinking NSFe could accomodate an optional chunk for N163 volume, and 2A03 square vs. equivalent is an easy enough thing to standardize the mix values on. Plus we could have Famitracker export an NSFe with a value that represents "FT standard mix" for it and people might stop complaining to me that NSFPlay doesn't match their Famitracker expectations. ;)

(The other expansions don't seem to need it. 5B / VRC7 only had one game. FDS mixing wasn't part of the game. VRC6 had 3 games but I think they had a standardized mix, even though there's a lot of variance in the part tolerance.)


Top
 Profile  
 
PostPosted: Sat Jan 06, 2018 6:02 pm 
Offline

Joined: Thu May 19, 2005 11:30 am
Posts: 560
I think I should expand the program to play both APU and Namco 163 at all fifteen volume levels. Right now, the APU plays at maximum amplitude while the Namco 163 plays at minimum amplitude, which might not provide sufficient information when taking into account the NES APU's nonlinear mixer.


Top
 Profile  
 
PostPosted: Sat Jan 06, 2018 6:26 pm 
Offline

Joined: Thu May 19, 2005 11:30 am
Posts: 560
And here it is, all 15 volume levels for APU, N163 single channel, and N163 eight simultaneous channels. As before, the N163 waveform is one 32 sample/16 byte waveform consisting of 8 bytes $FF and 8 bytes $00.

When recording the output, it must be kept in mind that at the maximum volume, the N163 becomes much louder than the NES, up to eight times, depending on the particular mixing resistor on the game's circuit board.


Attachments:
N163TESTv2.7z [1.1 KiB]
Downloaded 22 times
Top
 Profile  
 
PostPosted: Sat Jan 06, 2018 6:38 pm 
Offline

Joined: Sun Apr 13, 2008 11:12 am
Posts: 7313
Location: Seattle
When you catalog the cart volumes, would you be willing to open and read, or measure the resistance across, the AUDIO FROM 2A03 and AUDIO TO MODULATOR pins ?

It really ought to be the case that the resistor there should be the only thing that determines the loudness of the mix, but what data we have is inconsistent.


Top
 Profile  
 
PostPosted: Sat Jan 06, 2018 6:42 pm 
Offline

Joined: Thu May 19, 2005 11:30 am
Posts: 560
Is a simple $20 Ohmmeter sufficient for that task, or is something fancier required to do it correctly?


Top
 Profile  
 
PostPosted: Sat Jan 06, 2018 6:44 pm 
Offline

Joined: Sun Apr 13, 2008 11:12 am
Posts: 7313
Location: Seattle
A $20 ohmmeter is more than sufficient.


Top
 Profile  
 
PostPosted: Wed Jul 11, 2018 9:55 am 
Offline

Joined: Thu May 19, 2005 11:30 am
Posts: 560
I have now gathered all Namco 163 games except for Mappy Kids, which continues to be only available from overseas sellers. Since having to collect the package at the customs office is a long enough drive for me to want to avoid that at all costs, I would appreciate if a European-Union-based seller (or donor/lender) could offer for sale/provide me with a copy, so I can start making those test recordings from all games using the same console and setup.

I can already say that there must be several revisions of the audio circuit used on different runs of the same game. Sangokushi: Chuugen no Hasha is listed as having a 4.7k resistor, while I measure a whopping 32.82k on my cart. Other carts measure the same resistance as in that wiki article, so it's not my testing method being wrong. For that reason, I consider the proposed method of measuring relative audio levels between NES and N163 for all cartridges using that test program to be the more reliable choice.

I also have a hunch that later games seem to have their mixing resistors adjusted for the HVC-CPU-GPM console mainboard with its (relatively) louder expansion sound. The in-game expansion audio from Namco Classic II (1992) is almost inaudible against the RP2A03 on my AN-505BK Twin Famicom, and is just barely audible on a YouTube video recorded from (I think) an AV Famicom.


Top
 Profile  
 
PostPosted: Wed Jul 11, 2018 11:15 am 
Offline
User avatar

Joined: Sun Jan 22, 2012 12:03 pm
Posts: 6409
Location: Canada
Yeah, I've long thought the resistor values weren't useful data (at least not by themselves). I don't think all versions of the N163 have equivalent output to begin with. Measuring the output volume relative to a single source is good.

Also, every time I've gotten measurements from two different carts of the same game there's been a significant difference anyway, and that's not even getting into carts that had multiple runs with different parts.


Last edited by rainwarrior on Wed Jul 11, 2018 12:12 pm, edited 1 time in total.

Top
 Profile  
 
PostPosted: Wed Jul 11, 2018 11:35 am 
Offline

Joined: Sun Apr 13, 2008 11:12 am
Posts: 7313
Location: Seattle
NewRisingSun wrote:
32.82k
You can be confident that these are standard E24 5% resistors, so that's "just" 33k.


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 10 posts ] 

All times are UTC - 7 hours


Who is online

Users browsing this forum: No registered users and 3 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
Powered by phpBB® Forum Software © phpBB Group