N163 cartridge volume survey

[rainwarrior]

I've been taking measurements of N163 cartridges, and have come to the realization of how much it varies from game to game. So... I'd like to compile a survey of mixing levels for the N163 games. As many samples as possible would be helpful, so I'm requesting that anybody willing to record a test for me would do so with all of the N163 cartridges they have available. What you need:

1. A famicom with AV output (possibly modded)
2. A dev cart you can put an NROM code on
3. An N163 cartridge
4. Something to record audio with

To make the test, load the n163_level.nes ROM on your dev cart. On reset it will play a short buzz, wait five seconds, then a second short buzz. During these five seconds, pull out the dev cart, and insert the N163 cart to be tested. After this a short loop playing A440 on the 2A03 and on the N163 will follow. The test loops, so if you miss your window to swap it'll come back in about 10 seconds. Please record the output and send it to me (identifying your Famicom type and N163 cartridges for each recording), and I will measure and compile the results on the wiki.

Source code is also included, as well as an NSF version, in case you need to make revisions, or have an alternative way of playing NSFs, like a TNS-HFC cartridge. Just as a warning: hot swapping will usually corrupt any saved games you have on the cartridge, and I understand it could potentially damage the cartridge or your NES. I've personally done hundreds of hot swaps at this point without damaging anything (so far as I know), but if you're worried about the risk please don't do the test. Also, after swapping there's a random chance the program will crash; if you don't hear the second buzz after swapping, just restart the test and try again (for me it crashes maybe 1/5 of the time).

I realize there's a lot of factors that makes it hard to do this with much accuracy, such as variability between famicoms and between cartridges, but it would be nice to at least have a ballpark figure. I'm sure we could reasonably get 1 significant digit of precision, at least.

There are 9 N163 games that use the audio:
* Final Lap
* Mappy Kids
* Megami Tensei II
* Namco Classic 2
* Rolling Thunder
* Sangokushi
* Sangokushi 2
* Erika to Satoru no Yumebouken
* King of Kings

Also, if you happen to have a multimeter, try measuring the resistance between pins 45 and 46 on the cartridge, and report what you measure. To find pin 45, note that pin 31 is on the right side of the rear of the connector, and it will count up as you move left from there. See diagram: http://wiki.nesdev.com/w/index.php/Cartridge_connector

I've been talking with Lidnariq about this on the wiki, and the reported mixing resistances don't really seem to match with the measured volumes consistently, but it would be useful information to compile, just in case. It might help us spot different revisions of the same game, etc.

[mikejmoffitt]

Gosh, perfect timing - I *just* built a small preamp inside my Rolling Thunder cartridge to bring up the level of the N163 because it made EVERYTHING inaudibly quiet!

Sorry, not undoing all this:


I can report, however, that the resistance between the two pins was around 16Kohms. The 2A03 was very quiet, and the N163 was even quieter.

[rainwarrior]

Lol, well at least Rolling Thunder is one I've already got two samples for.

[Mednafen]

You're not even going to get a reliable ballpark figure with the requirements you've listed. Variability in cartridge audio relative volume between early-model Famicoms and AV Famicoms is extreme, IIRC.

[rainwarrior]

I did request the Famicom model be specified for a reason.

I'll take as much information as can be gathered. Any information is better than no information. Whether that information can be considered reliable depends on what comes in, but if it can be done I want to do it. (And I think it can.)

Also, mikejmoffitt, what was the value written on the resistor that I presume you removed?

[mikejmoffitt]

I did request the Famicom model be specified for a reason.

I'll take as much information as can be gathered. Any information is better than no information. Whether that information can be considered reliable depends on what comes in, but if it can be done I want to do it. (And I think it can.)

Also, mikejmoffitt, what was the value written on the resistor that I presume you removed?

It was SMD, so it tells us nothing. It measured to be 16K. Later replacing it with a 20K resistor in testing produced no obvious audible difference.

[rainwarrior]

Really? I'm used to surface mount resistors having a number on them like "234" which would mean 23x10^4 ohms, at least, all the N163 boards I've looked at had resistors like this. Are you sure it didn't maybe say 153 on it?

[mikejmoffitt]

Really? I'm used to surface mount resistors having a number on them like "234" which would mean 23x10^4 ohms, at least, all the N163 boards I've looked at had resistors like this. Are you sure it didn't maybe say 153 on it?

It was small enough that it had no markings. That, or I didn't see them. I measured it once, and then promptly tossed it, so I have nothing else to offer unfortunately :