Is it possible to improve JAMMA sound quality?

[Chacranajxy]

A lot of words get spent on how to get to get the best possible video quality out of older hardware, but audio tends to get neglected. Which is kinda sad.

I've been trying to figure if there's any way to ensure I'm getting the best possible sound quality out of JAMMA boards. I'm not talking about the games that have a separate stereo-out connector - straight up JAMMA. From my experience (running through a supergun), the sound quality tends to range from pretty decent to really bad, but it's never great. PGM and Neo Geo games tend to sound fine over JAMMA, but some of my relatively older boards, like Metal Black, tend to be prone to audio hum. Cave's first-gen hardware sounds pretty bad, though I'm guessing that's just the sad reality of that motherboard. Ultimately, I find myself preferring the console ports of a fair number of games solely because they're so much better to listen to.

I dunno, maybe that's just how it is. In any case, I'm curious if there's anything one can do to get better sound out of arcade games.

 

[ekorz]

Cave ddp era needs a resistor fix: https://twitter.com/moftsoft/status/1243347958575149056 it is embarrassing how bad those boards sound stock. Similar fixes have been found on a couple other boards. Night slashers comes to mind.

I’ve come across plenty of boards that sounded like crud. Most of the time it’s a bad op amp or other analog component and it’s easy to find with an audio probe.

Many boards have line level audio you can tap before hitting the jamma amplifier, which sometimes adds noise. There are a few threads on here that showcase adding rca output plugs using that line level. @SmokeMonster has a few so you can search by his name eg https://www.arcade-projects.com/threads/primal-rage-pcb-restoration.421/

Beyond that, if there’s poor sound I recap the audio section, and that usually helps. MAME is decent for the audio emulation so if your pcb sounds much worse, it probably needs service.

 

[Derick2k]

Not Really - If you are looking to take whatever amplified audio the pcbs are pushing and make them sound better while not doing anything to the pcbs.

Because of GIGO (Garbage In Garbage Out), since manufacturers used all kinds of DACs/OpAmps/Amps/synthesizers (they all produced their own sound signature) , etc.. on these boards, and those components, like caps/filters/resistor,etc... degrade and they will not sound great. So, input that into something else and expect it to clean it up "make it sound better" it will be a tough job and if possible not cheap. Audio quality is somewhat subjective also, what sounds great to you can sound horrible to someone else.

Besides making sure audio circuits/components on your pcbs are working properly, I doubt you will make it sound better than originally intended with the components they chose to use at the time without modifying things, like tapping low level audio signals before amps, hell even tap digital audio signals before all that and run them through your DAC, etc..

You can also try improving your cabs/setups speakers, adding an EQ/Tone Controls, maybe even a sub. You could try some devices like DSPs with EQs, etc.. and see if that helps, but usually, those are not cheap.

Every case/situation might be a different issue requiring a different solution if one is possible. In the case of audio hum, you probably need to look at possible ground loop issues or maybe you need some type of galvanic isolation.

 

[twistedsymphony]

There's plenty of threads around here on how people have fixed bad audio on boards, but there's no silver bullet for improving JAMMA output. Basically the JAMMA standard is amplified Mono audio out, which means that the only thing you really have control over is a single speaker because everything else is part of the JAMMA board. So that means nearly every audio problem is caused by something BEFORE it exited the JAMMA board... fixing it after the fact is like trying to un-crash a car.

 

[buffi]

The amplification of jamma audio is seldom very good on pcbs.

This sortof makes sense considering the usecase is small arcade speakers in a very noisy environment.

Hard to do much

 

[Hammy]

those components, like caps/filters/resistor,etc... degrade

The sound chips also degrade over time too (see system 32 / outrun type stuff with the dead custom PCM's)

I recently got a batch of newly manufactured OKI 6295's for the jaleco boards and was amazed by the sound quality.
The difference is so great, there's a high chance i will upgrade my favorite games with OKI's to the new as the 20 -30 year old ones have been caned to death at this point.

 

[stj]

recap the sound section with rubycon YXF series, and the 12v smoothing with panasonic FR series - that will get the best highs and lows out of the board.
make sure the cab has a decent speaker/speakers and not some midrange crap.

if your using a supergun style rig, consider connecting the jamma connector to a 10-30w hifi speakerbox.
anything that tries to reduce a speaker output back to line-level to feed a tv is probably going to trash the quality.