FS-A1ST and FS-A1GT MSX Turbo-Rs sound fix

FS-A1ST and FS-A1GT MSX Turbo-Rs sound fix

by sd_snatcher on 17-08-2017, 23:39
Topic: Hardware
Tags: Audio fix, GT, ST, turbo R
Languages:

The two Panasonic MSX Turbo-Rs have a very good audio circuit design that has everything it should have for its price range. But the result was poor because the circuit was terribly calibrated, resulting amongst other problems, in:

  • The slot sound was too loud, meaning you could barely hear the PSG drumkit when an SCC cartridge was used.
  • On the other hand, the OPLL sound was too quiet, so the soundtracks of Micro Cabin games, Valis-2, Starship Rendezvous and others that used the PSG and FM simultaneously were severely affected. Most chords were derailed, and Micro Cabin's trick of using the PSG to complement the OPLL didn't match anymore. The PSG kept screaming all the time.
  • The OPLL low-pass filter was even stronger than the already incorrect Yamaha reference design, resulting in a terribly muffled FM sound that made the previous problem even worse.
  • The global audio-out low-pass filter was also too strong, to the point that the borders of the square wave output of the PSG were totally round, degrading many beautiful chords of famous Konami soundtracks for this chip.
  • The global audio-out level was too weak, resulting in poor SNR and weak bass.

This fix recalibrates the audio circuit for maximum performance, and what astonishing difference that it does. It then blows any other MSX sound quality out of the water.

This recipe corrects all these problems, and normalizes the mixing volume between the slots (usually SCC or MSX-Audio), PSG and OPLL, to match the levels of the Panasonic MSX2+ and Sony MSX2+ machines.

Comments (35)

By raymond

Champion (290)

raymond's picture

18-08-2017, 07:37

Ah, nice. Improvements are always good Big smile

By KdL

Paladin (968)

KdL's picture

18-08-2017, 14:31

like+1000000 thanks!! Running Naked in a Field of Flowers

By jltursan

Prophet (2076)

jltursan's picture

19-08-2017, 14:16

Good work!, many, many thanks!

By sd_snatcher

Prophet (2540)

sd_snatcher's picture

21-08-2017, 00:31

I published four lists of soundtracks comparing the after/before of the FS-A1ST audio fix, so anyone can check themselves the difference in terms of sound quality and how much detail was being missed. I hope you enjoy it.

EDIT: I used VGMplay for the non-Micro Cabin soundtracks, but I noticed that some tracks have some weird glitches, regardless of the fix. It's very noticeable in the beginning of Metal Gear-trk2, in the drumkit of Mr Ghost and in the opening song of Greatest Driver.

PS: Be sure to use a decent sound equipment. Notebook speakers won't do. :)

By Grauw

Enlighted (6040)

Grauw's picture

21-08-2017, 00:48

Oh wow, what a difference.

Thanks for posting this extensive comparison, must’ve taken some time to compile!

Re. VGMPlay issues, will look into that…

By Victor

Champion (282)

Victor's picture

21-08-2017, 06:10

Grauw wrote:

Oh wow, what a difference.

YES!! The difference is huge!!

Great work FRS!!

By Guillian

Prophet (2991)

Guillian's picture

21-08-2017, 09:56

Great work! Thanks for sharing.

By raulsantacruz

Champion (466)

raulsantacruz's picture

21-08-2017, 14:58

Absolutely great!!!! I can't wait until the moment to fix my computer!

By sd_snatcher

Prophet (2540)

sd_snatcher's picture

21-08-2017, 15:51

Grauw wrote:

must’ve taken some time to compile!

I got a cold, so in my current condition you can imagine it was like a punch. The vertigo and dizziness returned quite strong.

But I can't just stay still, so I decided to do something that didn't require too much concentration. Smile

By JohnHassink

Ambassador (4893)

JohnHassink's picture

21-08-2017, 18:35

Wow sd_snatcher, not only is the comparison very interesting, your selection of songs is also really enjoyable in itself. Smile

My guess about the Greatest Driver glitches are warped parameters in pitchbending and "note linking" (new tone without retriggering the preset) commands.
Though it's puzzling why it only affects certain instances and doesn't seem to happen in the "original" version.

Maybe it just isn't...
(•_•)
( •_•)>⌐■-■
...using the greatest driver.
(⌐■_■)
YYYYYEEEEEAAAAAHHHHHH

By JohnHassink

Ambassador (4893)

JohnHassink's picture

21-08-2017, 18:31

If it helps, I noticed some skewed frequencies in the tracks from Psycho World (the 'brass' section shortly after the beginning), Undeadline (basslines and some piano notes) and Xevious (one note in the lead missing) as well.
As there doesn't seem to be any pitchbending or note linking going on during those instances, my earlier assessment is probably incorrect.
Again, the problems seem to be present in the Fixed versions only.

By Grauw

Enlighted (6040)

Grauw's picture

21-08-2017, 20:03

The Greatest Driver glitches are from too fast OPLL access, although as you say I only hear them in the fixed ST recordings. Which is a bit puzzling, especially if that’s also the case for other songs. It suggests a machine-specific difference.

@sd_snatcher Did you perchance upgrade something related to CPU speed on the fixed ST? Or maybe the other ST was running in Z80 mode? Otherwise, if there are no differences to speak of, I might’ve timed things a bit too tightly according to my own GT’s tolerances. I’ve had an issue with this in the past for an MSX-Audio modded with a clock crystal (Meits’s).

That doesn’t explain the PSG issues though. Maybe there’s something I forgot to initialise.

By Louthrax

Paragon (1602)

Louthrax's picture

21-08-2017, 21:31

Grauw, not sure if that's related, but about the PSG issues, that might be caused by the VGM file itself, if it does not contain initialization for all registers at start. For example, I did a VGM recording using openMSX from a simple BASIC PSG PLAY "A" instruction: this causes noise to be added to the "A" when playing that file back with VGM play. VGMPlay initializes all registers to 0 (not saying that's a bad thing), but by default this activates the PSG noise. Of course it works if you record things before the reset or power-up.

Maybe a full initialization sequence could be added in the openMSX VGM recording script (with the default after-boot values)...

By Manuel

Ascended (13382)

Manuel's picture

21-08-2017, 21:51

I think the idea is that you record in openMSX including initialization (for PSG that may be the BIOS starting up) and cut out some silence parts out later.

How could the script add an initialization sequence if it doesn't even know what it should be for the music that will be recorded?

By Louthrax

Paragon (1602)

Louthrax's picture

21-08-2017, 21:55

Manuel wrote:

How could the script add an initialization sequence if it doesn't even know what it should be for the music that will be recorded?

That's the question... Maybe if the registers are mirrored inside openMSX and accessible from TCL they could be written at script start? (my guess is that for now the script writes in the VGM file only what's written on the various audio ports / memory addresses).

By ren

Paladin (719)

ren's picture

21-08-2017, 22:14

Wow, differences seem insane, like the originals almost sound muted? Is there actually such a difference in volume/clarity/loudness, or does the recording itself also play part in this? I can hardly believe the original MSX sounds that bad.

Thanks for the (huge! amount of) recordings (and indeed nice selection Wink) Gonna compare some stuff with openMSX's rendering when I get to it Wink

Something I'm wondering about though: one may assume the various composers heard their work as well on an original (thus prolly flawed) MSX.. So now with the fix it may actually *not* sound the way it's intended right? (But then, there were already differences between models..)

By Grauw

Enlighted (6040)

Grauw's picture

21-08-2017, 22:55

@Louthrax In principle I should mirror the initial state from VGMPlay for PC, but I might’ve made a mistake. Writing the initial register state in the script is not necessary I think, the game should either initialise everything or rely on boot-up initial values, not on something arbitrary.

@ren Since everything sounds 1000% better, I think the original composers would have no complaints Big smile. The question what machine composers made their music on is a similar question as “did they make their game with an S-Video or composite or RGB connection”, “what was the dot pitch of their monitors”, “did all artists use the same monitors”, “what type of speaker did the musicians use” and “did they even develop the game on an MSX”. There is going to be differences, it’s part of the deal.

But I think bringing the mixing in line with popular models which have good balanced mixing is never a bad thing. And as for the low-pass filter, I would say at least the turboR was particularly terrible so upping the cutoff frequency is never a bad thing. And in emulators we’re also hearing the unmuffled sounds and nobody complains about that. Also, 1000% better Big smile.

By JohnHassink

Ambassador (4893)

JohnHassink's picture

22-08-2017, 00:37

Grauw wrote:

The Greatest Driver glitches are from too fast OPLL access

Is it safe to assume then that the glitches in the other games are caused by that same thing?

By Grauw

Enlighted (6040)

Grauw's picture

22-08-2017, 00:49

Yes, the OPLL ones at least. Nothing to do with FRS’s audio fix.

By JohnHassink

Ambassador (4893)

JohnHassink's picture

22-08-2017, 02:44

So, in terms that laymen (like me) can understand, the data is sent to the chip faster than it can process, so that it uses previous frequency information, that lags behind the 'action'?

By Grauw

Enlighted (6040)

Grauw's picture

22-08-2017, 11:45

Yeah, or part of the previous frequency information, since it is spread out over two registers.

Drawing attention back to the topic… Smile

sd_snatcher wrote:

I published four lists of soundtracks comparing the after/before of the FS-A1ST audio fix, so anyone can check themselves the difference in terms of sound quality and how much detail was being missed. I hope you enjoy it.

EDIT: I used VGMplay for the non-Micro Cabin soundtracks, but I noticed that some tracks have some weird glitches, regardless of the fix. It's very noticeable in the beginning of Metal Gear-trk2, in the drumkit of Mr Ghost and in the opening song of Greatest Driver.

PS: Be sure to use a decent sound equipment. Notebook speakers won't do. :)

By syn

Paragon (1616)

syn's picture

24-08-2017, 16:36

sd_snatcher wrote:

I published four lists of soundtracks comparing the after/before of the FS-A1ST audio fix, so anyone can check themselves the difference in terms of sound quality and how much detail was being missed. I hope you enjoy it.

Okay I did a quick listen. I don't own a Turbo R (yet) so I don't have much to gain by this. Nevertheless I would give you my personal opinion, to help you maybe further improve this mod.

btw I disregard the difference in overal volume level, since that is most definitely an improvement.

PSG+SCC: Balance is improved, overal sound is good. Improves a lot of the tunes.
PSG only: Sounds like an improvement, things are more clear. It would seem some of the noise register sounds (hihats etc) were a lot softer before the mod. Sounds has more "texture" i guess (if that makes any sense).

However the OPLL seems to have way too much treble. I've talked on #msxdev about this briefly (like a few minutes), it would seem your unmodded turbo R (st) indeed sounds a more "muffled" compared to a GT (that lowpass filter thing i guess). So fixing could be needed.

But in my opinion the fixed versions of some of the songs just don't sound right. For example your comparison of PSG+OPLL+SCC (sorcerian tune), I prefer the original unmodded version. The fixed version has so much treble around 0:48 that it starts sound unpleasant for me ears if I dont turn down volume. Same for some of the OPLL Fray tunes. I guess it depends on how much "high" was present in the original, other songs sound alright.

And no, this is not me based on years of being used to certain settings/machines, since I barely know half of the tunes you posted.

Btw does your mod for the sanyo make sound about the same as this? (not asking/expecting you to do a recording)

ren wrote:

Something I'm wondering about though: one may assume the various composers heard their work as well on an original (thus prolly flawed) MSX.. So now with the fix it may actually *not* sound the way it's intended right? (But then, there were already differences between models..)

This is what I am wondering about too. I dont know about the exact release dates of the games or development machines of Microcabin, but it seems that the "treble problem" that I talk about earlier seem to more affect "newer" microcabin games. I suspect they were made on a muffled turbo r, and the composers just upped the higher instruments' volume to compensate for the lowpass filter.

By Grauw

Enlighted (6040)

Grauw's picture

25-08-2017, 01:24

syn wrote:

it would seem your unmodded turbo R (st) indeed sounds a more "muffled" compared to a GT (that lowpass filter thing i guess).

In the course of some VGMPlay debugging, I felt my GT indeed didn’t sound as bad as the unfixed ST. Though of course the listening conditions were different, and this was only a casual observation. When I get around to ordering the components and sitting down to fix my GT audio, I’ll be sure to make before / after recordings.

About treble, I wonder how you feel about emulator renditions of those Fray songs?

Btw, regarding the part of the Sorcerian song that you mentioned, I love how it sounds really “snappy” after the fix. The fast attack on the modulator of the lead voice gets kinda lost in the muffled version.

By Louthrax

Paragon (1602)

Louthrax's picture

25-08-2017, 09:28

I like the fixed sounds too. Matter of taste here of course, could be compared to preferring CRT blurry display vs LCD sharp square pixels (in this case I prefer the CRT!).

By Grauw

Enlighted (6040)

Grauw's picture

29-08-2017, 23:19

Hey FRS,

Would it also be better to use polypropylene capacitors for C51 / C45 on the GT, or do they have to be ceramic?

By sd_snatcher

Prophet (2540)

sd_snatcher's picture

29-08-2017, 23:38

Thanks for asking, I'll add this info to the article. If you can find polypropylenes that fit in there without the risk of ripping the pads out of the board, you can used them. This means: *only* if they are the small 50V type. Do not use the 100V rating because they're way too bulky to install there.

Plz also keep in mind that the recommended type of ceramics, if used, are not the crappy Y5V or the not-so-great X7R. Use the more expensive C0G (aka NP0) type as they are of excellent quality and much more appropriate for this application.

By sd_snatcher

Prophet (2540)

sd_snatcher's picture

29-08-2017, 23:48

Oh, and you can use polystyrene 50V capacitors for the C51/C45 too.

By Grauw

Enlighted (6040)

Grauw's picture

30-08-2017, 00:48

Cool, then I can order all-Panasonic components Big smile.

Here’s my DigiKey shopping list (with assortment of caps so I can compare different values).

Index,Quantity,Part Number,Description,Customer Reference,Available Quantity,Backorder Quantity,Unit Price USD,Extended Price USD,
1,10,PCF1299CT-ND,CAP FILM 1800PF 2% 50VDC 0805,,10,0,0.36100,3.61,
2,10,PCF1177CT-ND,CAP FILM 10000PF 2% 16VDC 0805,,10,0,0.34600,3.46,
3,10,PCF1174CT-ND,CAP FILM 5600PF 2% 16VDC 0805,,10,0,0.37400,3.74,
4,10,PCF1301CT-ND,CAP FILM 2700PF 2% 50VDC 0805,,10,0,0.32100,3.21,
5,10,PCF1287CT-ND,CAP FILM 180PF 2% 50VDC 0805,,10,0,0.35700,3.57,
6,10,PCF1286CT-ND,CAP FILM 150PF 2% 50VDC 0805,,10,0,0.35700,3.57,
7,10,P22KDACT-ND,RES SMD 22K OHM 0.1% 1/8W 0805,,10,0,0.30200,3.02,
8,10,P15KDACT-ND,RES SMD 15K OHM 0.1% 1/8W 0805,,10,0,0.30200,3.02,
9,10,P47KDACT-ND,RES SMD 47K OHM 0.1% 1/8W 0805,,10,0,0.30200,3.02,

Tomorrow I’ll see if I can find some other nice stuff that I’d like to have to get above the $60 free shipping :).

By sd_snatcher

Prophet (2540)

sd_snatcher's picture

30-08-2017, 01:36

Good thinking! Polyphenylene Sulfide capacitors are an excellent choice too, specially in SMD form factor. I'll add this option to the article because they're very easy to install and it looks original. I'll probably remove the polypropylene option for the TRs because it's impossible to find them at the right size these days, and it just makes the text more confusing. Having two excellent options of capacitors for audio like the PPS and the C0G is enough.

BTW, for those interested in this topic here's an excellent article comparing the performance of the C0G capacitors with PPS and other plastic capacitors.

By Grauw

Enlighted (6040)

Grauw's picture

30-08-2017, 01:57

For me the “Stable Frequency Characteristics” graph in this overview was pretty illustrative.

For the resistors I picked thin film ones which are supposedly better for audio purposes (though a bit lower wattage, and I’m not sure the high-end audio characteristics will survive the rest of the MSX’s circuitry :D, so maybe just a bit of a waste of money). And the higher value caps are only rated for 16V, I assume that’s no problem either since line level is just 1.7V and before the opamps I guess it’s even less.

As for the Polyphenylene, I just saw “film” and “polyflufluflulene” so that was a bit accidental :D.

By sd_snatcher

Prophet (2540)

sd_snatcher's picture

30-08-2017, 02:00

Grauw wrote:

For me the “Stable Frequency Characteristics” graph in this overview was pretty illustrative.

Yes, X7R ceramic capacitors are known for being crap. C0G ceramics are a totally different beast though. BTW, the original audio capacitors in the Turbo-R were C0G, so they were worried about the sound quality. Too bad that excellent components were wasted with such an horrible calibration.

By roadfighter

Champion (336)

roadfighter's picture

31-08-2017, 10:08

@Grauw, you could order some more components, so you could make diy sets for the turbo-r's.
Maybe include all capacitors so we could do a complete recap of the computer's.
Are the differences between the St send Gt "big"? Component wise? Then one set could be used for St or Gt.

And I noticed something strange, the microphone of the turbo-r's are not completely muted.
When you put on your computer and blow or whistle in to the mic. You can hear it in the speakers (audio out).
I can imagine that this causes some background noise no one whants. Is there a fix for this?

By Grauw

Enlighted (6040)

Grauw's picture

31-08-2017, 10:33

@roadfighter Yeah, I am ordering at least 10 of each because it’s cheaper (bulk discount), and I want to get to the free shipping limit. I think I will put the components that are left over into little seal bags and bring them to the Nijmegen fair.

The ST uses the same components as the GT minus one, so the same set of components can be used.

I’m not ordering full recap sets as sd_snatcher told me earlier that the Japanese caps in the turboR are really good quality and not affected (as much?) by the capacitor manufacturing problems of the 80s. So since my GT’s caps are looking fine and I’m having no issues since I applied the jailbar fix, now I feel it’s best to leave it as-is. Less chance of me damaging the main board in the process as well :).

By roadfighter

Champion (336)

roadfighter's picture

31-08-2017, 21:23

@Grauw,
Nijmegen is a good idea, but I want to fix my turbo-r's before that Tongue
And good to know that the caps are of good quality, I will leave them be then.

By OeiOeiVogeltje

Paragon (1165)

OeiOeiVogeltje's picture

16-09-2017, 18:21

@Grauw i just sent you an email..

My MSX profile