Audio problem with MegaFlashRom SCC+ and a Sanyo Wavy-70FD

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By Louthrax

Prophet (2435)

Louthrax's picture

03-12-2016, 18:51

You can also check the "external SCC" option in SofaRun to force using a specific SCC slot (patching is done automatically).

By sd_snatcher

Prophet (3592)

sd_snatcher's picture

07-08-2017, 19:31

I have good news! With the audio schematics reverse engineered by Belavenuto of FB-Labs, and the guidance of the Analog Jedi Master Sturaro of MSXpro, I was able to finally create a fix for the Sanyo PHC-70FD/PHC-70FD2 sound issues.

It fixes the following problems of the audio circuit:

  • Solves the problem where the SCC and some other external sound cartridges got muted. The impedance matching was all wrong. (note: some machines won't show this problem with the real SCC cartridges because Sanyo's customer service seem to have implemented a fix. But that was a poorly designed solution too and many other cartridges still got muted. The solution presented here is much better)
  • Fixes the mixer volumes to be standard, just like Panasonic MSX2+ and Sony MSX2+ machines
  • Boosts the OPLL bass frequencies
  • Fixes the OPLL low-pass filter. Sanyo had done the best OPLL low-pass filter of all MSX2+ models (4.13KHz), but this fix enhances it way further, to 22KHz
  • Enhances the SNR of the sound output

It's available at this page. Have fun fixing your machines!

By MajorTOM

Master (209)

MajorTOM's picture

01-10-2020, 13:13

Do you know if the soundo problem exists with EVERY NMS8280 ? or may be some Hardware updates?
I am the proudly owner of a NMS8280 (ES version) and I´m using orginal SCC cartridges with no problem at all...



By Pac

Scribe (6841)

Pac's picture

04-01-2022, 13:09

Today, thanks to the sdsnatcher73's sale, I realised that a suffix "A" for the Sanyo Wavy PHC-70FD exists. Just out of curiousity, being probably a hardware fix according to the wiki, do we know if this audio issue is present in those A versions as well? I mean, if this hardware fix could be related to the audio mixer.

By sdsnatcher73

Prophet (3659)

sdsnatcher73's picture

04-01-2022, 13:52

From my experience the mixer on the A variant is not different. I have both normal and A and they both work well with real SCC cartridges (although that may be the modification as was also mentioned by FRS) but not with MFR audio. I have not done extensive testing. I have had a PHC-70FD2 with the audio modification and the mixer is close to perfect at that point. One advantage of the 70FD range over Sony and Panasonic 2+ machines with FM is that there is much less noise introduced from the OPLL.

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