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

Scribe (1548)

17-12-2015, 18:39

i thereby confirm the presence of this audio problem with Wavy 70 FD. SCC+ from MFR is very silent comparing to PSG. And Konami's chips are doing well (have some original cartridges + two flashrom's made from original carts)

By Daemos

Prophet (2052)

17-12-2015, 20:02

Try these

Original schematic included. Best is solder the modification on a small module first and test with cables and a scope. Once the signal is good build it in. This is a good summing amplifier. I hope the impendances will match with the SCC+ but you will have to experiment a little bit on that.

You can use any opamp. Couldn't find my favorite in the eagle list so I justed picked one.

Good luck for the brave ones.

Ohw yeah: Point A, B and D need decoupling, try 1uF with 100K for best result.

By syn

Prophet (2117)

17-12-2015, 21:26

Pencioner wrote:

i thereby confirm the presence of this audio problem with Wavy 70 FD. SCC+ from MFR is very silent comparing to PSG. And Konami's chips are doing well (have some original cartridges + two flashrom's made from original carts)

Thanks for confirming. That is how I remember it (like I say in my earlier post, I dont have a real SCC to check but I dont recall the last time had one (20 years ago) there were any problems.

Guillian wrote:

@sd-snatcher: there is no analog part in the cartridge.The sound output pin from the FPGA is connected to sound pin of the cartridge.

Interesting. I am curious, in konami carts, does the sound go directly to sound-in pin as well or is there something in between?

(i am 120% noob at electronics)

By Pencioner

Scribe (1548)

17-12-2015, 22:06

syn wrote:

Interesting. I am curious, in konami carts, does the sound go directly to sound-in pin as well or is there something in between?

as far as i remember there are nothing like that on cartridge itself, but that means nothing: you still don't know what's inside the Konami SCC chip, and there may be some audio circuit in there

By Daemos

Prophet (2052)

17-12-2015, 23:08

There is resistance between the SCC chip and the out pin.

By sd_snatcher

Prophet (3646)

18-12-2015, 22:40

Thanks for your ideas, Daemos! I'll have a look into it too.

By Daemos

Prophet (2052)

19-12-2015, 11:15

Quote:

Thanks for your ideas, Daemos! I'll have a look into it too.

Let me know the results. Audio is all about trial and error after aplying the rules. Make sure to check for overdrive with a scope. I have no clue about the sound volume of the sanyo so the amp may be amlifying too loud or too soft.

By sd_snatcher

Prophet (3646)

13-03-2016, 03:01

I did some tests on the PHC-70FD today. If I remove the C114 capacitor, the SCC and MFRSCC+ volume becomes normal. This also disables the PSG sound, of course.

But it gives me the impression that there's something wrong with that part of the mixer.

By Albert Pieter Dotinga

Resident (39)

03-12-2016, 15:43

I got the same problem in my wavy 70fhd2...
But i found a solution if i put my MEGAFLASHROM in slot 1 and put a scc cartridge in slot 2 scc sounds normal with psg lol.... I think the rom in the megaflashrom uses the scc from slot 2...

By Guillian

Prophet (3516)

03-12-2016, 18:24

Nice trick! BTW, if the ROM is not patched, it will use the SCC in the MFR SD.