PSG/SCC balance

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By Metalion

Paragon (1348)

Metalion's picture

30-04-2016, 11:27

Hi everyone,

I just recently fired up again my MSX machines, which had been taking dust for a number of years. I wanted to feel again the real experience. I even bought a Sony KX-14CP1 for display.

What bothers me is the PSG/SCC balance. I tried Nemesis 2 on two different machines (Daewoo DPC-200 and Spectravideo SV-728) and on both machines, the balance is off, giving too much room to the PSG (the SCC is almost mute on the Spectravideo).

Is there something I can do ?

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By Daemos

Paragon (1939)

Daemos's picture

30-04-2016, 11:33

Change a few resistors in the mixdown stage of each machine Tongue
Then there are potmeters wich can be installed on the SCC outputting carts but you don't want to mess with your expensive carts.

Get the schematics of the audio mixdown stage of each machine and start soldering.

By Metalion

Paragon (1348)

Metalion's picture

30-04-2016, 12:21

Is this something due to aging of the electronics ?
Or is it due to the conception of the machine itself ?

I've been soldering some stuff (mainly cables) but I never ventured into soldering electronics, so I wouldn't dare to do so. I don't think I'm able to do that. Furthermore, all I have is a standard soldering iron, probably not suited for this kind of work.

Alternatively, what are the machines which are known to have a good PSG/SCC balance ?
I do remember that, back in the '80s, the balance was just fine on my Philips VG-8235 ...

By Daemos

Paragon (1939)

Daemos's picture

30-04-2016, 13:00

Changing the balance of audiotronics is not rocketscience and certainly not difficult to solder. It is 9 out of 10 times simply changing resistor values and listen what has changed. So lets have a look at the schematics and see what we can try.

By Metalion

Paragon (1348)

Metalion's picture

30-04-2016, 18:27

I like your positiveness, Daemos Smile

OK, I'll get the schematics, and we'll get to work.

By Wild_Penguin

Hero (636)

Wild_Penguin's picture

30-04-2016, 20:43

There is a fix for SVI 728 .... it was a known issue on them.

I've done it myself, works quite well to my ears Smile

Here: http://msx.hansotten.com/uploads/msxdocs/svi728cart.txt

By Metalion

Paragon (1348)

Metalion's picture

01-05-2016, 20:46

Nice.
Thanks, Wild_Penguin.

By Mikael.h1

Supporter (3)

Mikael.h1's picture

09-03-2018, 11:20

Hi everyone,

I have just unpacked my SVI-728 after a pause of around 30 years (!) And I became aware of this sound issue. The Music from the SCC chip is so low that you can barely hear it. Almost all the sound comes from the PSG. I am not certain if this was the case when I played the game in my youth. Might not have occured to me then. Browsing around I found this interesting forum, but the link to the fix mentioned above does not work anymore. Can anyone give me an indication regarding what the fix was/is?

By Guillian

Prophet (3411)

Guillian's picture

09-03-2018, 12:10

SVI 738

Quote:

How to put SCC, FM-PAC and other sound expansions to work with X'press:
----------------------------------------------------------------------

Well, actually these expansions are working... Only probblem is, that you
can't hear them because PSG is played too loud.

This probblem can be anyway solved, if you just remove 4K7 resistor from
R2 and replace it with about 150K resistor.

SVI 728

Quote:

With the 738 instructions and 738 schematics it was figured out which resistor
should be replaced on 728 model. The resistor is R53 and is located near the
soundchip. It is to be replaced with 150K resistor (original 4K7) as with
the 738 model.

Sources:
http://msx.hansotten.com/uploads/files/svixsound.txt
http://www.msxarchive.nl/pub/msx/mirrors/hanso/hwmodsetc/svi...

By Mikael.h1

Supporter (3)

Mikael.h1's picture

09-03-2018, 12:54

Thanks a lot Guillian. Now I only have to find someone in Sweden daring enough to open the computer and if possible also know what they are doing!

By hamlet

Scribe (3528)

hamlet's picture

09-03-2018, 13:17

Welcome Mikael.h1. Where in Sweden do you live? I know a tuff guy near Mölndal, who will help for sure...
BTW, There is"The Big 'MSX users, where do you live'-thread", where you can set your flag.

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