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#1 2011-06-15 20:24:30

Timechimp
Bloody beginner
Registered: 2011-06-15
Posts: 1

Audio quality with the Commodore

Greetings..I am brand new MSSIAH user/somewhat seasoned SID voyager.   Ever since playing with the Synthcart SID program I've enjoyed the tone of
the instrument, and wondered if some folks have figured out a way to reduce the inherent signal to noise qualities ( I perceive it as a high pitched hum)
when connecting the audio to a mixer or amplifier.    I use the 6 pin to RCA connector with just a single mono audio jack plugged in, and when I do the Pepsi challenge with the RF Modulator TV connector, I can't detect much of a difference.   Perhaps some EQ can eliminate a bit of the unwanted noise, and maybe I just need to embrace the lo-fi goodness and/or mute mixer/amp signals when I'm not using the SID.  Any comments or suggestions?

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#2 2011-06-16 09:57:55

DjFluorescent
Space Invader
From: Texas,USA
Registered: 2010-01-16
Posts: 136

Re: Audio quality with the Commodore

Thats the power supply and a smidgen of it is the noisy SID itself. We all get that. Ground the audio input pin(26) using a 1F Cap (+side towards SID) then after cap comes a 100k resistor, and THEN to ground. It will not go away completely without a modern power supply, or some modding that is probably too much trouble then it's worth IMO.

You could always build your own, but again thats a lot of hassle for some people.

http://i77.photobucket.com/albums/j43/frightendghoul/two-sec-PSU.png

http://i77.photobucket.com/albums/j43/frightendghoul/c64ps.jpg


**** COMMODORE 64 BASIC V2 ****
64K RAM SYSTEM  38911 BASIC BYTES FREE.

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#3 2011-12-28 20:27:58

grimp
Bloody beginner
Registered: 2011-10-02
Posts: 5

Re: Audio quality with the Commodore

ok so i just strait grounded the pin 26 to the casing and the noise went away pretty substantially. BUT the audio Volume went down . AND the sequencer portion of mssiah works fine but the monosynth and drum machine do not make sound now(well it does but its so low its useless). so what am i doing wrong ? do the capacitor and resister i didnt install fix this problem ?

Last edited by grimp (2011-12-28 20:28:55)

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#4 2012-01-08 19:28:36

grimp
Bloody beginner
Registered: 2011-10-02
Posts: 5

Re: Audio quality with the Commodore

FYI i did the mod Above. grounded pin 26 to the capacitor then to resistor then to ground and fixed the problem .  the noise significantly dropped volume stayed high and the whole software suite works perfectly . the noise is down to what i id say is  a level that is ok  for studio and live use.

Last edited by grimp (2012-01-08 19:30:23)

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#5 2014-02-04 01:04:37

a.kasa
Bloody beginner
Registered: 2014-01-27
Posts: 1

Re: Audio quality with the Commodore

I wonder if it possible for some one to share some pictures of that mod grump did? I'm really newbie with schematics and all that so it would help quite a lot. I've also noticed that the noise seems to be different to what sid revision one has. I had commodore 64c(SID 8580) and the noise problem in that wasn't that bad but what happened is that the SID got fried because of analog tape delay and some power/current peak it caused. Or at least that is what I suspect. Then I got the breadbox edition with the SID 6581 and it's quite useless 'cause the noise is so loud. Though that SID seems to got fried too, and now I need to buy another one. I'm not sure what I am doing wrong but roland space echo re-201 seem to be quite bad combination, which is a shame 'cause they sound so good together. But if some one could post some images of that modification that makes the noise go away I would be really grateful.

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#6 2014-02-04 16:08:57

MadModder
Bomb Jack
Registered: 2012-11-03
Posts: 31

Re: Audio quality with the Commodore

Never power cycle anything while connected to the C64. And never connect or disconnect anything to the C64 while powered on. Because there is no input protection anywhere.
But that is somewhat impossible to follow. Like you have to connect the gear sometime...
Perhaps some sort of line buffer in between.

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