Log inRegister an accountBrowse CSDbHelp & documentationFacts & StatisticsThe forumsAvailable RSS-feeds on CSDbSupport CSDb Commodore 64 Scene Database
You are not logged in - nap
CSDb User Forums


Forums > CSDb Discussions > reduce the audio-noise
2007-02-09 19:06
Dr. 8 Bit
Account closed

Registered: Sep 2006
Posts: 25
reduce the audio-noise

How can I reduce the audio-noise from c64?? some ideas?? a capcitor...mmm..
 
... 68 posts hidden. Click here to view all posts....
 
2008-11-12 05:32
Grue

Registered: Dec 2001
Posts: 145
Just disconnect the ext-in pin from the sid socket. It can be done quite easily when you bend the pin straight so it doesn't make contact with the socket.

You can also ground the ext-in pin FROM THE AUDIO/VIDEO CONNECTOR behind the c64. Grounding ext-in pin straight from the sid will result most likely to hardware failure.. Its safe to ground it after the capasitor.

Also adding extra filtering to +12v/+9v voltage supply have helped along the way.
2008-11-12 09:29
SIDWAVE
Account closed

Registered: Apr 2002
Posts: 2238
Quote: Just disconnect the ext-in pin from the sid socket. It can be done quite easily when you bend the pin straight so it doesn't make contact with the socket.

You can also ground the ext-in pin FROM THE AUDIO/VIDEO CONNECTOR behind the c64. Grounding ext-in pin straight from the sid will result most likely to hardware failure.. Its safe to ground it after the capasitor.

Also adding extra filtering to +12v/+9v voltage supply have helped along the way.


So the first you write, is the only safe way ?
(which requires no soldering)
2008-11-12 11:21
Frantic

Registered: Mar 2003
Posts: 1626
Can anybody else confirm that you simply have to bend away the "ext-in" leg of the SID chip to fix the noise? If that is true (according to more than one person) I will add it to the codebase64.org article on this topic (noise reduction).
2008-11-12 12:29
Grue

Registered: Dec 2001
Posts: 145
Quote: So the first you write, is the only safe way ?
(which requires no soldering)


Its safe if you bend the pin CAREFULLY, its always possible that yuu break it. Its also risky to remove chip from the socket if you dont know what youre doing...

What comes into if its helpful, it is..

I instructed alankila to do this hack and here is what he as to say about it:

"Modify your C64. Take out the SID chip and locate the third pin from top right (number 26, I think). It is the AIN (audio in) pin, and it sucks in most of the system noise, especially the display whirr. We need to ensure it is grounded or floating. The easiest fix is to make it floating: bend it slightly off, so it doesn't enter the socket on chip insertion. If you are very adventurous you could also try to improve the SID input voltage with additional capacitors and coils. It will help a little, but this modification is what counts. "

http://www.bel.fi/~alankila/c64-sw/yourchip.html
2008-11-12 12:33
Mace

Registered: May 2002
Posts: 1799
Please note that Dr. 8 Bit started a thread but never replied to ANY of the suggestions.
2009-03-03 11:14
GT
Account closed

Registered: Sep 2008
Posts: 308
aeeben allready gave you guys the solution two years ago, and you are still talking about breaking legs on the SID chips. OMG. Just activate bit 3 on register $d417, the SID chip input should be disabled.

Replace the STA $d417 in a player with JSR to this code:

ORA #$08
STA $d417
rts
2009-03-03 11:23
Frantic

Registered: Mar 2003
Posts: 1626
Hmhöömhmhmhm...


Perhaps I shouldn't rely so blindly on AAY64, but it says:

http://unusedino.de/ec64/technical/aay/c64/sid23.htm

So.. two things...

1. What exactly is this bit in $d417 doing? Is it a flag to determine whether external input should be filtered or not (but still audible), or is it a flag to determine whether external input should be filtered or not routed into the chip at all?

2. If the info is correct, it seems to say that lda #8 sta $d417 would route the external input into the filter, and thus this code would in fact NOT disable it? (Perhaps the idea here was that if you route the signal into the filter, the *filter* will make it "silent" through filtering away some of the input noise?)


Anyone up for a clarification?
2009-03-03 11:41
GT
Account closed

Registered: Sep 2008
Posts: 308
With bit3 activated only, it disables the input. But setting a bandpass in $d418, the input gets filtered of course. Please give more feedback on this, I tried it on a C64 slim with 8580 chip.
2009-03-03 12:11
Frantic

Registered: Mar 2003
Posts: 1626
Not allowing the musician to use the filters as he wishes makes this "trick" kind of useless for general purpose use.

It also implies that bending one of the legs of the SID is in fact a better method for general purpose use.
2009-03-03 12:27
GT
Account closed

Registered: Sep 2008
Posts: 308
Quote: Not allowing the musician to use the filters as he wishes makes this "trick" kind of useless for general purpose use.

It also implies that bending one of the legs of the SID is in fact a better method for general purpose use.


At least you'll get rid of most of the noise when using filter. Especially on low cutoff tunes, using heavy basses etc... The noise makes in more lively IMO. I wouldn't recommend bending pins. We're talking vintage equipment. :-)
Previous - 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 - Next
RefreshSubscribe to this thread:

You need to be logged in to post in the forum.

Search the forum:
Search   for   in  
All times are CET.
Search CSDb
Advanced
Users Online
Higgie/Kraze/Onslaught
Exile/Anubis
Knut Clausen/SHAPE/F..
Oswald/Resource
Mason/Unicess
chronos/Therapy
McMeatLoaf
Isildur/Samar
Frostbyte/Artline De..
Guests online: 296
Top Demos
1 Next Level  (9.8)
2 Mojo  (9.7)
3 Coma Light 13  (9.7)
4 Edge of Disgrace  (9.6)
5 No Bounds  (9.6)
6 Comaland 100%  (9.6)
7 Uncensored  (9.6)
8 The Ghost  (9.6)
9 Wonderland XIV  (9.6)
10 Bromance  (9.6)
Top onefile Demos
1 Party Elk 2  (9.7)
2 Cubic Dream  (9.6)
3 Copper Booze  (9.5)
4 Rainbow Connection  (9.5)
5 TRSAC, Gabber & Pebe..  (9.5)
6 Onscreen 5k  (9.5)
7 Dawnfall V1.1  (9.5)
8 Quadrants  (9.5)
9 Daah, Those Acid Pil..  (9.5)
10 Birth of a Flower  (9.5)
Top Groups
1 Booze Design  (9.3)
2 Nostalgia  (9.3)
3 Oxyron  (9.3)
4 Censor Design  (9.3)
5 Crest  (9.3)
Top Diskmag Editors
1 Jazzcat  (9.4)
2 Magic  (9.4)
3 hedning  (9.2)
4 Newscopy  (9.1)
5 Elwix  (9.1)

Home - Disclaimer
Copyright © No Name 2001-2024
Page generated in: 0.053 sec.