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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.. |
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Grue
Registered: Dec 2001 Posts: 146 |
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. |
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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) |
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Frantic
Registered: Mar 2003 Posts: 1627 |
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). |
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Grue
Registered: Dec 2001 Posts: 146 |
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 |
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Mace
Registered: May 2002 Posts: 1799 |
Please note that Dr. 8 Bit started a thread but never replied to ANY of the suggestions. |
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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
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Frantic
Registered: Mar 2003 Posts: 1627 |
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? |
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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. |
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Frantic
Registered: Mar 2003 Posts: 1627 |
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. |
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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. :-) |
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