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aeeben
Registered: May 2002
Posts: 44 |
SID oscillator/envelope leakage in emulation?
Try this on a real machine:
poke54296,15:poke54277,12:poke54278,12:poke54273,15:poke54276,33:poke54276,33
After the sound has decayed you can still hear the note pitch, although very faintly. It's louder than static though. I've observed this at least on the old SID.
poke54273,0 or poke54296,0 mutes it
Has anyone measured this leakage, does it also happen on 8580, and is it emulated in any SID emulator? |
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chatGPZ
Registered: Dec 2001
Posts: 11386 |
And does it happen on ALL 6581? Is it dependent on temperature? |
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Jammer
Registered: Nov 2002
Posts: 1335 |
Quote: And does it happen on ALL 6581? Is it dependent on temperature?
It leaks on 8580 as well. Cutting sound with testbit/zero wave only (but without triggering release) is the main way to reproduce. I'm not sure if it's temperature dependend but behaviour occurs also right away after launching C64. |
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F7sus4
Registered: Apr 2013
Posts: 117 |
"Measured" as in tested what is the hardware cause behind it, or "measured" as in tested the behavior of the sound?
For the latter:
https://csdb.dk/forums/?roomid=14&topicid=163246#163676 |
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Jammer
Registered: Nov 2002
Posts: 1335 |
Quoting F7sus4"Measured" as in tested what is the hardware cause behind it, or "measured" as in tested the behavior of the sound?
I bet the former in the long run ;) |
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chatGPZ
Registered: Dec 2001
Posts: 11386 |
I'll point Leandro at this thread (no idea if he has csdb account) |
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vincenzo
Registered: Sep 2003
Posts: 83 |
Hypersynth SIDizer VST plugin does emulate osc leakage. Yeah, it's not an "emulation" emulation, but it does a pretty good job of SID sound emulation if you want to produce music with VST's. |
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chatGPZ
Registered: Dec 2001
Posts: 11386 |
https://github.com/libsidplayfp/libsidplayfp/issues/102 |
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Jammer
Registered: Nov 2002
Posts: 1335 |
Valid points there but I wouldn't underestimate the issue. Background noises are really minimal in amplitude, compared to this phenomenon. However, I'm recording SidFX output via interface with really decent parameters so that might also contribute. |
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Unknown
Registered: Dec 2023
Posts: 5 |
I will give this a try on a real C64 with three different 6581 and two different 8580. I could do the same tests on a C128, but only with 6581.
Unfortunately, the speakers in my available monitors add a very loud hum when the volume is cranked up, so I'm not sure how meaningful these tests can really be.
BTW, I'm reFX-Mike on GitHub. |
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Youth
Registered: Aug 2003
Posts: 43 |
ChipSynth64 also has oscillator leakage emulation.
From the manual:
Osc Leak: Turn on emulation of signal going through even when envelope is fully closed. |
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Jammer
Registered: Nov 2002
Posts: 1335 |
I'll try to do some thorough test with various register values before sound cut kicks in and record everything in free time. |
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chatGPZ
Registered: Dec 2001
Posts: 11386 |
r44982 implements this now - get a build here in 20 minutes and check it out :) |
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encore
Registered: Aug 2010
Posts: 67 |
I remember playing Yogi Bear on my C64C (with a 6581R4 inside) in the early 90s and hearing the sound effects continuously going on in the background (where it was supposed to be silent). It's nice to now also being able to hear it in emulation. |
