C64 SID trouble
SID chips fail all the time and especially the filters fail often. One SID chip is not equal to another.
Been experiensing various weirdness with the audio from the C64. Audio seems very sharp but some games sid tunes sounds as if a channel is missing. However the case is not that simple. Listen to the track at about 9 minutes in. Nice and crisp synth sound however the bass lead is missing..
You can hear the same tune but with propper filtered bass lead recordded from a good SID chip here at 6:28:
My video above also has a track of Jeroen Tel Robocop. To me it sounds fine. Great Giana sisters is missing some parts of the audio and the wind noise in the very beginning of the game is gone.
In the image below I've used a BASIC program called SIDBench, and all channels and waveforms seem fine except when filters are switched on. Below you can see three recordings of audio from running SIDbench on several chips.. Recordings are lined up in Audacity and view mode is Spectogram. The upper recording is mine, the middle a good reference SID chip, and at the bottom is another unknown chip. First of all, my chip is kapott. Here in this zoom we are looking at noise-generator to the very left, and then followed by noise-generator + low pass filtering sweeped on all three channels run individually. My chip is kapot as you can see. Chip in the middle seems good and the one below has a higher cut off point.
Here I am diagnosing the SID chip with SIDbench.
Then two days ago i got a C64 1983 model with a SID from 1983. Filters on that one works. Below you can see three recordings 1. reference, 2. my new breadbin C64, 3. My trusty old C64 (white with 6581R4AR broken). You can see that the filters in the breadbin (second recording) has its filters cut-off going from low to high very early compared to the reference recording.
Also there is noise in the breadbin box compared to my other C64. Here i have re-recorded the same chip in my other computer as well. You can see the characteristics are the same except for the noise. I did try the AUDIO-IN to GND trick and it did help even more, but not recorded here..
So what is the verdict ? Does it sound better? In some games yes. In Great Giana Sisters, the wind at the beginning sounds more like a swirl than a breeze. In Jeroen Tel's Robocop3 theme, when the filters come on and off, it's as if volume is changing. Wierd, but my broken SID sounds actually good there.. Strange. If i zoom in on the waveforms I can see that triangle wave has sharp edges, but the 1983 SID chip doesn't (might explain the lack of crispness).. Then what about the bass line in the 1983 chip ? It is there but the filters seem to be much more open than the one on youtube (second video from the top).., however i still think my broken chip sounds more crisp, but no bass though so whats the fun in that. Seems like there is no common denominator. All SIDs are different.
Been experiensing various weirdness with the audio from the C64. Audio seems very sharp but some games sid tunes sounds as if a channel is missing. However the case is not that simple. Listen to the track at about 9 minutes in. Nice and crisp synth sound however the bass lead is missing..
You can hear the same tune but with propper filtered bass lead recordded from a good SID chip here at 6:28:
My video above also has a track of Jeroen Tel Robocop. To me it sounds fine. Great Giana sisters is missing some parts of the audio and the wind noise in the very beginning of the game is gone.
In the image below I've used a BASIC program called SIDBench, and all channels and waveforms seem fine except when filters are switched on. Below you can see three recordings of audio from running SIDbench on several chips.. Recordings are lined up in Audacity and view mode is Spectogram. The upper recording is mine, the middle a good reference SID chip, and at the bottom is another unknown chip. First of all, my chip is kapott. Here in this zoom we are looking at noise-generator to the very left, and then followed by noise-generator + low pass filtering sweeped on all three channels run individually. My chip is kapot as you can see. Chip in the middle seems good and the one below has a higher cut off point.
Here I am diagnosing the SID chip with SIDbench.
Then two days ago i got a C64 1983 model with a SID from 1983. Filters on that one works. Below you can see three recordings 1. reference, 2. my new breadbin C64, 3. My trusty old C64 (white with 6581R4AR broken). You can see that the filters in the breadbin (second recording) has its filters cut-off going from low to high very early compared to the reference recording.
Also there is noise in the breadbin box compared to my other C64. Here i have re-recorded the same chip in my other computer as well. You can see the characteristics are the same except for the noise. I did try the AUDIO-IN to GND trick and it did help even more, but not recorded here..
So what is the verdict ? Does it sound better? In some games yes. In Great Giana Sisters, the wind at the beginning sounds more like a swirl than a breeze. In Jeroen Tel's Robocop3 theme, when the filters come on and off, it's as if volume is changing. Wierd, but my broken SID sounds actually good there.. Strange. If i zoom in on the waveforms I can see that triangle wave has sharp edges, but the 1983 SID chip doesn't (might explain the lack of crispness).. Then what about the bass line in the 1983 chip ? It is there but the filters seem to be much more open than the one on youtube (second video from the top).., however i still think my broken chip sounds more crisp, but no bass though so whats the fun in that. Seems like there is no common denominator. All SIDs are different.
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