Finally! No mouser package, but I was able to find all the needed ceramic caps in my junk boxes, and the last missing item, the sliding switch, arrived today from China, so my all-socketed C64 is finally up and running with a new RF modulator replacement. I'll have to submit to the same treatment one of my shortboards next year.
As soon as they're available again, I'll also buy a lumacode encoder for this C64, and will probably go for a sidkick pico too. The SID in here doesn't sound terribly good.
I also built a few KungFu Flash carts, so it's time to play around a bit... Any pointers to nice C64 games on itch.io, people?
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Also, why not replacing the DRAM with SRAM?
I used this for the carrier: https://github.com/go4retro/DRAMCarrier (there is an error on this board: pin 1, which is /OE, of one of the ICs is left floating, I had to jumper it to GND, like it is in a C64C) and https://github.com/jamarju/c64-sram (here the BOM lists an HCT32 to handle /RAS and /CAS but I had timing issues with that, the issues went away with an F32).
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Further work on the experimental C64, to attempt lowering the temperature inside the case: removal of VR2 and replacement with a switching module from Murata (I have an abundance of these). I also added some additional filtering with ceramic caps on the bottom, and, while I was there, replaced the 10uF caps across the board with newer, higher rated ones.
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Oh I ran into a small issue with the SRAM replacement board from the previous post!
See those two tiny pixels under the cloud? At the main screen of ZetaWing II there is a segment of flickering pixels just under that cloud. The issue disappears when using the original 4164, or even when replacing them with two 4464, so I'll go with the second option.
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I'm planning to get a few sidkick picos built by PCBWay, but while rummaging around looking for ICs to test I found an armsid I ordered as a spare in a lot that I got to fix up a friend's C64, so I decided to pull the original from this machine, store it away safely and install/update/test this one.
It's really, really good, at least to my untrained ears. Might just use the skpicos on other machines and leave this one in here.
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@hkz very interesting. I am working on a MIDI synthesiser with two SwinSID’s. They work fine, but I hear a lot of aliasing on filters. Most comparison videos I’ve seen test the different SID replacements only with complete tunes (that I don’t know). It would be easier to compare them using simpler sounds showcasing problems (aliasing, etc…)
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@davbucci If you can pull out a program that generates a sequence of the effects you're interested in, I can record the output on this machine and send it your way, and (provided the assembly order on PCBWay goes through and the courier does not lose my package) when I get the sidkick picos I can repeat the recording.
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@hkz thank you, I’ll try to write something in the next few dans. I have a C128D with the 8580 I think, I’ll try there, too.
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@davbucci This device (and the sidkick pico too) can be set to emulate either type of sid, so I guess I should record both modes.
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@hkz If you have some time, can you please record with this program?
10 b=54272
14 pokeb+21,0:pokeb+22,78:pokeb+24,31
16 pokeb,176:pokeb+1,2
17 pokeb+5,43:pokeb+6,2
60 for t=1 to 4
70 poke b+4,17
80 for i=1 to 2000:next
90 poke b+4,16
100 next
It should play four notes. I tested on Vice with the 8580 emulation and some aliasing is clearly present (I had to increase the volume).
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@hkz this is the output of VICE, emulating the 8580. I had to increase the volume as it was very low. I will give a try with the real thing on my C128D in the C64 mode.
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@hkz This is the output of one of my SwinSIDs (on the MIDI2SwinSID project). The settings should be more or less the same. The aliasing is evident.
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@davbucci The ARMSID allows for tweaking of the filters in its configuration.
For this test, I left everything as default. I recorded these directly from the C64, using the dedicated audio out plug in the replacement RF board I installed.
First recording: ARMSID set to 6581.
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@davbucci Second recording. ARMSID set to 8580.
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@davbucci Third recording. ARMSID set to 8580 but with ADSR fix enabled in its configurator.
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@hkz thank you very much! I haven’t yet listened to them properly, but even though the speakers of my cellphone they sound much better than the SwinSID! Can I include them in a blog post?
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@davbucci Absolutely free to do so. Please, let me know if you need further recordings!
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@hkz amazing, thanks. I summarized here some results: http://davbucci.chez-alice.fr/index.php?argument=varie/sidcmp/sidcmp.inc Just in case, would it be possible for you to record the results with a real 6581 SID?
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@davbucci Certainly. Note that I have connected EXTIN to GND with a 220 ohm resistor for this one, as it reduces noise.
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@davbucci SIDKick Pico with DAC, set for 6581, FW version 0.21
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@davbucci SIDKick Pico with DAC, set for 8580, FW version 0.21
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@davbucci SIDKick Pico with DAC, set for 8580 + digiboost, FW version 0.21. I don't think there's any difference in this one.
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@hkz thank you very much! I’ll add the files on the website within a few days (I have a quite crazy week).
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@hkz I listened more carefully. With the digiboost, you hear a small "click" at the very beginning, when the volume is set to 15. That seems logical.
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