Comparing Modern SID Chip Emulators: SIDKick Pico and ARM SID for 6502 Breadboard Computers

Summary:

This video explores modern alternatives to the scarce Commodore 64 Sound Interface Device (SID) chip for use with a 6502 breadboard computer.

The original SID chip is no longer produced, making modern emulators essential for hobbyists.
The first substitute, SIDKick Pico, is an open-source solution requiring a Raspberry Pi Pico and assembly.
It requires careful selection of hardware versions (e.g., with onboard DAC) and specific firmware flashing.
Initial testing showed the SIDKick Pico needed an external audio output connection and a solder jumper modification for direct SID socket output, which proved challenging due to solder mask.
The second substitute, ARM SID, is presented as a straightforward plug-and-play replacement with a form factor similar to the original chip.
Both modern replacements run on 5 volts, eliminating the 12-volt requirement of the original SID chip.
While output levels varied, both emulators offer comparable sound quality to the original.

Original SID chip versus the two emulators, SIDKick Pico and ARM SID, alongside oscilloscope waveform comparisons. [ 00:12:04 ]

Original SID chip versus the two emulators, SIDKick Pico and ARM SID, alongside oscilloscope waveform comparisons. [ 00:12:09 ]

Original SID chip versus the two emulators, SIDKick Pico and ARM SID, alongside oscilloscope waveform comparisons. [ 00:12:14 ]

Introduction to SID Chip Replacements [00:00:00]

The original Sound Interface Device (SID) chip from the Commodore 64 is highly sought after but no longer produced. [00:00:12]
- Its unique capabilities for its time led to significant creative works. [00:00:17]
Modern "clones" or emulators are available as drop-in replacements, using modern microprocessors. [00:00:28]
- The video aims to compare these replacements, their setup, and their sound quality against the original. [00:00:37]
- These modern replacements are easier to acquire than genuine SID chips. [00:00:47]

SIDKick Pico: Open-Source Emulator [00:01:14]

The SIDKick Pico is an open-source replacement for the SID chip. [00:01:21]
- Its GitHub repository provides documentation, which can be somewhat confusing. [00:01:26]
Hardware Versions and Assembly [00:01:46]
- Different hardware versions exist, including options with or without a Digital-to-Analog Converter (DAC). [00:01:46]
  - The version with an onboard DAC (v0.2) is preferred for a true drop-in replacement, as a version without a DAC would require an external one. [00:02:28]
- Assembly involves soldering header pins to the SIDKick Pico board and connecting a Raspberry Pi Pico microcontroller. [00:02:41]
  - The SIDKick Pico doesn't use the first four pins of the original SID, which were for external capacitors, as it has internal components for this. [00:03:00]
  - The Raspberry Pi Pico plugs into specific headers on the SIDKick board. [00:03:20]
    
    The SIDKick Pico board with header pins and a Raspberry Pi Pico attached, forming a compact module. [ 00:03:35 ]
Firmware Upload [00:03:56]
- The Raspberry Pi Pico needs to be flashed with pre-built binaries from the GitHub release package. [00:04:00]
- The process involves holding down the boot button on the Raspberry Pi, plugging it into a PC via USB, then dragging the appropriate UF2 firmware file (e.g., "DAC_LED_firmware.uf2") to the recognized USB drive. [00:04:11]
Installation and Initial Testing [00:06:11]
- The assembled SIDKick Pico is larger than the original SID chip, requiring extensions to fit easily into a breadboard. [00:05:50]
- The module is installed into the 6502 breadboard computer's SID socket. [00:06:11]
- Addressing 50Hz PAL Timing Issue: Corrected the interrupt timer setting for the music to play at the proper speed (50Hz PAL, which is 4E20 in hex for a 1MHz clock). [00:06:31]
- Audio Output by Default: Initially, the SIDKick Pico does not output sound through the standard SID audio pin, as it defaults to external output for potentially higher quality. [00:07:25]
  - The sound output is available on dedicated pins on the SIDKick board. [00:07:56]
  - Plugging an audio recorder into these pins produces clear sound. [00:08:03]
Troubleshooting Internal Audio Routing [00:08:10]
- To route audio through the standard SID socket (pin 27), a solder jumper (marked with "L") on the SIDKick Pico board needs to be closed. [00:08:32]
  - This process was difficult due to the solder mask between the jumper pads, requiring a large glob of solder without flux. [00:08:57]
  - After successfully bridging the jumper, the audio output was distorted. [00:10:04]
    - The distortion might be due to unadjusted gain or other configuration issues, which typically require a Commodore-specific program to set. [00:10:09]
    - The external audio output remains a viable solution for hobbyist projects where sound quality is paramount. [00:10:24]

A close-up of the SIDKick Pico board showing a solder jumper being bridged to enable internal audio output. [ 00:09:34 ]

ARM SID: Plug-and-Play Replacement [00:10:37]

The ARM SID is advertised as a "plug-and-play replacement" for the 6581 SID chip. [00:10:37]
- It claims accurate sound, lower noise, and less interference, running on an ARM processor. [00:10:50]
Installation and Testing [00:11:03]
- Its form factor is very similar to the original SID chip, allowing for a neat fit into the breadboard. [00:11:03]
- Installation is straightforward: simply insert it into the SID socket. [00:11:15]
- Upon reset and running the music program, it worked immediately with sound output through the standard SID audio pin. [00:11:20]
  
  The ARM SID chip, showcasing its compact, original-SID-like form factor, within its protective packaging. [ 00:10:59 ]

Comparison and Conclusion [00:11:32]

Power Consumption: Both SIDKick Pico and ARM SID run entirely on 5 volts, eliminating the original SID chip's requirement for an additional 12-volt power input. [00:11:36]
Sound Quality: All three (original, SIDKick Pico via external output, and ARM SID) sound good, with output levels varying. [00:11:58]
- The ARM SID's output is notably lower than the others. [00:12:16]
Both modern options are good substitutes if an original SID chip cannot be found. [00:12:12]