Stone Oakvalley's Authentic SID Collection (SOASC=)
The automated Commodore 64 SID Music recorded to MP3/FLAC. Project based on High Voltage SID Collection & Compute's Gazette SID (CGSC)


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Noise Reduction (HW) for ROTS
in SOASC= FAQ | Monday, August 31, 2015 | 18:23

In previous recordings of SOASC=, I used to solder a wire between PIN 26 (SID EXTERN IN inside C64 on SID chip connection) to GND internally to ensure reduction of hiss/noise into the recordings.

However, we can achieve the same effect by simply doing this externally inside a modified AUDIO/VIDEO 5-pin DIN plug instead, by putting a wire between PIN 5 (Audio IN) and PIN 2 (GND).

In addition for max reduction, thanks to PSID64, we can even blank the screen to ensure the VIC Graphics chip also is reduced to a minimum of noise/hiss. Allthough, that would not work for BASIC tunes recorded or other wierd rips in the HVSC (where parts of the graphics are still visible) during playback, but that's only 1% or less of the collection anyway :-)

Here are the actual results of that, recorded on a Delta Audiophile 2496 PCI soundcard which are used on all SOASC= ROTS recordings to produce FLAC and MP3 recordings.

The suspected SID file for testing was converted from SID to PRG with the excellent PSID64 before recording and loaded off a MMC64. Recording was done in Adobe Audition as well as showing the Spectral View pictures below.

You can also download the same WAV recordings and see/hear for yourselves.

Note that SOASC= ROTS does nothing else to the recordings, except for a normalize volume (described in the FAQ) applied to the recordings. Everything else is just as it comes out of of a real Commodore 64 with a standard SID CHIP into real analog wires into the recording card on a separate PC nearby.

The tune selected was randomized, and came from HVSC #50, DEMOS/G-L/Holy_Shit_part_2.sid by Daniel Mannestig (Madmax), 1991, Mocean.

All of the noise/hiss reduction, including the VIC chip can be seen in the link posted at bottom of this page.

Here with no modification inside the AUDIO/VIDEO DIN plug, but PSID64 was set to blank screen while running PRG/playing SID.

We can see a very thick line of HISS noise, along with some more garble inbetween.

The exact same recording, but here with modification inside the AUDIO/VIDEO DIN plug, and PSID64 was set to blank screen while running PRG/playing SID again.

We can see a that the thick line of HISS noise is now gone, along more cleaner signals inbetween.

Please review these related article links:
Click to open wavNo hardware noise reduction
Click to open wavWith hardware noise reduction
Click to open urlReduce noise in SID (

Posted by: Old-schooler, Stone Oakvalley | Publisher: Crazy Multi Talent, Stone Oakvalley
Last revised: December 07, 2022 - 17:34 | Page views: 3204

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