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View topic - Tomy - PSG Series 6 (Sega PSG SN76489)

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  • Joined: 07 Sep 2013
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Tomy - PSG Series 6 (Sega PSG SN76489)
Post Posted: Sat Sep 24, 2022 10:23 pm
https://tomy.bandcamp.com/album/psg-series-6


The PSG cyber world returns!
What do you plan to do?


I'm proud to present you my album "PSG Series 6". ~90 minutes of raw hardware Master System PSG music.
Everything recorded from a '87 Master System I.

If you are interested to see the music in action, every track also has an oscilloscope view at my YouTube channel.
Here is a link to the album playlist: https://www.youtube.com/playlist?list=PLQUeti6zlmnqYzV49fY9NEC3peX2PLH6u
psgs6.png (2.01 MB)
PSG Series 6
psgs6.png

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  • Joined: 30 Jun 2016
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  • Location: Melbourne, Australia
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Post Posted: Sun Sep 25, 2022 4:12 pm
You have done some absolutely phenomenal work for this album!

You did great!
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Post Posted: Sun Sep 25, 2022 4:56 pm
Doing the oscilloscopes from a real system is the icing on the cake, super correct and time consuming!
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Post Posted: Sun Sep 25, 2022 9:27 pm
Maxim wrote
Doing the oscilloscopes from a real system is the icing on the cake, super correct and time consuming!

Interestingly, the most recently uploaded video to YouTube (citing it because it's convenient) does buck a suggestion in SMSPower!'s SN76489 article regarding the decay of the waveform.

This has been discussed a fair bit on the Discord, but for the sake of having it recorded on the forums, what decay does happen seems to be rather subdued - and we're not even sure with the older videos if it (as well as the DC bias of the waveform) were actually being affected by a highpass filter with Tomy's recording equipment. And I learnt quickly from some technicians that virtually every piece of recording equipment does a mild highpass on the input as a safety feature.

Are the more curved waveforms inside the article due to how the waveforms were initially analysed at the time? I get the impression that recording from the RF modulator was done - which introduces its own can of worms. Which is interesting from an emulation perspective, but regardless.

I've been avoiding bringing up this subject because of all the uncertainties involved, but it's better that it's recorded in a forum post forever burnt to memory, than lost to the ether in Discord.
It just happens that Tomy's recordings presented onto YouTube happen to be the best recording we have of how the Master System variant of the SN76489 PSG behaves.
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Post Posted: Sun Sep 25, 2022 10:17 pm
The pictures on there were an exaggerated version drawn by me based on an SMS2 over RF into a late 1990s capture card. The high pass filtering could come from any number of places.
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Post Posted: Mon Sep 26, 2022 5:51 am
Thank you so much Flygon & Maxim. I appreciate it a lot!

I like to read about the technical side and I'll help any way I can. All the videos that are at my YouTube channel and my albums at Bandcamp are using a sampling rate of 96 kHz, recorded with ESI [email protected] audio capture card. The only editing I do is normalize the audio and add a fade out at the end.

Different about this latest album is that it is recorded from a Master System model I with the full volume levels. That took me the longest time to figure out what is going on with the volume levels in different models. Only after I got my '87 model I finally verified it. But I still don't know what exactly causes it? Something different in the circuits of some models?
In this album I reserve the highest volumes for the bass & drums, the kick drum being the only instrument hitting the full volume. That would sound much quieter if recorded from my other models.
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Post Posted: Fri Sep 30, 2022 5:44 pm
TomyS wrote
Different about this latest album is that it is recorded from a Master System model I with the full volume levels. That took me the longest time to figure out what is going on with the volume levels in different models. Only after I got my '87 model I finally verified it. But I still don't know what exactly causes it? Something different in the circuits of some models?
In this album I reserve the highest volumes for the bass & drums, the kick drum being the only instrument hitting the full volume. That would sound much quieter if recorded from my other models.

Scuse my delay. I kept being distracted and forgot to reply to this topic.

The SMSII has an incorrect value resistor on the audio output that results in the volume clipping the way it does. The output needs a specific value capacitor to ensure that the steps are in the roughly 2dB steps like they're suppose to.

This does technically mean any homebrew wanting to ensure the volume envelopes are correct actually has to have two sets of musical tracks and sound effects.
Which is a bit "yikes".
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