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  •  » Picked up a couple SwinSids... Small issue with my NTSC c64s though..

#1 2012-03-03 06:50:37

dJ dAb
Gianas Sister
From: USA
Registered: 2012-01-02
Posts: 21
Website

Picked up a couple SwinSids... Small issue with my NTSC c64s though..

Well, I just purchased a couple Swinsids and I think they are really cool thus far but I'm having an issue. When running two SwinSid on a Sid2Sid board they sound great together but when running one with a 8580, I notice that the SwinSid is running at about a semitone down from the 8580. Now, there is NTSC / PAL settings for the Mssiah to compensate for PAL vs NTSC machines but not individual chips. Hmm... I'm guess SwinSid's were designed to be used with PAL machines?  I wonder if there is a work around for this or am I going to be limited to running my second sid (the Swinsid) for drums only? Maybe there is a way to adjust the clock?  Otherwise, they sound off.  I bet this isn't the issue on a PAL machine.  Ideas anyone?  I might be the only one using a SwinSid on a NTSC C64 that has noticed the problem?


C64 User w/ Mssiah (2), Zoom Floppy & uIEC SD
Card 32 Midi Cart (Standard Pro-16 use or passport interface use with MyMidi)
Moog Song Producer

DIY electronics guy & vintage analog/digital studio gear collector.

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#2 2012-03-03 13:05:27

InactiveX
The Last Ninja
From: England
Registered: 2008-08-14
Posts: 280

Re: Picked up a couple SwinSids... Small issue with my NTSC c64s though..

Er, a pitch-shifter on one of the SIDs? tongue

Yeah, it does sound like a PAL/NTSC problem. That usually results in a discrepancy of just around a semitone.

Perhaps ask the SwinSID lot if they have any ideas?

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#3 2012-03-03 18:43:26

dJ dAb
Gianas Sister
From: USA
Registered: 2012-01-02
Posts: 21
Website

Re: Picked up a couple SwinSids... Small issue with my NTSC c64s though..

Could you imagine that, having to use a pitch shifter?  Yuck.  I hope there is a way to control the SwinSid clock?  I sent Swinkels and x1541 messages. Hopefully they can help. Cheers, Sean

Last edited by dJ dAb (2012-03-03 18:46:11)


C64 User w/ Mssiah (2), Zoom Floppy & uIEC SD
Card 32 Midi Cart (Standard Pro-16 use or passport interface use with MyMidi)
Moog Song Producer

DIY electronics guy & vintage analog/digital studio gear collector.

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#4 2012-03-03 19:23:07

Coralio
GI-Joe
Registered: 2012-02-20
Posts: 17

Re: Picked up a couple SwinSids... Small issue with my NTSC c64s though..

Funny, it's as if the SwinSID had its own clock. (Quite likely that is the case.) Fail? big_smile
Where exactly does the classic SID get its clock from? smile I know that the CPU is clocked differently for PAL and NTSC...
Does this have anything to do with the 50/60Hz of the 9VAC input?

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#5 2012-03-03 21:01:38

dJ dAb
Gianas Sister
From: USA
Registered: 2012-01-02
Posts: 21
Website

Re: Picked up a couple SwinSids... Small issue with my NTSC c64s though..

I don't know but I just tried a SwinSId in one of my 6581 C64's and got the same exact results... The SwindSid was just a tad flat.  I think the clock is pulled from the motherboard on both a real Sid and a SwinSid.  When using a PAL machine I'm sure its spot on but with a NTSC I think the SwinSid interprets or translates the clock a tad off.  But musically it's super noticable.  I don't think Swinkels / X1541 did complete testing with a NTSC machine.  Otherwise the potential is there... I mean it does sound quite good.  Next to a 8580, it's pretty darn close.  Just need a fix for NTSC.


C64 User w/ Mssiah (2), Zoom Floppy & uIEC SD
Card 32 Midi Cart (Standard Pro-16 use or passport interface use with MyMidi)
Moog Song Producer

DIY electronics guy & vintage analog/digital studio gear collector.

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#6 2012-03-04 00:59:06

Coralio
GI-Joe
Registered: 2012-02-20
Posts: 17

Re: Picked up a couple SwinSids... Small issue with my NTSC c64s though..

Well as far as I know the only difference between a PAL and an NTSC c64 - apart from the video modulation - was the clock rate. The NTSC runs a tad bit faster. When programming the SID, you need to provide pitches in the form of cycle counts, which means the PAL and the NTSC will need different values for the same pitch. Usually every c64 music coding tutorial starts with the formula used to calculate the values for the chromatic scale, and the multiplier constants for PAL and NTSC.
IF the SwinSID was getting its clock from the motherboard, then there shouldn't be any problem. The only thing I can imagine is that the creator of the SwinSID wanted to make sure the chip has a good steady clockrate, so he built in a separate oscillator.

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#7 2012-03-04 22:34:43

dJ dAb
Gianas Sister
From: USA
Registered: 2012-01-02
Posts: 21
Website

Re: Picked up a couple SwinSids... Small issue with my NTSC c64s though..

Update from Swinkels: "Current swinsid firmware generates sound that is synchronized with 32MHz oscillator, not the C64 CPU clock, so it always plays the same pitch on both PAL and NTSC systems. 32MHz clock is divided to get 1.0 MHz base frequency used to update pitch registers, while PAL SID is clocked at 0.985 MHz and NTSC at 1.02 MHz. This is the reason why it sounds a little bit out of tune when comparing SwinSID to SID. It is not a big deal when listening to music or playing games but this may be a problem when using SwinISD with other instruments or real SID.   There are two method to fix this: One is to change sampling frequency but this will give a little bit of aliasing effect. And the second method requires more CPU power to recalculate pitch value.  @dJ dAb: I can send you fixed firmware with samplerate fix included so you will be able to test yourself how it sounds (I didn't test this method yet)."

He's sending me different firmware and it looks like he has some cool variations he's working on.  Like extended resonance on the filter... sounds cool.  I will have to assemble a STK200 programmer but it's super simple. Just a DB25 port, a few resisters and a 6 pin header.  Attach the device to my LPT port and upload the firmware via PonyProg software.  Luckily, I have parts laying around.

I must say I'm impressed with Swinkels support. Very Cool!!!


C64 User w/ Mssiah (2), Zoom Floppy & uIEC SD
Card 32 Midi Cart (Standard Pro-16 use or passport interface use with MyMidi)
Moog Song Producer

DIY electronics guy & vintage analog/digital studio gear collector.

Offline

 
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