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I just thought of something that might explain the aliasing by PT. It's possible the sample volumes are reduced by 1/4 so the total output can't exceed 255. Which would mean you have 4x6bit tracks (64 levels per track)
Last edited by µB (Apr 6, 2012 1:18 pm)
Do you sample/convert natively on the Amiga? Comparing the input with the PT output might give an idea what's going on.
Yes, I am sampling with hardware on the Amiga. I could sample convert but I didn't have good results in the past. Should try again though.
I understand about the levels, it's what happens with the Game Boy's 4 bit samples, some of them are ridiculously noisy, like bassdrums.
I will have to figure out a way to circumvent this. Do you think recording at a higher volume, even maybe clipping it a bit, would help? How about amplifying by software? That'd make the noise worse I would tend to think...
I never had a sampler before on the Amiga so this is all new to me.
Do you think recording at a higher volume, even maybe clipping it a bit, would help? How about amplifying by software? That'd make the noise worse I would tend to think...
Clipping would make things worse, actually. Although, approximating the sine closer to a square wave might help a little- the closer to a square, the less volume jumps you'll have, or in other words you're decreasing the time period between voltage flips. The downside of this is of course the sound will approxiamte that of a square as well. Post-amplifying would only increase the sound (including the aliasing), as you said. The restriction is inherit, and if it's as I think it is, you're stuck with 6bit samples in one channel. A quick check with google seem to confirm this (4x8bit sample channels with 6bit volume)
I don't know.. my next impulse would be to suggest interpolation of the output signal. This doesn't work well (as the interpolation should ideally be on each individual channel) and will dull the sound, akin to a low-pass. You might be able to polish up the sound a little with post EQ.
Edit: Just did a quick test mixing square and sine waves. The square becomes very apparent wit as little as 15% mix, and the effect on the aliasing is neglectable. 
Edit 2: Currently testing with sigmoid functions and results are somewhat more pleasing, (1/(1+exp(p*x)))-0.5 makes the sound more bell-like for increasing p, but the faster voltage change reduces the aliasing
Last edited by µB (Apr 6, 2012 4:12 pm)
µB you are wrong, the samples are 8 bit. the six bit volume control is actually additional to the 8 bit samples. somehow using this, 14 bit sound playback is achieved even
Hmm I have no idea when you want use MOD. There is Milky for AMIGA (A1200/A4000) too...
But I think you want to do MODs on A500.
Last edited by Tinctu (Apr 6, 2012 9:01 pm)
There is Milky for AMIGA (A1200/A4000) too...
First off, milkytracker (a copy of FT2 which is inspired by PT), needs the SDL implementation for AmigaOS and therefore a super expanded Amiga to run at any decent speed (060 or PPC)., if at all on a 680x0.
Why would I even't use that? I have a PC I could run Milkytracker in if I was so inclined. BUT THAT'S NOT THE POINT. Milkytracker only supports the MOD format. That doens't even mean it makes and plays MODs like an Amiga running ProTracker. There's a reason the replay routine is special and proper players of MOD files like Modizer, XMPlay or Deliplayer implement a 680x0 emlation core to run the MODs.
It's how trying to say "hey why don't you play yoir MID files on any soundcard?". Because even if an OPL3 and an MT32 can play MID files, they don't sound even close to the same.
Why would I want to make MODs? Because I want to. And no I don't use an A500, I have a modestly expanded A1200. I 'm just not trying to use it to do modern tasks that make no sense at all.
I could ask you "why do you want to use real chips if you have emulators?".
µB you are wrong, the samples are 8 bit. the six bit volume control is actually additional to the 8 bit samples. somehow using this, 14 bit sound playback is achieved even
He's right, this is how the AHI stream driver for Paula works. You can even do 12 bit samples.
Last edited by akira^8GB (Apr 6, 2012 10:30 pm)
I love MODs. And on AMIGA1200 or ATARI FALCON they sounds great. And you can replay them with GBA on stage...
I was growing on 386 and Fastracker and SoundBlasterPro. So sorry for my opinions. Simply I can not say nothing bad on MODs but
I prefer and loves XMs since 1995... 
But I heard ATARI STE or AMIGA 500/600 live back in 90s.
And I must say, you are right it was really best MOD listening I ever hear in my life...
Better than on SoundBlaster or on GBA, PDAs, PCs...
Last edited by Tinctu (Apr 7, 2012 10:04 am)
µB you are wrong, the samples are 8 bit. the six bit volume control is actually additional to the 8 bit samples. somehow using this, 14 bit sound playback is achieved even
He's right, this is how the AHI stream driver for Paula works. You can even do 12 bit samples.
Ok, I'm confused now. Is there a doc I can read up on?
I saw one recently but cant find it just yet. I'll link you up once I find it again.
NEW @ VirtualANS & BASICSynth (update) april 10/02
Last edited by Tinctu (Apr 10, 2012 8:59 pm)
massive thanks, this is notalgia city for me right here.
I've used HivelyTracker to generate some fun samples. It's a softsynth tracker for amiga, windows, mac and haiku which can save in the AHX format and its own native HVL format (which has expanded capabilities). It has a bit of a SIDlike sound to it.
Last edited by SketchMan3 (Nov 4, 2013 5:41 pm)