Sample cartridge

[Fred_M]

Ahh.... Thanks for clarifying this. Nice to "see" you back after all those years!

[Mathy]

Hello Alphasys

 

So with the cartridges, all you need to do is desolder the connecting points and put in the extra stuff to turn it into the "non-moneysaving" version?

 

I never liked the idea of only using 4 bits. That's only 16 different levels. Piggyback would be the way to go. I'm looking forward to your photos.

 

Sincerely

 

Mathy

[Alphasys]

Hi Mathy,

 

Yes, that's about the idea. Since I lost my original lay-out for the cartridge PCB, I'm not sure about what goes where exactly. There may be a few points there that are just to connect the top with the bottom layer, but in basis, you're right. What would be "missing", are just a few discrete components. One or two capacitors and one or two resistors, something like that.

[carmel_andrews]

Alpha sys

 

Is this sample cart of yours similar to the 2bit systems one as I think 2bit systems also did some sort of sample cart for the A8 (i recall the free game they supplied with it) if only i had the interest in buying it at the time

 

Any chance of you suppling tech details of the sample cart to phaeron/thordbg so it can be emulated via altirra or atari++, it would be a shame to see another piece of atari history disappearing

Edited August 8, 2013 by carmel_andrews

[Alphasys]

Hi Carmel,

 

The Alphasys sample cartridge, as we sold it in Halle back then, is fully compatible with the sample cartridge of 2-bit Systems. It's why I have a switch on my prototype, because when I made it, I had a different control scheme in mind for high quality sampling. The switch selects which mode I would use. In the end, it didn't seem to matter what sampling mode was used, so we (John Maris and I) decided to hardwire it in "2-bit systems compatibility mode".

 

Emulating this thing would be horrifyingly simple though, when it's possible to "connect" a sound source to the emulator:

 

The cartridge occupies only 1 adress, which I remember to be $D500, but I'd have to check that for accuracy. (Checked, yep it's $D500.) When read in succession, this location keeps producing 8-bit numbers representing the input waveform. Silence would produce a constant stream of the value $80.

 

Sample rate is determined by how fast you read the one location and ofcourse playback would have to match that speed to reproduce the sound in the same pitch.

 

That's all there is to it. Can barely be any simpler.

Edited August 8, 2013 by Alphasys

[Alphasys]

Hmpf... Sorry to say, the prototype is not where I expected it to be. But at least now I have my bigtower in the house, so I'll make a load of pictures of that. I'll have to dig deeper to find the sampler prototype. I'll try to find it in the coming week, when I'm putting the tower back in storage.

[Mathy]

Hello Alphasys

 

How much better as this non-2bit-compatibility mode? Can it still be switched in (after adding a switch)?

 

Is there any software available that could be used with the cart after upgrading the cart to stereo?

 

Sincerely

 

Mathy

[Alphasys]

After careful testing, I noticed that the "original" mode of operation would only make the sampling routine more complicated, while the quality was the same. It would only be "better" if you have really high sample rates and are able to use the full 8-bits, but we're talking Atari here... There's just no way that it could utilise this mode to its advantage, unless maybe if you also have an 8-bit DAC to replay it. (Like a Covox R/2R ladder hooked onto a PIA port, or a DAC 080x on the cartridge port.)

 

I've been trying to get a 6-bit sample playback routine to work, but it didn't sound good. Too much latency while programming all 4 pokey channels. Sounded worse than just using the 4 MSB on a single pokey channel.

 

You also have to take into account that, even though the samples can be retrieved at something around 34kHz, it takes more clock cycles to play them back on the pokey, while you'll also use LOADS more memory to store the sample data. I guess if you have a harddrive attached and a megabyte of RAM, it has some merit, but otherwise it's just not a feasible solution.

Edited August 8, 2013 by Alphasys

[Mathy]

Hello Alphasys

 

With the BlackBox, it's no problem to have HHD's, ZIPdrives or even CD- or DVD-ROM drives shooting data into the 8 bit Atari. 1Mb also is no problem, although my 1MB (well, actually 64kB plus 1MB) XEGS has no PBI.

 

Covox R/2R ladder? When HARdwareDoc starts selling his Thunderblaster, I'm gonna order at least two of those.

 

Sincerely

 

Mathy

 

PS there are more modern interfaces that seem to be faster then the BlackBox, but I only have experience with the BB.

[Mathy]

Hello Fred

 

I'm still interested in one of the carts/pcb's. Please name a price.

 

Sincerely

 

Mathy

 

PS If the quality is as good as I think it is, would it be OK if I find somebody to have a look at the PCB and maybe redesign them?

[Mathy]

Hello guys

 

What kind of music/sound was the cartridge tested with? Real music or something that goes boom boom?

 

Sincerely

 

Mathy

[Alphasys]

...

PS If the quality is as good as I think it is, would it be OK if I find somebody to have a look at the PCB and maybe redesign them?

 

Be my guest. Since I designed them, I'm the only one who can really say "It's Public Domain now". I doubt you can get better quality out of it though, since I already took all "hi-fi" precautions. (Using an opamp just to stabilise the reference voltage, for example.) The PCB was designed with the housing in mind, so you might be able to improve something there perhaps. Specially the places where a signal goes from one side to another, can definitely be cleaner.

 

...

What kind of music/sound was the cartridge tested with?

...

 

I've sampled tracks as diverse as possible to test the thing. 80's & 90's pop music, classical music, speech, hardrock, pure sine/triangle/sawtooth waves ranging from 20Hz-22kHz off a Dolby test CD. For the resolution (4-bits) it sounded pretty darn good, but ofcourse it has a little trouble rendering low volume music, like the start of Ravel's Bolero. Gets a bit noisy then.

[Mathy]

Hello Alphasys

 

When I said "redesign" I meant "re-layout". To get it to do stereo, we'ld need to piggyback one ADC to another and run wires from the upper ADC to the LS138. By re-layout-ing the PCB, we might find space for both ADCs on the PCB.

 

Sincerely

 

Mathy

[Fred_M]

PS If the quality is as good as I think it is, would it be OK if I find somebody to have a look at the PCB and maybe redesign them?

 

Like Alphasys already explained, I cannot say yes or no to this question. That is up to her.

 

Let's communicate about buying one of the leftovers I found privately.

 

Kind regards,

Fred

[Mathy]

Hello guys

 

How hard would it be to patch the software for 8 bit stereo sound? And once the sound is sampled, do I need (someone to patch) the original or 2-bits software or will existing software that supports the Covox-update do?

 

Sincerely

 

Mathy

 

PS Covox as in the european Covox (DA convertor), not the American Covox (AD convertor).

[Alphasys]

...

How hard would it be to patch the software for 8 bit stereo sound? And once the sound is sampled, do I need (someone to patch) the original or 2-bits software or will existing software that supports the Covox-update do?

...

The "routine" to sample at 8-bits resolution with or without stereo, would probably fit in the space used by existing software, since there's no need for any shifting and adding. But you would need a program that is already fit to use a ram expansion.

 

Keep in mind though, that when you need to switch banks, this will take more cycles, that may produce clicks unless properly timed in the program.

 

The same will apply to playback programs.

[Mathy]

Hello guys (m/f)

 

I don't have (a use for) Eagle. Does anybody have the schematic of the cart in a format that's easier to look at?

 

Sincerely

 

Mathy