Digiblaster

[Bryce]

Ok, here's a picture (they tell a thousands words I'm told )

The Potentiometer is a dual channel type (hence the dotted line), so that you adjust right and left channels together. The value should probably be around 1K (just guessing, would have to calculate properly).

Yes an input from the AY would be a nice addition, just it adds to the cost.

Bryce.

[mr_lou]

Shouldn't there be a diode on each AY-input channel, to prevent AY from going mono?

EDIT: (Or should those diodes be on the Digiblaster output instead?)

So what's the price on a Digiblaster device with built-in AY-input and mixer? It should be put in a nice little box too of course. 

[Bryce]

When the signal has passed through half of the variable resistor, it has the choice of going through the speaker (approx. 8 Ohms) or back through the other half of the variable resistor and back into the AY (relatively huge resistance). Like many humans, signals also like to take the path of least resistance ie: through the speaker, so the signal goes where it's supposed to without the need of a diode.

Bryce.

[mr_lou]

Hm. But what I mean is, that the AY-left is connected to the Digiblaster mono-out on the diagram. The AY-right is also connected to the Digiblaster mono-out. In short that means, that the AY-left is connected to the AY-right, which in my head means that AY-output becomes mono.
To prevent this, I would put a diode on each of the two Digiblaster outputs, so that AY-right and AY-left can't possible  be connected. Are you still saying that's not necessary?

[Leonie]

What sense makes the Digiblaster?
Remember Wings Of Death/Atari ST...


http://www.youtube.com/watch?v=yXokFFlROfM

or Turrican/Atari ST...

http://www.youtube.com/watch?v=8_Y_5gnY68A&feature=related




...it sounds wonderful WITHOUT any expansion.
Is the Z80 strong enough to do it the same way like the ST?
If so, take advantage of the AY and forget the Digiblaster.

[robcfg]

If I remenber correctly, the ST had kind of a trick to use digidrums, that is a form of sampled sound, so it wasn't done only with the AY chip.

[mr_lou]

What sense makes the Digiblaster?
Remember Wings Of Death/Atari ST...
...it sounds wonderful WITHOUT any expansion.
Is the Z80 strong enough to do it the same way like the ST?
If so, take advantage of the AY and forget the Digiblaster.

It is explained here:
http://www.cpcwiki.eu/index.php/Digiblaster_howto

Amiga and the likes has internal D/A converters. And the Digiblaster is actually just a D/A converter for the CPC. 
That's why.

[arnoldemu]

If I remenber correctly, the ST had kind of a trick to use digidrums, that is a form of sampled sound, so it wasn't done only with the AY chip.

On a standard STFM, you only have AY, so what they did was mix the samples (8-bit unsigned), and then using a lookup table worked out volume values for each of the 3 AY channels. Then sent those. So they had better sample resolution by using 3 channels at the same time.
They also had a programmable interrupt timer so they also had the freedom to allow the cpu to do other tasks.

The STE had extra hardware that could play sample data directly (8-bit or 16-bit, mono or stereo) from a a buffer in memory automatically and signalled when it had done. (DMA sound playback)

Were you thinking more of the STE?

[Bryce]

@Mr Lou,
        In the circuit I posted, the output will be dual mono from the digiblaster and normal stereo from the AY. Although they seem to be connected, the path between the left and right channels are kept seperated by the variable resistor, so to answer your question: No, you don't need any additional diodes and will still have stereo AY output.

Bryce.

[mr_lou]

In the circuit I posted, the output will be dual mono from the digiblaster and normal stereo from the AY. Although they seem to be connected, the path between the left and right channels are kept seperated by the variable resistor, so to answer your question: No, you don't need any additional diodes and will still have stereo AY output.

Ok thanks. As you can see my knowledge is very limited (which is also why I prefer having someone else build my stuff) 

Anyway, you say that potentiometer probably must be about 1k, but that you should calculate to get a precise value. Would you mind calculating so we can have the correct value? :-)

Any progress in finding an estimated price for those interested in buying? 

[Devilmarkus]

Anyway, you say that potentiometer probably must be about 1k, but that you should calculate to get a precise value. Would you mind calculating so we can have the correct value? :-)

A potentiometer with 1,2k or 900ohms would work, too

[Bryce]

@Markus: Did you just pull those figures out of a hat? Or did you actually do the maths?

@Mr Lou: 1K is 99% most likely correct, but you will have to remove the 470 Ohm resistor from the Digiblaster output. To be 100% sure I would have to measure the peak output of both the AY output and the digiblaster. That could take a while as I don't have a fully constructed CPC at the moment.

Bryce.

Edit: just looking at the digiblaster circuit (v2): The 22µf capacitor seems to be a tad high? Not sure whether the author chose it because it was what he had lying around or whether there was good reason for it. Such a high value may slightly distort higher frequencies. A smaller value (maybe around 100nf) may improve the sound quality.

[MacDeath]

Then designing a version with an input so you can connect the sound output of the CPC on it (a minijack cable) is more than needed, or it simply makes no sense IMO.
Also 8 bit samples must actually make a good amount of Datas...perhaps depending on the "speedclock" ...er...frequency of such signal...

[mr_lou]

1K is 99% most likely correct, but you will have to remove the 470 Ohm resistor from the Digiblaster output.
...
A smaller value (maybe around 100nf) may improve the sound quality.

Two good things to know! 
But why do I feel you're avoiding the price-question? I think I've asked 3 times now. 

Then designing a version with an input so you can connect the sound output of the CPC on it (a minijack cable) is more than needed, or it simply makes no sense IMO.

I vote for the "More than needed" option then. 
What makes you think it makes no sense?

Also 8 bit samples must actually make a good amount of Datas...perhaps depending on the "speedclock" ...er...frequency of such signal...

Yes, but not necessarily more than the size of an overscan image (just to compare with something).

I've done a lot of experiments on the JavaME platform regarding sampled music too. That platform is mostly limited to MIDI music, but in all secrecy also offers something similar to MODs called MXMF files (Mobile eXtensible Music File). An MXMF file consists of a MIDI track + a corresponding DLS file containing the custom samples.
This format however is also greatly limited, mostly on Sony Ericsson phones, where the samples used in the tune must be max 30kb total - and the MXMF files are always played back in mono.

Squeezing all the samples into 30kb is a tricky challenge, but nevertheless doable. To get an idea of what kind of sound you can get out of 30kb-sample-data, try listening to these MXMF examples on your phone:
- Metal flowers
- Religions (I've already tried converting this track to CPC with success as well).
(the built-in player on the phone should handle it, but it does require a phone newer than e.g. SE K800)

The MXMF files are bigger than the 30kb, but that's because the MIDI data within the MXMF file takes up a lot of bytes.
If you're curious about MXMF on mobile phones, here's all my research on the subject.

Wouldn't it be neat to have the Digitracker MDL format (or maybe even STarKos SKS format) added to IndieGameMusic.com for CPC coders to find music for their games?  hehe
I'd do it if enough CPC musicians would add tracks.

[Bryce]

  I'm not avoiding the question, I just haven't had time to check the prices. The resistors and diodes are a no-brainer, but I'd have to check: A) How many parts could I produce on one PCB  B) The price of the connector  C) the price of the 2 Sockets and a mini-pot (assuming you want the AY throughput)

Bryce.

Edit: Ok, rough estimate: If I made a batch of 8 parts, they would cost 20€ + Postage each. (with AY throughput / two stereo sockets and a centronics connector).

[mr_lou]

If I made a batch of 8 parts, they would cost 20€ + Postage each. (with AY throughput / two stereo sockets and a centronics connector).

That seems cheap. Is that including everything? I can create a new poll asking who's interested in buying a Digiblaster for 20 euro + shipment (or you can).

Is there some kind of converter one can buy for other-than-german CPC's? Something that looks kinda like this but for the printer port.

[Devilmarkus]

@Markus: Did you just pull those figures out of a hat? Or did you actually do the maths?

Your circuit looks like a voltage divider.
So it doesnt matter if the potentiometer has exact 1k.
It could also have 2k or 100k.
But it shouldnt have less than 1k+/-10%
And you need both potentiometers the same resistor value, of course.

[mr_lou]

And you need both potentiometers the same resistor value, of course.

As far as I understand it's only 1 potentiometer, but it's a dual one.

[MacDeath]

What makes you think it makes no sense?

It would make no sense to get an audio upgrade if it's more complicated to get it working alongside the built-in audio system...
When doing thing, you have to do them correctly.

If I made a batch of 8 parts, they would cost 20€ + Postage each.

Pre-assembled or as a "solder-it-yourself-you-lazy-morons!!!" kits ? (humor intended...)
The Kit "sounds" good to me, I mean soldering some components on a board is not that hard and would waste your time.


Concerning the 8bit samples Datas, I suppose there may be some kind of Data compression, yet it may add some weight to the CPU work...


I'm soon to get a Breadboard...you know, the stuff allowing to make prototype montages and so on...
And my brother is soon to get a board to program microcontrollers... could be great if I can get some ACID erzatz with this...

[Bryce]

@Markus: It looks like a voltage divider, but it's not one. It's a balance of two separate inputs, so if the value is too high, both sources will have very low (or zero) volume. If the value is too low, the balancing effect won't work.

The other option could be to put a 37way Sub-D connector on the board so that you can connect it to your CPC via a printer cable, or leave the connect off completely and let the buyer add the proper connector.

Bryce.

Hmm, if I'd known you'd say that was cheap I would have suggested 30€

[Leonie]

If you want to play samples via the AY the main problem is the amount of CPU-Power it needs.
So I don´t understand why an audio-expansion like Digiblaster needs CPU-Power.
That´s ridiculous. 

[Devilmarkus]

If you want to play samples via the AY the main problem is the amount of CPU-Power it needs.
So I don´t understand why an audio-expansion like Digiblaster needs CPU-Power.
That´s ridiculous. 

So look @ the digiblaster's schematics.
It's only byte output to speaker. That's all.
Nothing is buffered.
So you need the CPU power to write the bytes fast enough to the printer port.

[Bryce]

Quite simple. To create a waveform of any decent resolution, say 4khz, you would need to pull the values from RAM and send them to the printer port at a rate of 4000 per second. Which doesn't leave much overhead to do other things. The higher the sample rate, the faster you need to be sending values. Using the AY normally, you send it a frequency value and the AY creates the waveform without any additional workload for the CPU.

Bryce.

[mr_lou]

Pre-assembled or as a "solder-it-yourself-you-lazy-morons!!!" kits ? (humor intended...)
The Kit "sounds" good to me, I mean soldering some components on a board is not that hard and would waste your time.

I hope it's pre-assembled!
It's pre-assembled, right Bryce?

The other option could be to put a 37way Sub-D connector on the board so that you can connect it to your CPC via a printer cable, or leave the connect off completely and let the buyer add the proper connector.

Yes... but somehow I think both options would be annoying for people. Too much cable.
The ideal connection would be a box that just clicked on there, just like a RAM expansion.

Hmm, if I'd known you'd say that was cheap I would have suggested 30€

If you can make a Digiblaster unit, pre-assembled with AY-input-through (meaning a female mini-jack input plug on the side of the box or else a cable with a male mini-jack sticking out of the box), for 20 euro, then I would think most people would buy.
But what's included in these 20 euro?
You assemble it?
Is there a box around it? (not too big I hope)

[Bryce]

Yes, that's assembled of course (with two female audio sockets), but without a housing. The circuit board is so small, it hardly justifies a box. I estimate the PCB would be the exact width of the connector (50mm) and about 25mm deep. If I build it with SMD parts it could be even smaller.

Bryce.