AmDrum Clone

[Bryce]

Hi All,
     while considering what my next hardware project might be, I stumbled across the AmDrum. Having had a very quick look at the PCB on the Wiki page, it seems to just be a simple DAC strapped to a particular address with an OpAmp connected to the output. This is more or less a complicated DigiBlaster, so with the right software it could work as an AmDrum, but also as a DigiBlaster V4.
Unfortunately the original design uses a ZN428 DAC which is no longer produced [nb]That's a pity because it was my favourite DAC back then - Yes electonics people have favourite components [/nb] but there are many alternative DACs still available that can do the job.
My plan is to first make a real AmDrum (I still have one or two ZN428 lying around) for comparison, and then make a new version using available parts.

The problem is, I don't have any schematics and the picture of the top of the PCB on the Wiki is at a slight angle, so not all part values are visible. Does anyone know who this device belongs to? Or if the person is reading this here, could they possibly take a new picture from directly above so that I can be sure that I use the correct values and have an exact copy to compare my clone with.

Thanks,
Bryce.

[CPCLER]

You got a PM!


/CPCLER

[Gryzor]

Why not actually design something that would be useful?

Your hobby, your decision of course, but what would be the point?

[Bryce]

Easy:

1) I always wanted one back then (parents wouldn't let me get a real drumkit either, spoilsports).
2) It may turn out to be a really good DigiBlaster.
3) There are lots of CPCers interested in making music on the CPC, not to mention all the Chiptuners out there.
4) If more people have one, more stuff might be done with them.
5) Because I can

Bryce.

[Gryzor]

I'll accept 1 and 5

[Bryce]

I'm sure there are others UltraSyd, MrLou ? who would agree with numbers 2,3 and 4

But I'm glad you accept at least some of my arguments.

Bryce.

Btw, I was nowhere near a shower when I came up with the idea

[Gryzor]

Only yesterday I saw online a waterproof notepad+pen for the shower. Mighty good idea!

[sigh]

Sounds cool!
Admittedly, I would love to see Bryce create some sort of joystick adapter that would allow 2 players to each use a 2 button joypad without interference with each other !
I would buy that in flash!

[Bryce]

I have a plastic board and waterproof pen that I use one when I go diving (you can buy them in most diving shops), but I've never tried designing a circuit at 30 metres, maybe next time

@Sigh: Send me more details in a PM. I was also doing something similar for my Plus at the moment: Lots of cartridge games ask you to press fire two for certain things, and my joysticks only have one fire button and I don't have any joypads 

Bryce.

[sigh]

I have a plastic board and waterproof pen that I use one when I go diving (you can buy them in most diving shops), but I've never tried designing a circuit at 30 metres, maybe next time

@Sigh: Send me more details in a PM. I was also doing something similar for my Plus at the moment: Lots of cartridge games ask you to press fire two for certain things, and my joysticks only have one fire button and I don't have any joypads 

Bryce.

PM sent (explained as best as I can)

[HAL6128]

@Bryce: How about an ZN448E which was often used in former times for AD converting stuff?

[Bryce]

The ZN448 is an analogue to digital converter (ADC), the AmDrum needs a digital to analogue converter (DAC). Generally all the ZN series were dis-continued quite a while back, but there are other modern equivalents available.

Bryce.

[HAL6128]

I found some at ebay. Maybe the AD7569JNZ 8BIT ANALOG I/O SYSTEM,7569,DIP24  > TYP:AD7569JNZ is an alternative?
Pricy stuff (both...).

[Bryce]

That's a high-end part, a bit much for what the AmDrum needs. Something like this should do the job and only cost €1.15
http://www.reichelt.de/ICs-CA-ISD-/DAC-0808-LCN/index.html?;ACTION=3;LA=444;GROUP=A213;GROUPID=2910;ARTICLE=7027;START=0;SORT=artnr;OFFSET=16;SID=13TdAKHH8AAAIAADtdFAUd46e73cc3021ced76447a4d1a6b4ef80

Bryce.

[rpalmer]

Hi bryce,

You can make your own Digital-to-Analogue converted.
I have the book "The Ins & Outs of the AMSTRAD" by Don Thomasson and the attached file is a picture of such a way to convert digital data to analogue.
maybe this may be of use to you.

regards
rpalmer

PS. I also go the parts you sent to me today, many thanks.

[Bryce]

Your attached diagram is a basic resistor ladder, which means buying lots of different valued resistors. This was used for the original DigiBlaster and later my DigiBlaster V3 moved to an R2R Ladder (does the same thing, but uses only 2 different resistor values). Although this would work fine for the AmDrum, this time I wanted to use a real DAC as the original AmDrum does. A real DAC also has the advantage of having a Chip-Select or Output-Enable pin, which makes it easier to enable/disable when the correct address is chosen. But I might fall back on this solution if I'm not happy with the choice of DACs available today.

Bryce.

Did the parts arrive in one piece? I was worried that the pins might get bent/broken.

[TFM]

That's a simple Digiblaster 

[fgbrain]

I have a 'first generation' self-built Digiblaster.

Still I would be very much interested in a new Digiblaster / Amdrum clone!!
Any news on this project, Bryce

[Bryce]

I built a batch of my version of the DigiBlaster, but that was it. I didn't intend building any new devices of this sort. What exactly are you looking for?

Bryce.

[fgbrain]

You wrote:

My plan is to first make a real AmDrum (I still have one or two ZN428 lying around) for comparison, and then make a new version using available parts.

I'm asking if you made a new version of AmDrum or whatever you will call this...

It would be nice if can we use AmDrum software through Digiblaster ( ?? ) since nobody has an Amdrum... Or the samples only..

[TFM]

Shouldn't be that big problem to patch Amdrum Soft for a Digiblaster.

[genesis8]

Hello,

any news about a new amdrum ?

Otherwise, would it be possible to buy either a centronic or edge-connector digiblaster V3 (or both if possible) if you have still some available ?

By the way, correct me if I am wrong but using a digiblaster eat a lot of CPU time sending data to play.

Would it be possible to make a digiblaster with some memory to load data and just send short commands to play the data when needed, without adding too much cost ?

P.S. : how much more to add VN96 like the SoundPlayer+ (Futurs) ?

[steve]

Perhaps when Bryce designs his 512KB ram expansion, it could include a DMA controller to send data to a digiblaster and maybe other destinations.

[Bryce]

The DigiBlaster is a completely passive design up to now, ie: it doesn't have any power supply. Adding anything new like a buffer would mean changing the design completely.

Yes, the DigiBlaster depends completely on the CPU, so at it's best quality, it would be using more or less 100% of the CPU resources, that's how it's designed.

I never did anything more on the AmDrum, it's still at about position 10 on my priority list.

@Steve: DMA isn't just about adding another IC, to add proper DMA to the CPC would mean major internal modifications, which most users wouldn't be willing to do. The 512K RAM is being designed with as low a cost as possible, so it definitely won't have anything even close to DMA.

Bryce.

[Gryzor]

so it definitely won't have anything even close to DMA.

Not even a tiny sticker saying "DMA"?