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Revision as of 20:44, 8 April 2016
The Amdrum is a 8bit D/A converter (hardware) with drumkit (software), made by the British company Cheetah.
Quality of the playback was nice, considering the time and price.
The samples were read from the suplied tapes.
There were serveral tapes with different themes.
Along with the Amdrum came a sequencing program.
It was possible to copy the samples to disc, but the sequencing program had to be patched!
Amdrum was probably Cheetahs version of the SpecDrum (As revealed on the PCB "AMSTRAD SPECDRUM")
No other software than Cheetahs own sequencer is know to use the Amdrum.
Now, thanks to Jose Leandro, the hardware specialist of the spectrum, with his famous page :
http://trastero.speccy.org/cosas/JL/JL.htm
We can know more about this hardware.
Contents
Technical Specifications
- Uses I/O Port FFxxh (Write only), ie. only /IORQ, /WR, A15-A8 are decoded. A7..A0 are not decoded, and /RD isn't used, too.
- Port usage: Write 8bit unsigned sample data to Port FFxxh. The D/A converter is mono and has only one channel (mixing multiple channels is to be done by software).
- After booting, the Amdrum software first sets port [FF80h]=80h. Emulators can use that feature to detect Amdrum software - and, after [FF80h]=80h was detected, map the whole range of ports FF00h..FFFFh to the Amdrum.
- During operation, the Amdrum software uses port FFxxh. Where "xx" is garbage coming from the Amdrums keyboard scanning routine (see disassembly below).
The five chips on the single-sided PCB are:
| 74LS30N | Single 8-input NAND | Port decoding, /ADDR_MATCH=LOW when A8..A15 all HIGH |
| 74LS32N | Quad 2-input OR | Port decoding, /DAC_WRITE when /ADDR_MATCH, /IORQ, /WR all LOW |
| SN74LS04N | Hex Inverters | purpose unknown? (used in the analog part, not for Port decoding) |
| TL064CDP | Quad Amplifier | no info how the 4 amplifier stages are used? |
| Ferranti ZN428E-8 | 8bit DAC | mono one-channel 8bit D/A converter (unsigned samples) |
- ZN428 Datasheet - 8bit D/A Converter
- TL064 Datasheet - Quad Amplifier
Partial dissassembly of player
exx ld a,(bc) ;get channel 1 add a,(hl) ;add channel 2 ex de,hl add a,(hl) ;add channel 3 inc hl ex de,hl inc bc add a,80h ;add bias (signed to unsigned) inc hl exx out (c),a ;out [FFxxh] with C=whatever ld b,0f6h in a,(c) ld c,a ;C=PIO Port C (keyb row, tape, psg control) xor 05h ;five ??? out (c),a ld a,0f4h in a,(66h) ld (404eh),a out (c),c ... ;something missing here? ld b,0ffh nop nop nop exx ld a,(bc) ;get channel 1 add a,(hl) ;add channel 2 ex de,hl add a,(hl) ;add channel 3 inc hl ex de,hl inc bc add a,80h ;add bias (signed to unsigned) inc hl exx out (c),a ;out [FFxxh] with xx=garbage (above PIO Port C value)
Pictures
- AMDRUM
Box
Amdrum inside box
Screen shot
Screen shot
- 300dpi scans by Robcfg
PCB Top
PCB Bottom
Interface Top
Interface Bottom
- Amdrum Layout, thanks to Jose Leandro
Amdrum - PCB Front
Amdrum - Layout
Kits
| Title | Front Covertape | Back covertape |
| Afro Kit |  |
|
| Electro Kit |  |
|
| Latin Kit |  |
|
- Afro Kit - Errata
Afro Kit Errata
Tapes
Amdrum Tape
- Amdrum Tape
Amdrum Tape side A
Amdrum Tape side B
Afro Kit Tape
- Afro Kit Tape
Afro Kit Tape side A
Afro Kit Tape side B
Electro Kit Tape
- Electro Kit Tape
Electro Kit Tape side A
Electro Kit Tape side B
Latin Kit Tape
- Latin Kit Tape
Latin Kit Tape side A
Latin Kit Tape side B
Manual
- Amdrum Manual (pdf)
Reviews / Commercials
- Commercials for the Amdrum
Commercial for Amdrum
Review of the Amdrum in Amstrad Computer User
Other playback devices
- Digiblaster (DIY) (8bit DAC on printer port)
- Music Machine
Videos
AmDrum on Amstrad CPC (emulated with JavaCPC)
{{#ev:youtube|0z-jGDOzwGQ|400}}
A presentation(from around 1985) of the ZX Spectrum version of the Amdrum(Specdrum), also mention of the upcomming Amstrad CPC version
{{#ev:youtube|m6R_W9CZWGU|400}}
Download
- Amdrum.zip (CDT for Emulators)
- Amdrum Afro Kit.zip (CDT for Emulators)
- Amdrum Electro Kit.zip (CDT for Emulators)
- Amdrum Latin Kit.zip (CDT for Emulators)
- Amdrum (Eagle).zip (Amdrum files for Eagle)
