The device connects to expansion port, and allows to copy data from an external tape deck to the CPC464's built-in tape recorder.
Draysoft & Evesham Micro Centre also produced a Doubler version for the ZX Spectrum.
According to adverts, the doubler also had "spectacular success on the CBM64".
Now, thanks to Jose Leandro, the hardware specialist of the spectrum, with his famous page :
We can know more about this hardware.
The hardware simply conists of an external cassette input:
Port F0E0h - Draysoft Doubler External Tape Data Input (Bit5) (Read Only)
- Port Conflicts: Port F0E0h may conflict with various Peripherals (which often decode only 1-2 address lines being low). Moreover, it conflicts with the internal Port F4XXh (PPI.PortA, which decodes only A11,A9,A8). To the worst, while running the Doubler software, PPI.PortA is set to 00h, so the Draysoft hardware must output a very strong HIGH level to pull-up the PPIs LOW level.
- Doubler software (Side A) executes an endless loop that forwards changes on Port F0E0h.Bit5 to PPI.PortC.Bit5 (and also to the Screen Border color). The software doesn't attempt to decode data blocks, it just forwards the data, and thus also works with any kind of non-standard data blocks. Similar results can be gained using a normal Dual HiFi Tape Deck - the advantage of the Draysoft method is that it outputs 'harder' digital transitions, however, it does add some timing inaccuracies, so the copy isn't exactly the same quality as the original.
- Speedcop software (Side B) is a baudrate conversion tool, allowing to select 1000, 2000, or 3000 bps. It's also allowing to remove SAVE"FILE",P protections. Speedcop is using only the internal recorder, ie. this program is not using the external hardware at all.
A M S T R A D D O U B L E R PREPARATION (1) Switch off your computer and plug the Doubler unit onto the edge connector that is marked "FLOPPY DISC". (2) LOAD the Doubler software provided in the normal fashion. (3) Plug one end of lead provided into the socket on the Doubler. Connect the other end of the lead to the EAR socket of a décent quality mono tape deck. (4) Put a blank cassette into the Amstrad's built in cassette player, put the cassette that you wish to back up into the other cassette deck. Adjust the volume of the extra cassette deck to just under maximum. STARTING "DOUBLING" You are now ready to start the process. Simply follow the screen prompts and the tape will be backed up. A visual indication of the process is provided by the flashing border, this can provide a useful indication to the suitability of the volume setting on the extra tape deck. The bars on the border should be solid, looking very similar to a Sinclair Spectrum while loading. There should be no break up of the border during the pauses between blocks of data, if this is happening then reduce the volume of the extra cassette deck. If by reducing the volume enough to get rid of border break up you lose the solidity of the flashing border, during blocks of data, it is unlikely that the extra tape deck that you are using is suitable for the job. ONCE THE TAPE HAS RUN THROUGH YOUR BACK UP IS COMPLETE. S P E E D C O P Once LOADed in the normal fashion Speedcop can be used to make back ups of all programs using conventional Amstrad loading Systems. Follow the screen prompts provided. It is possible as you will see to select your own SAVE speed and to "deprotect" programs. With some long programs it may not be possible to LOAD all the program to be backed up in one go. If this happens SAVE the portion of the program that has been LOADed then put the original back in and LOAD the rest of the program, Speedcop will know where to continue from.
- Doubler & SpeedCop.zip (tape) (CDT for emulators)
- Doubler (Eagle).zip (Doubler files for Eagle)