You can convert a tape-image (".CDT" or ".TZX") to a audio signal using the "PlayTZX" utility.
The "PlayTZX" utility can be downloaded from World of Spectrum.
This utility will convert the tape-image into a audio signal.
If you have a Soundblaster compatible sound card, and you run the utility in a pure DOS environment (e.g. The "Command-Line" of Windows NT, Windows 2000 or Windows XP is not a pure DOS environment. For a pure DOS environment in Windows 95 or 98 you must select "Shutdown" from the start menu and then select "Restart in MS-DOS mode"), then you can play the audio signal through your sound card.
If you are using Windows 2000, Windows NT or Windows XP then you can generate a "VOC" sample file which you can play through a sound player which can read this file format. (GoldWave can read "VOC" sample files. Go to Goldwave Homepage to download it).
If you have a CPC with a built in cassette recorder (e.g. CPC464, CPC464+), you will find that there isn't a cassette connector (5-pin DIN socket) like there is on CPC's with a built in disc drive. (e.g. CPC664, CPC6128, CPC6128+), therefore you will need to record the audio to a blank cassette. The program can then be loaded in the same way as any other Amstrad CPC cassette program. If loading is unsuccessful, then you may need to adjust the volume of the audio output from your sound card and re-record the sound. Repeat this until the program is loaded successfully by the Amstrad. Once you have found the correct volume, you can use this setting for all programs.
You will also need to connect a cable from the "Line-Out" of your audio card to the audio input of a cassette player (e.g. "Line-In"). The lead you will need is likely to be a 3.5mm phono plug to 3.5mm phono plug. Some Hi-Fi's have a 6.5mm phono socket, so you will need a 3.5mm to 6.5mm conversion adaptor.
If you have a CPC with a built in disc drive, then you will find that there is a 5-pin DIN socket. You have the option of using a special cable to connect the "Line-Out" of your audio card direct to the cassette connector of the CPC. In this case, you will need to adjust the volume of the sound output from the sound card until the program is loaded correctly by the Amstrad. Once you have found the correct volume, you can use this setting for all programs.
playtzx /voc /128 /freq 22050
ZXTape Utilities - Play TZX , TZX to VOC Converter and TZX Info v0.59b ZXTape file revision 1.10 Number of Blocks: 19 Creating .VOC file using 22050 Hz frequency. Block 1: Pause Length: 16.553s Block 2: -------------------- Length: 263 Speed: 70% ,Pause: 0.030s Block 3: -------------------- Length: 2069 Speed: 70% ,Pause: 2.617s Block 4: -------------------- Length: 263 Speed: 70% ,Pause: 0.042s Block 5: -------------------- Length: 522 Speed: 70% ,Pause: 11.548s Block 6: -------------------- Length: 264 Speed: 70% ,Pause: 0.017s Block 7: -------------------- Length: 2069 Speed: 70% ,Pause: 2.621s Block 8: -------------------- Length: 263 Speed: 69% ,Pause: 0.030s Block 9: -------------------- Length: 2069 Speed: 70% ,Pause: 2.620s Block 10: -------------------- Length: 264 Speed: 69% ,Pause: 0.025s Block 11: -------------------- Length: 2070 Speed: 70% ,Pause: 2.631s Block 12: -------------------- Length: 263 Speed: 69% ,Pause: 0.047s Block 13: -------------------- Length: 2070 Speed: 70% ,Pause: 2.630s Block 14: -------------------- Length: 263 Speed: 72% ,Pause: 0.038s Block 15: -------------------- Length: 2070 Speed: 69% ,Pause: 2.634s Block 16: -------------------- Length: 264 Speed: 69% ,Pause: 0.026s Block 17: -------------------- Length: 2070 Speed: 70% ,Pause: 2.617s Block 18: -------------------- Length: 264 Speed: 69% ,Pause: 0.019s Block 19: -------------------- Length: 1037 Speed: 69%