Description
CANFORD PPM DRIVE CARDS
These PPM drive cards incorporate a micro-controller to control the PPM characteristics. They can be run from single or dual power supplies and be driven from balanced or unbalanced sources.
Mono
These are suitable for use with PPM types 14, 22A, 22AF, 24A, 32A and 32AF, or any meter to IEC 268-10. There is a connection for a ‘peak’ LED, illuminating at +6dBu, and for external selection of ‘slow’ mode.
Stereo
For use with PPM types 74A and 74B. There are facilities for two ‘peak’ LED indicators. The default mode is for the two meter movements to indicate the two separate inputs. Connections allow for the external selection of the following modes:
| |
| A/B | The default, usually used for Left and Right signals, one on each pointer. 0dBu, applied to either or both inputs, will cause the relevant pointers to indicate PPM4. |
| M/S (BBC) | M signal on one pointer, S signal on the other. When 0dBu tone is present on both inputs, the M pointer will read PPM 4.75 (+3dBu). When present on only one input, both pointers will read PPM 3.25 (–3dBu). |
| M/(S+20)(BBC) | As M/S (BBC), but S signal amplified by 20dB. |
| M/S (IND) | As M/S(BBC), but the M pointer reads PPM 4 when both inputs are PPM 4 (0dBu). A single 0dBu input will read PPM 2.5 (–6dBu) on both pointers. |
| M/(S+20) (IND) | As M/S (IND), but S signal amplified by 20dB. |
M and S are often called, respectively, sum and difference, the meaning of which is different depending on the user’s preferences. The two M/S variants conform to the traditional preferences of UK BBC and Independent broadcasters, which are now blurring to an extent. (Please note that many PPM scales do not have graduations corresponding to these readings, and that the accuracy of the meters is not defined where there are no scale markings. These figures are given for explanatory purposes only).’Slow’ mode may also be selected in conjunction with any of the above.
Technical Specification:
| |
| Input signal adjustment range: | –3dBu to +3dBu |
| Resolution of meter drive circuitry: | 8-bit |
| Resolution of rectifier system: | 10-bit at +14dBu level |
| Input impedance: | 100k ohms (min.) |
| Frequency response: | 20-16000Hz |
| Power supply requirements: | 12-30V DC or ±6 to ±15V DC |
| Current consumption: | 25mA (Mono) 50mA (Stereo), plus any LED current. |
| Dimensions: | 67x 54mm (Mono), 85 x 88mm (Stereo) |
| Weight: | 25g (Mono), 60g (Stereo) |