Sonifex CM-HPR1 Headphone Volume Control
This product allows the connection of a stereo balanced line input via a RJ45 with StudioHub+™ pinout and creates a headphone output, with level control. It is transformer balanced, and can be used with any headphones above 150Ω impedance.
The transformer ratio of 2:1 ensures that any headphone load presented at the output is reflected through to the input at a 1:4 ratio (hence a 150Ω set of headphones looks like 600Ω at the input, a suitable load for most good quality line output stages).
Block Diagram
Connectors & Controls
Headphone Output
The stereo headphone output uses a stereo 6.35mm jack socket with the following connections:
| Pin Type | Connection |
| Tip: | Left |
| Ring: | Right |
| Screen: | Ground |
The headphone level will be at half the level of the incoming signal with the volume control at 100%.
Volume Level Control
The volume level control sets the output level of the stereo headphone socket and runs logarithmically from zero to the maximum output level.
Analogue Inputs CM-HPR1
The stereo analogue input is on a female RJ45 connector with the following standard StudioHub+™pin assignments:
| Pin No | Connection |
| 1 | Left Phase |
| 2 | Left Non-Phase |
| 3 | Right Phase |
| 4 | Ground |
| 5 | N/C |
| 6 | Right Non-Phase |
| 7 | N/C |
| 8 | N/C |
CM-HPR1 Technical Specification |
|
Audio Specification |
|
| Input/Output Level Ratio: | 2:1 |
| Input/Output Impedance Ratio: | 4:1 |
| Minimum Headphone Impedance: | 150Ω |
| Max Input Level: | +28dBu |
| Max Output Level: | +22dBu |
| Frequency Response: | 20Hz to 20kHz, +0/-0.5dB |
| Noise: | <-115dBu A-wgtd |
| Distortion Ref +8dBu (Output): | <0.01% |
| Common Mode Rejection: | >80dB |
Connections |
|
| Main Stereo Input: | 1 x RJ45 female StudioHub+™ pinout |
| Output: | ¼” (6.35mm) A/B gauge 3-pole stereo jack sockets |
Equipment Type |
|
| CM-HPR1: | Headphone volume control, RJ45 input |
Physical Specification |
|
| Dimensions (Raw): | 7.7cm (W) x 8.3cm (D) x 4.2cm (H) 3.0” (W) x 3.3” (D) x 1.7” (H) |
| Dimensions (Boxed): | 12.7cm (W) x 22.9cm (D) x 7.6cm (H) 5” (W) x 9” (D) x 3” (H) |
| Weight: | Nett: 0.22kg Gross: 0.33kg Nett: 0.49lbs Gross: 0.73lbs |