| Title | Value |
|---|---|
| Rated output : | 2x 50W (both channels driven, 4...8 Ohm load) |
| Maximum output : | 2x 90W (5 Ohm load) |
| Recommended load impedance : | 8 Ohm nominal |
| Output source impedance : | 0,1 OHm in series with 2200µF and 2µH |
| Rated sensitivity : | 2mV at 1Khz, RIAA equalized (phono ; for rated output ; 1V / 0dBv at pre-out) |
| 100mV, flat response (lines ; for rated output ; 1V / 0dBv at pre-out) | |
| Overload margin : | 40dB minimum (phono) |
| 35dB minimum (lines) | |
| 18V RMS (= +25dBv ; line output at clipping level ; power-amp in disconnected) | |
| Frequency response : | ± 0,2dB RIAA (typical) |
| ± 0,5dB RIAA (with 12dB/octave LPF, -3dB @ 30Hz) | |
| 20Hz...32Khz (-1dB, lines) | |
| Bass control : | ± 11dB @ 30Hz |
| Treble control : | ± 12dB @ 20Khz |
| Rise time : | 6µs (for rated output, tone controls off) |
| Input impedance : | 47kOhm (phono) |
| 27kOhm nominal (lines) | |
| Hum & noise output : | -80dBv (phono, 2mV input, standard A-weighted curve) |
| -88dBv (lines, 5mV input, standard A-weighted curve) | |
| -88dBv (lines, input at mini., standard A-weighted curve) | |
| -104dBv (lines, volume at mini., standard A-weighted curve) | |
| S/N ratio at loudspeakers : | 97dB (flat with 6dB/oct. rolloff at 15Khz to provide noise bandwidth of 23Khz) |
| 100dB (standard A-weighted curve) | |
| THD : | 0 (phono amp, rated level) |
| 0 (phono amp, +20dB) | |
| 0 (line amp, rated level) | |
| < 0,01% at 1Khz (line amp, +20dB) | |
| 0,02% (power amp, 1Khz, rated output) | |
| 0,01% (power amp, 1Khz, rated output, typical) | |
| 0,006% (power amp, 1Khz, 25W output) | |
| Mains : | 100 - 120 - 130 - 220 - 230 - 240V, 50/60Hz |
| Dimensions : | 43 x 11,5 x 28cm |
| Weight : | 9,5kg. |
Radford HD250
1975
A brand I know strictly nothing about except it was mainly known for its valve / tube amplifiers in the 1960s... but not its 1970s solid-state designs.
I just happened to have extra-rare leaflets for the HD250 and two other solid-state components which I sent to Paul Kemble - better visit his website for a serious study of the HD250.
Two Radford websites seem to coexist today : radfordaudio.co.uk and the Arthur Radford Appreciation Society, plus the Yahoo discussion group.
Wikipedia also has a somewhat slanted but detailed page, at least regarding the early and late lives of Radford - the 1970s seem to remain so far a bit... in the dark ?
page online since : october 2010
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page type : LGT / KNB
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page updated : not yet
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