Nagra Classic Phono Phono Preamplifier Lab Report

Lab Report

Although notionally replacing Nagra's venerable VPS phono stage [HFN May '13], not only does the new Classic Phono offer both MM and MC inputs, but also the option of 'high' and 'low' gain settings. The VPS's 12AX7EH/12AT7EH tube-based RIAA network is replaced here with 'equivalent' ECC83/ECC81 bottles and the Classic's equalised response with its broad ~0.3dB bass emphasis (20Hz-100Hz) and flat HF trend, good to within ±0.2dB from 200Hz-100kHz, is also directly comparable [dashed trace, Graph 1]. This newer phono stage also includes equalisation for the legacy Teldec and Columbia 'standards' [red and green traces. respectively], the latter subject to ~6dB less attenuation at 20Hz during LP cutting than either the Teldec or latter-day RIAA standards.

Moreover, aside from the Classic's more flexible +37.5dB/+47.4dB MM gain and +54.0dB/+63.9dB MC gain options (the MC stage is prefaced by a new step-up transformer offering +16.5dB), the newcomer sweeps away the VPS's principal shortcoming – its limited MC input headroom (just 2.45mV). In practice, the Classic's E88CC output stage clips first so the maximum useable input is 120mV for the MM stage and 18mV for the MC stage regardless of whether you choose the 'High' or 'Low' gain setting. This means the 'High' gain settings offer the most generous headroom relative to the lower-output pick-ups likely to be used, and the highest maximum output of 28.0V (vs. 8.6V for MM or MC set to 'Low' gain). The MC input also offers the wider 76.5dB A-wtd S/N ratio (re. 500µV) but distortion is largely unchanged at 0.03-0.1% [re. 0dBV, 20Hz-20kHz, see Graph 2]. Distortion does increase with level, however, from ~0.02%/500mV to 0.05%/2V and 0.12%/6V (re. 1kHz). PM


Freq. resp. from 5Hz-100kHz re. 0dBV (RIAA, black; pre-eq’d, dashed; Teldec, red; Columbia, green)


Distortion versus frequency re. 0dBV from 20Hz-20kHz (MM Low gain setting)

Input loading (MM/MC) 47kohm/100pF / User-defined
Input sensitivity (re. 0dBV) 13.4mV / 4.28mV / 2.01mV / 0.64mV
Input overload (re. 1% THD) 120mV / 18mV (MM/MC)
Max. output (re. 1% THD) / Imp. 28.0V / 425-450ohm
A-wtd S/N ratio (re. 0dBV) 73.9dB / 76.5dB (MM/MC)
Freq. resp. (20Hz-20kHz/100kHz) +0.35dB to –0.1dB / –0.2dB (RIAA)
Distortion (20Hz-20kHz, re. 0dBV) 0.031-0.10% (MM and MC)
Power consumption 24W
Dimensions (WHD) / Weight 277x300x80mm / 5.4kg
Price £17,000

Audio Technology Switzerland S.A.
Lausanne, Switzerland
Supplied by: Padood Ltd, Cambridge, UK
01223 653199