Vintage

These amplifiers remain as innovative and high-performing as they were over 30 years ago when I first tested them [HFC 124, Nov '93]. Both the pre and power amps are equipped with 'Compound-Class A' output stages driven via surface-mount NE5534s in the case of the DSP-200S and via DPA's own DH-OA32 op-amps and power transistors in the matching power amp. Feedback is also extended right to the output terminals of both amps – hence the vanishingly low 0.08-0.45ohm (pre) and 0.003-0.05ohm (power) output impedances (all re. 20Hz-20kHz). While the preamp will also make an excellent headphone amplifier and the power amp offers a massive damping factor, the latter's ability to drive low sensitivity speakers is limited by its 2x51W/8ohm, and 2x80W/4ohm output, increasing marginally to 56W, 93W, 79W and 54W into 8, 4, 2 and 1ohm loads, respectively, under dynamic conditions [see Graph 1]. Unusually, the power amp is phase-inverting, so do experiment with those red and black speaker leads.

Distortion [see Graph 2] is very low at 0.0005-0.0015% (preamp, 0dBV) and 0.0015-0.02% (power amp, 10W), and also very uniform with output as it holds to ~0.0015%/1kHz from 1W to 45W/8ohm. The responses follow the decrease in feedback/increase in output impedance at higher frequencies, gently rolling away to –0.25dB/20kHz and –4.78dB/100kHz in the preamp and –0.4dB/20kHz and –6.0dB/100kHz in the power amp. Noise is very low indeed, and the A-wtd S/N ratios correspondingly wide at 98.4dB and 96.0dB (re. 0dBV and 0dBW, respectively). Finally, as the DPA-200S is a dual-mono design, stereo separation is a hearty >85dB (20Hz-20kHz). PM