Back to the HPA.The default source for the evaluation was my €14'500 ten-years old still-in-production Nagra CDC spinner (I like to think of it as the Redbook TD 124) which handily doubles as a buffered analogue passive preamp with a separate balance control. In fact, I frequently use it in this configuration. So in the interest of completeness and to avoid the usual sand versus glass face off, I added it to the mix, making this a sand vs. glass vs passive confrontation. Now, as P.G. Wodehouse would have observed, there are many readers so constituted as to scream with excitement at the prospect of blow-by blow-descriptions on some twelve pre/power amp combinations, not counting settings and cable looms. However, since even a serious professional such as Roy Gregory has
warned of the burdens involved in preamp comparisons, I shall restrict myself to the setups I actually use: passive on Trends and 300p, hotrod (two tube) PL-P on F5 and 300p, full power (6 tube) PL-P on the TK 2A3. That totaled a manageable five variants in all. Cables were all Van den Hul, unbalanced The First from the CDC's variable output set at 3V, Integration from the PL-P's line or tape outputs and Inspiration power cables biwired to the Tannoy Canterbury HE. The stated Z-out of the HPA is low at some 50Ω, ideally matched to the conventionally high 100kΩ input impedances of all the amps, the partial but unproblematic exception being the Trends'
circa 50kΩ while the CDC's and PL-P's outs are equally exemplary at 80Ω and 60Ω respectively. Conveniently, pots on all devices were Alps Blue which neatly eliminated a significant variable. Listening levels were between 75 and (very occasionally) 85dB+, checked by iPhone meter in my large-ish but very reflective room.
