Pre/Power Amplifiers

All SPL's 'Professional Fidelity' series components feature its proprietary VOLTAiR line/gain stages, all based around single-ended and/or balanced versions of the brand's ±60V Supra op-amps [see inset picture]. Operational amplifiers (op-amps) are typically, but not exclusively, IC-based but discrete designs are not uncommon in high-end audio applications. Deltec's thick-film hybrid op-amp, the DHOA32, is an early example from the 1980s but SPL's Supra modules, based around complementary MJD340/MJD350 transistors from STMicroelectronics, are arguably closer to T+A's J-FET-based 'High Voltage' line stages [HFN Sep '13] in approach.

In similar fashion, SPL's Supra modules operate at an uncommonly high ±60V PSU rail voltage, endowing the buffer/line stage with a very high voltage headroom. Furthermore, because only a very small proportion of this 'swing' is used in practice, it allows SPL to operate the transistors over a limited but highly linear portion of their range without employing anything more than the absolute minimum of corrective feedback. PM