Each channel of the gain stage is based on an octal 6J5GT single triode followed by one triode-strapped 12GN7 pentode buffer at unity gain. The first medium gain valve of low transconductance is considered one of the most linear devices of its kind ever whilst the 12GN7 is a modern high-current/transconductance/gain power tube perfect for buffer duties. Reinhard exploits the same pairing in his award-winning EHT mono amps based on a very similar schematic. Tubes occupy Reinhard's hardware and mind not because of their sonic charm but being inherent linear so suitable for minimalist circuits. Rather than a standard hybrid, our man describes his circuit as a 'contemporary solid-state interleaved tube' scheme. It has very low distortion, output impedance of ~5Ω and no feedback loops. Both tube types are complemented by a clever set of light-emitting diodes, Mosfets and bipolar transistors. Their job is to provide optimal conditions for the signal-path glass which is heated by constant 300mA DC series current. A single bipolar operates as current sink whereas a bridge of clean-switching Schottky diodes handles rectification. Reinhard explained that due to the transistor's low heat dissipation, this arrangement is simple, stable, of very low noise and above all reliable.
Due to their clean switching, passive glass avalanche diode rectifiers are seen not only in this high-tension supply but all of Reinhard's amps. The reservoir capacitor is followed by a 3-stage RC-filter section based on electrolytic Fischer&Tausche caps which provide low ripple voltage to the 'simple yet outstanding' circuit Herr Thöress views as a stabilizer free from a sensor amplifier within a feedback loop rather than a standard regulator. Just as any other Thöress machine, the DFP is based on a low-leakage deadly silent power transformer handmade by Reinhard. Its coils are wound on a vintage Aumann machine and to reduce residual vibrations and interference, the final part mounts to the chassis via noise dampers. In-house made power transformers provide global mains readiness.
To review the Thöress Dual-Function Preamplifier as a linestage, fidata's HFAS-S10U handled storage and transport duties, then a LampizatOr Pacific DAC passed analog signal to either it or Kinki Studio's EX-P7. Then two distinctively different configurations came into play: Martin Gateley's sound|kaos Libération fronted by FirstWatt's F7 stereo amp; or Kinki Studio EX-B7 monos married to my Boenicke W8 floorstanders. Two LessLoss C-MARC power cords maintained the natural character of each preamplifier. C-MARC speaker cable followed as did two sets of Audiomica Laboratory Erys Excellence interconnects. As headphone amp, the Thöress was compared to iFi audio's Pro iCAN. Both were fronted by the same transport, DAC and all other components. Three headphones on duty were HifiMan's Susvara, Meze's Empyrean and Beyerdynamic's T1. Harnesses for them all were Noir hybrids from Forza AudioWorks.
The DFP for headphones interested me the most so its 6.3mm outputs were first under the loupe. On functionality the DFP was less generous than its UK/Sino competitor. All other products I know are. The Pro iCAN is exceptionally versatile and very powerful. Once all its bells and whistles are counted, the Brit enables such significant sound tuning that it gets along perfectly with all non-electrostatic headphones to market. To make a fair comparison, its bass and spatial boosters turned off and its mode switch set in the middle to get its JAN GE5670 tubes involved. The main goal of the exercise was to learn what Reinhard's machine sounded like flat so its tone control was set to either the third or sixth position. As the easiest load on hand, the Empyrean was first in line. Early on it struck me how pleasantly silent the DFP was. With no music on, mild noise kicked in a fair bit above 3 o'clock on the dial. With these specific headphones, this equaled instantly deafening SPL when normal listening didn't make it past 11 o'clock. So for purpose, the amp was dead quiet and several minutes into my first audition, its sonic profile became clear. The F2A11 integrated amp had been harmonically generous enough to know that valves were involved. It simply didn't prettify the music but showed it for what it was. With a suitable load it also was feisty. It simply didn't sound like a regular valve affair. Now the DFP did something very different.
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