LEHLE Sunday Driver

From the Source:

The Lehle Sunday Driver SW is a compact-format high-end preamp for all types of electrical and acoustic instruments - a preamp that enables electric guitars and basses, acoustic guitars, and also other stringed instruments (such as violins, cellos and double basses) to realize all of their musical potential. The switchable version expands the classical Lehle Sunday Driver's features by an On/Off footswitch. 

The Lehle Sunday Driver SW, with its high-quality JFET technology, provides two operating modes. In D (= Driver) mode, the input signal is amplified with zero modification, to eliminate the signal losses that long cable routings and/or effects chains can cause. The signal remains powerful and clear, and retains its dynamics. Mode S (= Sunday) multiplies input impedance by four, bringing out previously inaudible details and, as gain increases, imparting to the guitar a characteristic and unmistakable warmth. There is no distortion at any stage, and the signal always stays clean, even at a maximum gain setting of 15 dB. Thanks to its studio-standard signal-to-noise ratio of better than -100 dB, the Lehle Sunday Driver SW is totally free of background noise. To exploit the dynamics of tube amplifiers to the full, the input voltage is also rectified from the power supply socket, then filtered, stabilized and doubled to 18V. 

In OFF status, the Lehle Sunday Driver SW provides two different modes of operation - in TB (= True Bypass) mode, the input and output are linked with zero losses to one another via a switch with gold-plated contacts. True Bypass mode is the best option for a small set-up with short cable routings and for when a treble-booster or a classical fuzz pedal is looped in after the Lehle Sunday Driver SW. The line-driver function, located at the start of the train or in an effect chain, is the better solution for long cables and for complex effect board configurations. Switch the Lehle Sunday Driver SW to TS (= True Sound) mode, and it is active as a buffer, without amplifying or modifying the signal in any way. In this mode, the Lehle Sunday Driver SW operates as a totally neutral line-driver – equivalent to Mode D with the gain pot turned all the way to the left. The Bypass mode option enables the Lehle Sunday Driver SW to integrate ideally into any set-up, whether as a battery-operated stand-alone unit, or in an existing pedal board. 

Note: I removed the odd power network, which consisted of a diode rectifier and regulator, which should not be needed since it's supposed to run on +9VDC not +9VAC. According to the site, they claim there's a TB/Buffered switch which is not included on the schematic, nor did I see it on the PCB over at FSB when it was reversed engineered.