Well, here is my latest and final take on a vacuum tubed preamp. Since 2009, I've been working with the 6N6p 9-pin miniature tube  (NOS Russian military stock). It is similar in amplification to the 12AU7 and 6SN7, but has 1/4 the plate resistance. This makes it more suitable for transformer coupling. The 6H30 can also be used, as it is pin-compatable with the 6N6p without any adjustments. It has slightly less gain and plate resistance. I explored every known topology and a invented a few new ones, but was never impressed, until now! The breakthrough idea was to build a self-inverting push-pull amplifier in miniature.

(BTW, my circuit has been world copyrighted on June 1, 2013.)

At first, I built a breadboard outboard power supply and separate signal board, using parts from the junk box. When I first hooked it up, I was floored at the quality of sound! Here was something worthy of development. I then built 3 more breadboard preamps using better parts with different tubes and topologies. Because of the outboard power supplies, I was able to plug and play with different combinations. After many listening sessions with friends and family, in my system and theirs, I was able to finalize the design.

I now can offer (3) levels of performance, from $2,500-$7,500.

 A very generous warranty is as follows: 5 years parts and labor from us, 1 year on tubes from the supplier. The picture below shows the level one preamp with outboard regulated power supply on the upper shelf.

here are the significant features of this preamp design:

• NO coupling capacitors in the signal path
• class "A" operation
• dual-mono construction
• zero negative feedback
• regulated B+ high voltage supply using NO solid state devices
• AC operated filaments
• quiet single point grounding topology (SPG)
• true push-pull transformer output (600 ohm)
• slow turn-on with indirectly heated rectifier tube
• all point-to-point wiring done by hand (NO printed circuit boards)
• NO "audiofool" parts used or needed! only hi-quality USA made wherever possible
• only low-cost, readily available, current production replacement tubes are used
• BEST warranty in the industry

                    a few underhood shots of the level one preamp: (with safety covers removed)

THANKS for lookin'
JL.