Abacus Passive LDR

That appears to be substantially the same thing as the Tortuga LDR preamp, using the same parts except for maybe the input switching relays.  I too wonder how it sounds and compares to the Lightspeed.  The main differences are the addition of input switching and the auto-calibration for the LDRs which I believe George does not advocate in the design of the Lightspeed.

I have owned the same Abacus LDR for over a year now, and really enjoy mine when not using my integrated amp. I have also owned Lightspeeds, Bent Tap-X and Warpspeed LDRs. The Abacus sounded very close to the Tap-X, and better than the Warpspeed. I had a few problems with balance with two different Lightspeeds I owned, and the volume on them was not very suitable for low level listening with higher gain amps like my Job 225. No remote control on the Lightspeed made it very difficult for late night sessions when the family was sleeping. It did sound very good though. The Tortuga based Abacus has balance, remote volume, 3 input switching and selectable impedance settings.

I own one of these and have auditioned the Lightspeed. I think it is slightly better, but they are more alike than different. In my opinion it is an excellent sounding piece.

Shakey

After reading what I wrote, I wanted to clarify. The Abacus sounds slightly better than the lightspeed.

Shakey