The problem: the F-2b, according to the Alembic site, does not work. well with power amps with input impedances lower than 10k ohms, and. I've found that this is indeed true. The QSC's input impedance is. less than 10k ohms. If I plug the Alembic directly into the QSC, it does not sound very. good--not much volume and it's kind of dull sounding "The F-2B contains two independant preamp/tone control sections. The amplification is entirely vacuum tube powered. It is normally used as a stereo preamp to interface stereo instruments to power amplifiers. Jacks are provided on the rear for outputs from each channel. F-1X Tube Preamp. The F-1X is the mono version of our classic F-2B preamp. We kept the same tone section and added a few goodies like a direct output, built in effects loop and crossover. You can still use it in a simple set up since the F-1X also includes a standard full range output. The Alembic F-2B does more than that. It doesn't just give signals warmth, it gives them life. The picture I included on this page sums it up for me. The dictionary definition of an "alembic" is "something that refines or transmutes as if by distillation". An example, in the philosophic sense; "… filtered through the alembic of No need for manual, one branch with all knobs at noon and it sounds right now! The original model can also send the output of a channel in the entrance of the second to have a big greasy distortion. Not try at home, I mounted a canal. SOUNDS The sound is very respectful of the low, round and warm, it gives a feeling of fluidity, the "liquid". alembic.com/support/F2B_manual.pdf from a features standpoint the F2B is barebones It has separate outs for each channel, and a combined mono out as well, all 1/4" unbalanced. The FX1 has, DI, variable x-over with variable HF level and FX loop Dec 3, 2008 #3 andrew May 20, 2000 Vancouver BC/Pacific Northwest A transformer-isolated output feeds a 3-pin Cannon jack. Circuit detail Two input jacks provide the same functionality as found on the F-2B preamplifier. The input is buffered by a cathode follower tube circuit, which is a unity-gain impedance matching amplifier to feed the guitar level effects loop. Vintage Alembic F2B preamp. Made in Irvine, CA in the 1970s. Same model used by David Gilmour (Pink Floyd) and Phil Lesh (Grateful Dead). Amazing clean tones for bass or guitar. Good condition for its age. Sounds amazing and works perfectly. Recently serviced and modded by Alembic (new filter capacitors/foam and a rear input added). And according to manual, Gain of F1 only affects instrument input. Apr 2, 2009 #4. MESA power amp, the EQ and filters in the SWR just don't allow me to get the golden round tone I got when I had just an Alembic F-2B and the Mesa. How I regret selling it!! I think I paid like $250 for it in the early 90s Apr 5, 2009 #14. The instrument preamplifier is automatically connected thru 'normal' springs when no jack is inserted in the line level input on the rear panel. A jumper block inside the unit provides signal amplification of 0 dB, 10 dB, and 20 dB for the preamplifier circuit by selection of feedback resistors.