ALEMBIC F-2B

[mike1762]

What do you guys think http://cgi.ebay.com/VINTAGE-1970s-ALEMBIC-F-2B-BASS-PREAMP-DAVID-GILMOUR_W0QQitemZ120332522700QQcmdZViewItemQQptZLH_DefaultDomain_0?hash=item120332522700&_trksid=p3286.c0.m14&_trkparms=72%3A570 is worth?  The description says The Left and Right channels have been internally linked together.  Is the M output supposed to be stereo (a TRS jack) or a mono output of both channels (which is apparently the case with this unit).  I can't figure out why someone would have removed the A and B outputs.  The seller claims To convert it back to Stereo would only cost about $40.00 by a tech... do you think that is the case?

[2400wattman]

Mike, This was obviously owned by a guitarist because of the internal linking of the channels and the mentioning of David Gilmour. Linking the channels increases preamp gain, I think. If you knew any guitarists that used four input Marshall's(think plexi's) usually they would use a small patch cord to link two of the inputs together. The same thing can be accomplished with this pre amp, this guy just wanted it hard wired permanently for his use-so it seems. The M output is now a mono output of both channels, but I'm not sure if it's like this with a stock unit.  
Now about converting it back, I don't know ANY competent tech that would do the job for $40.00 as most guys I know charge $60-80.00 per hour for their time not counting parts. It probably is an easy fix though.  
So for quality parts and labor to get it back in original shape your probably looking at $60-80.00 plus cost of unit, shipping and your time to find that competent repair guy(unless you know one already-and I have'nt met one yet here in Knoxville, or you can do the work yourself).  
His price seems to be what newer-used stock F2-B's are going for, so I'd wait for one to pop up as they do pretty regularly.  
Oh and one more thing, these units don't have direct outs on them. so you'd have to go and buy two great D.I.'s because you would'nt want to put some junk piece of gear in line with all that Alembic quality now would you?

[David Houck]

It's sold.  But to answer the question, yes the M output is mono and combines channels A and B.  From the F-2B page: a Mono output jack is provided which combines both channels.  Personally, I wouldn't have paid that much for this unit unless I specifically wanted that mod done.  The seller did say that the work was done by Alembic, which is a good thing.  But as Adam suggested, I would have just waited for another F-2B.  Although I really do like the look of these older units with the red knobs; and they are a little harder to find.

[lbpesq]

The back and forth about the mono vs. summed vs. mixed is very confusing, at least to me.  I suspect what was done was to wire it so the output of Channel A goes to the input on Channel B resulting in a cascading gain ala Boogie.  The manual, as I recall, suggests that this can be accomplished by running a patch cable from the Channel A output to the B input.  Looks funky, but accomplishes the same thing.
 
Bill, tgo

[mike1762]

Bill
I never did understand what was done to the unit, but I bet you're right: the output of A must have been hardwired to the input of B.  As you say, the same thing could have been accomplished with a patch cable.  I'm glad I didn't bid on it since I was looking for dual inputs for my Series I.  I'm afraid the new owner may be in for a surprise.

[gtrguy]

My F-2B is wired that way, but it's no big deal. These are just the preamp built off an old Fender design and not too complicated.