F-2B Questions

[hammondd]

I recently bought an F-2B preamp on Ebay and have a few questions;  hopefully this will get to Mica, but I'm interested in anyone's input, of course--
 
Any way to tell the age of the unit?  Its serial number is:  903267.  The face design is the same as what's currently posted on the Alembic site, so I assume it's not too many years old.
 
Is there a preferred brand of tubes to use?  The ones in the unit are unmarked and the previous owner didn't know.
 
Is there a way to get a manual for it?  
 
I'd like to understand more about the dB differences between the two inputs on each channel.  
 
Can you describe how the Main input on the rear is used?  I thought there was a way to use both channels at the same time, but when I plug into the M, only channel B operates.  Is this a problem, or something I'm not doing right?  Both channels work fine, independently.
 
I own 2 Alembic basses, an Essence and an Epic, by the way.  Life if Good!
 
 
Mike

[shellfish]

Hi hammondd,
maybe you find it useful to read http://www.alembic.com/prod/f2b.html first.
Inputs #1, when used alone, give direct access to the grids of the first stage of amplification. This feature is the result of a special design which switches out the series resistance for the #1 jacks, resulting in substantially less noise than comparable designs incorporating series resistance. Inputs #2 provide 6 db pads. Both inputs #1 and #2 on a channel may be used simultaneously, too. In this case both signals are resistively mixed in equal proportions.
Both outputs are on the rear panel, as is a third,  mono, output (no main input!) if you want to use a mono power amplifier.
The tubes are two selected 7025.
 
Kai

[peter_jonas]

Hi Michael,
 
I first saw your post in the Swap Shop section, see my reply there:  
 
http://club.alembic.com/Images/395/14049.html?1100238726
 
It is essentially the same as Kai's but in a somewhat long winded form.
 
Peter Jonas