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Alembic F-2B + Markbass F1

Discussion in 'Amps and Cabs [BG]' started by eutgard, Apr 1, 2009.

  1. Can I use Alembic F-2B + Markbass F1 combination safely?

    Output voltage of F-2B is above 300Vpp, and max input of F1 is only 15Vpp.
  2. Bass Collector

    Bass Collector

    Aug 14, 2008
    Plug the output of the Alembic pre-amp into the FX loop return on the F1 and you should have no probs.
  3. Max input voltage of F1's FX return is 25Vpp...

    Will it be safe?

    And according to manual, Gain of F1 only affects instrument input.

  4. Bass Collector

    Bass Collector

    Aug 14, 2008
    Not sure of the tech stuff, but, I ran an Aguilar DB680 in to the FX loop return on a Mark Bass LMII for over a year and had no problems? sounded great!


    As far as "safe" is concerned, your ears are always the best judge, if you hear any distortion etc. stop doing it? my opinion is that it should be fine.

    I also ran it into my Eden WT800 FX loop return for a while too with no problems whatsoever?


    All the best!
  5. Thank you for sharing valuable experience :hyper:

    DIY FX site in my country has plan to builld single channel Alembic F-2B replica.

    A lot of members are worried about whether too much ouput voltage from tube preamp will damage their non-tube bass amp.

    Anyway, thank you again!
  6. Bass Collector

    Bass Collector

    Aug 14, 2008
    No probs man, I can only talk from MY experience and from a practical point of view, ie. doing it, both these rigs worked great.

    There no reason when using an Alembic or any XYZ external pre-amp would've been any different in my set-up's?

  7. bongomania

    bongomania Gold Supporting Member Commercial User

    Oct 17, 2005
    PDX, OR
    owner, OVNIFX and OVNILabs
    The output voltage of the preamp cannot damage any amp. The actual voltages you are talking about here are millivolts, not whole volts. 300mV p-p, 25mV p-p, etc. If the output of the preamp really was 300V then yes, maybe you'd damage something; but it's not. It's strange though, I would have expected the output of the F2B to be closer to 700 mV.

    The easy and no-problem solution to the higher output level of the preamp is to turn down the output level knob. :)
  8. murphy


    May 5, 2004
    Toronto, Canada
    I used to run my F2b into the loop of my SA450.
    Thought it sounded good at the time.
    Now I think it sounds better without!
  9. gerryjazzman


    Dec 31, 2006
    New Jersey
    Well, looking at the circuit for the F2-B, it IS possible to produce a reasonably large transient output that is a significant fraction of the power supply voltage when it is first turned on. Once the output coupling cap is charged it would settle down. However, depending upon the impedance of the input to a power amp, if it is appreciatively lower than about 90Kohms (approximate output impedance of the F2-B, i.e. 100k plate load in parallel with the 1 Meg to ground), that would attenuate amplitude of the transient. Hard to say exactly without taking some measurements. I would expect however that a lot have people have used this preamp with a solid state power amp with no problems.

    That said, if I were building a clone of one of these or something similar I'd probably add a pair of back to back series-connected zener diodes (maybe 15 - 20 volt) across the output to clamp any transients to be safe. I might even modify an original one just because I'm a bit of a worry wort.
  10. Buster666


    Nov 29, 2008
    How is that different from a Fender Twin Reverb?
  11. It will be called Alecbim :smug:

  12. murphy


    May 5, 2004
    Toronto, Canada
    My preferred rig at the moment is my F2b running into my SWR stereo 800.
    Incredible fat warm and punchy sound.
  13. Buster666


    Nov 29, 2008
    With my present setup: P-Bass w/Bartolinis + GT/SWR pre + 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
  14. Instead of crearting another thread...

    Here is a new idea for single channel F-2B clone/mod.

    Adding small opamp buffer to the output of F-2B clone - will it be a good idea?

    The opamp buffer will use single JRC4558.

    By lowering output impedance of F-2B clone, I hope I can seat the F-2B clone on pedalboard with long cable to bass amp.
  15. gerryjazzman


    Dec 31, 2006
    New Jersey
    You could do that. Actually the original circuit does have quite a high impedance output. A buffer would be a good idea if you're going to run long cables. Another idea is to just use a high voltage mosfet follower direct coupled to the 12AX7 like this:


    It'll save you from having to create a separate supply for the op amp.
  16. First application: Source Follower to replace Cathode Follower.

  17. gerryjazzman


    Dec 31, 2006
    New Jersey

    Edit: I would probably use a heftier device than he suggests, probably something in a TO-220 package like an IRF820 or similar. Make sure it's rated for at least 500 volts for a good safety margin.

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