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Is there a way to fit a bassman or at best a 5f4 into a more narrow chassis?

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  • #1

    Is there a way to fit a bassman or at best a 5f4 into a more narrow chassis?

    I had a plan a while back to put a Bassman (or Super 5f4) into a tall and narrow cab with 3 10" speakers kinda stacked or staggered on top of each other. I figure it would be easier to reach the knobs (yeah yeah...not that its hard to bend over) , but mostly save width space on stage.
    I emailed a few of the boutique tweed guys and they all seem to insinuate that I'm wasting my time tyring to make this project a reality.
    I'm not a tech, and was hoping that opposed to other forums , youz guyz would be the ones to know if its possible.
    My plan was to cut some corners, such as a single iinput jack (but internally jumpered)
    Eliminate the ground and maybe use a 3 way on/standby/off switch.
    These few changes would take some length off the chassis. But i cant even find a custom blank chassis out there. Just a couple cheap looking ones on ebay.

    Ultimately I'd like to get it all in a 18" length cab instead of 23".

    Prob not possible...?

    Maybe a longer top-bottom length chassis? With a couple relocated EQ knobs?

    Any suggestions?
    Thanx
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  • #2
    Have you thought of splitting the chassis into two sections, one chassis for the preamp and a separate one for the power amp? Should be easy enough to do.

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    • #3
      Sure you can make a narrower amp with a 5f6a or a 5f4 circuit, schematically speaking. It'll be a different amp. Not radically but layout has an affect on the performance. Since more vertical space availability doesn't help much with respect to reducing horizontal requirements what your asking to do means basically cramming everything more tightly together. I think you'll definitely need to rework the layout for stability. Custom chassis off ebay won't help much. What your looking at in a total redesign and one off fabrication effort. I've built several amps like that, but I never asked anyone to cover all my hours on the project either. The time it takes to design and build this way is probably why your getting the run around from builders.
      "Take two placebos, works twice as well." Enzo

      "Now get off my lawn with your silicooties and boom-chucka speakers and computers masquerading as amplifiers" Justin Thomas

      "If you're not interested in opinions and the experience of others, why even start a thread?
      You can't just expect consent." Helmholtz

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      • #4
        You'll have to give serious thought as to how you will be mounting filter caps etc, you'll probably need to dispense with the original style eyelet board/layout & wire many of the parts point to point, e.g. tone caps mounted directly on pots. Yes, fitting it all in an 18" chassis is just about feasible, going for a BF/SF style chassis over the tweed style will make life a little easier.

        The 5E7 chassis is 18 1/2", go with the Weber 5E7M version, hardwire the Presence control, or maybe fit it in the leftmost speaker jack hole? You'll need to use a "dog house" cap pan on the rear of the chassis.

        I have built the circuit into a 17.7" (450mm) BF/SF style chassis, which is about as small as I'd like to go & not easy to make it look pretty.

        Possible, but not really adviseable for a novice builder. If you go ahead, post a few mock ups and ask for feedback.

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        • #5
          I've built a few amps like this, my all time record is a 50w 2 channel amp with spring reverb, in a 5E3 cabinet.

          The first thing to do is lose the tube rectifier. Saves space, and makes cooling easier.
          Then, use miniature pots.
          Modern filter caps, in fact modern components in general, are much smaller than vintage correct ones.

          However, it will be harder to service, and it's a one-off job that requires a new layout. Mine has a double decker chassis with two floors of stuff. The top floor has the preamp components on it and unscrews/unplugs along with the front panel to allow getting at the stuff underneath.
          "Enzo, I see that you replied parasitic oscillations. Is that a hypothesis? Or is that your amazing metal band I should check out?"

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          • #6
            Losing the cathode follower stage frees up space too...& makes the 5E3 sized chassis a much more viable option.

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            • #7
              +++ to above. Since the 5f6a and 5f4 are pretty basic amps without reverb I don't think you'll need to go double layer as Steve did. I'm entirely confident that I could wire either circuit (using a diode rectifier) into a 16" chassis with no stability or cooling issues. If you must have the rectifier type sag for authenticity in feel/tone you can use a big chassis mount resistor in the power supply instead of a rectifier tube.
              "Take two placebos, works twice as well." Enzo

              "Now get off my lawn with your silicooties and boom-chucka speakers and computers masquerading as amplifiers" Justin Thomas

              "If you're not interested in opinions and the experience of others, why even start a thread?
              You can't just expect consent." Helmholtz

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              • #8
                What is the length on the 5c5 Weber sells?

                I've never seen this chassis...?

                It seems to be between a Deluxe and a Super.

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                • #9
                  My vote is to make it a slant cab where only the top speaker is angled. Doing the circuit point-to-point would free up a lot of space.

                  - Scott

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                  • #10
                    I built a 5F4 on a 16" chassis for a head. You could buid it upside down for a combo. Here's a flat layout for the chassis.
                    Attached Files

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