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Bassman (F56A) suggestions

Discussion in 'Shock Brother's DIY Amps' started by Quintin, Jul 22, 2009.

  1. Quintin

    Quintin Tele-Meister

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    I want a bass amp, essentially, but something that could double for guitar would definately not hurt. I'm 90% convinced it's going to be a bassman but I have questions.

    Questions:
    1. I'd like to have one input channel dedicated to bass instead of simply 2 channels that are the same, with their two inputs (Hi and Lo). What changes on the 'bass' channel would make it better for bass? I've read so many suggestions that I feel like I know nothing.:oops:
    2. Still want the 'guitar' channel inputs to do what the bassman and guitars do so well
    3. I like reverb...I'd like to add this on the guitar channel. Does this require a seperate reverb circuit and how do I isolate it for only the 'guitar' channel?
    4. Does something like this already exist? Could you provide a link?
    5. Please tell me why this is a bad idea
    6. Please tell me why this is a good idea

    Thanks in advance
     
  2. FenderLover

    FenderLover Poster Extraordinaire

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    Thats kind of a lot to chew on at once, but I'll give it a try.
    First, you realize that the 5F6A was pretty much a failure as a bass amp. It became the Holy Grail for may guitarist. Fender was having a hard time limiting the bass response to prevent tearing up the speaker with the huge cone excursions that low frequencies produce. That's why they went to multiple 10" speakers (I've read that in a Fender history book I have some where).

    The later Blackface models may be better for your purpose, and frankly, unless you build it yourself there will be compromises. If you want to skip ahead to 6) below, I would not suggest a Bassman as your starting point.

    With that in mind:
    1) Blackface models already have "Bass Instrument" and "Nornal" channels. The Normal channel is gain > EQ > gain > PI. That's about as 'guitar' as you're going to get if you like Blackface amps.
    2) The two inputs are separated as I mentioned, which gives you room to modify them separately too.
    3) You will need a separate reverb circuit for reverb, and it would be just like any other Blackface amp where the reverb is on the 'Vibrato' channel. Look at a Twin, Deluxe, etc. schematic for details. Again, unless you build something, you won't get exactly what you want. For off-the-shelf, you could use a reverb pedal on your intended Guitar side.
    4) Not that I know of. Really, there is no one amp that does everything well, especially being useful for bass AND guitar.
    5) It's not a bad idea to want what you want.
    6) It's a good idea to build exactly what you want. Expanding on 3) above, you could have all of this if you look at a Twin, Showman, or Bandmaster head which are already set up for guitar, then modify their respective 'Normal' channels suitable for bass. I suggest a head because you can pick your poison for speakers.

    Happy hunting!
     
  3. JohnnyCrash

    JohnnyCrash Doctor of Teleocity

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    1st, yes something like this sorta already exists... in a better format to build/mod.

    1. Build yourself a BF Super with some beefy 10"s... really beefy.
    2. Mod the Normal channel's preamp cathode with a 820 ohm cathode resistor and a large value bypass cap (perhaps 100uF-330uF).
    3. Mod the Normal channel's tonestack for more bass (maybe a 1M Bass pot and a 500pF cap instead of 250pF to start? IDK, some tweaking/experimenting will find the best tonal range for bass).

    In stock form the Vibrato channel will only have reverb and it will be perfect for guitars as-is.
     
  4. FenderLover

    FenderLover Poster Extraordinaire

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    The Super is also a good choice. I believe the Twin Reverb and Dual Showman Reverb have bigger output transformers, which is also a leg up. It might depend on the availability of your 'donor model' when you decide to jump in.
     
  5. Tim Swartz

    Tim Swartz Friend of Leo's

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    And they also have 2 more power tubes... so imo, build a Twin Reverb/Dual Showman Reverb sans trem if you don't need it.... And maybe even with 6550s if you really want some umph.
     
  6. Tim Swartz

    Tim Swartz Friend of Leo's

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    Oh, and it does indeed exist in a Fender 100w PA head.
     
  7. Quintin

    Quintin Tele-Meister

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    Really glad I asked!

    :eek: No I didn't. I'd always understood that it was a little under powered for larger venues and just so happened to be very guitar friendly. Thanks for the information.

    Hadn't seriously looked at BF, Twin Reverb or Deluxe...but will now.

    Thanks, that was the input I was looking for.

    Exactly, but I am looking for a happy compromise, i.e. something big for guitar (50 tube watts) which is what I get hired to play most often, and something acceptable to hone my love for bass ;)

    Yep, I think I was heading that direction too...

    I was looking at some Weber 10"s originally, further suggestions welcome.

    I'll be sure to ask once I get a look some schematics.

    Duh! That makes sense. Seems I over complicated my own thinking on this one. Thanks for setting me straight.


    Thanks Tim, I'll look at their schematics. Do you know what the Showman circuit code is? I think I have the Twin Reverb's.

    Thanks again for the information, much appreciated.
     
  8. JohnnyCrash

    JohnnyCrash Doctor of Teleocity

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    Well, I don't know about that :)

    For the time, it was better than most Bass amps for a few simple reasons - the main one being electric fretted basses were brand new technology. Another reason is the lack of power and technical development in amps of the time.

    The original early '50s Bassman (around '52) used a single 15" (Jensen P15N). Now that is much worse as a bass amp than the famous tweed 5F6-A.

    They're still decent as bass amps, but likely not loud enough for most bands onstage these days. As Tim pointed out a Twin or Dual Showman might be a better base for this project, but still not as good as a "real" Bass amp... also Twins and DS's are loud and cleaner for guitars.
     
  9. Quintin

    Quintin Tele-Meister

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    While I'm at it, looking at schematics, any suggestions on bass amp kits? I don't mind making the cab or putting it together, but I don't want to do what JohnnyCrash is doing, making all the pieces from scratch.

    Which BF Super Reverb circuit carries your recommendations?

    Thanks again for the help, much appreciated.
     
  10. JohnnyCrash

    JohnnyCrash Doctor of Teleocity

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    Hmm, a Bass amp kit? I can't think of anyone offering that.

    It'd be cool if someone had an Ampeg 300w tube head kit.

    Actually, depending on your volume needs, you could go the Lemmy Kilmister route and order a 100w Marshall SuperBass kit from Ceriatone. You could also easily modify a normal 100w plexi kit (paralleled preamp cathode to 330uF) - though the filteration on the SuperBass is a bit more (you'll need extra 2x50uF cans).
     
  11. callaway

    callaway Tele-Holic

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    Quintin--- have you built an amp before? It seems like with some of the questions you've asked, maybe you haven't. But this seems awful complicated for a first attempt. In order to get what you want, you'll have to piece together your own circuit from others. As mentioned already, there is not an ideal schematic or kit that already exists for this sort of thing.

    I would suggest building a dedicated guitar amp---perhaps from a kit. Then if you want something for occasional bass duty, you can then either put something together as your next project, or just buy an inexpensive solid-state bass amp for the time being. Since you would ideally want different speaker cabinets for each anyways, you might as well go ahead and do completely separate amps. I really think you'd get the best-sounding results that way. Then you also have a loaner guitar/bass amp depending on which one you are using on a particular day!
     
  12. Quintin

    Quintin Tele-Meister

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    Thanks for the concern callaway; I have built amps before, but ALL solid state kits, and very infrequently... I still have my first 1W amp I built in the 1980's (and it still works :lol:)

    I have built on-board preamps, mods to my amps, etc., yet not always understand the *electronic* reason for doing this fully, but mostly I trusted the judgement/reviews of others and gave it a try. Just trying to learn.

    I am not comfortable with making changes on my own, that is why I was asking for input/guidance or for kit or specific circuit suggestions for the mods on the models previously suggested.

    I'm not trying to reinvent the wheel, and I don't want to simply buy another amp... I prefer to try figure this out or settle for original plan. :oops:

    :(

    That's was how I got to the Bassman 5F6-A in the first place. I might end up going to my original plan...who knows.

    If someone wanted to, could you tell me what the primary differences are between a real bass amp and a guitar amp?
    :cool:
     
  13. Natstrat79

    Natstrat79 Tele-Meister

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    Correct me if I am wrong but from what I've picked up you seem like you are a guitar player who just want's to dabble a little in bass. So this is primarily going to be a guitar amp? I would think that if you were a guitar player who wanted to practice a little bass at lower volumes at home and you weren't a gigging bass player that a 5f6a bassman could work fine as is with the right speaker choice.
     
  14. Quintin

    Quintin Tele-Meister

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    Thanks for the input Natstrat79. I feel kinda bad having asked the questions... to some extent. But first, let me answer your question.

    Close enough. The live rig switched to aviom in ear monitors about a year ago, dbX and JBL's for PA/house amplification, no onstage amps, which works out well live. It's been more than a year since I lugged an amp for a gig. Only pedals, multi-fx, and the Mac :oops:

    Rehearsals, writing and jamming is another thing. Can't hook up the live gear for that. I was looking for something suitable for both purposes. My Jazz Bass V 24 sounds not quite 'wrong' through the guitar amps, just not 'right'.

    The other part of it, the reason I feel a little bad having asked the question. It's like building guitars etc. it comes down to doing something you've always wanted to do.

    I appreciate the help since it's better to see things in the light of the experience of others.

    For example, Mesa-Boogie's first amps were bass amps. Traynor/Yorkville too, and I'm sure there are others. Perhaps this is a gap someone will fill, because it looks like good bass amps make good guitar amps, but not the other way around ;) I just thought perhaps someone had figured that to be the case too.

    Thanks for the help so far guys!
     
  15. JohnnyCrash

    JohnnyCrash Doctor of Teleocity

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    OK, simple - build a 100w plexi kit - use a PPIMV on the back panel (I can walk you through that - just order an extra 250k dual pot and two 2.2Meg resistors).

    Use the Bright channel for guitar and use the Normal channel for Bass. Use the layout with a 330uF cathode bypass cap for the Normal channel.

    Not good enough for a Bass rig live (close for many venues though), but will do great in practice/rehearsals. It'll make an excellent guitar amp (especially with the PPIMV mod).
     
  16. jh45gun

    jh45gun Banned

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    I love the PA 100 I have now it is great for guitar and I suspect it would be great as a bass head too. Takes pedals great also.
     
  17. Quintin

    Quintin Tele-Meister

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    Thanks JC.
     
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