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Thank you Craig's list (B15N content)

Discussion in 'Amps and Cabs [BG]' started by animal52, Oct 19, 2009.


  1. animal52

    animal52

    Jul 1, 2006
    DC area
    The good: Picked up this '68 B15N at a wicked price.

    The bad: It's loaded with KT-77s and an Eminence Big Ben 15''

    The Ugly: I'm using it for GUITAR (and it smokes!)

    But... I'd like to use it for bass too. Even with KT-77s, I think it'll sound good, but caution tells me I should use a bass cab. So my question is this: what's the easiest way to hook up an 8 ohm 110 bass cabinet? At this point I figure I could get the 3-prong to 1/4'' adapter, but would there be a way to use the 1/4'' Ext. speaker on the back (perhaps just leave the primary speaker cable unplugged?) As usual, thanks for all the help.
     
  2. animal52

    animal52

    Jul 1, 2006
    DC area
    :bassist:
     
  3. gruda

    gruda

    Aug 19, 2009
    how much did u pay?
     
  4. silen7ce

    silen7ce

    Dec 11, 2006
    curious as well!
     
  5. gruda

    gruda

    Aug 19, 2009
    WELL IM DOUBLE CURIOUS!!
     
  6. Make that a Triple :confused::hyper:
     
  7. animal52

    animal52

    Jul 1, 2006
    DC area
    $660, with a Jensen replacement speaker thrown in for good measure.
     
  8. JimmyM

    JimmyM Supporting Member

    Apr 11, 2005
    Apopka, FL
    Endorsing: Ampeg Amps, EMG Pickups
    Get a 4-pin to 1/4" adapter from www.fliptops.net . Also, the earliest B-15's of that era used CTS 15"s and Altec 418B's as the speakers. Eventually they went to the Altec 421a as the upgrade speaker, though.

    Also, I'm not an expert, but I just did a web search and it said that there's only one wire you need to swap around for the tube socket to go back to 6L6's. Shouldn't be hard to do.
     
  9. animal52

    animal52

    Jul 1, 2006
    DC area
    Thanks Jimmy, I figured you'd find this thread sooner rather than later :) I do plan on eventually doing the full conversion back to a bass amp, unless of course I manage to get another Portaflex and use that for bass. This one sounds great for guitar.
     
  10. Ten Four One

    Ten Four One

    Dec 5, 2006
    That's a good price. I've been checking ebay (since I'm looking to sell my B15N) and the going price seems to be around a grand.... half what I paid for mine 10 years ago... looks like I'll hold on to mine for a while, until the economy recovers or I find someone who wants to deal with a person rather than ebay.

    Enjoy it - it's a killer amp.
     
  11. JimmyM

    JimmyM Supporting Member

    Apr 11, 2005
    Apopka, FL
    Endorsing: Ampeg Amps, EMG Pickups
    They sound great for guitar even with 6L6's. Look on Youtube for Jimi Hendrix on Dick Cavett. He's using a B-15N straight in. Sounds just like himself.
     
  12. Jim C

    Jim C Is that what you meant to play or is this jazz? Supporting Member

    Nov 29, 2008
    Bethesda, MD
    I remember using one with an SG with P90's as a teen and it killed WFO
     
  13. B String

    B String Supporting Member

    Apr 11, 2002
    Los Angeles
    That era B15-n was my first real amp. I upgraded with a JBL
    D140-F. I loved that amp. Played electric and upright with it.
     
  14. animal52

    animal52

    Jul 1, 2006
    DC area
    So does "8 ohm" by the Ext. speaker jack mean to connect an 8 ohm extension cabinet, or does it mean that the amp is running at 8 ohms with the extension cab plugged in? I found this in an older thread:

    "No, the main out is 8 ohms, and the extension speaker jack is 8 ohms wired in series with it. The extension out, if used by itself, is 16 ohms."

    What I gather from this is that I could order the adapter from fliptops, and run the main speaker out to an 8 ohm cab no problem. I'm confused by the second part though. Were I to connect another 8 ohm cab to the extension, things would still be fine for the amp? Wouldn't such a setup give me a 4 ohm total load (or 16 ohm depending on the internal wiring)?
     
  15. The output transformer has an 8Ω tap and a 16Ω tap. If you look closely at the external speaker jack you'll see that it's insulated from the chassis. When you use the internal speaker the amp runs at 8Ω. If you then connect an external speaker, which should also be 8Ω, a switch on the jack changes to the 16Ω tap and the external speaker is run in series with the internal one. You can't run at 16Ω unless you short out the internal speaker. That four pin XLR also completes the ground circuit for the power supply. This effectively puts the amp in standby with out the Ampeg cabinet connected.

    Paul
     
  16. Another point that tube rollers often overlook is heater current. The 6L6GC draws 0.9A while the KT77 pulls 1.5A. That means the power transformer is supplying 3A when it was designed for 1.8A (ignoring non output stage tubes). This is sressing the power transformer over its limits and WILL lead to earlier failure. You should get back to 6L6GCs ASAP.

    Paul
     
  17. johnk_10

    johnk_10 vintage bass nut Supporting Member Commercial User

    Feb 16, 2008
    Thousand Oaks, CA
    John K Custom Basses
    +1!

    and as Jimmy said, they sound great for guitar with 6L6's.
     
  18. animal52

    animal52

    Jul 1, 2006
    DC area
    That's some clever engineering, good to know.
     
  19. animal52

    animal52

    Jul 1, 2006
    DC area
    #@$%, Looks like this one will be in to the tech to get those tubes swapped mucho pronto.

    Seriously though, what an awesome little amp that it rocks for guitar or bass just by swapping cabs.

    It surprises me that no-one makes a dual-duty amp like this anymore. Could one reason be that the industry can make more money selling us two amps instead of one?
     

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