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Vintage Potaflex amps

Discussion in 'Amps and Cabs [BG]' started by Johntheson, Mar 22, 2013.

  1. Can anyone tell me if the later "rocker" switch type fliptop portaflex amps had the same tone as the early to mid 60's portaflexes? Should I hold out for an early to mid 60's model? I can get an early 70's model in sweet shape now for a decent price, but I've never owned either type fliptop, so I know nothing about them other than the tones I hear on the records they were used on. Thanks.
    John Sr.
  2. beans-on-toast

    beans-on-toast Supporting Member

    Aug 7, 2008
    The amps are very similar both in design and tone. The later amps are fixed bias, the earlier ones are cathode biased. This allows the later models to by 30 watt amps vs 25 watts of the earlies ones. At low levels they are going to sound much the same.

    The big difference is the speaker cabinets. The earliest ones has what was called a double baffle design. Porting was through six oblong ports. The later models had a cabinet based on a Theile specs. This translates into more mids.

    Older or newer revisions all sound great. Just slightly different.
  3. spacebassed


    Jan 31, 2009
    Yep, what Beans said. As long as we're talking about the B15N, a late 60's or 70's B15 with the rocker switches set flat will sound pretty much like a '65-'68 B15N(F) - they are the same basic circuit just with the switches added to match the other amps in Ampeg's line at the time (V4, SVT.etc.). The reason the two amps have a reputation for sounding different is the different cabs. The B15 went through a lot of changes throughout its life (3 different rectifiers, cathode to fixed bias, 3 different cabinets, etc.) so there really is no 'true' B15 - they all are just different shades of the same color. They all sound great.
  4. JimmyM


    Apr 11, 2005
    Apopka, FL
    Endorsing: Ampeg Amps, EMG Pickups
    Word to these guys. Having said that, I had a 70's B-15N at one time but kept the 64 because I dug it better. The guy I sold it to prefers the 70's models, so we're both happy.
  5. mr.gone


    Jan 23, 2011
    Saint Paul, MN
    What's so strange for me as a guy who played in high school bands when equipment like that Portoflex were new is that my association with them is that they all sounded like ****. I played in two bands whose bass players had what now are considered classics -- the Ampeg B15 Portoflex and a guy who bought one of the first Acoustic amps -- a monstrous thing that barely made it into my basement. And of course the reason these things sounded awful was because NEITHER OF THE BASS PLAYERS COULD PLAY. I think back then a lot of the guys who tried to play bass really were just so sucky at everything else that the bass let them kind of hide their lack of skills in the blur of sound. I swear, the guy with the Portaflex absolutely was tone deaf. I'd play an E on my keyboard and he'd hunt around for it on his Gibson EB3. "That's a D, Frank," we'd say. Thump, thump, thump, tune, tune, tune. "Now you're playing an F sharp, Frank." You can imagine why I don't automatically associate an old Ampeg with good sound!
  6. JoeWPgh


    Dec 21, 2012
    A major difference is in the power supply. The early ones had a rectifier tube, the later ones had solid state rectifiers. Tube rectifiers can suffer from sag under a demanding load - such as low frequincies. SS rectifiers can provide more power and more low end. I'm not sure there is a bass amp made today that doesn't use a SS power supply.
    I'm not saying tube rectifiers suck. They can sound very sweet. But in practical terms of a live mix, they'll probably leave you wanting. In a controlled environment, it's a whole other story.
  7. spacebassed


    Jan 31, 2009
    Nope, the only B15N's that use a SS rec are the NA/NB made from mid '63 into '64. Earlier ones use a 5U4 and later ones used a 5AR4.
  8. JimmyM


    Apr 11, 2005
    Apopka, FL
    Endorsing: Ampeg Amps, EMG Pickups
    You can get a solid state rec for it if you want. Me, I'll take the 5ar4. That's how it was designed, that's how it shall stay.
  9. Thanks very much; to all of you. I'm a guitar player of 50 years, who now has almost 3 years as a total bass player. I've been using a 65 showman at home, and one of the newer acoustic amps also. The showman has the D130F so I don't play it loud at all due to the wrong speaker being in it. The Acoustic B200H and 1x15 cab is ok but I'm ready to get an amp I'm going to stick with. I thought about a D or E140 for the showman cab, but I think I'll keep it intact, and just get a nice tube bass amp. I've always been able to "sit in" or "fill the gap" as a bass player; but I never gave the bass role enough credit. I have a slew of vintage 6 string guitars and amps that I have absolutely no interest in playing now. The bass is IT. Thank again.
  10. spacebassed


    Jan 31, 2009
    Just keep in mind that a B15N is only 25/30w - not enough for most people to gig with. Great tone, just not very loud.

    A D130f is NEVER the wrong speaker. :D You'll be fine playing bass through a D130f as long as you don't push it too hard, although a D140f will handle it better. The D130f and D140f are the same motor just a different cone and voice coil. A Showman makes a GREAT bass amp - especially through JBL's. A Showman through two D140f's is an amazing sound! Since you play guitar and bass, I'd look into getting a 2x15" and loading it with 16 ohm D140f's (assuming you have an 8 ohm Showman and not a Dual Showman), then you could use the D130f cab for guitar and the D140f cab for bass. If you're looking for a similar modern cab you might want to look at Greenboy's Dually loaded with Faital Pro 15PR400's.

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