Discussion in 'Amps and Cabs [BG]' started by barroso, Sep 7, 2000.

  1. barroso


    Aug 16, 2000
    i'm really interested in buying an ampeg portaflex b 15 amplifier, but i have to collect more information. i'd like to know how much is a second hand one and if there are differences between the b 15 portaflex during the years
    i think i'll searh for a second hand one because the new one is really high priced!
    thanks for the attention
  2. There is usually one or two on eBay. They run anywhere from $500 and up. A pretty popular amp. I had just the head from a 70's B15-N, and it had an unbelievable sound. I traded it because I had replaced the power tranny and it didn't have the speaker cabinet with it.

    Here's one that is already sold:

    If you want a similar sound, with more flexibility and power, consider an Ampeg V4-B, 100 Watts tube, or B25B, 50 Watts tube. Then hook them up to the cabinet of your choice and be amazed! I have both of the above amps, and I love them.

  3. snapper


    May 16, 2000

    Here are some web sites you might find useful:

    The Unofficial Ampeg Page


    has information on the history of the Portaflex line of amps. I wish there was more information there, but it does tell you what the different model numbers mean. Also contains links to schematics.

    GGJaguar's Ampeg Page


    contains some pictures and specs of various Ampeg amps.



    mostly sells (high-priced) parts for Ampegs, but they also have a classified page where people sell all kinds of Ampeg stuff.

    Good luck!


    (Note: I have no affiliation with any of the sites linked above; I'm just an Ampeg enthusiast.)
  4. barroso


    Aug 16, 2000
    thanks guys! i've noticed that the new edition of the b15 is 100w and the old one is 30 w. i'm afraid that this is an huge difference. can i play live with the 30 w of an b 15?
  5. The old B15N is probably not enough for gigs. 30W will match up to a small guitar amp and small drums for jamming, but for gigs, you either need more power or a PA to back you up. 100 Watts tube will cover you with a huge cabinet to a small to medium bar. Just my opinion.

  6. This post is six years late...but better late than never. Former Ampeg VP Jess Oliver who designed the original B-15 and still lovingly restores them at his own amp shop recommends a couple of easy modifications to get more sound from the amp. 1- Replace the 5U4 tube with a solid state rectifier, one source is Fliptops.net, cost is $7.75 plus shipping. 2-Pull out the original 8 ohm speaker and replace it with a 4 ohm speaker that has an edgewound voice coil. Your choices on makes of 4 ohm bass speakers are limited but one choice is the Emminence Kappa-C for about $125 available from a few different vendors. Apply both these mods will at least effectively double the apparent loudness of the amp.

    There is an interview with Mr. Oliver discussing these mods here: http://www.keithrosier.com/jess.asp
    In this interview he also explains the difference in some of the models. I found it interesting that the A-15 and B-15 are exactly the same product but with a different model name applied merely to appease accordianists. Brilliant marketing.

    Another option for more volume from this same basic design is to step up to the Ampeg B-18 which outputs 50 watts. It basically is a B-15 on anabolic steroids. Similar mods to the B-18 will also result in a substantial volume increase that might rival a contemporary 100 watt transistor amp such as the Ampeg BA-115. The downsides to the B-18 are that the size of the B-18 is only slightly smaller than a Volkswagen Beetle and that 18 inch 4 ohm speakers are a tough find but still can be had.

    Based on my experience, when you compare power output from tube amps versus solid state amps it is like comparing apples to oranges. 35 tube watts will pound 35 transistor watts into the ground. I don't know why.

    The B-15, B-12 and B-18 amps are all similar designs and yield clear fat tone. Properly maintained they should last nearly forever. The B-15 is suitable for live performance and evidenced in the film "Standing In The Shadows Of Motown" where Bob Babbitt uses a B-15 in the live concert with the full Funk Brothers Band.

    Jess Oliver himself sometimes has a B-15 on eBay for sale that he's restored with his own hands. He usually does the two above mentioned modifications on the amps he sells and will personally autograph the amp for you if you win the auction. He also works on his own Oliver line of amps and other tube makes in his shop too. You can email him at Oliversoundco@aol.com or phone him before 5 PM Eastern time at 516-799-5267 if you need him to work on your amp or if you are in the market to buy.

    You gotta love Jess Oliver. He is a working bass player in the NYC area himself.
  7. 62bass


    Apr 3, 2005
    I've used the B15 live and for recording. Nice sounding amp but very limited in power. I did the solid state power rectifier mod which gave me slightly more clean volume. There's no way I could keep up with a rock band with it unless I ran through the house sound. As a stage monitor it wasn't very loud either. And it was heavy and tough to haul around even with the dolly. Nice amp for playing standards in a dance band though.

    I also used the B18 for a while. it too suffered from too little volume and was a bit muddy with the 18" speaker. And it was even tougher to haul around.

    My biggest use for the B15 was using the head to drive a small, efficient 1-10 cabinet I built and micing it up for recording. Great sound and easy to get a good sound to tape. Engineers liked it.

    I tried the re-issue B15 in a music store. Nice, louder, but way too much to haul around and the price was more than I'd be willing to spend considering the limited use I'd get from it.

    But for recording the old style bass sounds and playing small rooms at very quiet levels the old B15 is a very nice amp.
  8. For a higher output flip-top, don't rule out the B15 S, which is a 60 watt version, with a little larger cab. The only ones I've seen have the very early '70s cosmetics.
  9. I've been low-key about this out of respect to the man, but those are BS mods for power and/or volume. First, ONLY the very first few production B15's used a 5U4 rectifier, which is a pretty pitiful rectifier, especially for bass. It has a large voltage drop which means it's not very efficient. If you replace one with a s/s rectifier, especially in an old amp, you risk blowing a set of filter caps. Later, most B15N's used a 5AR4 rectifier which is better for bass, but the same cautions still apply.

    S/S rectifier replacements ARE a good thing, but only the proper ones like Weber's Copper Cap which has a built-in resistor network to create a similar voltage drop to a tube. The Sovtek plug in rectifier has destroyed MANY amps.

    Similarly, substituing a 4 ohm speaker for the stock 8 ohm speaker results in LESS power, not more. An edgewound voice coil tends to be brighter and thus louder- ie vintage JBL's, but you could do that with ANY more efficient speaker. There is also no advantage with power handling, edgewound coils' strongest attribute, for such a low powered amp as the B15N.

    That's not true at all. There are substantial differences between the B15N and B18, the biggest of which is that the B18 uses a 7199 pentode driver tube, a HUGE departure from the dual-triode 6SL7 of the B15. The B18 also has a larger filter cap bank to supply higher voltage to its outputs, but realistically, it's not that much louder than a B15N and has a significantly different tone.

    Not to diss a fine amp, but Jamerson's B15N is non-functional and was there solely for looks/vibe. Bob Babbit played through a Carvin combo mic'ed up out of sight.

    I have nothing but respect for Jess Oliver, but the mods he recommends do not do what most people believe they do. A s/s rectifier will decrease heat and help the power transformer, which is the most common failure in the B-series amps, just be sure you understand not exceed the filter caps' voltage or you'll see them literally explode. The 4 ohm speaker will also increase longevity in cathode biased B15's (they were made both fixed and cathode biased) as the reduction in power will help the tubes run cooler.

    I have never heard or read about Jess Oliver equating the B18 to the B15 which is a stretch to say the least, so I'll just chalk that up to your overenthusiasm, equally with the "Standing in the Shadows of Motown" comment. I LOVE the B15N, I have one and gave my other to a good friend, but let the amp stand on its real merits without embellishment.
  10. Overenthusiasm PSYCHO BASS GUY? Just what in blazes did you mean by that?

    I'm not the one who has made 1700 posts. NOW just maybe THAT is overenthusiasm!

    So what you are saying is that I am 100% wrong about EVERYTHING and that the man who INVENTED the B-15 and owned his own amp company is 100% wrong too?

    Wow you sure are an expert. Where's YOUR amp company? Where's YOUR classic design?

    You are saying that a 4 ohm speaker is NOT louder at the same power than an 8 ohm speaker? Then why is Ampeg putting 4 ohm speakers in their combos now? Are they cheaper or are they doing it just to spite Psycho Bass Guy?

    I accept some of your criticism of my information as valid because you obviously know a little about tube circuitry. Good for you!

    HOWEVER I agree with Mr. O that the 8 ohm speaker is NOT louder. Because it never has been when I've used 8 ohm cabs vs 4 ohm cabs.

    I NEVER said that JESS OLIVER SAID the B-18 had the same sound as a B15. I gave a link to the Jess Oliver interview and stated the mods he recommends for the B-15 and said that similar mods for the B-18 would yield similar oomph. The B-18 is the heck of an amp based on Mr O's design but NOT designed by him. To me they deliver good thump like a B-15. I did not say JESS OLIVER said that. BROTHER DAVE said that. Did the post say that info was from Mr. O? Nope.

    I never knew that Mr. Jamerson owned an Ampeg. I'm still not sure he did just because YOU said so. I knew that JLJ used the studio's Ampeg but I've never been able to learn of any personally owned amp except for a Kustom stack.

    I use the FLIPTOPS solid state rectifier in three different amps including the B-15 and a B-18. No problems so far with them for me. But YOUR mileage may vary.

    Both amps are good for recording. The B-18 is great for double bass. I've used both amps live in the past but no more as I'm using a SVT-3 and B2RE now. But they CAN be used if miced. The B-15 and B-18 are somewhat anemic in volume but micing them works fine and the tone is awesome.

    I took time out of my day to try to help someone out that might want to extend the usefulness of their B-15/B-18 and what do I get? A smart alec know-it-all.

    This is my last post at this site. I don't have time for this kind of abuse.
  11. Eric Cioe

    Eric Cioe

    Jun 4, 2001
    Missoula, MT
    Your post count is 4, so it doesn't seem like you have too much invested here anyway. Still, I'm sorry to see you go.
  12. Sorry to see you go, ignoramus.:spit: