Ampeg Portaflex SB12

Keith Cordell · Post by **Keith Cordell** » 21 Feb 2008 1:27 pm

I picked this up awhile back and am pretty floored by it; great amp! Does anyone have experience with them in terms of adding clean headroom with tube changes, or any issues I should look for?

Ken Fox · Post by **Ken Fox** » 21 Feb 2008 1:48 pm

Just did an electronic resurrection of one a few months back. Be certain those latches are tight! That is the connection to the speaker. No connection to the speaker can result in a blown output transformer.

Makes a great guitar amp for sure. Lots of tone!

Parts can be had at Fliptops Amps, on the web.

Steve Alcott · Post by **Steve Alcott** » 21 Feb 2008 2:01 pm

I don't recommend messing with these amps to get more output; be happy with the tone and use it for recording. Just get the best tubes available and as Ken said, keep the latches tight.

Jon Light · Post by **Jon Light** » 21 Feb 2008 2:16 pm

Thanks a lot. Break my heart. This was my amp with my Farfisa mini compact that I got with bar mitzvah money in '66. I was not a gear head at all---probably couldn't have told you whether or not it had tubes. I must have run it without the latches fastened a hundred times. No, I'm not suggesting that it's ok---just that god looks out for fools.
Sold it to a music store in '76 for $40 because I needed to pay the rent.
Can I have yours?

Keith Cordell · Post by **Keith Cordell** » 21 Feb 2008 2:45 pm

No, Jon.

Steve Alonzo Walker · Post by **Steve Alonzo Walker** » 21 Feb 2008 3:43 pm

My Father bought a B-15 from a dealer at a music store over 40 years ago and I am still using it to play Bass through. It even has some of the original tubes! You know the old saying, "if it ain't broke, don't fix it!" I did replace the original speaker with a 15" Altec 421A. I have four quality bass amps to choose from, but I still take my Ampeg every now and then. Enjoy it!

Keith Cordell · Post by **Keith Cordell** » 22 Feb 2008 8:07 am

It has 12AX7's in it for the preamp and the elusive and rare 7868's for power; I thought about using a 12AU7 in the first position to cut drive at the top end, but maybe not? The power tubes will be a concern, but I'll find an extra pair at some point and just put them away for later. It sounds great as it is, except for the early overdrive; I can live with that, though.

Post by **Dave Mudgett** » 22 Feb 2008 6:13 pm

Great amps - I've owned a few. I actually think I prefer the SB-12 to the B-15 for most things. I know a guy who has one - one of these days I'll talk him out of it. One of the best amps I've ever heard for jazz guitar - blues too. No bells and whistles, just great tone.

IMO - just get it gone over by someone who knows what they're doing, make sure the filter caps are fresh, and perhaps try a high-efficiency, high-headroom speaker in it, storing the original away. Gotta make sure the chassis will fit in there with the speaker, though. But I wouldn't try to mod this amp with a different power supply, power tubes, etc. I suppose you could try a 5751 or 12AY7 - that would cut the gain a bit. I think 12AU7 would be a bit too low-gain, to my tastes, but YMMV. Simple enough to check out different preamp tubes.

As everyone says, definitely make sure the latches are tight. I watched a guy fry his output transformer by being careless.

Keith Cordell · Post by **Keith Cordell** » 22 Feb 2008 6:28 pm

I already pulled the speaker and stored it in a 2X12 cab that isn't being used. I put a gold Jensen alnico speaker in it and it is about perfect; I am thinking about trying a BW1201 in it to see how that sounds but I like the organic tone of the Jensen. The original speaker is a little spongy and might be fried a little. I put a long plate 12AX7 from a '40's console radio in it and that brought the volume at the top end up a bit, and made the overdrive a bit smoother. I am leaving the power tubes until they need replacing. It will be a bit before I get it in to a tech, but I set the latches so they can't lose contact. I am pretty much bonded to it at this point.

Bill Hatcher · Post by **Bill Hatcher** » 22 Feb 2008 6:32 pm

Used one of these to record many sessions with at the Mastersound studio downtown Atlanta. Nice sounding amp for low volume bass or guitar.

Steve Alonzo Walker · Post by **Steve Alonzo Walker** » 23 Feb 2008 4:53 am

Used my B-15 last night in a big club with no mike and it sounded great and the Volume was at half-way. What a great amp!

Jon Light · Post by **Jon Light** » 23 Feb 2008 5:05 am

I trusted a studio owner when he informed me that he was proud of his great stable of amps including bf/sf Fenders, etc--and I wouldn't need to bring anything to a recording session. Well, the Twin was out on the road, the Pro Reverb sounded lack crap, the Bassman broke up above 3 for some reason and the Magnatone collection that he was the most proud of were great guitar amps, poor PSG rigs. I finally stopped him from carting out yet another inappropriate amp and pointed to the B-15 and asked "does that work?"
It sure did. Holy Grail, B-15, fantastic sound and salvaged session.
Pretty different animal from the SB-12, though. Are the two amps similar, circuit-wise, beyond the power differences?

Keith Cordell · Post by **Keith Cordell** » 23 Feb 2008 4:37 pm

B15's and SB12's are quite different. The SB12 should never have been marketed as a bass amp, but it is a fine guitar amp with a lovely tone. The B15 is a GREAT steel and bass amp, IMO, and works well as a guitar amp if you are pushing it with a preamp. I love the bass sound from a B15 almost as much as any other bass amp I've ever heard.

Ben Lowengard · Post by **Ben Lowengard** » 16 Mar 2008 10:34 am

I have a B-15 XY which is like a B-15 and a B-12 crossbred, Jess Oliver
(who designed these things) told me once that it's kind of a custom amp,
and indeed, a 15 inch + HF speaker and Dimension Reverb (not to mention
space age tremelo) it is kind of an oddball in that it's a real clean tube amp
(until about 3 O'clock) but it is wonderful with a hollowbody guitar. I don't play my steel through it- Im using a Peavey Companion which is great and runs on batteries.

Keith Cordell · Post by **Keith Cordell** » 16 Mar 2008 12:52 pm

I sold this locally through craigslist, by the way. The buyer was quite pleased!

Boo Bernstein · Post by **Boo Bernstein** » 17 Mar 2008 4:41 pm

Hey, Jon Light --

My brother got a B-15 and a Farfisa for HIS Bar Mitzvah too! LOL. He still owns them both -- although the bottom cabinet and the speaker are long gone. I used to love to play guitar through that amp.

Funny story: the B-15 is designed so that when it's turned on, the plexiglass name plate that says "Ampeg" glows. Ampeg offered a custom feature where they would engrave your name on that plexiglass so it would also light up. My brother bought the amp used from someone named "Tony" -- which had the custom feature. Everytime you turned the amp on, Tony would glow brightly. When I first got to Los Angeles in the early 80s, I played a lot of gigs with Buffalo Bruce Barlow from Commander Cody's band. He always used a B-15 for club gigs. I told him the story about my brother's amp and to this day, he still refers to his B-15 as his "Tony amp." Still makes me smile!

Boo

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Ampeg Portaflex SB12

Ampeg Portaflex SB12

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