Ampeg SB-12 Portaflex

emblymouse · #1 03-07-2011, 11:04 AM

For sale is this sweetheart of a vintage amp, I believe this is a '66. It's just back from the shop for a checkup where a bias pot and fuse holder were replaced, and a new rectifier tube put in. When I got it from stingray56funk last year it had a Celestion Vintage 30 speaker which I switched out for a neo Celestion bass speaker. That plus the biasing makes the most of it's 25 watts. It has it's limits, but damn it sounds nice with my old Jazz! I also tracked down a new plexi nameplate for it!
The tubes are:
2 Amperex 7868
1 12AX7 Russian Mesa
1 12AX7 Fender USA
1 G234S JJ rectifier

There are lots of pics to see, I think they will tell the rest of the story. http://s438.photobucket.com/albums/q...mblyouse/sb12/

$675 and I'll split shipping with you. PayPal or money order OK. I have this up locally too, guitar players love these. Questions cheerfully answered.

emblymouse · #2 03-08-2011, 07:37 AM

Bump'm

fenderhutz · #3 03-08-2011, 07:40 AM

Where are the Uplands?

emblymouse · #4 03-08-2011, 07:54 AM

These uplands are in Wisconsin. I've gotten that question before so I better change my location in my sig. Sorry!

bassdoubler · #5 03-08-2011, 11:12 AM

What's the deal with the cab? Definitely doesn't look like an SB-12....way too small....and the whole point of the SB-12 was that it connected to the speaker by clicking the latches down, not plugging it in in the back....the amp part is definitely an SB-12 but I'm very curious to know more about the cab....

emblymouse · #6 03-08-2011, 11:43 AM

The old label inside the cab says Model No SB-12-N C.

This is the only one I've ever seen in the flesh so I don't have a reference for size. I do know that every other one I've seen in photos has the speaker off to one side with only one baffle. The condition looks the same on both the head and cab. If they weren't born together, the marriage happened a long long time ago.
Also, there is a factory speaker jack in back of the amp, and it has a side mounted speaker jack on the cab. Would those be there if there was supposed to be a latch contact?

Any Flipsters want to chime in?

bassdoubler · #7 03-08-2011, 12:20 PM

oh got it it's an NC....different cab than the original SB-12 design but it is original! Does it also connect to the speaker by the clamps?

emblymouse · #8 03-08-2011, 01:03 PM

No contacts for the clamps/latches and no evidence there ever were any. 1/4" out of the head and a 1/4" side mounted speaker jack.
The thingie on the back of the cab is not a jack. My best guess is it is a fixture for some kind of tilt back rod. There is a clamp at the bottom of the cab that may have held it when not in use. This is my best guess.
I feel like I'm on Antiques Roadshow.

dave88 · #9 03-08-2011, 02:10 PM

Yes, tilt rod, exactly.

bassdoubler · #10 03-08-2011, 02:47 PM

oh got it....so it plugs in on the side like a B-15 does....I used to own a '64 SB-12 and it's a taller box and the head connects to the speaker by locking the clamps over the screws....I wonder how the tone compares....

emblymouse · #11 03-08-2011, 04:03 PM

OK,for 10 points...what's N C stand for?

bassdoubler · #12 03-08-2011, 04:54 PM

supposedly the C in NC refers to the "column" design cab that they used....I could be wrong but that's the deal with the B-15NC and B-215NC

emblymouse · #13 03-11-2011, 03:31 PM

emblymouse · #14 03-14-2011, 06:14 PM

Hello

John D · #15 03-14-2011, 06:29 PM

Looks like an SB-12 with a B-12NC cabinet.

FS: Ampeg SB-12 Portaflex (1966) with B-12NC cabinet.

emblymouse · #16 03-14-2011, 06:35 PM

Yessir, that is the fella right there. So what does the NC designation stand for? Would this have been special ordered?

John D · #17 03-14-2011, 07:12 PM

I can't find any reference to the B-12NC in the "Ampeg - The Story Behind the Sound" book. You may want to post the question on the Portaflex Club thread. Beans-on-Toast and JimmyM are the resident experts on Portaflex amps. They will probably pop in here soon.

Edit: I think the C in NC simply refers to an amp revision level; perhaps cathode bias or solid state rectfier.

John D · #18 03-14-2011, 07:38 PM

OK, here we go. On page 67, the Ampeg book states that, "This amps (B-12N) circuit was identical to the B-15N, but with a 12" speaker..."

Then, "Toward the end of 1964, the B-15NB regained its rectifier tube and appropriate power transformer with 5-volt filament winding to become the B-15NC (not to be confused with the 2x15 B-15NC of 1967-68).

Therefore, one could infer that the B-12NC had the same circuit revisions as the B-15NC, although the book does not specifically say so.

I hope this helps.

**ddbassGA** · #19 03-14-2011, 09:11 PM

Different tube combination. I'm sitting here with my '66 B-15NC and it has :
(2) 6L6
(3) 6SL7
5AR4 rectifier

John D · #20 03-15-2011, 04:52 AM

The OP's head is an SB-12, which is a totally different animal. The OP is asking about the speaker cabinet, I’m fairly sure he has a couple of orphans that came together some time ago. Still, it should be a very good sounding amp.