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"new" SB-12 ?

Discussion in 'Amps [BG]' started by lexington125, Sep 29, 2013.

  1. lexington125

    lexington125

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    While my ’65 SB-12 gets my vote for the best sounding amp in the world, they certainly have their little ‘quirks’. The ‘speaker cable through the head latch’ almost seems like they were playing a joke on all of us. There are at least 3 or 4 basic features that I would change if I ever got hold of a semi-thrashed SB-12 and was going to have it restored into a great player, not show piece. The wacky speaker cable would be replaced by a normal speaker output jack on the rear chassis and an input jack on the speaker cabinet. Not sure if the amp is configured to also drive a 4 ohm load, but a second speaker out that would allow for a second speaker (an outboard 1-12 cab) is another wish list item. A proper grounded AC power cord would be an improvement, and if we are going to modify the cord, I always prefer a standard (removeable) IEC power cord. A stand-by switch would be nice.

    A lot of folks will disagree with me, but I believe that amps like mine, that are dead stock, should be restored, not modified. Obviously, its up to the owner, but I wouldn’t make those changes to my amp; I’d like to find a heavily used SB-12 (for cheap) and use that as the starting point for an “improved” SB-12. But inexpensive, used flip tops are mostly all uncovered by now; there are no longer thousands sitting in attics and closets waiting for that final garage sale. So I was wondering how difficult it would be for someone with the appropriate skills to assemble a new SB-12 from all the parts available from Vintage Blue, Fliptops and other Ampeg parts suppliers?

    The good news is that this ‘player’ would not have to be an actual flip-top. A separate head chassis and single 12 cab would work fine; I’m after the sound of an SB-12; not the one of a kind head/cab configuration. The speaker cab is already an available product from the Fliptop and Vintage Blue folks. So I’m asking if the SB-12 amp head could be built from components available in 2013? Would it be a straight forward assembly (for someone who knew what they were doing?) In other words, would it be practical? There are countless remakes of more popular amp designs; I’m hoping that once you move past the head/cabinet configuration, building a new SB-12 amp head would be a realistic undertaking? Or not?
  2. JimmyM

    JimmyM Supporting Member

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    It could be built with parts available today. The questions are can it be built cost-effectively, how close to the original look do you want to get, things like that. Cost effectiveness probably isn't there, but if you know how to build amps, it's not a very complicated schematic you have to follow.
  3. beans-on-toast

    beans-on-toast

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    Yes, it can be done.

    There are a lot of options. Check out www.hoffmanamps.com for instructions on how to build a turret board. They offer a good supply of parts. Or buy one from www.turretboards.com. Look at the chassis available at www.tedweber.com. You could adapt a chrome Fender one. Or you can buy an aluminum box made by hammond (www.hammondmfg.com) and build one from scratch. Other sources include www.tubesandmore.com and www.mojotone.com. There is also a good builder community at www.ax84.com.

    The easiest option would be to be patient and find a junker SB-12 on ebay and restore it or rebuild it to your specifications. The later SB-12's had the speaker cable on a ¼" jack, not built into the lid. The three-conductor power cord can be done in a reversible way. Look for a 70's SB-12 and you'll have most of what you want except for the IEC power connector.
  4. beans-on-toast

    beans-on-toast

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    I would experiment with your SB-12. Try carefully trying the head with some alligator clip leads to another cab. Is the tone that you like just coming from the head or is the cab a big part of the equation. If you could just build a head and use it with another cab, it would safe on the cost.

    A lot of people like the SB-12 over the B-15 for example because of the specific tone of the 112 cab. So a 112 might be the way to go. It would be fairly easy to reproduce the cab without the lid on the top where the amp flips into. You could also build a dummy lid with a jack in to for your cab and use the vintage cab with a newly built stand alone head.
  5. nysbob

    nysbob

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    When it comes to recording, the SB12 is unbeatable IMO. I got mine ('64?) in the early '90s and the speaker jack mod and 3 prong plug had already been done somewhere along the line. I've got an EV instead of the stock speaker too, but that to me is an improvement as well. The old cable tie downs to the latches are still in the box...but I don't think any of these things significantly change the character or diminish the amp in any way. They just make it useable.
  6. jnewmark

    jnewmark Supporting Member

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    How much lighter is a stock SB-12 as compared with a stock B-15N ?
  7. nysbob

    nysbob

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    I never weighed mine, but I'd guess at about 50lbs. I'm sure the EV is a bit heavier than the stock driver.
  8. Standalone

    Standalone

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    I have an SB-12 with this mod. And the nicks and scuffs that make it a "play it and don't worry about it" amp. The mod also makes it possible to hear the head through other cabs, which I've experimented with a little. An inexpensive simple lower-wattage tube bass head would be great to see on the market.
  9. beans-on-toast

    beans-on-toast

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    According to the 65 literature, the stock B-12N weighed in at 49 lbs net, the optional JBL added 5 lbs extra. This is a B15 with a different cab design and it had a 12 inch speaker. The B15N was 66 pounds stock with 7 additional lbs for the optional JBL. The B18 was 85 lbs.

    The 70's SB-12 shipping weight listed as 67 lbs. This would put the net weight at around 60 lbs. The earlier 65 era SB-12 models were lighter. About 48 lbs with the CTS. Like Bob said, the weight will vary with the speaker.

    The SB was marketed as a String Bass amp with a tighter sound than the B-15N.
  10. beans-on-toast

    beans-on-toast

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    Drilling a hole in an SB-12 for a speaker jack can be considered heresy. The revision of the amp that followed the one with the speaker connections in the two side clamps did have the jack on the chassis. So I don't think that installing one is a big deal since some models came that way.

    Some people have problems with their amps with the clamps. If the speaker connection contacts get dirty, it affects the sound of the amp.
  11. JimmyM

    JimmyM Supporting Member

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    Have to admit it wasn't Jess' shining moment, that latch/speaker connection, but I'd never change it if it hadn't been changed already.
  12. beans-on-toast

    beans-on-toast

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    If was also a student model which means that they did things to reduce production cost so that it could be offered at a lower price. It was a single channel amp. They used two latches instead of four. They integrated the speaker cable connector into the latch to save money on the cost of a connector. The earliest model had the chassis mounted directly onto the lid rather than use a chassis try like they did with the B-15. The cab was a single baffle design. All contributed to a lower price. Better to skim there than on the electronics.

    I wouldn't blame the designer. The designer was tasked on saving money in the design. They did what they were asked to do. It is rare that a designer is given carte blanche in terms of specifications, quality, and cost. Shows you how things haven't changed.
  13. JimmyM

    JimmyM Supporting Member

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    Ya, Jess was never once given carte blanche at Ampeg...good point.
  14. jnewmark

    jnewmark Supporting Member

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    What was the " optional " JBL 12 " ?
  15. beans-on-toast

    beans-on-toast

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    For the B-15NL the JBL upgrade was a D130F. The earliest SB-12 came with a Jensen C12N. Good for bass and guitar I suppose.

    They don't say which 12" JBL was used other than it was a premium upgrade. Maybe a D120F ?

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