Ampeg SB-12 Portaflex

I'm the original owner of this little amp, which I bought as a teen in 1966 so I could join a band in high school as the bass player. I used it for a few years, then bought a bigger transister amp (Acoustic) for playing out. I sold the Acoustic but have kept the Ampeg. Right now I mostly record in my home studio as a hobby, and occassionally jam with friends. This has basic features: on/off, volume, bass, treble. Two inputs, but I honestly can't hear the difference between them. I pulled this out of storage after sitting there for 20 years, turned it on, and it's off to the races.

It's got enough power for me at 25 watts.

I rated it 10 on features because it has exactly the features I want: amplification and a speaker. If you front it with the efx of your choice, you can get the sound of your choice.

I play guitar mostly now, using a Line6 Pod X3 Live in front of the Ampeg. The guitars are a ES225, LP and a Strat American Deluxe. I also have a recent Fender MIM Jazz Bass, and the Vox Cougar Bass I bought the same time as the Ampeg.

The amp's sound is clean and full, exactly what you want. I love it with the Pod, as it provides the natural amplification you want but leaves all the effects to the Pod. It's very quiet until you turn the volume up, then there's a bit of hiss. Around 8 it starts to break up, I can't tell if it's the amp or the speaker.

When I pulled it from storage after 20 years, it started crackling after it was on for about 20-30 minutes. An Ampeg authorized dealer cleaned all the contacts and tube sockets, fixed the 'luggage clips' which hold the amp head on the speaker cab and also form the circuit for the signal, and replaced a $0.30 resister (yes, that's what the part cost. Labor was another $120). Other than that, it's never been inside a shop in 42 years.

I love this amp, both because of it's simplicity and it's sound, and also because of the sentimental value of having a vintage amp which I actually bought new (I guess I'm vintage also). I don't know if I would buy another if it were stolen, as it wouldn't be 'mine', but I would replace it with another simple tube amp. Don't need no effects or fancy stuff with the Pod in front.

My unit was built in 1965. I bought it in 1989 as a practice amp.
What a little powerhouse this thing is. Clean and clear it has never missed. It's been used and abused but it keeps on kickin'!

I was using it for jamming and, you know how it is, after a while the volumes keep rising. I managed to rip the paper on the Jensen speaker. I had it repapered but the idiot put guitar instead of bass paper on it. ("That's all I had")

So, I replaced it with a 40 ounce magnet 12" speaker that moves a lot of air. Sounds even better.

Never has needed a repair. Electronics and tubes are all original. Never failed.

Plenty of info on the web.

I had a Crate but the tube sound cannot be beat. Not gonna part with it.

My Ampeg Portaflex SB-12 was made in 1967 and looks brand new - she's obviously lead a charmed life. No tolex rips, chrome still shiny, all lettering clear and present. Museum piece for sure. Got her from a vintage dealer in Detroit - which is appropriate considering this amp was a MoTown studio staple. This is a super versatile amp akin to a Vox AC30 in that it was designed to do both Bass and Guitar. The SB stands for String Bass and a Fender Jazz with flatwound strings has a very close tonality to a standup bass. Two inputs - one for Bass, one for Instrument (ala Guitar or Keyboards). All tube. A pair of 7686 power tubes, pair of 12ax7's preamp tubes, and one GZ 34 rectifier tube. One single 12" speaker that appears to be an AlNiCo magnet. Jensen? Bass and Treble controls and one volume control. Simple but effective. Am using all NOS vintage tubes - RCAs and Mullard rectifier.

Super quiet circuits. With knobs set at 5 she has ZERO noise. Perfect for the studio. Plug in a Fender Jazz bass and off she goes. Acoustic bass sounds, funk, poppin', MoTown or heavy distortion she's got it all in spades. The early Ampeg amps are renowned for their versatility and quality of sound and this has all of the classic Ampeg traits in spades.

Plug in a guitar (Les Paul Jr) and she sings - clean and clear like a good amp should. Great bandwidth - big bottom, warm mids, and clean as a whistle highs. Turn up the volume past 7 and she can growl with the best of them. Pure American Rock n Roll or Jazz or Blues.

I would use this on a gig with no back up for sure. No fear.

Never tried to get customer service from Ampeg for their vintage amps so I have no clue how they would respond. I do know that there are some darn good Ampeg techs out there though all around the USA.

I've been playing for 45 years and have played EVERYTHING out there. This is without a doubt a classic amp. As good as the VERY best amps I've ever played. Tone to die for. Volume? Perfect for recording and for practicing but playing a 5,000 seat colliseum? Nope. Gotta mic it up Brother! I predict the vintage US made Ampeg amps are going to be THE next collectible amps. Get one while you still can afford one as they are WAY under valued for how damn good they are.

This amp is a '65 flip top Portaflex, with the original Jensen speaker. It has two inputs (Instrument and Bass) and one channel, no effects. The speaker wiring is connected through the latch to the top when the amp is secured to the cabinet. I play mostly 'chunky' rhythm chords, so I like a fat bottom end. This amp was original made for bassists...but, just like the old '57 bassman, the Ampeg will roll over into a guitarist dream come true. This thing is in the studio to stay. It's all tube, of course. Folks looking for a vibrato or tremolo will not be happy. Those of us who started out without those features on amps will be happy.

I've tried several guitars and my bass out with this kit. The bass is an '80s Fender Jazz bass special with a P-style body, P and J pickups and an attenuator pot for tone. The bass qualities of this amp are very flexible...punchy at the high end for slapping or pulling, and it has a great big bassy bottom. In spite of its forty years, there's very little buzzing...althought, if you get the pick ups too close to the CRT on your computer it can get really noisy, particularly with single coils. For guitars, I tried my 72 reissue Tele deluxe (Japan, three bolt neck) and my 1960 Gretsch Single Anniversary. I also had one of my friends over with his HSS American Strat. The treble and bass controls give you a lot of flexibility and you can dial this in a crisp or as muddy as you want. I like the higher end bite. My friend loved the muddy bluesy bottom end. The distortion is far more natural than a stomp box and it doesn't overdrive the speaker at all.

It's a little too soon to say how dependable it is. The guy that gave it to me said that one of the tubes got hot. I didn't experience any of that in the first four hours I had the amp up and running. The provider had changed out the original two prong plug for a grounded three pronger. He must've done it right, I didn't get electrocuted and the wires in my walls didn't melt. I am psyched about taking this amp out for a gig or two to try it out on an audience.

I've played around with Ampeg equipment before, most bass stuff. I have an acquaintance that collects these beasts from the '60s and '70s, so I have a little bit of familiarity with the line. Denver has no great gurus of amplifier repair, so the best recommendation around here is become a basic electrician and learn something of the schematic of the amp. Ampeg's website has links to sites with schematics for most models. The warranty was probably great whenever it was in effect... I wouldn't know.

I've been playing 40 years. I own a '57 reissue Les Paul Custom Black Beauty, a '60 Gretsch Single Anniversary in basic sick green, '72 reissue Telecaster Deluxe (Japan), '93 Chandler Strat with the Fender style headstock and EMG selects, '96 Guild Starfire IV, and an '80s Fender Jazz Special bass (Japan). If the amp were stolen, my heart would be broken. I love the sound, hate the weight.

Just read the other reviews. they say it all. As simple as can be. the way I like it.

The amp is so quiet you don't even know when it's on until you pluck a string on your guitar or bass. Perfect for studio work. I use it for both my electric and acoustic basses, primarily for coffee house gigs. The amp cannot cut through on medium to large venues unless it is mic'd. The sound is clean and sweet with that warm vintage tube sound. The original Jensen speaker distorts too much for bass, although it kicks ass with a guitar. I replaced the original Jensen with a 12" Eminence bass speaker. Now I can get a little more clean volume out of it. I'll put back the original speaker if I ever sell it. I play R&B with a little funk. The sound is clean as long as I keep the volume at a resonable level. I also use an Aphex Aural 204 Enhancer in front of the bass input. This adds more bass presence/volume without having to drive the speaker to a distortion level. Remember, even though I have added a higher wattage speaker the amp itself only puts out around 25 watts. The amp, when driven too far will distort. Also I wouldn't try to put an active bass into this puppy. You will definitely push her too far. All in all the sound is incredible for both studio, practice and very small venues. This amp is a genuine classic, to say the least.

I bought it used and decided to replace all the tubes. That was one year ago. So far so good. Everything works well. The only problem that I have encountered was the speaker grill. The original grill would vibrate off the speaker back-board on low notes. I replaced the grill with new matching vintage cloth and the problem went away. The old grills will lossen up over time. No big deal. The new grill makes the amp look showroom new.

Well, the amp was made in 1966 so warranty issues are out of the question, but part replacement is very easy. There are many suppliers of vintage tubes and harware for this amp. They can be restored and repaired very easily. The electronics are very simple to work on too.

I have been playing since 1963 and have owned virtually every amp that Ampeg has ever made. I even own an original 1969 SVT head and cabinet. The Ampeg Portaflex series are the most sought after amps on the planet and rightly so. They are simple in design, look cool and best of all sound great! They have been used in virtually every recording studio around the world. You don't get better then that. Right now these amps are still a bargain to pick up. Just wait, in a few years the supply of good used ones will disappear. My recommendation is to pick one up before it's too late. Everyone talks about the B15, but the SB12 and the B12 are just as good, if not better. The amp is perfect. The only thing Ampeg could have done better was to supply a slightly higher output speaker for the bass. No problem since I added it myself. If it was stolen I would buy a new one for sure.

Well, everyone already knows how basic the SB-12 is. It has one volume, treble and bass control. That's it! It's a perfect studio, practice or small gig amp. It's almost perfect. If I were to add anything it would be a standby and polarity switch, but that's it.

The amp is super quiet. Perfect for studio work. The sound is very clear and articulate. I have quite a few monster vintage bass amplifiers, mostly Ampegs. I bought the SB-12 off of Ebay for $375.00. The amp is almost mint. It is truly a time capsule. I love to sit down with my Fender basses and play for hours on this amp. The sound is amazing. The original Jensen speaker cannot handle high volumes, though. It will start to distort with too much bottom end dialed in. It may be just the age of the original speaker. I am going to buy a new eminence 12" bass speaker and replace the original one. I want to get a little more clean volume. I'll put the original speaker back in, if and when I ever sell the amp, which will not be anytime soon. I plan to use the bass out on small gigs. That's why I bought it in the first place. I use both Jazz and P basses, both vintage and active ones. They all sound great through the SB-12, but my 1991 single coil 51 reissue Fender Tele bass sounds the best. I play finger style and the notes, as mentioned before, are very clean and articulate with the SB-12. I am very pleased with this amp. I would recommend that you add the SB-12 to your collection. Pretty soon these babies will become very hard to find for a resonable price.

I have not had the amp long enough to really give feedback on reliability. However, these old Ampegs are very easy to have repaired if needed. Typically a tube replacement is not expensive and the tubes do last for a very long time.

Once again I have not had this amp long enough to give feedback on customer support. However, there are many repair shops around the country that can support the older Ampeg amps. Also replacement parts are readily available from quite a few tube and restoration parts dealers.

I have been playing bass for over 30 years. I own a 1969 first year SVT amp and matching 8X10 cabinet, a modern SVT410HLF cabinet, a 1991 SVT-II Ampeg rack head and an Acoustic 370 head and 408 (4X15) cabinet. I also use a Fatboy compressor and other electronic accessories. My basses range from many vintage P and J basses; an Ampeg AEB-1; Guild Ashbory; Washburn acoustic bass; a vintage Framus bass and others.

My SB-12 has an original Jensen speaker with "June '66" rubber-stamped on it's gasket, so I assume it's a 1966. Simple pre-amp section as mentioned in the other reviews. I added a speaker extension jack many years ago but have never needed it.

I use this amp with a Fender Mustang bass - short scale neck and a single coil pickup. The Ampeg fits this style perfectly, with a hi-fi type of sound at mid-volumes and smooth distortion when cranked. Very touch sensitive.
The Jensen speaker has a problem, though, and it results in a distinct fuzztone. Am looking to replace the speaker and am leaning towards a Weber Blue Pup alnico magnet. Any suggestions?

I've had this amp for 28 years and it has never let me down. I have replaced the rectifier tube but (luckily) not the 7868's. Every so often the clamps feel a little loose but this can be fixed by turning the nut that the clamp makes contact with.

I began playing guitar in 1966, the year this amp was made. My other amp is also an Ampeg, a 1964 Gemini IV. I use the SB-12 for bass and play a '72 SG Standard through the Gemini. I love the circuitry on these amps - a pair of tubes putting out around 25 watts. I have used Fender amps in the past (6L6's) and never liked the overdriven tone. Not a problem with the Ampegs, though, as they sing when pushed into overdrive. Great amps.

Simple, straight ahead features on this amp. I like it like that. Less junk in the way of your signal path. Volume, treble and bass. Cool looking amp too!! Flip it over and latch it down and you are ready to go. Has the original dolly which screws into the bottom of the cabinet, cool!

This amp sounds great for bass or guitar. I gave it some more gain by adding cathode bypass capacitors on the first two gain stages. This helped out the cranked up tone of this amp to sing more. Nice for blues and gets pretty hairy with my overdrive! Nice cranked amp tone at listenable levels. Great with single coils or humbuckers.

This amp as any other older point to point wired amp is pretty reliable as long as you keep her running right. Filter caps, along with the bias supply filter caps should be replaced if needed and any of the power supply components checked for problems. The 7868 power tubes are expensive but if the power supply is ok these tubes can last a long time. Ampeg probably won't be working on this one for you. I work on all of my amps and am not afraid to say that this amp won't let me down in any situation.

I work on amps for a living so I don't need support from Ampeg.

Overall this amp is a great value when you think of the sky high prices that the old fenders are selling for. The tones and look of this amp are better in my experience. This is a great practice or small venue amp and works great miked up.

The features are perfect for what it does. This is a great little 25 watt amp, it doesn't try to compensate for lack of talent with a bunch of knobs. Volume, Treble, Bass, and tubes is as pure as it gets.

This is without a doubt the best sounding amplifier I have heard in 35 years of playing, and I mean playing a lot. I have a real job making enough money I can buy anything I want within reason and I have had 20-25 amps over the years. This one and a 67 Deluxe Reverb are the only amps I will never sell. I use this little guy exclusively for fretless bass. I have 5 that I have stuck with. With the Fender 7120 tape wound strings and the right bass the sound quality is as pure as it gets at low volume. I have a fretless Precision A/E that is unbelievable with this amp. That bass with the tape strings is as close to an upright as I have ever heard (I also have an upright that I learned to play on in 1968 so I know what they sound like). If you intend to get one of these to play out get yourself a good mic because you will need it. Mine has never left the house since I got it except to record or do pure acoustic sets. I use either an SWR Super Redhead or an Ampeg SVT tube rig with 4X10 and 1X15 cabinets for gigging.

Mine is totally stock from 67 as far as I can tell. It looks like the tubes are even original. Hey the cool plexi logo even still works. This thing is awesome and has got to be the greatest looking amplifier ever made. It looks like a giant toaster from a 1950 Kitchen. Mine is kinda weird in that the tolex is black with gold piping verses the standard blue diamond. I bought a Hartke 2115 and the thing literally fell apart in 6 months of gigging. Nobody except possibly MacIntosh has ever made gear like the old Ampeg stuff.

I tried dealing with St Louis Music for my SVT (I guess they now own the name) and it's a joke. Unfortunately in this economic climate a big handfull of money can buy a name and try to convince people that they are the same as the guys that spent years learning how to handcraft products. It's really unfortunate that suits and numbers now run what should involve passionate music people.

I've played 35 plus years and have had a ton of stuff. I stress the played for 35 years because I am not really a collector, I play. I have convinced my wife that everything I own does something different. Currently I use an 81 Alembic fretless, 72 lined Precision fretless, Japanese fretless Precision A/E, Carvin LB75 fretless, Ovation long scale fretless, 72 tele bass, and a 67 p-bass. I also have a Ric 610-12 and a 78 tele for electric guitars. For amps I still have the pieces of my Hartke (these pieces of s*** should be sold by the pound for salvage), a 65 Champ, 67 Deluxe Reverb, Ampeg SVT-100T, Big Boy SVT300 with 4X10 and 1X15 cabinets, SWR Super Redhead, SWR LA-12, and the SB-12. I also play a Ramirez classical (a lot) and a couple Yairi's for acoustic. If anything happened to everything I owned I would go out and find the best condition SB-12 available and buy it immediately before replacing anything else, they are that good. Believe it or not the Japanese Precision A/E would be next.

Limited features as been said. No reverb as this is a "Bass" amp but what a great little guitar amp!

I bought this in 1967 for $50. from someone at school to use for my bass. I ended up going in the military for 6 years and when I returned this was my guitar amp. Just turn it on and play! It sounded so sweet at medium volume. I usually played with the volume pretty high and in many rehersal situations it just couldn't cut it as it gets really distorted all the way up w/ my Les Pauls. So in live situations I miked it.

Reliability! I have played this thing maxed out for thirty five years w/ the same old tubes 7968's and narry a problem. The tolex long since disintegrated and torn off and a speaker output jack put in to replace smashed clamps. Falling down a flight of stairs, no less. I have had it on maxed out without the speaker hooked up...nada...no problem. No scratchy pots...

Bought it used and abused 35 years ago and needed no support.

I once had a band member with another one that I used in a stereo set up but he wouldn't sell it to me. If I lost it i would be sad but I love the way it looks so beaten and sounds so sweet. I think I will replace the tubes if they have any more over at Fliptops.com. I think since i'm doing the home studio thing i may try recording it.

I do not know what year make this amp is, but it most certainly is an Ampeg SB-12, and very old. I looked vaugely for a serial # and found 3183305 on the back by the speaker jacks, but this # didn't even come close to any of the #'s that I found on a " Date your Ampeg " site that I came across before stumbling upon this one. SHOOT! It's probably not even a serial #. The amp has one channel and 2 inputs labeled "bright" and "normal". There are "volume", "treble", and "bass" knobs respectively and that's it on the front panel.
On the back, it holds a 3 amp fuse slot, an AC outlet for 500 watts, a stand-by switch, and Hum balance knob, and 3 jacks for a speaker cable, ext. amp, and another speaker cable respectively. It houses 1 5AR4 tube, and a pair apiece of 6L6GC's and 12AX7's. All of which were replaced with Groove Tubes .....Maybe 10 or so years ago.

I have used the amp for both guitar and bass. Both seem to work quite well through it. It seems to start to break-up/ get distorted at about 10 or 11 o'clock on the "volume" knob. Which doesn't particularly suit my style. But It's a useable tone for sure. After that it's "Iggy Pop and the Stooges" all the way. But a nice, clean, round, tube sound until then. That will cut through a band to boot.

I have not used this rig extensively, and have only recently "got it working", at all. I have not used this amp on a "gig" but I'm sure that it's nothing that it could'nt handle. It seems to be very eager and sturdy.

One thing that I must stress, is that this amplifier was bought second-hand and sat around for years before I even considered getting it fixed. I recently got it up and running about 1 or 2 years ago. It was my brother's, you see, and it didn't work at all. So I offered him a $100 bucks for it and had my friend fix it up for me. At first he got only the head working. So for a long time I would use the head with an external speaker cab. A 15" speaker. With which it worked fine. Now!!...the speaker that we got with the flip-top, SB-12 cabinet was/is a JBL D140F 14", yes 14" speaker, that my afore mentioned friend fixed a small hole in. So any True, vintage Ampeg freaks can probably dismiss this "write-up" from here on out, because this is not a "true" Ampeg SB-12. But the head is!!!!

So I hope that this will help someone, but further more and more importantly, I hope that someone can help me......anyone willing to coorespond or share information with me about this amp should please contact me at dmtzo@yahoo.com . any information would be quite useful to me I'm sure....Hell!...I'm not even sure if this is a bass amp at all...but it sure works as one...anyway, it is now, whether it likes it or not........HA!! HA!!!!

Thanx.........D. Matz

Volume, Bass and Treble controls; that's two more knobs than my tweed Champ. My amp still has the original "through latch" speaker connection - no speaker jack or external cable. My amp is one of the earliest models that I have come across, all of the individual components are dated in the second half of 1964 which means the amp is probably an early 1965 model. When I bought the amp from Cambridge Music in 1985, it was in absolutely flawless original condition. I wish I had asked what background info the store had received from the previous owner - my guess is that this was a present that got left at mom's house for 20 years and then sold with almost no prior use. Now (1999) the blue check tolex is still near perfect, I have not replaced any parts, nor has there been any need to replace tubes (7868s) or filter caps ! At 34 years of age, this amp is still museum quality. For the first 14 years that I owned it, it was my primary practice amp at home and only left the house for studio sessions. Recently, I have been backing up a singer/songwriter type at coffee house gigs and this amp is the perfect "unplugged" bass amp. I just bought a padded cover for the amp so it should survive the occasional gig with no signs of wear.

Without question, the best sounding amplifier that I have ever owned, ever heard or can imagine hearing. Either of my two early 60's P Basses produce the warmest, roundest bass tones imaginable when played through this amp. To put things in perspective, my main live rig is a Mesa Boogie Bass 400; when its time to go in the studio, the Boogie stays home and the Ampeg gets mic'd straight to tape with no EQ and NO compression. Oh, yeah.....its also my favorite clean sounding guitar amp. Truly one in a million.

See above, 35 year old components still operating flawlessly. Earlier this year I blew a fuse, replaced it and it blew again. I took the eamp to my local tech and they found a loose solder joint. This is the only service the amp has received in the 14 years that I have owned it. Remarkably, the tech found the tubes and filter caps in perfect working condition.

I have had no contact with Ampeg regarding this amp. It is unfortunate that I did not contact the authors of the recent Ampeg book, as this amp is the equal of any of its vintage.

I've been playing for over 25 years and have owned this amp for 14 years. I currently own a Mesa Boogie Bass 400 and numerous Fender amps, from tweeds to silver face models. If my SB-12 needed to be replaced I would borrow money from my retirement plan to find the best one available. If anyone out there has the earlier model B-12(n) in totally original condition, I would like to make you an offer.

American made (New Jersey) Ampeg SB-12 "Portaflex" amplifier, a 1965 model according to the schematic I discovered glued to the base of the amp head. Although the features seem to be on the light side, I found that this section took up the most of my time to describe since there are so many little things of interest found on this humble amp.
Control features are few compared to today's equipment, but the most necessary stuff is there: 25 watt single channel w/ Volume, Treble and Bass controls, an on/off switch and two inputs "Instrument" and "Bass". I had an engineer friend look at it and he says the only difference between the two is that the Bass input is a little hotter than the Instrument input (there is no special Bass EQ-ing, etc). Unfortunately there's no Standby switch. Considering the fact that it has two very rare 7868 power tubes, a standby switch would be nice so the tubes don't fry while powering-up or while taking a break. Speaking of the tubes, the 7868s are Sylvania tubes, but are also stamped "Made in the USA for AMPEG"! Also, the 5AR4 GE rectifier tube is stamped with a 1966 date code. This evidence leads me to believe that they are possibly the original tubes. One of the two 12AX7A's looks like a newer replacement, but the other one looks vintage. The 12AX7A's also have black metal twist-on covers with springs in them to hold the tubes down. The other tubes don't have covers.
It has a 12" Jensen 8-ohm speaker contained in an over-sized speaker cabinet with a tall, narrow sound port running up the left side. Other than that, the plywood cabinet is fully enclosed and covered in the infamous Blue Diamond vinyl material. There is also a curious small plate that is screwed to the bottom of the cabinet with a threaded hole in the center. It's not big enough to support anything big and I have no idea what it's for (?). After all these years, it is still very sturdy and vibration-free. I'm not sure about what type of wood it is made of, but I am convinced that the cabinet design adds significantly to the overall tonal qualities this amp system exhibits.
The unique head design warrants a couple of extra points in the features category: There is a clear plastic plate with the Ampeg logo on the front which lights up when you turn it on. This is screwed to a boxed-in metal grill type enclosure which protects the tubes, but still lets the heat escape, plus you can see the tubes glow as you play... very cool! This enclosure is painted with a black "wrinkle finish" paint and has oval holes, one on each side, which serve as handles. Mine has the speaker output cable coming from the bottom of the head, which is then plugged into a jack located on the back of the cabinet. It is absolutely NOT the original cable, and I am also unsure if the jack is original (at least it does not seem to be). Most likely a modification made by a previous owner.
The entire head is secured to a vinyl covered plywood panel, which sits on top of the speaker cabinet. When flipped over, the head fits snuggly inside and the panel can then be clamped down. This side of the panel is supplied with a handle, ready for transportation. Weird, but cool.
If it had a standby switch and more commonly available tubes, I would have given it a perfect score in the features category.

I first discovered this amp at a friend's house. He found it at a swap meet for $25 bucks!! I played it a couple of times during some late night political debates (and beer drinking) and I couldn't help but notice its pure sound and vintage tone. One of the sweetest tube amps I've ever had the pleasure to hear. This was like eight years ago, and I've been bugging him to sell it to me ever since. I vowed that someday I would make him an offer he couldn't refuse. That day finally came when he needed cash for a new sound system. The $450 I paid is really far more than this particular unit is worth (its covering is in less than perfect condition). But since he's a friend, and especially due to the fact that the amp section and (most surprisingly) the Jensen speaker were in such excellent shape, I paid him "top dollar" for it.
The sound quality is nothing less than pristine. I've heard that the 7868 tubes were originally used in some of the hi-fi equipment of the day. The tone is warm and full. It has a hollow midrange quality to it. When cranked, it exhibits moderately high gain characteristics, "brownish" and smooth. I can just sit around strumming my guitar all day, and even after several hours, still be delighted. I find that I don't even miss not having reverb. It's probably loud enough for playing rhythm stuff live, and maybe leads in a small club or if miked. I found an unofficial Ampeg web site (http://users.aol.com/bluemuse/portaflex.html) that claims the output of the SB-12 is 25 watts RMS with a peak output of 57 watts. That 57-watt figure seems a little high, but it could be possible. Either way, I don't think it's a good idea to be running it at full blast all the time anyway.
It perfectly compliments my setup, in the sense that none of my other amps have this caliber of sound. It works as well with my Fender Telecaster as it does with my Epiphone Casino. I've also played an old Hofner Strat-style guitar through it and it even made that sound good. Sonically it rings and glows!
You really can't compare its sound to any of the more modern amplifiers, nor can today's amps compare to it. If I had to describe its overall sound quality in one word, it would be "authentic".

The fact that it sounds so good after 34 years speaks for itself. The usual problems, like scratchy pots and loose connections, are typical and easily fixed so they warrant no real concern. All I want is for it to last a few more years before a major overhaul is required and I will be more than satisfied.
Someday I may be forced to have my amp guy set it up so it can use 6L6 tubes, since finding good 7868 tubes may be very difficult. Finding a matched set may take a miracle. I will hold out as long as I can, and hope the current tubes last for a good long time. I haven't checked the condition of the capacitors yet, but as long as it still sounds good I'm not going to worry about it.

I would really like to contact the current company and see if they could re-upholster the cabinet for me. But since I honestly don't expect that to happen, I hereby release them from any further obligation and commend them on a job well done... retro-actively of course.
Also: I found a place that says they can replace the covering on old Ampegs. Email me if you want info on their site.

I have been playing guitar for almost 20 years. Besides the Portaflex, I also own a Mesa/Boogie Rect-o-verb (which is awesome!), a Carvin X-60 (good clean channel) and a little Marshall G10MK.II practice amp (no comment).
I feel this amp falls in the "desirable collectable" category. It is neither an absolute necessity to have - nor is there any major advantage in having one, but it sure is fun and very unique. I don't expect to see another one ever again, so I will make sure to take extra good care of mine.
What impresses me the most about the SB-12 is the simplicity of its design. After studying the schematic and looking at the electronics, I almost had delusions of making a copy of it as a project. I soon realized that the problem isn't recreating it, but in finding the vintage electronics, which would be impractical, if not impossible. It does go to show that great sound doesn't have to be complicated, just done right!
If you do happen to find one at a swap meet for $25 bucks, grab it and run like you've never run before!!! (Just try not to knock over any little old ladies on your way out, OK?). Peace!

Cool Flip top head Bright and Normal inputs. Tube distortion via bad biasing or rectification

This amp is good for guitar and bass. Mine is super distorted from the amp and I love it. Sounds just like the Beastie Boys. I could take it to the shop but they would just fix it. Since it distorts it isn't all that loud but loud enouph to play with drums. So it has ONE really good sound.

I could break any minute but hasn't. that rectofyer is screaming Orange! I could care less.

uhhhh.... I have been inside it and there is like 15 parts. So fixing it will be cheap unless the transformer goes.

I use this amp as a studio tool and it is good for one great sound. I would buy it again but not as my only amp. Punk and funk guyz dig on it. Wordz like Dope and Pimp come to mind. Dig that silver grill cloth Daddy.

My 67 SB-12 just has three knobs, volume, treble, and bass. That is all that I need. No fancy gain channels, no effects loops. All tube 2 12AX7's and 2 7868's and 1 GZ34. All I wished that it had is an ext.speaker jack. It has plenty of power for studio, home and small gig use.

I play a Tele and a Strat through it. The Tele sounds dark and menaceing with the neck pup and the volume on the amp at about 4 o'clock. It has a low hum with single coils when you have the amp and guitar volume pretty high. I usually plug the guitar into the bass input, it sounds better to me. I replaced the original Jensen Concert Series 12 with a Celestion Vintage 30 and it just cranks. The Celestion gives it a more clean and brighter tone IMHO. The stock speaker has that vintage tone. The Celestion handles it better with I crank the amp all the way up. Smooth and creamy natural distortion.

No problems yet, (knock on wood). Soon as I bought it, I took it to an amp tech to give it a tune-up. Everything check out fine, good caps, good pots, good tubes. He just had to re-solder a couple of wires, and I had him put in a black three pronged power cord. The original owner put in an orange extention cord. But since it's almost 30 years old and it hasn't given me any trouble I'll give it a 7.

huh? None probably

I've been playing only for a year, but I am really enjoying the learning process and exploring all musical facets. I love guitars and vintage amps, I would like to start collecting. I have a 98 Collectors Edition Telcaster, a 82 Am Std. Strat, an 98 Ibanez Artstar Archtop, a 67 Gibson LG-1, a 97 65'Re-issue Twin Reverb, a 98 Ampeg Jet-II with Tremelo, and of course my SB-12. I don't think that I can find another SB-12 if it were lost or stolen. It there is I don't think that it would be in as good condition as mine, my SB-12 is one in a million. I hear that when you ordered these you can get your name engraved in the plexi glass plate, I like mine because the person who bought it didn't get his name platered on it, so I don't have to stare at someone else's name.

The low rating reflects quantity of features, not quality.
Probably '66 (warranty/sales sticker inside dated Feb. '67). Two inputs ("instrument" and "bass") to one channel (the "bass" input has a little more bass and just generally sounds better, but they seem to have the same gain). Volume, Treble, and Bass controls. No standby switch (unfortunately), just on-off. That's all there is. One 15" (Jensen Concert) speaker. It's a Portaflex, so the top part (held down with two metal clamps) has the amp on one side (all components under black metal grille) and a handle on the other. When you clamp the top down amp side up, the speaker connection is made through the clamps! All tube, about 25 watts. Tubes are 2x12AX7, 2x7868, 5AR4 rectifier, numbers helpfully printed on back of chassis. The only extra feature the amp has is the stylish set of thin white stripes across the control front of the chassis. This amp only does one thing, namely sound good;

I'm not sure if Ampeg meant this to be a bass or guitar amp. It sounds great for bass (especially recording-basically same as a B-15). If you turn the Bass control all the way up (using the bass input) it has a ridiculous amound of bottom end for such a small amp. However, I think it's probably one of the bast sounding guitar amps I've ever played through. (using the bass input I put the treble all the way up and the bass at about 1/3 up). The clean sound is warm and very 'tubey,' but not at all muddy or indistinct. Beautiful harmonics. As you turn it up it just gets better. About halfway to max (there are no numbers on the controls) you get a great harmonically rich clean sound if you play easy--if you strum hard (or play a high output guitar like a Les Paul) you can get some very nice overdrive. It's very chimey at this level. If you crank it up all the way it has smooth but roaring overdrive that sounds like an old Deluxe or Vibrolux, but a little less grainy. Not punishingly loud all the way up, but definitely loud enough for rehearsal or club. I play a LP and different Fenders through it and they all sound awesome-the amp emphasises the distinctive sounds of the different guitars and doesn't sound any worse with any of them.

Well...like many old Ampegs it has tubes that were probably a good idea at the time; however, a duet of 7868's will cost about $40, and the rectifier (which I believe is the equivalent of the one in a VOX AC-30) is about $30. I don't know of anyone making the power tubes anymore. Besides rarity of tubes, the amp does have two drawbacks. Although I think the speaker-connection-through-clamps thing is very cool, the clamps have to be TIGHT or the connection gets jiggly, and the speaker cuts out. (NOTE! unlike the Portaflexes which connect through an XLR cable, there is no built-in 'standby' if the speaker is not connected. This means if you turn the amp on but forget to tighten down the clamps, it could go runaway and blow the tranformer!) The clips being loose (probably because over the years the rubber 'seal' stuff inside has gotten old or compressed) may also make the cabinet buzz (although in general the Portaflex system, which creates a sealed cab when the amp is flipped up, sounds very good and increases bass out of a small amp).You can fix this by either replacing the rubber inside, or putting something between the top and cab (like strips of cloth or foam). This seals the cab, stops buzzing, and keeps the speaker connection tight. Other than that, the amp itself has never given the slightest hint of a problem, noises, what have you.

Never dealt with them.

Like I said, one of the best sounding guitar amps I've ever met(and great for recording bass, too)and I would hate to lose it. I once dreamt my house was burning and as I escaped, I took my cat, my Jaguar, and the Ampeg (leaving the Les Paul to roast, I guess). It's beautiful, too! Blue diamond ("shower curtain") tolex, neat gold-tone grill cloth, amp under a metal cage (like an old hi-fi amp), big metal Ampeg logo, and the cool light-up plexi front panel intead of a pilot light. Apparently when you ordered your new Ampeg you could get the plate personalized for $5. Well, I guess James Chakedis from Brooklyn (the name on the warranty tag) had a nickname, because the plexi plate says "Chico" right under the Ampeg logo. Just about the coolest looking, sweetest toned, best priced vintage amp I can imagine.