Ampeg B-15S 115 Combo

71 model here-I use it daily,also small gigs at the local club.I run the 3 position switch on "bass",but"flat"woks well,too.I play fretless J-bass-GHS Flats,polished,55-105's.Pickups and tone wide open,fingerstyle-thumb-on-pickup into an Ashly comp.It has the dolly,cover,and the Altec 421A upgrade speaker.

I use the Ashly CL-50 compressor because I dig pretty hard with 3 fingers on a VERY high action.I use it on all my amps,but this one needs it to keep from clipping too quick.

Owned it for 9 yrs.I have great tubes and backups-haven't needed a tube yet.

I will not be without this amp.If I had to replace it I'd buy another,or build a tube/JBL "clone"-I already have the speaker and cabinet.You need one of these.You already know that....or ya wouldn't be reading this!

Year of MFG-1973
Perfect set of controls for that Ampeg thump with note definition.
Used primarily in wedding bands, Bar bands, Beatles freview (I know it ain't Vox, but it worked well), 50's+ 60's bands, dinner club, Highschool gyms with additional spkr cab.
Will not do slap, plink, plank very well

uised a 72' fretless P bass, 74 P bass with Tape wounds, Ampeg Baby Bass, Decca w/ Tape wouns, '72 Ibanez monster, 76 Guils JSB2 with Tape wounds (detect a pattern)

Bought in 1974, no issues, slight hum now, needs a new 12DW7, OCCASIONALLY HAD A BACK UP FOR SOME REASON.

They sent me a schematic once, that was cool

I just shipped to someonetoday, the 35th anniversary of my first guitar lesson, this amp needs to be used. I would buy another in a heart beat, if I had use for it. Most every new amp I have tried sucks, depth maybe but little tone.

My current B-15S is from 1971. It's a wonderful amp. I had another B-15S but sold it for this one because it is in much better shape cosmetically. I use the amp mostly for upright bass, although I have plugged a P-bass as well as a jazz guitar into it as well. It's the best upright bass amp I've ever found, in nearly 30 years of upright playing, and this review is really about its suitability for jazz playing.

It's a barebones machine. Two similar channels. Useful features include: external speaker jack, external amp jack, grounded power outlet. Controls include volume, treble, bass for each channel. The 3-position "Response" knob ("Bass", "Flat", or "Guitar") is useless - I use the flat setting fo all instruments. "Hum Balance" on back is very useful after service/tube changeout. Selectable impedance is useful for speaker changeout or for running an additional cab. Cannon plug from head to cab really should come as an L-plug to allow one to push the cab right up against the wall (easily changed out), but that's the only design gripe I've got.

The amp is not designed with many features, unlike most modern bass amplifiers, but sounds better than almost all of them for upright. I also play upright through an older-style SWR Baby Blue II (2x8+5 combo), when I need better portability.

I run the B-15S cab with a JBL K-130 (same as a D-130), which is a wide range speaker, unlike the JBL K-140 (same as a D-140), which is a bass speaker. I've tried a Polytone head to drive the cab, and at least half of the magic is in the Thiele/Small ported cab design.

The Ampeg caster dolly is permanently attached - the amp is heavy and a bit bulky, but is quite easy to push around. Good handles on both sides and the top, but two people are needed for stairs.

Because I use the amp for mainstream jazz in club stages, with an upright bass and carved top guitar, I run into the feedback zone well before I run out of headroom. I use a 3/4 sized all-carved bass and have driven the amp with pickups from Fishman, Underwood and Barcus Berry (all without any intermediary pre-amps) - they all sounded great.


The amp is very quiet and good for studio use as well (I got this amp out of a studio, actually).

When doubling on guitar and bass, I don't bring a separate guitar amp. I run a little reverb box between the guitar and the B-15S for reverb, and that works fine. The guitar sound with the reverb is excellent.

Rated conservatively at 60 watts, the amp kicks hard, but if you want to play really loud, this is not the amp for you. If you are a fool for snappin'n'poppin', this is not the amp for you. It's a round machine. A big fat round machine.

Neither of the B-15S amps I've owned ever needed service. My first one was fairly beat from plenty of road use, but the fellow who bought it from me has had no problems (he's a P-bass/rock/blues player).

The amp works like a charm. I always take a back-up head (a Polytone Baby Brute) in case of an accident, but have never needed to use it.

Everything on the amp is built very heavy, with no particleboard to be seen. The fliptop head seats nicely and there is a rubber gasket that seals the joint once the head is locked down with four latches. The head is isolated from its mounting panel with several rubberized shock mounts, none of which have failed to date.

My understanding is that the transformers are potted, so that if they ever fail, they need to be entirely replaced. I've had no problems with them. There is a misconception that tubes for these and similar Ampegs are hard to find, but I have had no problems finding the right tubes. As well, the 7027A power tubes can also be swapped out for 6L6GC's (with very little modification), or for 6550's (with slightly more but still very little modification).

I'm sure the people at St. Louis Music are swell folks, but there is virtually no connection between them and this old amp. There is a very friendly network of Ampeg aficionados across the continent, so parts, tubes, repair advice and service are readily available.

The main advantages of this amp are its sound and its low price. Because it is not a "blue check" Ampeg (it's covered a black tolex), many folks don't "get" it, so these amps are obscure and cheap.

The main disadvantage of the amp is its weight. It's not actually very big compared to today's typically more high-powered rigs, but is bigger than many current low-power bass amps. But it's worth it.

If it disappeared I'd find another one. The likelihood if it ever being stolen is remote, however, given its weight.

This amp was made in 1970. It is the result of bassists needing more power in a tube combo. Thus, I believe this Portaflex is a growth version of the B-15N Portaflex. The output is 60 watts into an 8 ohm speaker cabinet below. I play mostly jazz, with some pop ballads thrown in. There are 2 channels, external speaker jack, external amp jack, along with a 500 watt grounded power outlet that comes in very handy onstage. Volume, treble, bass knobs exist for each channel. A "Response" knob lets you choose between "Bass", "Flat", or "Guitar." Also, "Hum Balance" (don't ask me what that is), and a fuse exist on the back. It has enough power for most club gigs - face it, if you're going into a big place, you'd better use the PA anyway. The tubes are 2-7027A power, and preamps are 2-12AX7, 12AU7, 12DW7. I just put in brand new tubes using Philips/Sylvania 7027A, JJ 12DW7, and Electro-Harmonix 12AX7EH and 12AU7EH. All of these are readily available, and sound really nice. A dolly is included; Better be, since this guy weighs in at 120 lbs. The grill cloth is just too cool.
See a large picture: http://www.loncohen.com/pix/70ampegb15s.html

I use this amp with a Fender Precision Bass, and a Fender Jazz Bass. It brings out the best in both of them. The tonal versatility of the Jazz Bass is beautifully captured. I was always amazed at the long sustains you get out of these amps. If you want sustain, you need to go with tubes, no doubt about it. To compare, I also have the B-100R, and tone-wise they are close, but sustain-wise, the B-15S has a 50% longer advantage. Very warm indeed. Ampeg patented the speaker cabinet, thus I believe that has something to do with it (the bottom 2 inches are open to the air on the front). Now, about that Response knob. I play bass, but use the "Flat" setting because it allows for the most control over the tone. And, putting the Bass knob on 3/4 and the Treble on 1/4 seems to be the ultimate set up. The "Bass" setting is too bassie for me. Never tried the "Guitar" setting, so I can't say either way. One thing I noticed is that with both the Jazz bass' volume knobs on full, the hum is not very noticeable, as compared to my B-100R which really buzzes. The range of sounds is very good - anything from an irony, tinny sound, to a Jaco-like tone, to a round ballad bass sound is attainable (again, use the Jazz bass, obviously). Overall, you can play most any style with this, but it's best used for jazz and soft pop in my opinion. Get an SVT-CL head for hard rock, and brute power (300W).

I can depend on it, but would take a backup anyway because the backup doesn't weigh nearly as much (67 lbs). Ampegs are built like tanks - case in point, the logo on this is metal weighing about 3 lbs. I have not owned it too long so I can't comment on durability. Looking at the tubes, when I bought it, it still had the original tubes in it from 1970. So, maybe that's a sign of toughness. Although they had lost 50% of their power, everything worked fine. Also replaced 2 capacitors, and the speaker cone.

Never dealt with Ampeg. A local shop did the head work, and another shop did the reconing. You can probably find a person in the phone book that services tube amps. Where would all the guitarists take their Fender Twin Reverbs?

I love this amp. Been playing since 1985. I chose this because I wanted a tube amp, and the sustain and warmth that comes with it, and had played this model in high school. Some people say you can have a V4BH 100W head, and a cab, and get a similar sound, but that would be something to investigate. There is nothing like a Portaflex combo, thus I did not compare it to other tube combos (very few exist for bass). Jazz players should own one in their lifetime. Thus, if you can find one (not easy), and are willing to probably put a few bucks into restoration, I think most would be happy with it.