Ampeg B-12N

koipond · #1 01-27-2012, 02:41 PM

I'm considering buying an Ampeg B-12N.

This will be my first vintage amp. The power supply caps, power transformer, a few tubes and power cable have been replaced. Is there anything I should look out for when checking out the amp?

Thanks,

Alex1984 · #2 01-27-2012, 02:47 PM

The main thing is the sound. SS or tube rectifier? Speaker?

stiles72 · #3 01-27-2012, 02:57 PM

Most likely it will have a tube rectifier. Ampeg only used a factory solid state rectifier for a brief time in 1963, and you don't see too many of those around. As long as it fires up and puts out a good sound that you like- I would say you're good to go. Even if it's not 100% stock, part of the fun of owning a Portaflex is fixing them up and making them look purdy again!

koipond · #4 01-27-2012, 03:27 PM

Not too sure about the rectifier, but it's a '65/'66 so I'm assuming tube.

The speaker is a 12" Jensen.

I'm getting excited just thinking about getting it!

Ric Vice · #5 01-27-2012, 03:34 PM

Quote:

Originally Posted by koipond

Not too sure about the rectifier, but it's a '65/'66 so I'm assuming tube.

The speaker is a 12" Jensen.

I'm getting excited just thinking about getting it!

Koi Pond
Unless, it's been modified, it will be a 5AR4 tube rectifier. The B-12N's are essentially a B-15N head on a 12" portaflex cabinet. Very nice amp, as powerful as the B-15's but a little lighter.

Ric

beans-on-toast · #6 01-27-2012, 03:44 PM

The amp is the same as the B-15N. The B-12N cabinet is smaller, has a 12 inch speaker and is of a different design than the B-15.

Carefully check out the condition of the cabinet and the amp. Many of these amps have some rust and scratches on the chassis but, in terms of value, the less the better. Note the condition of the knobs and the cabinet tolex. Some of these amps have a dolly. It was an option when they were new.

The fact that some maintenance has been done is a good thing. This saves you money down the road. In addition to what you mentioned, ask if any additional maintenance has been done. For instance, has there been any modifications. Is the speaker original and has it been repaired or re-coned. Ask how old the tubes are and if the amp is due for a re-tube. Ask if the knobs are original. These can be hard to find and sometimes newer replacement plastic ones are installed. The originals are bakelite. Ask how old the amp is.

Turn on the amp and listen for how much it hums. A small amount of hum is normal. Test all inputs with a bass plugged in. Test that the tone controls are working. Start with the tone controls set flat (12 o'clock), and listen for a change in tone as you rotate each knob through the entire travel of the pot. Listen for distortion as you turn up the volume. The onset of distortion will be heard at 10-11 o'clock with the tones set flat. Everything up full on your bass. Listen for any vibrations from the cabinet at higher volumes. There are a lot of things that can vibrate, including things in the room. As you rotate the knobs, notice if there is a scratchy sound. It is normal for the power transformer and tube cage to get hot.

These are very nice amps. There isn't anything that can't be fixed on them and it is rare to find one without some issues. It is always a good idea with any vintage amp to take it to a good tech and have it checked out after you have bought it.

koipond · #7 01-27-2012, 04:10 PM

Thanks for all the information, guys. Hopefully I will be able to join the Portaflex club within the next week or so!

koipond · #8 02-14-2012, 12:46 AM

Hi guys,

I ended up getting the B-12NF. It needs some work (hum when amp is out of standby and hiss in channel 1) but it sounds much thicker and better than my b50r.

The cab isn't in the best of conditions, but it sounds good so I'll probably leave it as is, possibly getting a Vintage Blue cab instead of restoring the original if I need it.

I'll be busy for the next few days reading over all the Portaflex threads and I'm getting a few books on tube amps just because I'm curious as to how they work; but I'll probably have a few questions after that.

Here's a few pics:

koipond · #9 02-14-2012, 12:47 AM

A few more pics:

Query: What are the red numbers to the left of the schematic?

stiles72 · #10 02-14-2012, 10:28 AM

Nice score! Your cabinet actually looks like it's in decent shape, and from the pics it looks all original. As long as it sounds good, I would just re-glue the insulation to the back wall and call it a day.

coreyfyfe · #11 02-14-2012, 10:56 AM

Nice amp. Not sure about the numbers. As Stiles said, glue up that insulation foam and rock away. Looks great.

Ric Vice · #12 02-14-2012, 01:08 PM

Quote:

Originally Posted by koipond

A few more pics:

Query: What are the red numbers to the left of the schematic?

Koi Pond,
My guess is that it was serviced in the 70's and that's the techs notation's. It has a solid state rectifier and a new cap up top.

Ric

Alex1984 · #13 02-14-2012, 01:34 PM

That cab looks like it's in great shape. Yeah, it does look like there's a solid-state rectifier. Great amps, very tight sounding, and the kickback feature is really nice too.

Jim Carr · #14 02-14-2012, 01:41 PM

Will you use this amp in performance? I never found the B-12 my neighbor lent me on occasion useful in blues or rock performance without PA support. I think it might be OK in small cafe, and of course it can great in the studio. Just curious.

Congrats on a great find!

koipond · #15 02-14-2012, 09:21 PM

Thanks for the info, guys. I guess my concerns with the cab was biased based on the cosmetic appearance.

Jim, I haven't played in about ten years and just picked up the bass again a few months ago. I don't think anyone would want to hear me play...

Right now it's just used for practice, and it makes my practicing so much more enjoyable since I like the tone much better with the B-12 than with my b50r. I do plan to record with it though sometime in the future, once my playing improves.