1967 Ampeg B15N 2x15".... rare bird!

 Just had a day servicing two huge amplifiers made in the day of, well, huge amplifiers. 

This may easily be the coolest amp I've ever seen from Ampeg:

I believe this may have been a custom order. It's a later model, with 7027 tubes rather than 6L6, and a 7199 driver tube. Grid bias, 5AR4 rectifier and those lovely 6SL7 preamp tubes. The tweeters are a cosmetic addition having never been hooked up. 

Not going to get into anything technical, I just wanted to share this behemoth with y'all.

The cabinet has that ultra cool Austin Powers era cosmetics. I have a friend who has a single 15" version as well. Big amps really are no longer in vogue in NYC. This one was on the Reverb cheap as chips and still sitting there. Today the world is about small amps and efficient PA systems. I mean, who wants to move a refrigerator every time you have a gig?

That being said, if I owned a little coffee / wine shack where I featured jazz and folk music, it would be kinda against the law not to own this and stick it in the corner next to the house Slingerland drum kit.

One interior shot:

I did grow up in the last age of the big amp. I used to play a Marshall half myself. Can't say I miss moving these things but, damn. Nothing sounds or looks as cool as that oversized backline!

J

 

1966 Ampeg B15, your studio requires one.

Simple job today, just re-cap the power supply. Amp was running quiet but now it just sounds better with a stronger low end. It will be mated with a beautiful P-Bass soon and ready to cut phat tracks. You have a studio? It's not a serious studio without a real B15!

Stick o' dynamite cap, 30uf@600v, replace with a C.E. Manufacturing 25uf@800v stick:

Also replace the big can with a C.E. triple 40uf@525 volt can.....

I left the audio circuit alone. I like these green .02 Cornell Dubilier capacitors. They're still good and the amp sounds great! Ampeg in those days didn't skimp on small parts. They are built to last.

My client and I bought this amp from a new shop in Brooklyn called Rock N' Roll Supplies. Great place and they have a great tech working there. Give them a visit! Some mighty nice amps hanging out there and reasonably priced!

http://www.rockandrollsupplies.com/cm/

https://reverb.com/shop/rock-and-roll-supplies-inc

JB

8/15/2017 Three Ampeg B-15 amps, one week!

Simply put, the Ampeg B15 is a legend of the studio. This plus a Fender Precision Bass plus massive amounts of talent and persistence equals the legendary Motown sound. But, any passive old school bass sounds great on one of these. I've had the pleasure of working on many of these. This week offered a nice journey into 3 versions of this lovely amp.

First a 1963 model:

This one came from MSR studios in New York City. Countless artist probably recorded through this amp including the Stones, Talking Heads, Roberta Flack.....

This was the best of the 3. It's an early cathode bias version. Probably in the 25 watt range. What do I like about it? Punchy, great low mids, clear sound with a nice bit of growl.

This particular amp was sitting neglected for over a decade. It was a hot mess when I got into it. Random wires clipped, some components flopping about and the tag board burnt through where the cathode resistor resides. Typical, that resistor gets hot. Something blew up in this amp and the power transformer was also fried. This is typical too. I replace power transformers in about one of these a year. This year it's been 2 so far. Weak part I suppose. I didn't need to replace any of the Cornel Dublier caps, they are almost always still good. Surprisingly the circuit is dead quiet with all of the original resistors as well. They didn't mess around with making things cheap back then.

After replacing the power transformer and re-capping the power supply it roared back to life. Glad to say it's making music again in another studio. I'm stunned anyone would let this one just sit unused for that long. The tone is simply perfect. Loud enough for a small combo live too. But best suited for studio tracking.

The next one is a 1966 model:

Similar cosmetics, the differences are it's now a printed circuit board rather than the old school tag board. Ampeg did these so well that it's still fun and easy to get around in. It's also fixed/grid bias rather than self/cathode bias. Result is more power, more headroom, more 'clinical' sound. Haven't dug into this one yet but will be re-capping the power supply.

It doesn't hum so why re-cap it? Isn't it best to leave it original?

Short answer: no way. Just do it. Why?

First is safety. This amp is 51 years old. Caps fail. You don't want this happening.

Second is sound. I can always tell and feel the difference. Stronger low end and more even across the range. My clients agree. Most of them spend years listening carefully in the studio and they say the same thing. Amp got 'bigger' sounding.

Right now the amp sounds good, but we're going for great.

Amplified Parts (CE Distribution/Antique electronic Supply) makes brilliant caps for these. The grid bias amps require a 525 volt can and they also have a beautifully made 25uf@800V "firecracker" cap for the first stage.

Here's your can:  https://www.amplifiedparts.com/products/capacitor-ce-mfg-525v-404040uf

And your firecracker:

https://www.amplifiedparts.com/products/capacitor-ce-mfg-800v-900v-surge-25-f-electrolytic

The firecracker cap saves a good amount of time on installation. I used to use the Sprague Blue Atom 20@600V cap, but you need to monkey around with stuff to make that work. These come with a wire tie and easy mounting. Takes a whopping 60 seconds to install.

Oh yeah, order this too:

https://www.amplifiedparts.com/products/insulator-4-section-fp-cap

Spend the extra $1.95. It's worth it.

Next photo is one I worked on last winter. It's a 1968 model. Similar 'drip edge' cosmetics to the Fender amps of that year. Pretty much the same amp as the '66 but with a new sexy look. Great amp.

I needed to replace the power transformer on this one as well. Full re-cap of the power supply. Powerful. Great live or studio rig.

The 3 amps above all have the original CTS speakers loaded into them. Still making music!


Last but not least is an early 70's model. These are great live amps and are a bargain:

This one also came from a studio that let it rot away. Didn't take much, power supply re-cap, new preamp tubes (6SL7) which were all dead. I left the signal caps alone in this one as well. 1/2 are the Cornel Dublier green pill types, the preamp is loaded with the turquoise little fish caps. 2 of the input jacks were opening up so with nothing plugged into the amp it squealed like a electric hog. I've seen people re-cap amps and go to all sorts of trouble when all that was needed was a good closed circuit Switchcraft 12 jack.

These late model amps have nice but not really necessary filter switches for 'ultra low' and 'ultra high'. These share the most similar sound to the SVT out of all of these, probably due to the preamp. More of an analytical sound than the amps above, less warm but still plenty of warmth. Not nearly as attractive, which is typical of the 70's designs over the 60's. But, this is the best live amp choice. Lots of power! This particular amp was loaded with an Eminence speaker and is now slated to be a live workhorse.

On all of the grid bias amps above, I installed a bias trimpot. Why not do this? They do tend to run quite hot. And hey, you may save the life of that very expensive power transformer:

http://www.mojotone.com/amp-parts/Transformers_1/Ampeg-B-15-Power-Single-Primary-Transformer

So if you have a serious recording studio, don't go without a real flip top. Even the B12SB amp is a fine choice for your bass tracks. I wouldn't buy a new one, there are so many good old ones around and they can be had for not too much. A late model can sell for less than a grand, middle period between $1.5k-$2k. Early ones can be a lot more but if you have the dough, a good tech or some good skills on the bench, you will not regret it.

JB

1968 Ampeg B-15

Here's a lovely beast. A 1968 Ampeg B-15 with that super sexy drip edge styling you only see that year. These are rare. Most are the more classic blue tolex earlier style, this is the classic bell bottom zodiac bling jam.

This one was bought from the original owner. He took great care of it. It showed up at my place with a blown fuse. Amp was turned on, fuse fried. Like many Ampeg B15 amps, the power transformer simply died!

Fortunately Ampeg or someone else makes a suitable replacement. They even got the paint super close. And if you scratch it during installation, it simply matches the rest of your 50 year old amp better.

Pretty easy to install. You do need to get around the p.c. board a bit, takes some creative thinking and action to do so but no biggie....

I also always make sure I put the little cardboard piece with the date and part codes. The new part is better than the old I hope. I replace one of these about every year and a half on average! So if this goes 48 years from now, maybe that tech will think it's lasted 96 years??

Notice the micro fiber cloth under this transformer. I did all I could to install it scratch free! I also replaced the electrolytic caps as well. I never want to see a 50 year old can in one of these.

Amp is back to making music again and yeah, sounds lovely. These make cool guitar amps as well as the worlds greatest studio bass amp....

If you can find it, Jimi's first appearance on the Dick Cavett show, he plays "Hear my Train A Comin'" through one of these with the Dick Cavett studio band. He sounds, exactly like Jimi.....

JB