Jess Oliver's legacy - AMPEG PORTAFLEX CLUB part 9 - Page 18

spacebassed · #**341** 11-12-2012, 08:36 PM

Ric, the B15N(A) was a blue check amp with a solid state rectifier made in '63. It was a very close relative to the B15N(B) that followed later that same year (what was the difference in those two circuits anyway? it's slipped my memory). The "prototype" or "pilot light" B15N's are the same circuit as the other '61-'62 B15N's, they just don't have the plexi logo (or the slot for one) that the production amps do - and in the case of the pre-June '61 amps, they have the convertible side ports that the original B15's had.

...And Bass45 is right, there were probably only around 10 of them ever made.

TheDialog · #**342** 11-12-2012, 11:02 PM

I think I'm done buying amps to keep for a while...
Very, very happy with my set ups.
Together:

Bedroom rig:

JimmyM · #**343** 11-12-2012, 11:41 PM

That 61 is absolutely sick!

JimmyM · #**344** 11-12-2012, 11:43 PM

Was not mentioned in here yet, but hodgy says a lower priced B-15 is coming. Will be black instead of chrome.

christw · #**345** 11-12-2012, 11:50 PM

What Jimmy said.

I can't wait to get Hodgy's impressions of it when it makes its way to him.

beans-on-toast · #**346** 11-13-2012, 06:06 AM

Quote:

Originally Posted by spacebassed

Ric, the B15N(A) was a blue check amp with a solid state rectifier made in '63. It was a very close relative to the B15N(B) that followed later that same year (what was the difference in those two circuits anyway? it's slipped my memory).

There isn't a lot of documentation on the NA vs NB revisions.

In terms of the circuits, the B-15NA and B-15NB are identical. The schematic for the NB was updated in minor ways:
- The schematic for the NA had a hand drawn A, the NB looks like a draftsman updated the lettering.
- The NA had reference voltages on the schematic, the NB doesn't.
- The NB labels each component, R33 for example. The NA doesn't.
- The NB cabinet came with an octal plug on the speaker cab although the schematic indicates a 4-pin connector so there could be ones like that out there. The NB schematic also shows a 4-pin connector on the schematic. Maybe this is when they were switching to the 4-pin locking Switchcraft connector like on the NC.

My 63 has an NA head and an NB labeled cabinet. This is found fairly often. I have seen a number of 63 cabinets that are simply labeled B-15N, with no A or B indicated.

coreyfyfe · #**347** 11-13-2012, 06:32 AM

Quote:

Originally Posted by beans-on-toast

My 63 has an NA head and an NB labeled cabinet. This is found fairly often. I have seen a number of 63 cabinets that are simply labeled B-15N, with no A or B indicated.

This must have continued for a while I think, at least until they were out of B-15-N labels

. The pots in my head date to the last few weeks of 64/first week of 65 but the cabinet has a B-15-N label, and hand written "5AR4" in the tube chart. Sorry the pic is blurry, it's the only one I have...

beans-on-toast · #**348** 11-13-2012, 10:26 AM

Maybe it is just my imagination but is seems like a lot of the cabs have a designation of B-15N rather than a revision number like the earlier ones.

The amps changed a bit here and there but the double baffle cabs first went from the basket weave to the checked vinyl and then the connector changed from octal to 4-pin. Maybe that is why the specified a revision on the earlier ones.

beans-on-toast · #**349** 11-13-2012, 10:34 AM

Here is the B-15NA schematic.

Here is the B-15NB schematic.

christw · #**350** 11-13-2012, 11:43 AM

Well, the "E130" arrived today. It will most definitely clear the transformer because it's actually a freshly reconed D130! I guess I ended up with a period correct 8 ohm speaker for cheap...

I dropped the speaker in and it sounds killer. So far I've only hit it with the P with Roto 66. The D130 plays nicer with this particular bass than the CTS did. I'd imagine I'll like the CTS better for flats. Too bad I found a new rattle I can't seem to trace...

spacebassed · #**351** 11-13-2012, 12:35 PM

Quote:

Originally Posted by beans-on-toast

Maybe it is just my imagination but is seems like a lot of the cabs have a designation of B-15N rather than a revision number like the earlier ones.

The amps changed a bit here and there but the double baffle cabs first went from the basket weave to the checked vinyl and then the connector changed from octal to 4-pin. Maybe that is why the specified a revision on the earlier ones.

You're right David, the switch from the octal connector to the 4- pin xlr is the revision i was thinking of - I knew there was some small difference between the B15NA and B15NB. As far as the labels go I've never seen a cabinet labeled B15NA, all of the A cabs are labeled B15NB, and most of the cabs after that were simply labeled B15N. Labeling wasn't anyone's strong suit back then, but at least Ampeg would write in corrections by hand - Fender jut seemed to slap on any tube chart that was laying around sometimes.

Quote:

Originally Posted by coreyfyfe

This must have continued for a while I think, at least until they were out of B-15-N labels

. The pots in my head date to the last few weeks of 64/first week of 65 but the cabinet has a B-15-N label, and hand written "5AR4" in the tube chart. Sorry the pic is blurry, it's the only one I have...

I've got an amp from the same time period (#00447) but mine dosen't have the second, larger, "Ampeg" label. What speaker does yours have? Mine has a square mag CTS, but it isn't black, and it has an aluminum dustcap.

Quote:

Originally Posted by christw

Well, the "E130" arrived today. It will most definitely clear the transformer because it's actually a freshly reconed D130! I guess I ended up with a period correct 8 ohm speaker for cheap...

Lucky dog!! I'm almost 100% sure that you wouldn't have been able to flip the amp with an E series JBL. I think the Alnico speakers are smoother sounding than the E series anyway. Let me know how it works out - especially on the lowest notes (Xmax) - I'm still considering putting a D/K130 in one of my B15's.

**ddbassGA** · #**352** 11-13-2012, 04:41 PM

Quote:

Originally Posted by christw

Well, the "E130" arrived today. It will most definitely clear the transformer because it's actually a freshly reconed D130! I guess I ended up with a period correct 8 ohm speaker for cheap...

Yes!

coreyfyfe · #**353** 11-13-2012, 04:59 PM

Quote:

Originally Posted by spacebassed

I've got an amp from the same time period (#00447) but mine dosen't have the second, larger, "Ampeg" label. What speaker does yours have? Mine has a square mag CTS, but it isn't black, and it has an aluminum dustcap.

Mine is currently sporting a reconed 73 CTS that came from my B25 cab. It had a JBL K140 when I bought it, and I've swapped a few speakers around since then, but I've been trying to get back to "stock" specs with this amp so I decided to recone the dead CTS and drop it in. The 66 I had previously had a standard black-cone CTS and I really liked the tone of that amp. Not sure what the story is with the aluminum CTS speakers, my R12R has an early 70s CTS with an aluminum dust cap (though I may try to find a period correct jensen at some point) so maybe it was part of an upgrade package or just coincidence?

christw · #**354** 11-13-2012, 06:35 PM

The rattle seems to be coming from my baffle. It does it with both the CTS and D130. With the head removed it does it to a lesser extent. The baffle was definitely loose (as was the CTS). I unscrewed the bolts with my fingers! I torqued the baffle down lightly when I swapped speakets but didnt want to crush the spacers. I'm going to pull it out altogether later. It almost sounds like it might be chuffing around the edges with the thicker cloth? It's definitely not the cloth flapping or slapping the baffle board though. Ideas?

JimmyM · #**355** 11-13-2012, 06:39 PM

Just keep futzing with stuff till you find it. That's all you can do.

christw · #**356** 11-13-2012, 06:43 PM

That's half the fun of it, right?

**ddbassGA** · #**357** 11-13-2012, 08:23 PM

Chris, when your done with yours you can come over and we'll do mine.

beans-on-toast · #**358** 11-13-2012, 09:11 PM

It can help to separate the amp from the cab during the testing. It helps eliminate some possibilities by decoupling things.

Sometimes I feed a low frequency loop that causes the buzz into the amp. Apply pressure with one finger in different places to determine what stops the buzz.

Baffle boards can have loose plies in them that vibrate. With the speaker removed, you can look at the plies in the cutout. Holes here are common. They can be filled from the edge after anything loose is cleaned out. You can tap the baffle wood and listen. If you can identify loose plies in the board, you can shoot cyanoacrylate glue into the wood with a needle to stabilize the loose bits.

Check that the vinyl covering is glued down around the edges. It can flap and vibrate like a reed. Especially in front of a port.

The single baffle spacers have to be in good shape.

The grille cloth needs to be tight. Heat can be carefully used to shrink it. You'd see it flapping if that were the problem though.

christw · #**359** 11-14-2012, 12:15 AM

Thanks for the ideas guys. I'll do some troubleshooting tomorrow.

Does anyone know if Kustom used the same CTS 15" speakers as Ampeg did during the late '60's? The speaker in several late '60's Kustom 2x15's I've seen look identical from the basket and the magnet down to the cone, ribbing, and dust cover. There's one with those CTS ('69s) on craigslist local to me for $100. I'm thinking I may well stick the B-12XTC on top of that for an uber B-15. ...and maybe the 300 Pro.

Quote:

Originally Posted by ddbassGA

Chris, when your done with yours you can come over and we'll do mine.

Right after I buy that B-18X and fix it up too.

jemfleabass · #**360** 11-14-2012, 04:14 AM

Hi Guys,

I have the chance to own a B15S head, but I don't have the cab. I from Belgium and as the B15 were not available in Europe, it is very hard to find a cab. I know that fliptops.net can provide me a replica but the shipping and customs cost are too expensive.

So I decided to build a replica with the help of a friend joiner.

The only problem is that I can't find any accurate drawing and measures for a B15S cab and wich kind of wood is needed.

Does someone could provide me these informations?

btw, wich speaker would be the most appropriate? I heard that eminence are nice

Thanks

(sorry for my bad english)