Speaker questions

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Postby jeffm725 » Sun Sep 07, 2008 11:51 am

good call jason,

I ended up just toughing it out with the celestions last night. They are not jbls but they arent dog crap either. I just didnt want to risk anything with the 40 year old cream puff when I havent even had it a week yet.


Vic,
ATC did a factory recone kit on the one I already got back.

I am curious if anyone has had Weber do a JBL recone? And what their thoughts are. They will recone an e-120 for under a 100 bucks which is 75 less than I paid ATC
.......................................................have you heard the one about the yellow dog?
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Postby paulinnc » Sun Sep 07, 2008 2:49 pm

Since this thread is about speakers, does anyone here use the Eminence Commonwealth 12" or has anyone tried it out? I just saw them the other day for the first time and was jus wondering what some of you guys might think about them.
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Postby jonarobb » Sun Sep 07, 2008 4:01 pm

Good move. BTW is the 68' Cathode biased? You'd have to pull the tray to tell.
Last edited by jonarobb on Sun Sep 07, 2008 4:07 pm, edited 1 time in total.
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Postby jonarobb » Sun Sep 07, 2008 4:06 pm

jeffm725 wrote:I am curious if anyone has had Weber do a JBL recone? And what their thoughts are. They will recone an e-120 for under a 100 bucks which is 75 less than I paid ATC


Yes, Weber does all the JBL recones for my customers. Without incident. He's also reconed speakers out of some of my amps, both K's and E's, and they're still going strong.

He doesn't use JBL factory kits. No need to since JBL doesn't have any domestic kits any more. Completely gone. JBL has all their recone kits made in China. Same place that DBM, AST, Orange County and US Speaker and all these other reconers get em' from. So it's actually ridiculous to pay the $260 or so to have Northridge recone em. You're getting the same exact kit as the aftermarkets only the ones from JBL say JBL in nice red letters on the packaging.

Weber has his kits made to spec. They're beautiful. The cloth surround and cone material are superior to anything going right now.

Additionally JBL Northridge does not demag and remag the K's and D's unless requested and it's an additional charge. Weber does this as a matter of the recone process at no extra charge.


Lastly, if you really dig the response and tone from the JBL E series then do yourself a favor and start snatching up the 2202H and 2204H drivers. You won't be disappointed.
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Postby playingdead » Sun Sep 07, 2008 4:30 pm

My last two E-120s were built on old frames with new-old-stock factory parts. It's a shame they don't make the originals anymore.

That being said, I had an aftermarket reconed E-120 that lasted one half of a show; its paper was a darker black instead of the textured grey.

I had another reconed up here at the JBL dealer (New England Speaker) recently and it looks identical and sounds correct to me. It was $180 or so.
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Postby jeffm725 » Tue Sep 09, 2008 10:36 am

jonarobb wrote:Good move. BTW is the 68' Cathode biased? You'd have to pull the tray to tell.


What is the easiest way to tell once I pull the tray?
.......................................................have you heard the one about the yellow dog?
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Postby jonarobb » Tue Sep 09, 2008 12:30 pm

On the left hand side you'll see the tops of the power tube sockets. There are 8 pins with a space between pin 1 and pin 8. Looking from the top the pins are numbered 1-8 going clockwise.

Very simply, on pin 8 you'll either have a short copper, steel or plastic insulated wire going right to ground. There's usually a big blob of solder for each tube socket.

If, you have a 68' with the AB568 circuit, which is pseudo self/cathode bias circuit, instead of pin 8 going right to ground, you'll see a large 5 or 10 watt cement resistor there between pin 8 and ground.

You might see a pair of tubes sharing one cement resistor or each tube might have it's own.

If you don't see the resistor on pin 8 (cathode), then there are ways to tell if you have a late 68' or early 68'.

1968 is a rough year. The Twin Reverb saw 3 distinctly different circuits all with their own anomolies and problems. One of the main problems besides the dress and passive selection, is the brain surgeons at Fender wanted to make the Twin grind. They did this by dropping the plate voltage and lifting the cathode from ground.

The cathode is easily reversable but the plate voltage was dropped by sacrificing the power transformer. It's a low voltage tranny that Shumacher wound specifically for Fender for the few short months that this amp saw the light of day. It's not the worst thing but if your amp has this transformer you're not going to get the headroom that most Twins are capable of. The most you'll see on the plates is 405v-415v. Whereas most Twins are running upwards of 430v-450v. Doesn't sound like much of a difference but the loss is felt on the overall headroom, or punch.

So, some guys that are in the know love these amps because they can be made to growl with very little fanfare, or mods.

It's unfortunately about the worst year you can buy for any Fender unless you know how to backdate the dress and passives.

Let me know what you find. I can make some suggestions if you find you want to bring this amp up to spec circuit wise, comparable to a pre-cbs Twin Reverb.
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Postby jeffm725 » Tue Sep 09, 2008 1:27 pm

Thanks jason....

here is the deal, I was told at the shop I bought this at that this has been confimed to be a January 68 amp and is the AB763 circuit.

The tube chart on the Inside of the amp says "AB763" However I am fully aware that the "brain surgeons" :D at Fender kept shipping the newer twins later on in 68 with the same AB763 tube chart even though it was other circuits.

I do trust the people at the shop (It is a mom and pop shop that has a lot of vintage stuff, in fact, I was playing a 72 and a 79 Twin for comparison as well as a 65 reissue when I picked up this one, so they are pretty familiar with this stuff) By the way, it was AMAZING how different the 4 twins sounded...I had all 4 side by side and i had my own guitar with me and I would plug into 1, play a riff, yank the cord, go to the next one, play the same riff, and right down the line with all 4 and then back again. They thought I was slightly unbalanced :oops: I didnt care for the master volume 72 that much (it needed work too, it was noisy) but the 79 was quite intriguing, linear, 135 Watts and devastatingly Clean, talk about headroom! The New Reissue sounded pretty sterile to me and didnt sound like any of the other 3 twins. The 68 was just so sweet and buttery. The low end was nice and tight and the higher notes had this bloom to them that was just so musical.............

However, because I am anal like that :? you better believe I am pulling out the chassis tonight or tomorrow looking it over and taking some pics.
.......................................................have you heard the one about the yellow dog?
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Postby jonarobb » Tue Sep 09, 2008 2:27 pm

jeffm725 wrote:Thanks jason....

here is the deal, I was told at the shop I bought this at that this has been confimed to be a January 68 amp and is the AB763 circuit.

The tube chart on the Inside of the amp says "AB763" However I am fully aware that the "brain surgeons" :D at Fender kept shipping the newer twins later on in 68 with the same AB763 tube chart even though it was other circuits.

I do trust the people at the shop (It is a mom and pop shop that has a lot of vintage stuff, in fact, I was playing a 72 and a 79 Twin for comparison as well as a 65 reissue when I picked up this one, so they are pretty familiar with this stuff) By the way, it was AMAZING how different the 4 twins sounded...I had all 4 side by side and i had my own guitar with me and I would plug into 1, play a riff, yank the cord, go to the next one, play the same riff, and right down the line with all 4 and then back again. They thought I was slightly unbalanced :oops: I didnt care for the master volume 72 that much (it needed work too, it was noisy) but the 79 was quite intriguing, linear, 135 Watts and devastatingly Clean, talk about headroom! The New Reissue sounded pretty sterile to me and didnt sound like any of the other 3 twins. The 68 was just so sweet and buttery. The low end was nice and tight and the higher notes had this bloom to them that was just so musical.............

However, because I am anal like that :? you better believe I am pulling out the chassis tonight or tomorrow looking it over and taking some pics.



Very cool. If it's that early in the year you're in good shape. You'll know soon enough. If you want to take some pictures of the circuit I can give you a general idea.

Remember that the AB763 circuit is just that, a circuit schematic. So an AB763 amp wired in January of 1964 is significantly different from an AB763 wired in January 1968. Most notably the quality of the caps and resistors change dramatically. Funny things start to show up that make the amps unique and completely out of spec like resistor values that don't match the circuit design. I had a 67' in the shop this weekend that had original 470k volume pots on both the normal and vibrato channel. Just funny and cool stuff like that.

Gotta love amps, I sure do!
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