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1966 B15N with an 8 pin speaker connector?

B

B15Nsteve

Jun 23, 2026
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5
#1
I’m new …please forgive me if I’m not on the correct sub-forum 🙏
Question: my Ampeg B15N appears to have been built in 1966 based on its cab sticker serial number. Is it odd that I have an 8 pin speaker connector instead of the 4 pin XLR? I thought the 8 pin connector was used way prior to 1966. Thank you.
 
#2

Speaker Connectors​


The earliest Portaflex amps employed an octal speaker cabinet connector. The speaker cable had a female eight-pin plug and the speaker cabinet had a male mating connector mounted in a metal cup. The female plug was used on the cable to avoid any accidental contact with the dangerous voltages and currents carried in the speaker cable. Octal connectors like this were typically used in combo and hi-fi amps at the time, interconnecting pre-amps, power amps, and power supplies. Like on octal power Tubes, there was an index pin in the center to ensure that the plug could only go in one way. With the introduction of the B-15NB, Ampeg switched to interlocking Amphenol four-pin connectors. Switchcraft C4M and A4F are the modern equivalents. With the octal cable, it didn't take much force to pull the speaker cable plug from the cabinet. The four-pin locking connectors were a step up and avoided accidental disconnections.

 
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#4
That sure sounds like an earlier amp/cabinet. While it might have been converted from the 4-pin to the octal, that sounds like a lot of work for no real benefit. Do you have any photos of the front of the amp (particularly the input jacks) and the inside of the cabinet? If your amp is a 1966 it will have text labels over the input jacks. Those did not appear until sometime in 1965. If the speaker baffle in you cabinet has 8 slotted ports surrounding the speaker it is the double baffle version, which started getting phased out in 1965. In general, a lot of weird changes started happening in 1965, including the change from eyelet board to PCB construction. Another way to narrow down what year it is from would be to pull the amp chassis off of the tray that it is attached to and check out the date on the schematic.
 
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#6
I don't have mine anymore, but my 66 had an 8 pin connector. I never opened it up to see if they used all 8 pins though and it may be one of those design things Jess Oliver / manufacturing did based on parts that they just had lying around for other equipment. Sure was heavy duty though!
 
#8
mikecd1 said:
I don't have mine anymore, but my 66 had an 8 pin connector. I never opened it up to see if they used all 8 pins though and it may be one of those design things Jess Oliver / manufacturing did based on parts that they just had lying around for other equipment. Sure was heavy duty though!
Click to expand...
Thanks very much for your response. It makes sense that Ampeg might use left over parts inventory in 1966 👍👍
 
#12
B15Nsteve said:
I’m new …please forgive me if I’m not on the correct sub-forum 🙏
Question: my Ampeg B15N appears to have been built in 1966 based on its cab sticker serial number. Is it odd that I have an 8 pin speaker connector instead of the 4 pin XLR? I thought the 8 pin connector was used way prior to 1966. Thank you.
Click to expand...
My 1963 B18N came with the octal, too. I converted it to 1/4".
 

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