ampeg b15 output transformer question

[funkydiplomat]

anybody know what the primary impedance is? Specifically for the cathode biased models... but I'll take any info you've got.

thanks,

-joe

[J M Fahey]

Hi funkydiplomat
If nobody answers with factory or service-manual info, it can be calculated.
Please post or link the schematic you are interested in, I guess there are more than one version.
Which output tubes will you use?

[Steve Conner]

I just did some googling there.

According to some thread on TalkBass, early B15s used the OT-208 transformer and later ones used the OT-214.

According to more googling (finding a post here: http://music-electronics-forum.com/t3314/ ) Both transformers are 6.5k to 8/16 ohms.

The OT-214 is still available at fliptops.net, but I expect a 6.6k Hammond would work fine.

[funkydiplomat]

yeah on talk-bass somebody posted:

OT-149 10k, 8 ohms 7591
OT-150 10k, 8 7591
OT-151 6.6k, 8 7591
OT-208 6.5k, 8/16 6L6
OT-213 6.5k, 8/16 6L6
OT-215 6.5k, 8/16 6L6/7591

Hope it's right. I've got something I think will work. I just wanted to be sure. The one in the circuit I've been looking at uses the "OT-208". Thanks all for helping in the hunt.

-joe