Ampeg B15 preamp: Drive balanced transformer from PI?

[Bigwan]

I'd like to build a bass preamp for recording purposes. Loads of options, but the style of amp that appeals to me most is the Ampeg B15 portaflex/fliptop. A lot of info on the web suggests that much of the B15 "magic" happens in the phase inverter section. Any suggestions as to the best method of deriving a balanced output from the phase inverter of the B15? I had considered going down the "small power section into dummy load" avenue and tapping off the dummy load, but that seems a little excessive if I can do it from the PI instead (although a low power practice amp would be kind of cool too!)

Thanks in advance folks!