Ultimately, best way to do this is to put the BAM between preamp and main power amp so you can use the extra pair of outputs on the Joule Preamp to run to your sub. Is it a perfect solution? Maybe not? But any small loss in performance (generally fullness IMHO) of the BAM from not buffering it is made up for in running a good stereo sub-woofer system (assuming the room is large enough).
I have a customer with such a set-up (Joule Preamp, VZN-100s VSM-MXe's and a 2 channel large sub-woofer system - BAM placed between preamp and the Joule OTLs) and... it sounds great. With a low crossover point on the sub (very flexible Bryston sub crossover is used for the subs) the integration is excellent.
The only other possible set-up I can think of is that if you have a sub or sub system that has some type of DSP xover system that can be programmed to make up for (un- equalize) the BAM's signal in additional to EQing the subs output for smooth response in the room. This would allow the BAM to remain in the tape loop - fully buffered - so you can get the best of both worlds.
I have a customer with such a set-up (Joule Preamp, VZN-100s VSM-MXe's and a 2 channel large sub-woofer system - BAM placed between preamp and the Joule OTLs) and... it sounds great. With a low crossover point on the sub (very flexible Bryston sub crossover is used for the subs) the integration is excellent.
The only other possible set-up I can think of is that if you have a sub or sub system that has some type of DSP xover system that can be programmed to make up for (un- equalize) the BAM's signal in additional to EQing the subs output for smooth response in the room. This would allow the BAM to remain in the tape loop - fully buffered - so you can get the best of both worlds.