Mcintosh MA-7900 home theater bypass with subs - not doable?


I acquired the MA-7900 and would like to use it in HT bypass mode.  I have my front mains and two subs (via Pre Outs) hooked up to the Mcintosh.  I want the front speakers AND subs to work on HT bypass, but can only get the front mains to work.  The subs will not play in "Passthru" mode.  

Does anyone know a work around to this or is this just a product of the amps age?  My Anthem has HT bypass for subs and mains.  
dtximages

I think the preamp outputs will work. Have you thought about high level inputs to the subs and bypass EQ when listening in stereo?

I don’t own the 7900 but you can do it with an external crossover. You could pull the bars in the back that connect the preamp section to the amp and insert it there. Out of the preamp to the crossover then back into the amp input. From the crossover then out to the subs and from the home theater processor into the subs at the same time. 
 

An active crossover like the JL audio CR1 will take both a 2ch preamp and home theater LFE at the same time. Something like a mini dsp might work too but I have not used one before.