Using Adcom GFA-555s as monoblocks to power magnepan 3.3s in active biamp

Thanks.  Seems to be the consensus that it will "work" but not sound great, with some chance of actual trouble. I may stick with the Nak there for a while - it's not bridged, and it's beefy.

My 16 year old came upstairs and asked me to turn down the volume!

Wow, thanks.  So, another question: is there any harm in running 1 channel of each Adcom?

Thanks again. There are some posts in various forums that it's worked, but just about as many opinion that it won't.  

I guess bridged mode isn't all that useful, given that most of the really power hungry speakers are 4 ohms.  I 'm sure there are exceptions. 

Thanks.  You really think they'd see a 2 ohm load with just the bass panels?

And, why does a single GFA-555 not do it for you, sounds like a room issue or some kind of a synergy mismatch. A 555 is no slouch in stereo mode, 331.9W into 4 ohms. If that’s not enough power, something else going on there

There's no problem to solve.  I had a single Classe CA-200 powering the bass panels and it sounded wonderful.  I moveed the Classe to power some newly acquired KEF R11s and temporarily put in a Nakamichi Pa-7 powering the bass panels, and it still sounds pretty good.

But since I had the open question of what is best in place of the Classe amp, and I have two GFA-555s, I thought why not try and see if they can well power the magenpan bass panels as monoblocks. Intuitively it seems two monoblocks of that power should do better than a single Nakamichi, but not if it's going to damage anything. 

Vertical biamping is an interesting idea - as I've always used different type amps it's always been horizontal.  But I have better amps than the Adcom as a stereo amp to use for the biamping (except the vertical as an experiment).  

Right now I do have a Krell amp as part of the biamp but it's on top.  I figure the better spot for the Nakamichi is on the bass. 

What sound levels are you hoping to achieve? 

Loud, but I can get there with my current setup and it sounds good. This was just a thought that maybe 800WPC monoblocks would be good to try on the bottom.  But not if they're going to struggle because they're bridged. 

Have you tried the Krell on the Bottom?

Yes, had it there for years and sounded good.  I thought the Classe CA-200 was actually a little better on the bottom with the Krell on top which is what I had for a long time.  I just moved the Classe so thought I'd see what else might sound good there. 

I think the basic point is there's a stability issue into 4 ohms with bridged amps, and if my goal is to be able to pour a lot of current into the bass panels, this isn't the most stable way to do it.

That's fine.  The Nakamichi actually is pretty muscular there.  I may try the vertical biamping idea at some point.  I wonder if the uneven load on the channels in that configuration would be a long term issue?

No, there's nothing precious about the Adcoms.  I have them mostly as backups or to run stuff I'm testing.  

But yes, mostly rock.  I've been spending more time listening to my (new to me) KEF R11s.

I think I've decided not to bridge the Adcoms. 

I wonder why so many amps are bridgeable when most of the inefficient speakers are 4 ohms anyway. 

Which do y'all think will sound better with KEF R11s:  a single Classe CA-200 or 2 Adcom GFA-555's in vertical passive biamp?

Adcom GFA 555 and a Nak PA-7...that's a blast from the past !

They are fun amps.  I do have a number of more modern, beefier amps for the Maggies but I've been doing some swapping as I also added some speakers I wanted to hear with the better/newer amps.  

I think especially the Nak is a good value - bought it for like $250.  Basically a buck a watt for the current the thing will put out.  Also helps to heat the room in the winter!

i do not use the crossover boxes and changed the jumpers on the back of the speakers. 

This is what I do as well. Magnepans are the best for biamping because of the external crossovers. I have a Marchand crossover - or to be precise a custom built one using a Marchand board.