Splitter on gpa 555!pre amp output

I have had two bridged Adcom gfa 555s since 1989 into 4 speakers. Is it safe to buy a one into two splitter for the left and right outputs on my pre-amp so I could run each amp independently for each pair of speakers?


Each of the gfa 555 input impedance is 22kohm, using a splitter your preamp will see a 11kohm load.

If your preamp output impedance is 1kohm or lower it should be fine, otherwise the low frequency output will reduced. 

The pre-amp is a GFP-555. Would you think/guess this is a better way to run these two amps vs bridged in mono? I will search for the GFPs output specs. Thanks

Keep remembering stuff because its been so long since I set this up. I also have an Adcom GFS-3 speaker selector in place. It has one input that would accept only one amp. I guess if I’m really wanting to separate the two 555s the selector needs to be removed? Is a speaker selector with 2 sets of inputs a possibility?

You have a GFP-555 preamp, two GFA-555 power amp, a GFS-3 speaker selector and two pair of speakers and want to connect all these thing up?

Please tell us how you want it to be setting up, play both pair of speakers at the same time? or you want to listen to one pair of speaker at a time?

By the way, if you want to play both pair of speakers at the same time, and bridging the amp as mono blocks and connect two speakers to each mono block is NOT advisable!


I am trying to play all 4 at the same time using both GFA 555s. I have been running them in mono and wired as per the manual states. I am trying to run them both amps independently in stereo using the GFP 555 and remove the GFS-3 speaker selector. The way it has been set up is not the best I understand. Please give me your thoughts so I do not cause damage. 
Thank you

If you want to play all 4 speakers simultaneously, run both amps independently in stereo and remove the GFS-3 speaker selector is the best approach.

By the way, your GFP555 has two sets of output - Main and Bypass. It is safe to connect one GFA555 to Main input and the other one to Bypass input, OR you can connect both GFA555 to either input via a splitter.

Hope this helps.


Thank you this helps tremendously. Now I am trying to remember about the 2 Polk SDA 2Bs. I think the hifi store I bought them from sold me a different interconnect cable that connects the two speaker to each other after I bought the second amp. I am not sure but think the interconnect cable for running two mono amps has a box on one end. Would you happen to have knowledge of this also?   Called Polk but not any help….30 years very hard  for me to remember!! Any help is greatly appreciated.

So I removed the inner connector cable and it has a box on one end saying

“polk Audio SDA Non-Common Ground Amplifier Interface”

Does anyone know if because I had two GFA 555s bridged it causes a need for a non common ground cable?


Does anyone know if because I had two GFA 555s bridged it causes a need for a non common ground cable?

Yes, If you use the original interconnect cable to connect both Polk SDA 2B together while using two bridged GFA 555 to power the speakers, it may damage your amplifiers! That's why you need the SDA Non-Common Ground Amplifier Interface.

If you using only one GFA 555 in stereo to power both speakers, it is safe to use the original interconnect cable.

Thanks! Appreciate that! Polk customer service sucks for old stuff. Sounds like their in a rain forest country. Calling Adcom just want to sell me a different amp! Wtf