"... I've used an Adcom 555 II with an SVS 20-39 that I used to own, but didn't enjoy the combination. When I later swapped out the Adcom for an old Marantz SS amp from the 70's, I noticed an enormous improvment in the quality of bass. I know other people recommend Adcom, but I found it to be thin sounding for subwoofer applications..."
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coulda been the combo w/the svs', or even a faulty adcom amp. i used a pair of original 555's (pre-ll iteration, supposedly better, according to those who mod these), to drive my vmps larger subs, & they worked great. almost as well as the present pair of electrocompaniet aw75dmb's i'm now using...
also, may wanna try the dirt-cheap art sla amps that have been receiving good user feedback. they're only ~$200 from a place like fullcompass.com...
also may yust wanna consider repairing the perreaux - these are supposed to be killer sub amps in their own right.
doug s.
btw, i found the adcoms worked better instereo mode than bridged - a tad tighter sound. even when i used only one channel of each amp for each sub, prior to adding separate binding posts for each of the subs' two drivers.