Marantz Ruby PM KI amp vs Accuphase e-480 or e-380

@wadia150 May I ask how you connected the REL subwoofer to the PM-KI? Is any component getting warm at the touch? According to Marantz, the PM-KI was not meant to have a subwoofer connected to it. 

This is their reply when I contacted them (Marantz). Even the guy from Rythmic subs warned me about connecting subs to Class D amps.

Thank you for contacting Marantz Support, we value you as a customer and appreciate the opportunity to be of assistance!
The PM-KI Ruby is not a Fully (or true) Balanced amp. Only the PM-10 in our Reference line is Fully Balanced.

We do not recommend connecting a speaker level sub to this unit as it may cause damage to the amp channels. Unfortunately, the PM-KI Ruby is not designed to handle a sub. It's designed to be used with 2 speakers connected only.

If you have any further questions please feel free to contact us again. 
Thank you for contacting Marantz Customer Support.  Have a great day!
Regards,
Anthony
Customer Support
Denon | Marantz
Sound United North America

We do not recommend connecting a speaker level sub to this unit as it may cause damage to the amp channels. Unfortunately, the PM-KI Ruby is not designed to handle a sub. It's designed to be used with 2 speakers connected only.

patently ridiculous

I have my new Ruby connected to my older Pinnacle Baby Boomer powered subwoofer.  So far I have no issues whatsoever.  The Baby Boomer has left and right speaker level in lines and then lines back out to the speakers themselves.

I too was concerned at first about hooking up a sub to the Ruby because of the above quote, which is a strange one coming from a Marantz rep, but I have been assured by several other reputable sources that any such concerns are simply strange and wrong... Perhaps if one is hooking up a non-powered sub, there might be a legit concern of draw on the amp?  I don't know, but two reputable Ruby sales sources and both SVS and REL reps have told me there shouldn't be any worry at all. 

I guess if one is concerned, there are (too expensive) external crossovers available and also inexpensive speaker line to "RCA"-in converters as well...?  

As for external crossovers, though, imo it'd be best just to replace my sub w a more modern one that can be more fully controlled for a customized blend... think SVS.

The Pinnacle is a heck of a nice, tight sub in a compact form, dual 8" drivers facing opposite directions, sealed design, attractive finish.  I do wish my Pinnacle had a lower crossover so I could cross it at 40 instead of the 50 which is the lowest the Pinnacle offers.  50 is good with the Heresy IV speakers, but 45 or 40 would be better in my current room as the Heresy do a pretty good job down to 50.  40 or 35 would be better for my EPI speakers with Human parts which do an amazing tight articulate job down to about 45.  But a new SVS would have the advanced customization capability to blend close-enough to perfectly with either speakers, and based on the information that I have, hooking up via speaker level a sub to the Ruby should not be a problem at all.

@curtdr thanks for your reply. I feel better now and will probably try a REL.

I've had 2 REL subs linked to my Ruby's speaker binding posts for a year or so with no issues. Sounds wonderful. 

Also, I have played around with tons of amps on extended basis. This amp is an exceptional performer. It is a reference level piece that can compete and best stuff costing way more. 

Opening the box of the Ruby products is a treat.  The Japanese build quality is something to behold.  I think Ken should have added some bling to the cosmetics because it looks smooth and strong but could use a bit of flair.