To All --reporting back on results of using impedance buffer. Ok, I hooked up Tom Tutay's buffer. As a threshold matter, let me say a couple of things about Tom. He is very professional and knowledgeable -- a real gentleman. He turned around my order in lightening time. The shell of the buffer device is made wholly of metal, and is about 9" x 5" x 2". By all appearances from the outside, the device seems to be very sturdy and well made.
Now . . . as to how it works. As you can see from the posts above, the device was designed to: (a) load my Ref 3 symetrically (i.e., Main 1 and Main 2 in balanced mode), (b) sum the left and right channels without shorting the Mains since I am using only one sub, and (c) raise the impedance level of the two Mains to a level that better matches ARC's design specs.
As to tube life, I take it on faith based on conversations with ARC that by reducing the load on my Ref 3's outputs, tube life will be extended. I will have to wait and see.
As to sound quality, I can say with 100% certainty, my rig does NOT sound worse. Does it sound better?? Yeah, I think so. I think the imaging, detail and sound stage are a little bit improved. The highs seem a little smoother and better refined. But quite honestly, I don't think the change, if any, is day and nighgt. It's just subtle, kinda like a tweek, maybe two or three tweeks.
Now the impact on bass is more noticeable. Although I removed one active artifact from the system and added another, I think the X-30 crossover/controller did more than the buffer because the X-30 could adjust loudness, phase, cut-off and summed the channels. By contrast, the buffer has an active unitary op amp that raises the input impedance and just sums the channels. That's it.
When I first inserted the buffer, I initially thought something happened to the bass output from the sub. On Tom's suggestion, I tried using the old hook-up again by running an SE I/C from one of the SE Mains off the Ref 3 directly to the sub (sans X-30). I then ran the Ref 3 in mono mode to sum the channels. Interestingly, the bass seemed equally lame this way too.
Then I realized what was going on. I had set the cutoff frequency on the sub at 35 Hz to blend into my fronts. What I realized is that there simply wasn't very much going on below 35Hz in my source material. By contrast, when I raised the cutoff frequency -- bass galore.
So realizing what was going on, I then critically listened to some bass heavy source material, e.g., Norah Jones CD and Solti conducting Chicago Symph Orchest., Beethoven 9th 1st and 4th movements LP. Tons of bass in these source materials. But when I raised my sub's cutoff to about 50 Hz I had more than enough tight and smooth bass -- NOT boomy.
In summary, Tom Tutay of Transition Audio Design is a great resource for audiophiles. He is not limited to just buffer devices, but can custom design many different types of devices. Keep him in mind. Tom's phone number is: (850) 244-3041.
Thanks guys for the terrific advice.
