You can use spades AND bananas in the A21.
If you actually wanted to bi-amp, the A21 has XLR in and outs, so you can add a second A21.
No, I mean bi-amping...
Traditionally speaking, bi-amping means the use of two separate amplifier channels connected directly (no passive crossover in the signal path) to individual loudspeaker drivers optimized to reproduce a particular frequency range.
@hog_tech - You cannot bi-amp with a single 2-channel amplifier, like the A21, regardless of how many speaker connections it has. 2 channel amplifiers that have A&B speaker connections share the 2 channels of amplification between the 4 speakers. The amplifier connects the 2 Left speaker cables and the 2 right speaker cables inside of the amplifier.
If you want to bi-amp, you need 4 channels of amplification.
You can bi-wire with a 2-channel amplifier that has 2 sets of speaker connectors. However, you can also bi-wire with one set of speaker connectors, running bi-wire cable that are 1 into 2 (one set of connectors on the amp side, 2 sets of connectors on the speaker side). Or you can stack 2 pair of speaker cables using spades, or spades and bananas, as Eric suggested.
I’m afraid the previous posters are correct. Bi amping requires 2 stereo or 4 mono amps (or 1 4 channel amp). As mentioned if your amp or receiver has an A and B speaker terminals it is still a two channel amp. It is not the same thing so if you want to bi-amp with the A 21 you will need two of them. I think you will be better off bi wiring them. I prefer using two separate sets of speaker cables and keep them separated from each other to avoid EMI interaction with each other and keep them off the floor as well. One of the main reasons for improvement with bi-wire and bi-amping is the elimination of the bad sounding jumpers that most speakers that are bi-wire capable come with. Omega Mikro sells pure copper ribbon jumpers that are a big improvement over most factory jumpers. At about $40 they are cheap to try. See them here: http://shop.mapleshadestore.com/Clearview-Biwire-Jumpers_p_1187.html
Might just save you another $3000. The sonic improvements of bi-amping/wiring are subtle and I can think of many other upgrades I would rather make for $3000. I think you would need a serious highly resolving system to justify it. But as always in this hobby YMMV.
So here's how we settle this little argument. Its really very simple. You take your best shot at bi-amping. You add up everything you spent. Then you go on-line and buy whatever Synergistic Research cable you can find for that amount of money. Which one does not matter. New or used does not matter. Not for this. Well technically it does a little, only because new you have 30 days to return for any reason.
Which is indeed a technicality. Because when you hear how much better it sounds than anything you can do bi-amping it will not be going back. But all your bi-amping stuff will be going in the dumpster. Because nobody wants it. Because bi-amping hasn't been a thing for like 30 years. Because you can always do better for less with just one good cable. Always.
But please do not take my word for it. Don't argue it. Settle it. Go and listen.
Millercarbon, and everyone here, Happy New Year. Miller, as always, you are very opinionated, and I disagree with you on this particular subject. I encourage, vertical, passive biamping, to many of my clients, and not once have they though of going back to a single amplifier, whatever speaker wire was used. Again, to each his / her own. Reading the entire description by Denon, they make it very clear of what they are speaking of, but, to a newbie ( we all were one, at one time ), it can seem confusing. As far a speaker switching on an amplifier, it is, of course, for convenience, as mentioned above. But, it has been my experience, that eliminating these switches ( electrically bypassing them, mostly on older Japanese and European made products, using as an example, the Yamaha M2 power amp ), there is plenty more SQ to be gotten out of the product. I would rather run several, separate, dedicated amplifiers, to specific sets of speakers, if this was a necessity. I do not see speaker switching on the majority of the top end amplifiers. In fact, when Adcom released the GFA 535 series II, getting rid if the speaker switching was paramount, in the sq upgrade, Adcom was looking for ( as well as better speaker binding posts, and other internal upgrades ). Sorry for going off on a tangent. To the OP, welcome ! Enjoy ! MrD.
Two things here, one, "technically," as far as "power" goes, you can not bi-amp with a single amp, but, two, as far as a speaker is concerned, if you have two sources of power, whether they’re A + B speaker connections off the same amp, or simply one set of speaker connections off two amps, the speaker doesn’t know the difference. All the speaker knows is that you have removed the speaker terminal connecting band and it is getting separate power to each set of terminals.
So, I’ve gathered that to some, you could have 1, 2 or even 3 different sets of speaker terminals on a stereo amplifier, and "technically" speaking, even if you use 2, or more sets of those terminals to "bi-amp" your speakers, it is their opinion that the speakers still haven’t been bi-amped because that’s simply splitting the power off the same amp. This I understand completely, in theory, since I do have a BA in Electrical Engineering, although retired, but as to the "term," bi-amping, it simply refers to a specific way to hook a speaker up. It doesn’t refer to where the power comes from or how much there is. It only references removing the speaker terminal connecting bands and powering the speaker with two separate sets of power.
But, is that really so much better? is the power at the speaker terminals sensed on the inside of the speaker really so much different using the speaker terminal connecting band than it is to remove it and bi-amp the speakers?
What I have come to understand is, that the woofers take 70% of the power powering a speaker, and that by separating the power to the terminals and bi-amping it to give the tweeter it’s own power, the sound has more detail because the speaker woofers aren’t eating up all the power before it gets to the tweeter.
OK... so that brings me back to my initial question, keeping in mind that bi-amping theoretically sounds better, no matter if it’s splitting the power off the same amp with multiple sets of speaker terminals...
..."then is it better to find an amp with 2 sets of R, L speaker terminals instead of just 1?"
Yes, I realize the Parasound Halo only has 1 set. That’s what sparked off this question. That’s why I hesitate to buy one. I’m currently powering my Bowers & Wilkins CM-10’s in the front room with the new Yamaha Aventage RX-A3080, which I can bi-amp with and am doing, but a home theater receiver isn’t the best for 2 channel listening, that’s not what it was designed for, but the Aventage does have R, L, XLR outputs, so I have thought of adding an amp for when I occasionally listen to music. Mainly because the B&W do love power.
Well, obviously someone here has to get snippy. I wondered if that was going to happen. Evidently every forum has at least one person that has to have everyone succumb to their opinion or they have a tizzy.
Well, not going to waste any more time here trying to have a mature, rational conversation with snippy people.