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SS Amps for C4 Signature II's

OK, I’m curious about amps.

I have a set of C4 Signature II's that are running with ODYSSEY KISMETS and seem to sound pretty darn good. But, they aren't the be all to end all amps, and they never were meant to be. A good sounding "value", well yes. I have no major complaints on their sound for the price. So, lets not pick on them but look at what might be an upgrade for these speakers. Dragging amps home to audition is a physical exercise in and of itself with 75 pound and heavier weights I'm seeing!

I have just a few amps that seem to be very compelling for different reasons and I’d like some viewpoints from all of you that have been here, done that, and especially C4 users. C4’s can be an odd load at the low-end.

1.0 The first thing is CLASS A verses A/B. The image stability of CLASS A amps is derived from the voltage rails being sag proof (or more so) than class A/B since the are charged up all the time. Yep, that eats power, too. Still, this is an advantage if you pick the right amp.
2.0 A/B amps come in two flavors, high bias amps like an old McCormack DNA-225 (it gets plenty hot when running!) or a lower bias unit like my ODYSSEY KISMETS that refuse to even get warm. The “hybrid” high bias amps that are around (PASS LABS as an example) can run CLASS A pretty high (up to 40 watts in the case of a X350.5). Is that enough to capture the CLASS A “flavor” and A/B efficiency?
3.0 Weight. Man, how do you move your stuff? Some amps are frighteningly heavy making a dual MONO set-up seem logical, but even more expensive. I may get the sound, but the weight can drag you down. Yes, weight is part of the deal in a good power supply, which means get the power you need.
4.0 I HAVE to be able to listen to them before I buy. I don’t need “more” of the amp I have now, worse or the same general sound, but better. So in-house audition is a must. I can’t easily get the PASS or ANTHEM products making auditions and service a pain. But, if it’s worth it, I can try. I can get BOULDER products but they are WAY high priced.
5.0 I am using a PASS LABS XP-10 pre amplifier so I have full balanced or RCA outs.
6.0 Is it just me, or are the specs on these units hard to come by? VA transformer ratings, CAP values in the power supply ETC? Not that this is all there is, but it helps.

So considering those points, and if I’m seeing all this right, we can sort of claw through some of this on paper.

My first choice, again, on paper; Plinius SA-103.
I have heard the Plinius on Theil CS2.7’s, and it imaged VERY well. Can’t comment on the musical balance on my speakers, though.
All CLASS A capability but can run A/B with the flick of a switch so I can listen to the radio with A/B!
Seems to be a solid design with good sonic ratings.
Plenty of power (125 watts / 220 watts) for the volumes I listen to (83 dB SPL average where I sit 15 feet away).
I can get another one if needed for silly amounts of power.
Seems to be nice at low impedance and high current situations.
Wow, it gets warm in CLASS A so keep the music going!
Good paper specs on S/N and separation.
I can actually pick this amp up at 85 pounds.
Price is “reasonable” for a high-end amp.

My second choice is a PASS LABS X350.5 as I’m told that the sweet spot for PASS A/B sound is this amplifier. PASS pure class A is too expensive.
40 watts of class A capability may capture the sound I need?
Seems to be a solid design and also with good sonic ratings.
WAY more power than I’ll ever use, though.
Never need to buy another amp for power.
Stable into low impedance.
I CAN NOT safely pick this amp up at 135 pounds!
Price is “reasonable” if you can find a used one for a high-end amp.

My third choice is an ANTHEM P2 that some say is a giant killer (I don’t see any dead giants laying around anywhere, though).
Seems to be a more standard A/B amp for home theater but…I keep being told to listen to it.
Seems to be a solid design (full of protection circuits).
WAY more power than I’ll ever use, though.
Never need to buy another amp for power.
Stable into low impedance to an extreme.
I can pick this amp up at 75 pounds.
Power rating and light weight make me wonder about the current delivery capability.
Price is “reasonable” for a high-end amp.

My fourth choice is a BOULDER 860.
Doesn’t seem to “double-up” on power into 4-ohms.
Can’t be run “mono” to add one later on.
Built well.
Paper specs are impressive (S/N and separation) but gets a knock for harshness in the midrange.
Seems awful light at 45 pounds to provide a big current reserve in the power supply.
Price seems high for the lightweight power supply.
rower30
ejlif's avatar
ejlif
1,366 posts
 
I would go for the pass amp. I have the C4s also and have thought about this amp myself. I have an Innersound ref 500 which is a cool running solid state amp that sounds really good considering you can leave it on all the time and it won't make the house hot in the summer. I'm not keen on having to turn my gear in and off all the time though so cool running solid state is the only thing ill consider.
rower30 OP
211 posts
 
When you mention, "Bi-amp vertically" does that remove the X-over and use an external one? C4's, of course, don't allow bi-amping. The best speaker would have no power sucking passive cross-over at all. Run amps right to each driver with electronics adjusting the gain into the amplifiers (not a passive speaker cross-over at high power levels!).

Yes, Ayre has come up and I checked it out. I'm trying to decide what CALSS A can bring but, like you say, the end sound result is all that matters not how you get it there.
I can get Ayre, Plinius, and Boulder. PASS LABS dealers are far and few between in the mid west.

For Ejlif...yes, the ODYSSEY's KISMETS are cool as cucumbers and do sound nice. Who knows, I may have the amps I like now and not know it. The Plinius has the A/B option when you want to cut the heat. Hybrid A/B PASS LABS, like my previous DNA-225 hi-bias amp, will run warm all the time.

I'm in the basement so heat isn't as big an issue. The room is 4,000 SQ feet.

Suck-up on the weight? Well, I'm 150 pounds soaking wet and at 55, I ain't no mighty mouse. Oh I'll git-er-done all right but WHEW, it's still a weighty issue. I wasn't so much complaining about the weight, if I USED it! If I buy a big old amp and use 30-100 watts, could I have bough a better sounding amp for less? Still, sound over weight.

Some design does matter. In a given brand (PASS) I'd have to figure the CLASS A amps sound better or why bother? So, ultimately the class A design should "sound" the best if done right. I want to go up a notch in resolution if I can hear it.

I'll tell you one thing, the CS2.7 Thiel speakers with two SA-103's imaged terrificly in the midrange. Positionally stable, pure and full of texture. The speakers can't do that if the amps don't hand it off to them to use or destroy.
ejlif's avatar
ejlif
1,366 posts
 
In a room that size I would go for as much power as you can afford unless you pretty much only listen at low volume or listen only to delicate music. I would assume not since you have C4s. I have never been satisfied with lower power amps. If it were me I'd be looking at the pass 1000 watt amps or the big Bryaton amps. There is nothing like a speaker being driven by plenty of power, unless you play at low level and even then it's noticeable. And for what it's worth I tried the Ayre V5xe and didn't care for for it at all.
zd542
5,339 posts
 
I didn't know that your speakers don't allow for biamping. The reason I mentioned vertical biamping is that it eliminates all kinds of problems that you run into when you biamp traditional (horizontal). This is how it works. You need 2 stereo amps that are the same. Each amp powers one of the speakers. You run a cable from the right output on your preamp to both inputs on one of the stereo amps. (If your preamp has 2 sets of outputs, you can run 2 IC's. If you have only 1 output, You'll have to split it.). You then run speaker cables from the stereo amp to your speaker. One for the high's and the other for the low's. Do the same thing to the left channel.

The advantage of doing it this way is that you are working each amp the same because it is powering a whole speaker, as opposed to using 1 amp for the highs on both speakers and the other for the lows on both speakers. There's no need for active xovers or anything like that. You just hook it up and it works. Keep in mind, though, it only works with stereo amps.
xti16
1,525 posts
 
I have to mention the Burmester 911 or 956. My Dyn dealer had Sim and Burmester and I like the Burmester much better. I listened to those with the original C4's not the MKII/Signatures. I now have the C1 Sig's and they don't seem to need as much power as the originals.
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