Whether or not you hear a difference between the two modes of operation on a given amp like the Plinius is going to depend on several factors. The first is how much power your speakers require to generate your average listening levels. This is directly related to impedance (because what we're really talking about is current and how much is required at a given frequency), and to a lesser extent sensitivity. The next factor is your room size, and then the third factor is how loud you typically listen.
In a small room, on efficient speakers, if you tend to listen in the high 80's or low 90's you may in fact never leave class A when in the sliding bias mode, hence you don't hear a difference between the two modes. However if you throw on a very dynamic piece of music, say Mahler, and play it full tilt boogie in a large room on inefficient speakers... well that's another story altogether. You will likely either be out of class A entirely or constantly at the bias point, switching between Class A and Class B (which is the worst possible scenario sonically speaking)
Now as for comparing two different amps from the same manufacturer, that's another story and it's hard to say whether a different amp will sound like the one amp in AB mode, or completely different.
OK I spoke to the manufacturer and they replied that SA amps work for 8 Ohms in class A upto the specified wattage: SA100 -- 100W/ch SA50 -- 50W/ch SA250 is certainly 250W/ch. For lower load impedance they switch to A/B operation type to double the current.
Plinius 8200p is not identical to SA100 since it has lower switching point to the class B and that point is relatively high as well i.e. ~25...30W/ch of class A. I assume that these two units have completely different power supplies and heat sinks if you just take a look even on the pictures of them.
Plinius 8200 MKII has M14 preamp and 8200p poweramp integrated into one chasis with separate power supplies for each part.
Overall I can say that there is a Plinius sound signature on all of above stated but flagship SA series are more open worm and defined.
Despite working in class A on 8 Ohm loads all of Plinius models love the heavy speakers such as Thiel, JM Lab or Apogee and to my thought they do the best job on them.
You owe it to yourself to listen to the Plinius SA 102.
I own an SA-250 MKIV and I can honestly say that there is a perceivable sound difference between AB and A (A sounds better, smoother).
I also tend to agree with HACKMASTER in that the amount of power required to drive the speakers will invariably affect whether or not you'll hear a difference between class AB and class A.
Youll have to be able to stand the heat though. The Plinius amps run murderously hot in class A. Youll see a difference in your power bill too. Happy listening!
My SA100 MKIII has just the slightest amount of grain in AB mode that is gone in A mode, also in class A there seems to be better definition, or maybe it is my imagination, it is that close. It sounds superb in both modes (driving Maggie 1.6s).
I had an SA100 III and had the same question, so I listened blindly as a friend switched the amp from A to AB with several different types of music. For each song, he switched the amp back and forth, and I indicated which I preferred. For all tests, I preferred the amp (no surprise) in class A. There was more bass, smoother top end (less grainy), and much better depth. For me the difference was big enough that I always preferred the amp in class A, by quite a bit.
I haven't heard the 8200, but I doubt that it sounds as good as the SA100 in class A.
I own the SA-102, so I'm not sure if my observations will be the same compared to the SA-100. I can hear a distinct difference between A and AB, although much of the sonic character is maintained in both modes. Class A provides a more focused, layered, and densely populated soundstage, the bass has subjectively greater reach and better pitch, the highs have a more crystalline quality, and there is slightly more warmth and body. Class AB sounds great as well, and is possibly more open, although less focused, and slightly more forward sounding. Even though the SA-100 is only rated at 100 wpc vs. the 8200p's 175 wpc I would think that it is capable of more current delivery than the 8200p due to its larger power supply.
I agree with Judit: you owe it to yourself to hear the SA102.
I traded up to the SA102 from an 8200 integrated. For the money, the 8200 is great, but no match for the SA102. The 8200 is rated at 175 watts at 8 ohms, and the SA102 is 125 watts at 8 ohms. But the SA102 is capable of delivering something like 4500 watts at clipping and even the gutsy 8200 can't match that. The SA102 can really swing that woofer like no other amp I've heard (except the SA250).
As to your question, Symphony Sound is theoretically correct, but I admit I can't hear a difference between A and A/B on the SA102. But who cares - this amp is awesome!
Here is another vote for the Plinius SA-102. As far as your question on the difference from A/B to class A, in my system it's quite noticeable. Much more subtle detail and more spacial clues. The definition of each note is more realistic. I must advise that on my older less revealing system the differences of the original SA-100 were not as pronounced but still easily discernable. I would not advise anything less than Class A if your looking for the ultimate and your system is capable of delivering.
I totally agree with all review before me on this forum,
its obvious they own and indeed they are full of information
and i learned too. Thanks you guys.
Let me just share, to my experience with my plinius
mark 11 when i played to AB its really good, but to me
switching to A its a differrent level of listening,IMHO i
notice the first 10 to 15 minutes after switching to Class
A i dont hear the difference too, at least 1 hour after
music began to involve me more,it disect the inner part
of the emotions of the music,more transparent and clearer.
but i believe i like the Class A mode.
anyway thanks again.
Does the Plinius 102 run hot in ab mode ?? --- I have a problem with a heater in the house during the summer months, and was hoping to be able to run it in ab mode and still get good sound.......
To elaborate on my response - I agree with Jayctoy's description, after reading this post I listened to my amp in class ab for a few nights and was less involved in the experience than in class a. It is nice to be back to class a, it is more liquid and pure. In class a the music has a nice 'inner glow'. This is fine amplifier.
I guess switching back and forth between the two tells you very little, I agree it must take a while for the change to occur.
Reziech: I have an SA102 and it barely gets warm in A/B mode.