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Need Advice on Multi-channel Amp Choices.

Hi All, basically I am in need of a new Multichannel power amp for my room.

Setup consists of 7.2 configuration

  • Arcam Av950 preprocessor
  •  Monitor Audio Platinum Pl300 fronts
  •  Platinum pl350 Center
  • 4 x Gold GXFX Dipole Surrounds
  • Dual Monitor Audio Gold Subwoofers. 

My listening is 50 / 50 HT and Music. Music is 50 percent 2 channel and 50 % multi-channel sacd's.

Room Dimensions are 20ft long and 13ft wide.

Basically I have my eye on a number of used options but no way to Demo them.
  1. Earthquake Cinenova 7 Grande
  2. Audiocontrol Savoy G3
  3. Classe CA-5100

All of the above are pretty close in price, a shade over 2 grand. The Audiocontrol is new, The Earthquake 2 years old and the Classe from 2010. I am struggling to make a choice between them. Anyone got experience with these models, need a push to make a choice, thanks.
melmoth76
erik_squires
16,011 posts
 
I found your comments about frequency response interesting. That would imply that they have high output impedance (or low damping factor) which they do not, by themselves have. Tube amps of course tend to behave this way. If you can point me to any measurements for the ICEPower or nCore amps which do this I’d love to check them out.

Most amps reduce DF (increase output impedance) as F increases, but older class-D amps pretty bad in this respect. If memory serves though, nCore and the later generation ICEPower units solved this quite well.

In solid state amps improving (reducing) output impedance is usually a matter of feedback, and in D class amps where the feedback is applied.

If memory serves, the feedback on the nCore is at the output stage, instead of before, a good thing. They have ridiculously low output impedance as a result. Any "frequency tracking" of the speaker impedance is not due to the nCore design.

I use bare ICEPower 250ASP based monoblocks to drive 4 Ohm speakers (min impedance 4 Ohms through mid bass) and they do superbly. The ICEPower amps replaced a pair of Parasound A23s, which are fairly well biased into Class-A for the first 30 or 40 watts. I could not hear a difference, so I completely converted. I was running the Parasounds in a 4.0 HT configuration, so 1 amp was left, 1 amp was right.

Best,


Erik
auxinput
2,920 posts
 

This was 7-8 years ago when me and my cousin were into Class D amps for a while. ICE and Hypex UCD were the only two. We were using the Channel Island which had the Hypex UCD - we chose that for some reason I can’t remember (it may have been the design of the negative feedback, not sure). What we experienced was that it drove different speakers differently. I had some Focal speakers that were easy to drive. However, when put on a Aerial 10T, it had good midrange body, but we lost all bass punch/impact and the highs were severely rolled off. Others had problems with the Channel Island, such as pairing with B&W Diamond. When we matched the 10T up with an Aragon 8088BB high-current, the problems went away and the sound was significantly better.

That being said, the Channel Islands did well with the Focal, but we could tell that it wasn’t perfect. It did have a somewhat forward sound, as some frequencies were pushed and others were not (the high frequency rolloff actually helped the Focal a bit).

Moving on to B&W Diamonds. I had a Crown CTS2000 - Class I (variation of Class D). It was decent, but the Crown had weird tube-like overtones and wasn’t exactly neutral/dry. The Channel Islands did much better. But when I put on an Emotiva XPA-1 (high current), it pretty much blew the other two away.

There was an article/document I read years ago about Class D - I can’t find it anymore. The guy had worked with Class D amp design a lot. What he said was that the speaker itself must be part of the Class D circuit design and influences the circuit itself. So, in a Class D circuit, the engineer has to make some design decisions on the assumption of what kind of speaker is going to be placed. In a perfect world, a speaker with a flat 8 ohm impedance (across the entire frequency range) would be very good. However, when the impedance starts to go all over the place, it will influence how the Class D circuit responds. (don’t ask more I cannot technical explain more than the bits I have remembered from the artical which I stated above).

A linear Class A/AB amp will still be influenced by the speaker impedance curve, but it is much more resistant to this when compared to a Class D circuit.

I don’t know how nCore compares as it wasn’t around at that time. It could be something related only to Hypex UCD.

auxinput
2,920 posts
 

Thanks for your additional comments, Eric.  It may be that the newer ICE and ncore amps work better with difficult speaker loads.  I did some quick browsing on ICEpower and nCore.  One of the things that stood out was that nCore was designed to remove any coloration on the sound - extremely low distortion.  The idea was to reproduce exactly as the sound was input.  More searching indicates that this is the nature of these new Class D amps - no coloration.  Some have commented that they are lean or a bit bright/cold.  I do not have any direct experience with ICE or nCore, but it could be the preamp/source that is dictating this nature.  The Wyred 4 Sound amps use ICEpower and I know the general approach from Wyred is to make things as transparent as possible.

I'm wondering if the listener experience is dictated by the preamp/source.  If they are using an opamp based preamp/source, the nCore may be too transparent and you end up getting a lean/thin sound.  When paired with a Class A or tube preamp, the nCore may really shine - as you are putting a limit on how much coloration is going into the audio signal path.  The only thing that catches me here is that you could not hear any difference between ICEpower and the Parasound A23, which is very interesting.

Don't know.  If you pair the nCore NAD M27 amp with the Arcam AV950, you might not get that sweet/full sound - it may be too much transparency.

Thoughts?

auxinput
2,920 posts
 

I was just looking around and came across this Classe CA-5200. It is twice as much as your budget (around $2k), but it has a shared power supply twice as large as the CA-5100 -- at 200w/ch 8ohm, 375w/ch @ 4ohm. It’s expensive, but if you were liking the idea of Classe brand, you could look at this. It is a beast at 121 lbs (like the Theta Dreadnaught), but I think it will do better because of it’s huge shared power supply - akin to the Krell Theater Amplifier Standard.


It's on the Echo hifi website, but it seems that Audiogon won't let me paste the direct link.
erik_squires
16,011 posts
 
I’m not sure about the nCore, but as for the ICEPower units, I would say that’s true, they really don't add anything to the signal so if you need warmth or liquidity added these are b. .... however....

Using my current reference speakers I could not tell a musical difference between an ICEPower 250ASP and Parasound A23. The A23 is often described as warm, and my system is as well by listeners who do not kwow what the amps are.  My sources are a Mytek Brooklyn DAC feeding a Parasound P7. I could see myself trying out a tube preamp here or there to add some liquidity to the top and magic to the midrange, but the sound is most definitely not lean or soul-sucking like I have heard some mass produced processors to sound. I’m pretty happy with what I have, but tubes are tempting. :)  I have heard from a couple of users who attempted to use the ICEPower amps directly from PC sources, that did not go very well for them, I'm afraid. :D

Certainly for movies I lack nothing. Engagement, dynamic range, dialog intelligibility and transparency across the audible range are excellent.

Some of this may have to do with having relatively easy to drive speakers. Min 4 Ohms, and 8-10 in the treble, where I have read at least 1 complaint of the ICEPower units with Maggies. The ribbon tweeter in Maggies becomes inductive, while my speakers use an AMT which remains resistive from the crossover frequency upwards. It may very well be that there is some speaker dependent behavior. On the other hand, the Monitor Audio speakers are fairly straightforward to drive and nCore have an even lower output impedance than the ICEPower units.

My surrounds are even easier to drive, remaining around 8 Ohms through the midbass, and min 6 elsewhere.

So, to sum it up, if you have reasonably normal speakers without reactive tweeters and your sources have all you need in terms of warmth, tone, etc. I think the current batch of Class-D amps is an excellent choice, and the NAD 7 channel nCore a fabulous bargain.

Best,


Erik


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