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Best Solid State for Avalon Isis

I would appreciate informed comments regarding best solid-state synergy with Avalon Isis. I’m looking for an amp that will maintain absolute control of deep bass, while maintaining a rich and dynamic mid-range, and clarity without sacrificing musicality. It should be transparent, and allow a vast and layered soundstage to appear. Although the Isis appear relatively efficient (90db at 4ohm), the paired 13” woofers are going to need an amp with muscle.

Source is a Wadia 9 series. It runs direct. It does not need a pre-amp.

I listen to big, loud, congested orchestral music (ie. Mahler, Bruckner, Wagner). I like to hear all the detail, including the musician's technique and subtle alterations in tempo. Orchestral sections need to have mass. I want to feel the bass at low in addition to high volumes.

My room is 20 x 30 ft, and has plaster walls/ceiling with wood floors and padded area rugs. Tubes are not an option. Because of the room and source, I am not looking for an amp that is artificially fast or tipped toward the higher frequencies.

A company which is solvent, established, reliable, and with good customer support is important, with preference for an American manufacturer. I plan on trying to home demo some of these, but need advice on where to concentrate and expend my efforts.

These are some I'm considering, and additional suggestions are welcome:
Pass Labs XA200.5
Boulder 1050 Monoblocks
Halcro DM78
Spectral DMA 360
Edge NL Sig One
Hovland Stratos

Thank you,
Rob
rtn1

Showing 3 responses by bombaywalla

bombaywalla's avatar
bombaywalla
1,958 posts
 
Rtn1,
re. the Karan 1200 amp 16A fuses - *if* the amp is 1200W/ch into 8 Ohms (I assumed from the model # that it's 1200W/ch into 8 Ohms. I could be way off the mark!) then it seems that it has a +/- 98V rail. It also seems that it could be drawing 12+ Amps from the wall when providing its full 1200W/ch into 8 Ohms. So, I can see why it needs a 16A fuse.
The other thing is that the power supply caps must be huge in their capacity. So, when the power amp is switched on, there is a huge in-rush current that the fuse needs to withstand. There is probably an in-rush protection ckt but despite that you will need a large value fuse to ensure that it does not blow during switch-on.
However, all this does not tell us whether the amp is class-A or class-AB. All it really tells us is what the amp will draw from the wall -it's a large wattage power amp & it has the potential to draw some serious current!
You can get hint of whether it's traditional class-A or not by seeing if the output power is 1/4 the power consumed from the wall & whether it's sliding class-A or not by seeing if the power consumed goes up with increasing input signal amplitude.
bombaywalla's avatar
bombaywalla
1,958 posts
 
Tuboo,
good comments re. class-A. I agree with you - there's a LOT of marketing hype. The more the consumers do not understand, the more the manuf seem to take advantage playing the spec game. I see this more in the USA than in Europe, Asia or Australia.

One comment from my side - an amp can also be biased in sliding class-A (rather than in full power class-A such as the Alephs). A sliding class-A amp can support only a very small output signal - one that would probably not create an acceptable SPL for listening - but has no x-over distortion characteristic of a class-A output stage. As the input signal increases, the bias for the output transistors increases (slides up).

>> one of the heavy class A contenders are indeed the big
>> Gryphons. boy they get HOT.
Indeed they do!
A couple of more contenters - the Plinius SA-250 Mk4 when switched into class-A mode. The Threshold T200. These amps get HOT too! I measured the fins of the T200: 54 deg C when stabilized.
bombaywalla's avatar
bombaywalla
1,958 posts
 
Rtn1,
Is there anyway to measure class A power other than the continuous power it draws from the wall?
you could get hold of a 10W resistor & put banana connectors or spades on its terminals. Then connect it to your amp's speaker binding posts. Feed a low amplitude signal into the amp, measure the output signal & note the power consumed from the wall. Increase the amplitude of the input signal. The output amplitude should also increase. Does the power consumed from the wall increase? if yes, the amp must be sliding its bias. Increase the input amplitude & see if the power consumed from the wall increases each time.
If the power does not increase, then the amp must be biased in fixed class-A mode (wherein it should be dissipating ~4X the power w.r.t. its output power).

However, I do believe that in general an amplifier should sound better in class A than in class AB, with all other things held constant.
It is generally believed that a class-A amp does not have x-over distortion hence its sonics must be better than a class-AB amp. This is just 1 aspect.
yes, if 2 amps are practically identical in amplifier circuit topology, power supply, components used then perhaps yes.
In the real world you could have a marginal class-A design that is out-done by a much better implemented class-AB design.
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