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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
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.
rtn1 OP
535 posts
 
I think this is a good discussion. The Karan slides the bias to achieve class A, but is touted to be unique in the way this is accomplished. I am not an engineer, so I cannot speak to whether this makes sense. Milan Karan designed the amplifier to use balanced power (+60, -60), and has designed a circuit to send a signal to increase the bias prior to the main signal. Thus, the claim is that the bias is increased fully and proportionally to the main signal before the main signal passes through. So maybe the argument is how effectively the bias can be increased ahead of time.

Is there anyway to measure class A power other than the continuous power it draws from the wall?

Of course, all this is beside the point when considering what the amplifier actually sounds like. 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.

Does any of this make sense?
philb7777
401 posts
 
I would certainly consider Jeff Rowland products. Rowland is an outstanding company that has stood the test of time. His 301 monoblocks or 312 stereo amp may be right up your alley. Rowland has characteristically had a smooth top end sound, great midrange clarity and a nice bottom end. I think Rowland is a great match with Avalon and Wadia. I have the same combination myself - a Rowland/Avalon/Wadia rig with Cardas cables. I can tell you more about the combo if you would like - just email me. By the way, I prefer running the Wadia direct, but have a Synergy IIi for vinyl.
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.
rtn1 OP
535 posts
 
Here is a clue regarding how much power is pulled from the wall. The Karan 1200 has a true dual monoblock design (4 power cords total, 4 on/off switches) with 4 fuses total. I ordered 4 replacement HiFi fuses, and here is the response I got:

______________________________________
"Would you please give me a call in regards to your order for 4 of the HiFi tuning 16Amp Slow Blow fuses. When I placed the order for this item with the importer, he asked me to confirm the amperage and size of the fuses on this order. Large 16A fuses are a pretty uncommon value, since that value implies that each fuse would be protecting a device that could pull almost 2,000 Watts from the wall and you’ve ordered 4 of them.

Because of this, the fuses are not in stock here in the US and would have to be special ordered from Germany. Before we do this, we need to confirm that 16A is in fact the value you require.

So, could you please confirm that you actually need 16A fuses and to eliminate confusion, what device you plan to install these fuses in?"
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