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,
Lamm M2.2 hybrid monoblocks should be on your list. My friend with similar musical tastes uses them with his Rockport Antares speakers.

(FYI: they do have one 6922 tube per amp, so technically they are not a "true" solid state unit, but only having one tube makes them very easy to retube. In addition, they usually are listed as a solid state amp, if the categories are either tube or solid state, with no hybrid being a third category.)

They are among the best amps I have ever heard, (regardless of being tube or solid state), and they have a rock solid, deep bass response, and are quite powerful. With that one tube, they manage to impart a sense of life to the music that most solid state amps seem to lack, IMHO.

My two cents worth.

PS He also used these same amps on his Avalon Eidolons, prior to getting the Rockport Antares. They sounded great with them too!
From europe youi can use:

Symphonic line
FM acoustics

These two last only can be bought in Germany, awesome and with reasonnable price, not very cheap but reasonnable.
spectral, but add a spectral pre...wadia or not
Spectral has the reputation for working with Avalon. Jaybo offers good advice.
do the Isis come like the Sentinel with to monoblocks for the bass ?

I have only heard the Sentinel which is working marvelously with Pass electronic; either the big integrated !! (of course because the monoblocks are there) or the XA 200.5 ... extremly beautifull mid-high range, a dream!
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. I listen to big, loud, congested orchestral music
Likewise. You also want American, so go for Pass 350 upwards (i.e. 600) or the Spectral 360 or 250 stereo or the Boulder Mono. For a more intimate sound & not so loud on Mahler, the Pass 200.5 and the Lamms mentioned above. (The Halcro is great but Australian, afaik.)
In keeping the story short, I strongly advise you to opt for an amp with tremendous output power rather than the quintessential "few golden watts". You can't listen to orchestral music with a few "golden" watts with those speakers.

BTW, the Isis is a serious design, produced by a serious manufacturer. Some other manufacturers are amateurs by comparison.
It also sounds nice. Hold on to it. You may one day purchase (sub)woofers; or you may not.
I am very happy with my Wyred 4 Sound amp. I have the 4 channel 250/500 biamping Magenpan 3.5Rs. Proper cabling is needed to let it be all it can be.

I use Tek Line Cables Reference and micro Reference Xtreme power cords, PS Audio Transcendent Silver interconnects and Clear Day Cables solid core silver- double shotgun
Hello Rob,

You may want to add the BAT 600se mono-block amps to your list. I believe they could easily fill all of your requirements. Boy would I love to be able to afford a pair of Isis!
Good luck and enjoy your search.


I would looking into the new Berning monos (Quad Z)...I am auditioning next month. If you are looking at Boulder, perhaps Gryphon Coliseum or Antileon Signatures...both full Class A. Good luck.
Rob, was it you who called? Save yourself time and trouble :)
Email user Branimir - he went through many solid state power amps with his Isis and may offer you a valuable advice.
Zdravo, here's an update: I've got the Karan Acoustics M 1200 monoblocks. More info to come...

For now:
1) Dual monoblock design with balanced circuit and power.
2) Over 2kw into 4 ohms.
3) First 75% of power is class A.
4) Each weighs 167 lbs.
5) Stays on 24/7 - at idle, consumes a few hundred watts and measures 91.8 F at the heat sinks.

Hvala for all the recommendations and help.
"A company which is solvent, established, reliable, and with good customer support is important, with preference for an American manufacturer."

I'm surprised Ayre MX-Rs were not on your short list. Sounds like you made your choice. Happy listening - I'd love to hear your system!
Hi Rob,

I own the ISIS and uses the David Berning Quadrature Z 200-watt monoblock ZOTL Power Amplifier. They are by fare the best I have ever used, and I have tried a LOT.

Plays the dCS Scarlatti and uses Edge 1.1 Sig SE preamp.

Hope this helps,

Br, JK
Although I have no experience with the ISIS I heard the Avalon Eidolon Diamond sounding excellent with the inexpensive cj Premier 350 and ART preamp.
The well known hifi critic Martin Colloms lived for a long time with cj premier 350 and and ACT2.
Rtn1: congrats on your new toys!
Stays on 24/7 - at idle, consumes A FEW hundred watts...
No way!
Please don't be discouraged -- but an amp rated at 1 kW with 75% in class A, is going to consume around 3kW idle or otherwise. That's MANY hundred watts:)
(Or it's not really class A & your electricity bill is safer)

Most importantly, Enjoy the tunes:)! Regards
Hi Rob,

first congrats again on your new amps.

what power cords are you using? Do you have the amps on their own designated lines?

Are the amps ontop of any type of isolation? (Sistrum) if they are have you done any comparison and what did you notice.We both at one time owned PASS X-600.5 mono's so we know what they are all about including the difference once put ontop of the SP-101's.

Referring to the Pass amps did you try those on your Isis? if so what is the difference between them and the Karan 1200's.

Some new pics of your system would be nice.
Hi Rtn1 (Rob)

I was just wanting to bring this thread back to life, kindly refer to my above questions to you thanks.

You have had the amps for a while now so any further thoughts.
there is a lot of misconception about 'pure class A'.
there are not much pure class A amps around. the old Pass Alephs were pure class A and they had not many watts.
most (almost all) amps are class AB.
it is all about bias. as an example if an amp has 600 watts into 8 ohm and the manufacturer claims 'pure class A' this amp should draw about 4 times 600 watt out of the wall. not very likely.
many tube amps manufaturers claim pure class A too.
you only have to look at the continuent current draw, ie if a tube amp draws say 400 watt continuely it will have about 100 watts pure class A. this is not an exact math figure.

i see another statement like 'this amp has big watts so it does bass well'. most of times this will work out, but i have experienced 50 watters which can put ashame any 1200 watter. watts never claim bass alone on amount of watts. its all in the powersupply..

Nelson Pass has a great article concerning pure class A at his website. check it out.
one of the heavy class A contenders are indeed the big Gryphons. boy they get HOT.
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.
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?
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.
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.
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?"
I have had several Avalon speakers (but not the Isis in particular) - The best sound came out from a Gryphon Anthileon followed bt a Rowland 8.

Hope ths helps you out.
I used to own the diamonds and tried many amps. As far as solid state goes, I strongly prefer the Boulder 1060 over the rowland 312. Switch mode power amps and ceramic drivers are not a good match ( too dry),. The best sound was from the Luxman pure class A amps. I would think Gryphon would be good too. I also tried pass x.5 and pretty good too. No exp with Karan. Tubes also good but another story all together.
Thanks to all for the advice.

I settled on the Karans based upon several people who have actually heard them with the Isis. Roy Gregory from HiFi+ used Karans for his Isis review, and I thought that review was very accurate. I find most reviews to be quite vague in lathering-on the praise, but this one was consistent with my own listening. Roy also has separate reviews of the Karan 1200 and 650s.

For tube amps, I think the choices are basically CAT, BAT, and VTL.

For other SS amps, I think the choices include Boulder 2000 series, Ayre, and Spectral. Gryphon may be good, but no one heard this combination. I think the key with solid state is to have something that is powerful, and with a full mid-range.
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.
I just heard Isis with the Stratos & Odin

beautifull but a little bit slow for my taste

source was dCS Scarlatti, preamp also Howland
My system has been posted. Thanks again for everyone's help.

I suspect the amp can make a big difference in how these sound.

The similar Avalons I heard were on a very expensive Boulder amp and sounded quite sweet! I seem to hear this pairing come up often it seems.
Just for the record - I talked to Neil some years back and liked Spectral by that time with his Eclipses.

I'd like to experience the Hovland Stratos and DCS Scarlatti with the Isis. I'd imagine it would be quite special and a different flavor than what I have. If you perceived some excessive slowness, then I wonder whether there is a room or speaker set-up issue at play.
I don't know ... but what is certain is that for Pop / Rock music even some Jazz, the bass was too slow ... they told me that with Boulder or VTL it was even slower ... a problem with electricity or powerchord?? ... Odin is fast, the room was a acoustically prepared room ...
I would also consider the JC1 monoblocks.
Rob, Where did you purchase your 1200's if you don't mind me asking?
I'd consider the Rowland 300 series too. Great amps.
Most probably this:



Discalaimer: I'm the Italian Viola distributor but the match with the Avalon Isis is really incredible and worth to be mentioned.
I have heard the Viola preamp ... fantastic! never heard such a precise soundstage

for me the only "mistake" on the picture is the EMM Lab, dCS Pucini is quite better ... I am not dealer ;-)
I have a related question. I am thinking about buying the Avalon Isis but wonder if my SOulution 710 (ss 125 watts pc) will have power enough. My room is big (about 12 m x 4m). Currently the Soulution powers a pair of Eidolon Diamond without any problem.
Does anyone have experience with this particular combination?
Many thanks

FWIW, I have been speaking with someone else with SF Strads (4ohms but 2.7ohms across fairly wide amount of the bandwidth)...and he thinks he may need to go up in power from Soulution 710 to Goldmund Telos 600 monos. I think AValon Isis is also a difficult load to drive effortlessly...and you have a big room.
Cpcorreia, I think the Isis may a bit of an easier load than the Eidolons.

FWIW, I just began using a pair of Carver AT180Ms 180-230 watts with my Eidolons. The presentation is definitely not your typical tube amplifier. These things have a very good grip on my Eidolons with surprisingly good mid and low bass. They also offer a 305 watt version. If your interested call 770 667-5633 for a good price.

I became board of my solid state amps soon after I purchased the Eidolons but the speakers are so me, I endured. I did try some big tube amps but they still had their typical limitations especially with the load and heat. By contrast the Carvers just loaf along. They run cool and maintenance is simple.

On the solid state side I compared my Ayre V1xe with a Sanders Magtech on another system. The Magtech should be a serious consideration. The audition is absolutly free.

Thanks, Lloydlee.
On paper the Isis is an easier load than the Eidolon Diamond and it has about 2 db more, which is good. But I am afraid the 710 may not be able to control those big 2 (make it 4)woofers. Roy Gregory, in his HiFi+ test said the Isis played well with the Hovland, which has less grunt than the Soulution. But his reference amp for the test seems to have been the huge Karan 1200.
Obviuously the safe bet would be to hear the speakers with my amp, but I leave in Europe and no retailer seems to have a pair of Isis for a test.
Many thanks for your help.
Thanks Vicdamone. Do you have the Eidolon Diamond? I have never had a tube amp big enough for the ED, but they seem to like valves. For the Isis they are not a real possibility, since we would be speaking about mono amplification and that is less practical. An then there is the heating factor.


No Diamonds, the earlier version. Since I've owned the Eidolons almost every change to the system seems magnified compared to the lesser speakers I was monkeying around with when I was looking for my direction.

Starting with a 35 then a 75 watt stereo tube amps then came the Eidolons which necessitated two solid state, and three switching amplifiers, every one had an obvious difference in presentation. All the while I was missing the relaxed sense of a tube amplifier which would explain my excitement for these Carver's.

Unfortunately, despite my years at this hobby I don't consider myself experienced enough to accurately or successfully describe the differences of equipment I've actually had in my own system. IMO compared to the other big tube mono's I auditioned (from memory) the Carver's handle the Eidolons bass output much better. I can't say that means they are distorting less but it certainly sounds like it.

For the Isis? The Carver's are mono's and the heat is far less than the 75 watt stereo amp I was temporarily using just prior to receiving the Carver's. A bit warmer that a warm running A/B solid state but less than a class A solid state. Geez, I should just get out a thermometer.

Another tube amp I was considering was the Music Reference RM200 which I believe can be had in a 200 watt mono block, a little out of my budget. The RM200 has the ability to power difficult speaker loads and their distortion figures are outstanding. This might be of some interest. A reply regarding using tube amplification from Avalon Acoustics in 2009.

["Thanks for the mail, and glad you like the Eidolons. I still think they are amazing, and expect to continue to sell their current iteration.
My first experience with tubes and Eidolons was with Audio Research 100's. Clearly not enough power to have the full bloom of the capability of the Eidolons, but, there was still enough info to let me know that with a bit more power there would be some very nice results. Indeed, I later heard them with both the AR 300, and later the 600. These are both super amps, and priced accordingly, but in the interest of letting you know that it will work, I give you those examples. On the other extreme, if you can find a small tube amp, called the RM9, RM10, or RM200. These little tube amps are quite extraordinary. Probably on the
low end of power requirements, and admittedly I have not heard them with Eidolons, but many years ago I lusted for the RM9 for myself. The company is very small, but passionate, and is still in existence, and I believe in California. Also, a bit more mainstream, is VTL, also a California based company, with a variety of 'affordable' mono and stereo tube gear. We shared a room with them at the recent Audiofest show in Denver in early October. Always a good match, and we share a number of dealers and distributors around the world. David Berning also makes a few very good amplifiers. We used their amps at CES a lifetime ago, and never forgot that sound, and now people have started to tell us how good the combination still is.
Lucien Pichette
On Nov 24, 2009'}

The Isis do benefit from good power, and lots of it. While amps like Soulution, Vitus, Dartzeel, FM Acoustic may have their merits, I think 100-200 watts is too little. I would look for something with a lot of class A, at least 300 watts into 4 ohms. Amp matching with the Isis is so crucial. Nothing else will come together until you get that part correct. The overall efficiency does not belie how much power it takes to get those woofers moving like they should.
Of course, I see where you're coming from. Still, if you ever get a chance to audition any big tube mono's I strongly suggest the experience would be well worth the effort.

I did see this post here a few weeks ago from a dartZeal owner which may be of interest.

Regarding many of the Avalon products, I have read that they're somewhat easier to drive than their specifications would suggest. I hope you post your experiences, I'd be very interested in hearing your impressions and where this path take you.

Take care and happy shopping.
Many thanks, Rtn. My concern is the ability of the Soulution to control the woofers, but I may have to take the risk.
I see that you started with the big Karans, which are extremely powerful (1000 watts?) and then "downsized" to the Pass 200. Did you notice a big difference resulting from the less power of the Pass?
Again, thank you very much for your input and congratulations on your great system.
Thanks, Vic. I will keep you posted on the evolution of my system.
Rtn1's Karan 1200 monoblocks had pins 1 and 3 on the XLR inputs reversed, which he could verify. Normally pin 1 is ground and pin 3 is return, however in this case pin 1 was return and pin 3 was ground.

It is my understanding this is true of some amplifiers that are popular in Asia, although that practice may have changed. Using an amplifier internally wired this way without matching interconnects can give false impressions of the sound.