Recommendation for a highly resolving amp

I have Don Sachs 2 tube preamp driving Pass Labs X350.5 driving Sound Lab M545 ESL speakers. I like the sound very much, but when I went to hear my friend’s Spectral system (driving Quad2912 ESL) I realized my system can benefit from having a higher resolution amp. Spectral amps need all Spectral preamp/cabling, which would be quite expensive. What would you recommend?
Chord’s Ultima line is very resolving. They have also addressed historic brightness issues and these are more neutral than the old CM line. They also deliver big power, run cool and don’t take forever to sound good.

I would also look at Boulder and Constellation.  I sell Chord and am very familiar with their line.  I have no affiliation with Boulder or Constellation.  
I don't know your budget but a Luxman m-900u is a solid contender. Very resolving but never neutral or dry.
@chungjh   are you sure the issue is with the amplifier and not with room and speakers?  
or possibly the preamp or preamp tubes?
have you tried different tubes for the sachs preamp?  
most 6SN7s can be overly smooth.  
just trying to help you avoid chasing the wrong dragon.  
@chungjh Are you streaming with Fibre into your Lumin X1. If not that would be the first thing I would do. Pretty simple and cheap to set this up with a Network switch that has Fibre outputs. This could make a big difference depending on the quality of your Ethernet setup.

Then try different amps.

it all starts in the front end but if its good next are the amps
my amp and preamp are Aesthetix very resolving

Enjoy the Music 
Can you explain exactly what 'resolving' is or means?
Not intended as bait; I really do not know what this means.
I have tried fiber optic and other top 6SN7 tubes. Not big difference. By resolving, I mean high resolution, clarity, detail.

What do people think about the Bryston cube series? Specs are similar to Spectral amps.
You have a very nice system so it's hard to say where your issue is. However I would try a Sanders Magtech amp if you are looking for a new amp, they are designed for electrostatic loudspeakers and do that job really well.
why don't you have your buddy bring his amp and pre over to listen in your system.
Can verify that cubed series is indeed highly resolving. I can hear the difference immediately when I change IC between the DAC, pre amp and my 4B3.  Speakers are magnepan.  Transparency is their thing but I think much is attributed to their patented Salomie input circuit. Have never had the pleasure of listening to a Spectral amplifier.  
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@phcollie.    Have you compared Bryston cubed to other amps?

@mboldda1.  My friend is reluctant to move his amp as it is >60 lbs.
What makes you believe your amp is not sufficiently resolving?  Speakers, placement, room and source, IMO are far more likely culprits.  Pass Labs are excellent amps.  And for the record, i design amps yet doubt that's where you need to put your money if you want to biggest result....
Don’t know your budget, but if you are seeking detail and if your budget permits consider the Ayre Acoustics VR-Twenty. See review below.
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Don’t know your budget, but if you are seeking detail and if your budget permits consider the Ayre Acoustics VR-Twenty. See review below.
Only a few. I did the research before choosing the 4B3 and chose the preamp (EAR Yoshino) because the seller confirmed the pairing and Dr. Mertins at uses this pairing in a reference system to evaluate audio products. One of the other guys there uses the 7B3.  I think they are a German outfit similar to Stereophile?  Auditions are basically impossible where I live. 
The BAT 255SE amp is a fantastic amp, amazing value for money. I run 3 X BAT VK 655SE in one of my systems which has a similar sound to the VK 255SE but more power, but I don't believe your Pass Labs amp is your problem, if you feel it lacks some resolution.  Often pairing a tube pre amp with a solid state amp does not work well.  
You may wish to try a Pass Labs Pre-amp with you system but you may loose some warmth at the expense of detail and resolution. 
From my experience its always best to use amplification from the one manufacturer.
If you are seeking both warmth and resolution try a BAT pre-amp which is designed to work with BAT solid state amps and may work with the Pass Labs amps.  
Most panel speakers require warmer sounding amplification, I use Accuphase amplification, which has amazing detail and resolution without being analytical, with my Analysis Audio planar magnetic speakers.
Try and find dealers that will lend you the some equipment to experiment before committing.
The Don Sachs preamp is probably not your issue. I have this's incredible.

If you took your friend's system and dropped it in your room, it would probably not sound the same anyway.

If the room is wrong, you will get time smear among other things.

The sounds seems to be really good until you reduce some smear and then you think, 'how did I think that was sounding good at all?' 

You really won't know until it's reduced. I say reduced because I don't think you can realistically remove all of it...nor would you want to...everything would sound dead. 

I now have dedicated AC lines, 15k more in upgraded components and the room in my old home kills this system. I was using an old Carver amp (although I too was using a Don Sach Model  2 preamp).

Is your room a dedicated listening room or a living room situation? If it's a living room, then you need to be clever about the acoustics.

Some highly resolving amps I am personally very familiar with:
Benchmark AHB2
Bryston 28B cubed
First Watt SIT-3 and M-2
This one is super easy to figure out!
If you want to be 100% sure it’s the amp, connect your Lumin directly to the X250.5 using XLR or RCA interconnects and use Lumin volume control.
My money’s on the preamp as a culprit. 
Pass Labs amps and preamps are very transparent and resolving. I used to own Pass X250.5 and I am pretty sure the amplifier isn’t your issue.

Btw what cables are you using?
I am not sure what your budget so I can’t make a recommendation but I do not think you issue is the amplifier. Your pre-amp has a tubed output stage with 6SN7 tubes. What tubes do you have in there ? They can impact your sound significantly. You might try a Pass Labs pre-amp or other solid state linestage as well.
Other things to consider,
speaker set up.  How are your speakers setup compared to your friends?  How is your room setup compared to your friends?
Mine are four feet from the back wall and three feet from the side walls. Mine also sound better when raised higher off the floor.
 I know it might be a pain, but try a speaker swap with your friend.

All the best.

I don't think the amp is your problem.   I would consider a different pre.

@chungjh If I am not mistaken. You have big speakers in a small room. I believe I recommended in the past you use either acoustic paneling and /or contact Mitch Barnett at

to have him measure your room remotely and then have him create Convolution files for your ROON server. So when you stream from ROON to your X1 (before the DAC) your will have the sound optimized for your listening space. This is like using an old time Equalizer but today you do this in computer software.

Some very detailed amps I own or have owned, though I think chasing an amp is not worth it unless you have tamed your room first.

- Benchmark AHB2 (my favorite)
- LSA Voyager 350 GAN (after mods by EVS)
- various Brystons
- CODA #8 (not as detailed but close)

BTW - You replied that you tried Fibre Optic cable. That makes it sound like you tried it and switched to something else. This does not seem correct, because Fibre is so much better than the other connector types. I am not referring to TOSLINK optical cable but Fibre Optical cable.
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When I tried fiber optic, it sounded a bit harsh and I didn't like the sonic character. I do have room treatments, behind the speakers and on side walls.
have you tried different tubes for the sachs preamp?  
most 6SN7s can be overly smooth.  
This statement is false. Design can have an enormous effect, but 6SN7s of themselves are quite linear.
I have Don Sachs 2 tube preamp driving Pass Labs X350.5 driving Sound Lab M545 ESL speakers.
The Sound Lab ESLs do not expect that the amplifier will behave as a voltage source.  To deal with this fact, the Sound Lab has adjustments on the backplate to allow it to compensate for different amplifier types. So you have a wide range of amplifiers you can use.

They are best driven by tube amplifiers. The reason for this is that tube amps generally do not double power as impedance is cut in half, and are less perturbed by the 30 Ohm peak in the bass region (put another way, they don't have their power cut in half as impedance is doubled). ESLs generally have an impedance curve that varies by about 10:1 from the bass range to 20KHz and the Sound Lab is no exception. But the nature of the driver itself is that it needs the same power at any given frequency (and thus any impedance) to make the same output. That is the nature of ESLs. So they are not 'voltage driven' as so many box speakers are.

That is why the Sound Lab has so many adjustments on the back. You'll find that to really make the speaker play with transistors, you'll need about 600 watts, since into 30 Ohms a solid state amp will make about 1/4 of its 8 Ohms rated power (and thus is really about 150 watts on that speaker). But a tube amplifier might make considerably more power into that impedance. For example, our MA-1 power amp makes about 150 watts into 30 Ohms and about the same power into 8 Ohms. So you can see how an amp like that can keep up with a 600 watt solid state amp on this speaker.

The best Sound Lab installations I've seen and heard have used Purist Audio Design cables. We've shown with them a lot at audio shows and that tends to be the cable of choice. You've not mentioned the dimensions of your room, but I am assuming that its of average size since you didn't mention any power restrictions while using the Pass Labs amps, which are a bit underpowered for this speaker (although as solid state amps go, is one of the better sounding ones out there; if it comes down to your use of a solid state amp, if they have enough power for you I would **not** change them out!).

But you do want to be sure that there is at least 5 feet between the rear of the speakers and the wall behind them. In this way the reflected information bouncing off of that wall can be used by the ear as soundstage information and will make the imaging more palpable. If the speaker is less than that 5 foot minimum, the delay will be too short and the ear will interpret that as harshness!

If your speakers are properly set up in this regard and you don't want to go with a tube amplifier, then I would be looking upstream to get greater resolution. The Pass Labs amps really are some of the best solid state amps you could lay your hands on.

Your equipment is great. It’s the room that is the problem. Take your gear to your friend’s room and then see how it sounds. Or, spend and spend on equipment to no avail. 
I have owned spectral for since the mid 90’s. I don’t know much about your quad but if they are anything like Maggie’s you need at least 250 wpc to Get the panels moving.  
Spectral had or has a universal amplifier that can be driven by any solid state device, so you can use a dac or any other preamp.  The resolution is going to be limited by a tube preamp so I don’t suggest this.
as to spectral. I love their products but they are down to perhaps 3 dealers.  I sold my products through sky fi and at 20 years all passed.  I have seen threads concerning waning repair and customer support.   That is why I chose a different brand when revamping my two channel 

Symphonic Line Kraft, if at all you change the amp for power and resolution
My friends room is significantly larger than mine, so the comparison is really apples and oranges. I can't do anything about the tiny size of my room. Since I do not own a Roon, I don't know how to get the room analyzed. I am using Audiosensibility cables, which are considered one of the best reasonably priced cables.

I am also realizing that the needle never even goes close to the midline, which marks the class A limit of 40W. So, even though ESL are considered power hungry and my M545 is 86db, I think I could get by with around 100 W.
Your equipment is great. It’s the room that is the problem. Take your gear to your friend’s room and then see how it sounds. Or, spend and spend on equipment to no avail.
Sounds about right to me. 

The Convolution stuff I mentioned cost me $750 for the software service + $100 for a mic. I also repurposed a camera tripod for the mic. You do not need ROON to run this DSP filter. I mistakenly thought you ran ROON. Convolution also works with JRiver ($75)  and likely other streaming clients. This Convolution DSP is better than anything any hardware vendor stuffs into their preamps or other audio devices.

I did not know how to use the mic or do any measurement for my small room with big speakers. However, the instructions were clear and the guidance via email was also available. It was simple to generate that measurement data file and then send it to the audio engineer.

BTW - the Sim Audio 860 is a favorite of mine. A very neutral and clean sounding amp. Sort of like the AHB2.
I should add that I inserted a new acoustic panel to cover my CD rack and also moved the audio rack further away from the speaker. The audio rack is on the side wall of this very small room.

When I did this my 'old' Convolution filter no longer sounded good because the room measures differently. So I no longer use the old Convolution. If I were to use Convolution again I need to have the room re-measured and a new Convolution created. I am not planning to do this because my changes made the room sound good enough without the Convolution.
I will certainly consider the room treatment. Mean while, I want to go back to the amp question.

@yyzsantabarbara, are you talking about Simaudio 860 or V2? How do they compare with W8?
I am going to suggest Ayre VX-5 or VX-R/ MX-R mono blocks. This starts at $10k and goes to $32k retail. Ayre is all about resolving sound and great detail without sounding harsh. I have tested the VX-5 with several preamps from $1k to $14k. It made them all sound great. 
You should have brought your Don Sachs’ preamp to your friend’s house and tried it into his system just for fun.
I have Roy Mottram’s SP 14 preamp with NOS tubes driving a PS Audio S300 amp. Source is a Marantz Model 30 SACD and a Blue Sound Node 2i.
Don Sach’s preamp is a modified SP14, if I may say so.
Great Sound.
Another vote for the Benchmark AHB2.  They have a free 30-day trial.  BUT, it only accepts XLR/balanced inputs.  Not sure if your Don Sachs has that modification for outputs, or else you'd need adapters.
@edilita, Unfortunately friend's Spectral amp only works with a Spectral preamp.

@jdjohn, Don Sachs does not have XLR, I could get the RCA-XLR cable from Benchmark. How do you like AHB2?
@chungjh, I enjoy the AHB2 quite a lot.  It is very transparent and clear, with no coloration, especially when compared to typical/traditional class A, A/B amps.  It has a small footprint, and barely runs warm.

I had been running a PS Audio S300 class D, which is also quite clear, but the Benchmark AHB2 sounds better to me (and many other owners).  Again, it is very transparent, with no harmonic distortions to add warmth or color.  I'm not saying those things are is just different, and comes down to personal taste.

I also have two different McCormack DNA amps, and a Symphonic Line amp (which was the inspiration for Odyssey amps).  These are very fine amps that have a nice warmth to them and plenty of power (can run a little warm if driven hard).  Of course they are big and rather heavy as well.  But, as far as 'highly resolving', the AHB2 brings out more detail.

I have actually gone all-in with Benchmark at this point.  I have their DAC3/HGC preamp, HPA4 preamp, and the AHB2.  I should be set for awhile :)

FYI:  I had a Don Sachs Model 2 for a bit, but decided that tubes are not for me.  I know Don made some units with XLR outputs, but I think he quit that, and I know he no longer does mods on older units, except (I think) for original owners.