[Sedona Sky Sound]

My Son of Ampzilla finally has enough hours on it that I feel confident to start my usual battery of acceptance tests. I had originally planned to start with the RM/X but due to a customer request to hear the RM40s plus multi-channel audio, my demo room is currently set up in HT/multi-channel mode.

Part of the "pre-test" was just letting the amps burn in for a few days and watching a few movies. Even just out of the box, the amp sounded relatively good with no overly apparent pre break-in edginess. While watching movies running the RM40s full-range, I could tell zero difference between the SoA and the Ampzilla 2000s. But when I finally decided it was audio test-time, I started taking things seriously.

First, I re-aligned the speakers to my usual anal precision using my trusty tape measure and laser level. Next, I checked each individual driver (except for the NEO panels which must be checked as a group) using my SPL meter and a special test disc I created for this task. I then used the balance on the pre-amp and the pots on each speaker to ensure that drivers in the left versus right speakers were matched to approximately .1 dB.

To ensure I was comparing amp to amp, I am using the exact same bi-wire cables and XLR interconnects for both amps. When I wanted to switch amps, I would just move the XLR and the amp end of the speaker cables to the new amp and leave everything else alone. To really keep everything the same, I decided to not touch the pre-amp at all during the test. I picked a volume up front and left it there. That meant that some songs were just a little louder than normal and a few others were just a little softer than normal but it would be the same across both amps. To verify that, I rechecked each driver when I swapped amps. I expected there to be .1dB - .5dB difference in the two amps just due to typical manufacturing tolerances (even though the Ampzilla and SoA are both rated at 40x gain on the XLR input) but they were exactly the same (or at least to the .1 dB that I could measure). It seems that the tolerances for the A2000s and SoA are pretty tight so kudos go to James for that   .  There will be zero issues bi-amping with a combined SoA/Ampzilla setup using fully balanced XLR    (but no such luck if using single-ended RCA   )

For actual listening tests, I used the following CDs and SACDs:

Guainluigi Trovesi Nonet - Round About a Midsummer Dream
Mark Levinson - Evening at the Red Rose
Natalie McMasters - In My Hands
Cirque De Soleil - Allegria
O Brother Where Art Thou Soundtrack
Taiwan Audio Association Hi-End HiFI
Branford Marsalis - Trio Jeepy  

My first impression was that the Ampzilla 2000 and Son of Ampzilla sound more alike than different. The second thing that struck me is that the SoA were doing a fantastic job powering the RM40s. I had expect, and thus was listening for, a slight bass bloomyness due to the SoA not controlling the woofers, but I heard none. At the end of each listening session I also measured the temperature of both the Ampzilla and SoA and was somewhat shocked to find the SoA was actually running a little cooler than its dad (something I had not expected given the hard load of the RM40s).  

That being said, the Ampzilla and SoA were definitely not exactly the same. However, trying to figure out what exactly the differences were was somewhat difficult   . The most noticeable difference to me was that the bass seemed a little softer and/or the upper-mids were just a little louder when using the SoA. The bass was just as tight with the SoA, but lacked just a slight bit of the impact that its father had. Had I not specifically tested each woofer and passive with my test disc prior to testing both amps, I would have just assumed that my volume was off by a half dB or so, but I know that was not the case. I tried to pick up on standard deficiencies that I know tend to cause this but I could not narrow it down to the usual suspects no matter which disc I threw in   .      

The other noticeable difference was in the upper mids. The SoA seemed to have the edge on its father in this area. The words airyness, tubelike warmth, and extreme detail come to mind (yes, I realize those three words are typically mutually exclusive) but that doesn't quite explain it correctly. I think the best way to explain it is by example:

The Guanluigi CD is by far the best recorded CD I have ever come across and rivals even the best SACDs on the market. In one passage where Guanluigi plays a slow bass clarinet solo, the Ampzilla 2000 portrays the sound as a clear tone with a slightly woody ringing to it. However, with the SoA, the tone is still clear but the woody ringing is replaced by the sense of the movement of air inside the clarinet. Instead of the vibration of the clarinet by the air inside it, you actually hear the air swirling that causes the vibration. On second thought, this example probably raises more questions than it answers but it is the best I can do at the moment   .    

As for the treble, the SoA seemed to have a slight edge in clarity and decay but that could have just been my imagination. I tried my usual treble torture test (the violin track on the Mark Levinson SACD) and the SoA passed with no problems at all. If an amp is even the slightest bit bright, this track becomes unbearable. In fact, this is the track I use to set the treble pot on my speakers. I go to the point where the violins start squawking (or the fillings in my teeth start hurting, whichever comes first) and then back off two clicks.  

As for other major differences, none have jumped out at me yet. All in all, if these amps were used in a non-optimized room or with non-optimized RM40s, I think I would be very hard-pressed to tell them apart. I expect the differences will be a little more pronounced once I get them on the RM/Xs but only time will tell.

Upcoming tests include testing against the Marsh and Ampzilla with the 626Rs and trying several configurations of bi-amping with the RM/X. Stay tuned....

Julian
www.sedonaskysound.com

[JoshK]

What preamp were you using in this test, might I ask?

[Sedona Sky Sound]

The pre-amp I am using is the Marsh P2000B fully balanced pre-amp. I have a couple of others that are far more expensive but I always seen to be drawn back to the Marsh since it sounds so good with the RM40s (and the RM/X for that matter). I think one reason for the synergy is that the Marsh uses Auricaps just like those in my RM40s and RM/X. The other thing I like about the Marsh is that I can fine-tune the balance exactly which I cannot do with my pre-amps that use step attenuators.

At this point, my front-end is definitely the weakest sonic link in the chain. I am using a slightly modified Pioneer Elite DV-47A. It is not the absolute best sonically (but still quite respectable) but it has two traits that are essential for someone running a business:

1) It has been absolutely reliable since I got it 3 years ago
2) Since it is a universal player, a customer can walk in with just about anything, put it in, and it is going to play

I have been looking for a new CD/SACD player for over a year and have not found one yet that fully meets my primary requirements:

1) Retails for under $1000 new
2) Fully reliable (ask all the SACD 1000 users what they think of this)
3) Without mods, at least 2 levels better sound than my Pioneer 47A

Requirement 2 is by far the most important and the one that most concerns me. All the ones that I have heard that met requirement 3 have not met requirement 1 (and most did not even meet requirement 2    ) Right now I have my eye on the new Sony and my wife will be checking out a few players on her next trip to Asia. Until then, I will stick with the Pioneer especially since it is a known variable.

Julian
www.sedonaskysound.com

[JoshK]

I was just curious as to what good matches for the ampzilla amps were in the preamp arena.  20db of gain for a preamp is quite high it seems.  Do you find that you have too much or tons of gain?

[John Casler]

Great Review Julian,

I too would expect very little difference in "sonic qualities" except for those which arrise from power/amperage differences, particularly at higher SPLs.

As far as I know, the amps share a great deal of circuitry and key components meaning the most significant differences should be from any sonic affects of the toggle (RCA to XLR) on the A2K and the power differences.

James told me that he would not be using the toggle on the A2K in the future, which should make them even more similar.

I look forward to your 626R review, since I think they may actually be a more difficult load than the RM40s.

Obviously, I also have to admit envy that you will be able to run the the RM/x with the SoA on top and the A2K on the bottom.  That will be the "REAL" review.  It would be hard to imagine what kind of hardware would have to be put together to match that.  

[shokunin]

Excellent write up Julian.  I'd love the know how the SOA performs on the RM/x bi-amped or not.

[shokunin]

Obviously, I also have to admit envy that you will be able to run the the RM/x with the SoA on top and the A2K on the bottom. That will be the "REAL" review. It would be hard to imagine what kind of hardware would have to be put together to match that.

John, you need to try and get a loaner A2K from Mr. Bongiorno.   Then we can do somparisons .  Between you, Mad DOg and myself, we have plenty of good SS amps to compare them against.  

[John Casler]

Obviously, I also have to admit envy that you will be able to run the the RM/x with the SoA on top and the A2K on the bottom. That will be the "REAL" review. It would be hard to imagine what kind of hardware would have to be put together to match that.

John, you need to try and get a loaner A2K from Mr. Bongiorno.   Then we can do somparisons .  Between you, Mad DOg and myself, we have plenty of good SS amps to compare them against.  

Actually that is "in the works".  A couple local reveiwers are on the list to review the Pop and the Son in the not too distant future.

I have a feeling we may be able to "pry" the Monoblocs away from them long enough to maybe plug in your RM/x's for a few hours.

Only problem then (might be) getting you to let them back out the door  

[shokunin]

Only problem then (might be) getting you to let them back out the door  

If anybody can picture iron-pumping John next to little ol' me, I think you'll be able to get the Ampzillas out of my grubby little hands  

Julian, have you tried any passive preamps?  I'm curious how they stack up to your reference preamps.

[Sedona Sky Sound]

JoshK,
As for having too much gain, I really have not seen that as a problem at least with the pre-amps I have tried with them. I am running the Marsh with 14dB of gain and tend to keep the volume knob at about the 11:30 position (approximate 1/3 of total travel). My active pre-amp using the attenuators I believe has 16dB of gain and tends to be set at around 5-7 clicks out of 24. I think a majority of the active pre-amps on the market should work just fine with either amp. The caveat is that the pre-amp MUST be internally grounded. If the SST amps see any additional signal besides the audio signal (i.e., current via the negative or neutral wire), the "Peak" light on the amps will come on. I have seen this a couple of times and better grounding of the pre-amp usually fixes it. This is actually not a ground loop issue even though it is somewhat related.  

Shokunin,
If your source has a reasonable output,  just about any passive pre-amp will drive both amps with no problem at all. However, my feeling is that the Ampzillas really like to fed a true balanced signal which can be quite difficult with a passive. I have tried two different DIY type passives using the single ended RCA input (one with a shunt stepped attenuator and one with a potentiometer) and the results were lack-luster at best. There seemed to be a loss in dynamics and the soundstage tended to be a little different. I have not tried the transformer type passives with the Ampzillas but would like to at some point.

Julian
www.sedonaskysound.com

[jimmyp58]

Have you tried any of the Creek passive pre-amps?

[sica]

Just curious, does anyone know what pre-amp Mr. Bongiorno uses?

[Sedona Sky Sound]

I have not used the Creek passive but I believe that one of the DIY units I tried used the same Alps Blue Velvet pot that is used in the Creek. Most passives are pretty straight-forward, so unless Creek is doing something strange to the circuit my guess is that it would sound the same.

As for what pre-amp James is using, I can almost guarantee it is his own Theadra or Thoebe pre-amp. My guess is that his new Thoebe prototype unit is in his system right now. I talked to him about it a few weeks ago and I think his quote was "This is going to be the most complex pre-amp in the world but it is going to be the best product I have ever made and is going to revolutionize the market". James originally had a significant list of features so I am still waiting to see which ones are going to be in the "budget" Thoebe and what is going to be in the "cost-no-object" Theadra. He is still sourcing parts right now but I think the design is now totally complete on the Thoebe and the construction blue-prints are printed. This looks like it is going to be a hot product since I am already having people ask about being put on the pre-order list and I don't even have a list price yet   .  

Julian
www.sedonaskysound.com

[dfolson]

I have had my Son for a few months now.  I am convinced through A/B tests it is the most pleasing amp I have ever owned. Goldmund Mimesis3, Electrocompaniet AW75 and AW100 DMB to name my previous favorites. For preamps I own a Electrocompaniet 4, GAS ThaedraII, GAS Thoebe, and a Sumo Electra.  By far my favorite with the SOA2K is the Thoebe.  (The Thaedra is a MkII.....)  This is of course just my opinion.  Why am I posting here?  I have concluded that I need to upgrade my speakers.  I would like to know from the VMPS folks, which of their speakers matches the best with the SOA2K. fyi: I have a 12 x 20 room and currently run Monitor Audio Studio 6 speakers.  I live in the Minneapolis MN area otherwise I would have listened to the VMPS line by now.

Regards,

David

[JoshK]

david,

I think you are a good candidate for the RM30s.  I own the RM40's but if I had your size room and gear I'd opt for the RM30s, which many feel give better soundstage and imaging than the RM40s but dont' go quite a low.  You can always add a sub for that.  My $.02.

Cheers,

[dfolson]

I now have it narrowed down to the RM30 or the RM2.  I need to do some traveling to listen to these puppies....

I will be REALLY interested in a modern Thoebe with balanced in/out.  Is that just rumor?

David

[John Casler]

I now have it narrowed down to the RM30 or the RM2.  I need to do some traveling to listen to these puppies....

I will be REALLY interested in a modern Thoebe with balanced in/out.  Is that just rumor?

David

The new Preamp will be called the "Ambrosia" and is no rumor

[Sedona Sky Sound]

I had expected to have the SoA-RM/X review done by now but customer demos and a mild case of the flu have kept me from it   . I finally had a chance to remove all the speakers from my demo room this afternoon so that I could put my RM/X's back in. However, before I did, I decided to go ahead with John's suggestion and do a full set of tests on my 626Rs first (and they are MUCH easier to move than the RM/Xs so easier to do the 626R test now than later). My 626Rs are the bare-bones stock model with spiral tweeter and no cap upgrades.

For this test, I used my custom built 626R stands to make sure I had the best possible bass. These stands are 25" tall, exact same width as the 626Rs, and have a slightly curved, sloped front beard that extends about 2 inches further forward on the bottom. Filled with sand, each stand weighs about 85 pounds or so. So that cables/interconnects would not influence the results, all tests were done with the same pair of my ScorpionWire 14 AWG speaker cable and balanced XLRs. The Ampzilla and SoA would have probably benefitted from using my 10 AWG cables but unfortunately I did not have any non-bi-wire pairs made up that were the correct length.

The three amps I tested were the Ampzillas, SoA, and the Marsh A200S (2x100W stereo amp). Hopefully John can explain why he thinks the 626Rs would be harder to drive than the RM40s since that is not my experience at all. My 626Rs are extremely easy to drive (comparatively speaking) and all three amps had zero issue with them. Previous tests trying to drive the RM40s with the Marsh showed that it was just not up for the task.  

As for my test results:

I heard no difference between the Ampzilla and SoA when driving my 626Rs. I had expected to hear at least some difference but that was not the case. Bass was the same, mids were the same, and even the highs were the same. Basically, I could have changed the sound by a greater degree by changing interconnects or speaker cables versus using either of the two SST amps.  Had my 626Rs been fully upgraded with FST, TRTs, and 6.5" megawoofers, my guess is that I would have heard at least some difference when I swapped amps, but I don't even know that for sure.

As for using the Marsh, that is a different animal entirely. Considering the price, the Marsh continues to amaze me. It is still one of the cleanest sounding amps I have come across. There is just no "grain" to the sound at all. Compared to the SoA, the Marsh is a little forward on the top-end and just slightly lean on the mids. The bass is also just slightly looser using the Marsh but I am not exactly sure that is a bad thing in this case. In the past, I always used my Marsh for demoing the 626Rs just because the Ampzillas were way overkill and the Marsh/626R had a slighly foward sound that many people tend to like. Now, figuring out which amp to use for a demo will be more of a toss-up. I have no doubt the SoA is a better amp than the Marsh, but in this case the stock 626R seems to be the limiting factor.  

So what are my suggestions/recommendations? For those that have little $ but still want a taste (more like a full plate-full) of the high-end, the stock 626R/Marsh A200S combo is still really hard to beat. The Marsh seems to have more than sufficient power/current to do the 626Rs justice. If money is not the issue (most likely space or Spouse Acceptance Factor is), then the fully tricked out 626R with the SoA would be a perfect combo. The SoA would complement the megawoofers to give a solid bass, the Auricaps/TRTs for a nice warm/full mid, and the FST for sustained highs.    

Stay tuned for the SOA-RM/X review coming soon.....

Julian
www.sedonaskysound.com

[John Casler]

 Hopefully John can explain why he thinks the 626Rs would be harder to drive than the RM40s since that is not my experience at all. My 626Rs are extremely easy to drive (comparatively speaking) and all three amps had zero issue with them. Previous tests trying to drive the RM40s with the Marsh showed that it was just not up for the task.
...

Hi Julian,

Great stuff!

Looking forward to more of your impressions.  I didn't think there would be too much difference sonically between the two considering they share so many parts and circuitry.

My  suggestion that the 626Rs might be harder to drive, was not based on actually having a pair of RM40s here for comparison, so it may not be true at all.

Generally speaking more drivers will offer higher efficiency and higher "relative" SPL than less drivers, while also having lower distortion.

The "load" itself of the 626R (8 ohms) might actually be slightly more stable, but with the Transformer of the SoA, the 4 ohm and higher efficiency of the RM40 is probably not "all that"

Having heard how Big B, "blasts" away with a single Son on the RM40's I thought that might be the case, since I can make the red LEDs flicker with the 626Rs at higher levels.

Let us know what you find when you compare the two.

[Sedona Sky Sound]

I am not sure about the countless times I moved cables over a 3 day period, but I am finally done with my Ampzilla-SoA-RM/X testing   . Once I compared the SoA/Ampzilla using the RM/X, the differences became extremely apparent.

The tests I did were:

1) Four Ampzilla monoblocs (baseline system)
2) Two Ampzilla monoblocs for bass, Son of Ampzilla for mids/treble
3) Two Ampzilla monoblocs for mids/treble, Son of Ampzilla for bass
4) Single Son of Ampzilla running RM/X full range
5) Output clipping test using set-up 4
6) Output clipping test using set-up 3
 
While most things were as expected, there were a few surprises. Due to the time/effort involved in these tests and the "customer preference" aspects of my findings, the results will not be available for public/internet distribution   . However, I would be happy to provide my 3-page write-up to those interested who are not being serviced by another SST dealer (standard non-disclosures apply   ). Just send me an e-mail with your City/State and current/planned speakers and equipment. Thanks.  

Julian
www.sedonaskysound.com