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Home Theater Shack 2015 High-End Amplifier Evaluation Event Reporting and Discussion Thread

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#1 ·
Home Theater Shack 2015 High-End Amplifier Evaluation Event Reporting and Discussion Thread



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This thread is a continuation of the High-End Amplifier Evaluation Event Preparations Thread previously under way.



The event has begun. Coming to you from southern Alabama, the Home Theater Shack Evaluation Team has assembled at Sonnie Parker's Cedar Creek Cinema for the 2015 High-End Amplifier Evaluation Event. We have amps, we have speakers, we have tunes, we have great eats, what more could one ask for?

Be reminded of the first law of audio evaluation event execution. They never go exactly as planned. Not everything gets there, not everything works, but you endeavor to persevere and get things done.

We have deal with speakers not able to reach us in time, with cabling issues, with equipment not interfacing properly, a laptop crash, with hums and buzzes and clicks and pops, with procedural questions - - - yet we forge ahead, adapt, evolve, redirect, and forge ahead some more - - - and the task of evaluating amplifiers is underway.

Speakers: We were unable to get the Chane A5rx-c and the Acoustic Zen Crescendo Mk II speaker pairs. We are running the Spatial Hologram M1 Turbo v2 and the Martin Logan ESL. Both are very revealing speakers, baring a lot of inner detail in our recordings. They will serve us well. The A5rx-c will be reviewed for HTS when available.

At the moment, the Holograms are serving as our primary evaluation tool. I will post setup details and interesting discoveries a little later. They are giving us a monstrous soundstage, the kind that eats small animals for breakfast, with extremely sharp imaging and very good depth acuity. They are extremely clear, getting into the realm of rivaling electrostatic transparency. Their in-room response is very good, with some expected peaks and dips, but still very listenable. The high frequency response is extended and smooth. The bass gives you that "Are you sure the subs are not on?" feeling on deeper tracks.

We decided to start with sighted comparisons and open discussion today, and blind tests tomorrow. The Audyssey XT32 / Dirac Live comparison has not been completed yet.

Have we heard differences? Yes, some explainable and some not. One amp pairing yielded differences that several evaluators are convinced they could pick in a blind AB test.

One thing I have learned for sure: The perfect complement to good southern barbeque is a proper peach cobbler. Add great company and you have a perfect get-together.

The Event
  • Date: Thursday evening, March 12th through Saturday evening, March 14th.
  • Place: Cedar Creek Cinema, Alabama, hosted by Sonnie, Angie, and Gracie Parker.
  • Evaluation Panel: Joe Alexander (ALMFamily), Leonard Caillouet (lcaillo), Dennis Young (Tesseract), Sonnie Parker (Sonnie), Wayne Myers (AudiocRaver).

The Amplifiers
  • Behringer EP2500
  • Denon X5200 AVR
  • Emotiva XPA-2
  • Exposure 2010S
  • Krell Duo 175
  • Mark Levinson 532H
  • Parasound HALO A31
  • Pass Labs X250.5
  • Sunfire TGA-7401
  • Van Alstine Fet Valve 400R
  • Wyred 4 Sound ST-500 MK II
The Speakers
  • Spatial Hologram M1 Turbo v2, courtesy Clayton Shaw, Spatial Audio
  • Martin Logan ESL
Other key equipment special for the event:
  • Van Alstine ABX Switch Box, recently updated version (February 2015)
  • miniDSP nanoAVR DL, courtesy Tony Rouget, miniDSP
  • OPPO BDP-105

As mentioned, our deepest appreciation goes to Sonnie, Angie, and Gracie Parker, our hosts, for welcoming us into their home. Look up Southern Hospitality in your dictionary, and they are (or should be) listed as prime role models thereof.

This first posting will be updated with more info and results, so check back from time to time.




Amplifier Observations
These are the observations from our notes regarding what we heard that were supported by being consistent between sighted and blind testing and across reviewers. While we failed to identify the amps in ABX testing, the raw observations from the blind comparisons did correlate in some cases to the sighted observations and with the observations of other reviewers. Take these reports for what they are, very subjective assessments and impressions which may or may not be accurate.


Denon X5200 AVR

Compared to other amps, several observations were consistent. The Denon had somewhat higher sibilance, was a bit brighter, and while it had plenty of bass it was noted several times to lack definition found in other amps. At high levels, it did seem to strain a bit more than the other amps, which is expected for an AVR compared to some of the much larger amps. Several times it was noted by multiple reviewers that it had very good detail and presence, as well as revealing ambiance in the recordings.

We actually listened to the Denon more than any other amp, as it was in four of the blind comparisons. It was not reliably identified in general, so one could argue that it held its own quite well, compared to even the most expensive amps. The observations from the blind comparisons that had some common elements either between blind and sighted comparisons or between observers are below. The extra presence and slight lack of bass definition seem to be consistent observations of the Denon AVR, but everyone agreed that the differences were not a definitive advantage to any one amp that would lead us to not want to own or listen to another, so I think we can conclude that the Denon held its own and was a worthy amp to consider.

Compared to Behringer
- bass on Denon had more impact than Behr, vocals sounded muted on Behr
- vocals sounded muted on ML compared to Denon
- Denon: crisp highs preferred compared to Behringer which is silky.
- Denon is more present, forward in mids and highs than Behringer.

Compared to Mark Levinson
- Denon seemed to lack low end punch compared to ML.
- Denon is smooth, a certain PUSH in the bass notes, cellos & violins sounded distant, hi-hat stood out, distant vocal echo stood out, compared to ML.
- Denon bass seemed muddy compared to ML which is tighter.
- ML more distant strings than Denon.
- Denon is slightly mushy and fat in bass. String bass more defined on ML.
- ML seems recessed compared to Denon.

Compared to Pass
- vocals sounded muffled on Pass compared to Denon
- crisp bass on Denon compared to Pass
- Denon & Pass both even, accurate, transparent, natural, no difference, like both
- Pass seems soft on vocals but very close.
- Denon has a bit more punch on bottom, maybe not as much very deep bass, more mid bass.

Compared to Van Alstine
- bass on Chant track was crisp for VA while Denon was slightly sloppy
- sibilance not as pronounced on VA as it was on Denon
- VA super clarity & precision, detailed, space around strings, around everything compared to Denon which is not as clear, liked VA better.
- sibilanceon Denon, VA has less “air” but more listenable, both very good
- Very deep bass more defined on VA, overall more bass on Denon.


Wyred 4 Sound ST-500 MK II

In the sighted listening we compared the ST-500 MK II to the Van Alstine Fet Valve 400R. The assessments varied but were generally closer to no difference. The Van Alstine got comments of being fatter on the bottom. The Wyred 4 Sound was noted to have slightly better bass definition but apparently less impact there, and slightly less detail in the extreme highs. Most comments about the midrange were not much, if any difference. An interesting observation here was by Wayne, noting that he did not think he would be able to tell the difference in a blind comparison. Considering the ST-500 MK II is an ICE design and the Fet Valve 400R is a hybrid, we expected this to be one of the comparisons that would yield differences if any. As I am always concerned about expectation bias, this was one that I was particularly concerned with. Van Alstine is a personal favorite for a couple of us so I expected a clear preference for it to be present in the sighted comparison. I felt that the Wyred 4 Sound amp help its own with the much more expensive and likely to be favored VA.

In the blind comparisons, we compared the ST-500 MK II to the Emotiva XPA-2 and the Sunfire TGA-7401 in two separate sessions. Of course, in these sessions we had no idea what we were listening to until after all the listening was done. In the comparison to the Emotiva, some notes revealed not much difference and that these were two of the best sounding amps yet. The ST-500 MK II was noted to have the best midrange yet, along with the Emotiva. It was described as having less sibilance than both the Emotiva and Sunfire. Both the Emotiva and the ST-500 MK II were described as unstrained in terms of dynamics. In comparison to the Emotiva it was noted to have solid highs, lively dynamics, rich string tones, and punch in the bass. The overall preference in comparison to the Emo was either no difference to preferring the W4S.

In comparison to the Sunfire, comments ranged from preference for the W4S to not much difference to preference for the Sunfire. The Sunfire was described as having more presence in the midrange, while the Wyred was noted to be shrill, lifeless, and hollow by comparison.

These comments varied a lot, but the points of convergence were generally around the similarities to three amps that would be expected to be most likely to be different, if we found any differences at all. The objective results is that we failed to identify the amp in ABX comparisons to two other much more expensive amplifiers. I would have to conclude that based on the results, the ST-500 MK II represents one of the best values and certainly should satisfy most listeners.​





Audyssey XT32 vs. Dirac Live Listening Comparison

Last year HTS published a review of a the miniDSP DDRC-22D, a two-channel Dirac Live Digital Room Correction (DRC) product. The review included a comparison to Audyssey XT. A number of readers requested a comparison of Dirac Live with Audyssey XT32. That comparison was recently completed during the Home Theater Shack High-End Amplifier Evaluation Event at Sonnie Parker's Cedar Creek Cinema in rural Alabama. This report provides the results of that comparison.

Go to the Audyssey XT32 vs. Dirac Live Listening Comparison Report and Discussion Thread.


Spatial Hologram M1 Turbo Speakers

I was very pleased with the Spatial Hologram M1 speakers we used for the amplifier evaluation, and felt that they more than fulfilled our needs. They did not become "gotta have them" items for any of the evaluators, although I had thoughts in that direction once or twice. But they were speakers we could easily ignore through the weekend. I mean this as a high complement. Never did an evaluator complain that the M1 speakers were "in the way" or "holding us back," and we were able to focus on the task at hand unhindered. That alone means a lot, and may say more about them than the rest of the review just completed.

Here is what they did for us:
  • Because of their high efficiency, amplifiers were not straining to deliver the volumes we called for. We could be confident that the amps were operating in their linear ranges and that if we heard a difference it was not due to an amp being overdriven.
  • The stretched-out soundstage opened up a lot of useful detail for us to consider in our evaluations. In discussing the soundstage at one point, there was a consensus that it might be stretched a little too far and might be "coming apart at the seams," showing some gaps, although this did not hinder our progress. My final assessment is that this was not the case, all due respect to the fine ears of the other evaluators. I elaborate on this point in the M1 Review.
  • They served well as a full-range all-passive speaker, able to reach deep and deliver 40 Hz frequencies with lots of clean "oomph," all without the need for DSP boosting and without subwoofer support.
I thoroughly enjoyed spending time with them, and wish to again thank Clayton Shaw of Spatial Audio for loaning them to us. A complete review of the M1 speakers has been posted.

Go to the Spatial Hologram M1 Turbo Version 2 Speaker Review.


A Soundstage Enhancement Experience

Sonnie's MartinLogan ESL hybrid electrostatics were set up very nicely when we arrived, so we avoided moving them through the weekend. There were some improvements made to the soundstage and imaging by way of treatments, and some interesting twists and turns along the way which turned out to be very informative.

I have documented the exercise in a separate post.

Go to the Soundstage Enhancement Experience thread.
 
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#51 ·
Hey guys, a few things I'd like to add.

1. Yes, my results could be chalked up to chance.
2. 5 out of 7 is statistically significant and should not be ignored.
3. I admitted to fatigue at toward the end if the testing.
4. I did not start to miss until the end of the testing. My last few pairing evaluations took considerably more time due to this fatigue.
5. There is only so much time in the day and the group dedicated DAYS to this test, so we did the best we could with the time we had.
6. I feel that I could repeat this test and expect a similar outcome.
7. Each person used different, non standard methods to evaluate the pairings. This was probably the biggest deviation from control in the entire evaluation effort. I am not certain that a standardized method would be useful as we all hear differently and like different music.
8. Our sighted evaluations had better soundstage and imaging properties than the blinded, due to the bulky (but necessary) shrouding used to hide the amplifiers from view.
9. Audible differences in amplifiers are generally very small.
10. I have a favorite amplifier and will reveal that favorite after Leonard has crunched the numbers and posted the results. ;)
 
#63 ·
Whether 5 of 7 is statistically significant depends on how you define it. By most research standards it would not be, as the probability of getting 5 of 7 if the probability of each choice is .5 would be about 84%. That means that there is a 16% probability of it being by chance. Most would consider 6 of 7 statistically significant, where the probability of it happening by chance is down around 5%.

I did not find that the imaging suffered in the blind tests. My big issue with the blind testing was time and confusion about trying to recall what X sounded like.

You have to consider our overall results, however, for 28 trials, to reach a 95% certainty we would need to be right 18 times. I think we could easily do that with more time and not restricting X for such a limited listening time and fewer amps.
 
#57 ·
Having been through this a time or a hundred, I am so glad you gents are doing this. I had a listening session this weekend and it was fun.
These types of get together s are never easy and will take repeated attempts but are always fun and educational. I look forward to your findings, whether they agree with mine or not.

Thank Y'all
 
#59 ·
I think the point Tony is making is that not all expensive amps have torroidal transformers. They offer some advantages in terms of hum and magnetic fields, but for the same price (and probably less space) you can get more power from a traditional transformer.

Neither necessarily has much to do with the sound of an amp, other than perhaps not having enough power available, perhaps.
 
#60 ·
I think the point Tony is making is that not all expensive amps have torroidal transformers. They offer some advantages in terms of hum and magnetic fields, but for the same price (and probably less space) you can get more power from a traditional transformer.

Neither necessarily has much to do with the sound of an amp, other than perhaps not having enough power available, perhaps.
I'm steadily growing on this bolded part. Power power power... more power... cleaner output. I'm beginning to wonder if 125w all channels driven if that really should be like 400w each channel that the Emotiva XPR-5 can deliver.

I can literally sell my Krell and buy a new Emotiva XPR-5 for the same price. Hmm....
 
#66 ·
Indeed. It was a large investment in time and money, the latter more for Sonnie and the guys who travelled farther. The experience of working with this group is well worth it, however. We always have enormous fun and learn something, even if it is exhausting.
 
#65 ·
I think it is curious that even though we felt that we could hear differences in some comparisons, everyone came away convinced that the differences were so small, if real, that we would all opt for the cheapest amp that had the power we need.

I will be publishing the comments on individual amp impressions in the context of the comparisons made soon.
 
#70 ·
I like the idea of repeatability, and agree that leaving the room can help offset fatigue.

My first few evaluations went quickly, I was done in just a few minutes. Sitting and listening to others do their evals was fatiguing, and toward the end of the day, my evals were 3 to 4 times longer and my notes reflect my uncertainty at this point.

I feel confident that I could have picked up at least one more correct answer if I had not felt so weary toward the end. Those last few were VERY difficult.
 
#75 ·
Some (non-serious) observations ...

1. Are you guys insane? That's some serious work for a single weekend!
2. Did anyone think we needed even more reasons for Dennis (Tesseract) to be cocky?
3. This amp shootout, while not necessarily intending to, somewhat showed why higher efficiency speakers are a good thing.
4. This amp shootout makes me want to get a pair of Martin Logans or Magnepans.
5. Thanks to everyone for a really great read already, and looking forward to reading more.
 
#77 ·
Some of these points ring very true indeed. Never the less, I think point three misses the point...so to speak. We need to acquire our amplification based upon the speakers we have in our rooms. While higher efficiency speakers can help if we just cannot obtain sufficient power to drive lesser efficient or difficult loads. Frankly even highly efficient speakers can benefit from serious power behind the cables. Try watching Fury or the depth charge scene in U571 for some extreme examples of needing power and an incredible reserve.
 
#83 ·
I think another thing that this session proves is that you do need more than just 30 - 50 watts of power to drive good speakers at comfortable listening levels. This also means that many low end receivers that drop to below 50watts per channel under load would fail at giving good levels of undistorted sound.
 
#84 ·
It depends on the speaker efficiency, and how loud you want it.:T
 
#86 ·
Unless power ouput is measured it is only speculation on the actual values.
Lots of numbers can be bantered about, but unless you measure it you don't know what it is.
When the SPL is really high it is possible the speakers are the cause of the distortion as well as its possible the amp is the cause of the distortion.
Subwoofers go a long way towards amplifier relief.
 
#87 ·
Oh, and Sonnie and I spent some quality time Monday fine tuning the two channel soundstage with his MartinlLogan ESLs. Cannot believe I forgot to snap any pics of that. I will have him take a couple.

The results were pretty fine. Even got the density that gives super depth acuity. Thick as pudding.

He is a brave soul. A couple of times I admitted that a piece of the process might seem a little outlandish, and he always responded "as long as it sounde good." he seemed pleased with the final sound.

Part of what prompted this exercise was a wandering acoustic guitar on a Nickel Creek track We turned to placement of absorptive panels to control reflections, then to manipulating where the reflections fell, then on to other fine points. A report will follow.
 
#89 ·
Scatter shooting...
For me one of the unexpected outcomes of this endeavor even before the "official" report is posted is the apparent sudden about face in opinion by some members on the premise that amplifiers sound so different from each other that they can be easily identified.
This type of testing has been done many times, one well known test had $10,000 on the line for anyone that "passed" .... The $10k stayed in the challenger's pocket...... Probably a good thing for the promoter that tesseract was not around when that challenge was going on.....:D
I wonder if this about face on the amplifiers will hold once the detailed report is posted or will there be a sudden retrenching with countless objections and justifications of how the test was wrong.
Another belief to ponder is in regards to magic power cords or specially designed speaker wires and interconnects.
If amplifiers are so similar they cannot be distinguished from one another, how can a wire change the sound enough to be distinguishable from any other wire?
Just pondering the mysteries of the universe this morning.
Enjoy your coffee.
 
#103 ·
A wise man said ..... "And we all know who we are, don't we? ...ponder, ponder... sip, sip "
That line forms behind me.

A second wise man said ..... "There's something about those trademark McIntosh analog meters that turns many a mere mortal into Pavlov's dog ...drool... but I'll never be able to afford one."
That is pretty much the only amp I want to own and just for the record it would sound better than my Pioneer even if it sounds exactly the same....

And a third wise man said ... My EVs are 96db efficient and at reference levels I am still running at at least half the amps output level as shown on the amps vu meters."
Are the VU meters linear scale or logarithmic scale ?

Interesting observations about the SPL various speakers sound good at, when I was shopping I tried to listen to all the speakers at the ~volume we typically listen at and picked based on that ~level.
It never occured to me to do anything else.

My wife plays the violin, we typically listen to music at a much lower level than the violin's SPL.
BTW a violin is surprisingly loud.

I envy/admire those with musical talent.... my musical talents pretty much end at operating the stereo (I am really good at that though).
 
#104 ·
And a third wise man said ... My EVs are 96db efficient and at reference levels I am still running at at least half the amps output level as shown on the amps vu meters."
Are the VU meters linear scale or logarithmic scale ?
Here is the specifications on the Samson servo 600 that I use, no mention that I can see as to if its linear scale or logarithmic scale.
Attachment of the PDF below
 
#112 ·
It really depends. Caps can last a long time, but the heat is what causes them to break down. Heat, of course, is one of the characteristics of class A amps. I have seen caps that are 30-40 years old test fine and some just a few years old with issues. It has a lot to do with the initial quality and specs as well.
 
#114 ·
Thank you and blacklightning both for confirming. Right now the amp doesn't sound weird or anything just no clue if I should send it in for a check.... knowing krell they would probably say "OH YA... it needs to be replaced" since what I've seen it's around 800 bucks to recap the showcase 7.
 
#121 ·
This is why I really enjoy the sheffield labs direct to disc recordings like the Harry James disc http://www.amazon.com/King-James-Version-Harry/dp/B0000009F6

for testing systems. one stereo mic placed in the front row center stage and the imaging you get is what you get. GREAT sound! The music may not be for everyone but for testing a system.... by far amazing!
 
#122 ·
The fact that I already know the answer to the riddle puts me at an advantage. The track was Nickel Creek's House of Tom Bombadil, here is a

The effect could be heard somewhat throughout the song. With both mandolin and guitar, the LF "body" of the sound was 50% to 70% out from center in the soundstage, and the HF "string" part of the sound was at 70% to 80% out, just inside the speakers, all wandering a bit as the playing proceeded. But the part that stood out is at 1:18, where the guitar run descends and goes back up, The guitar sound moved from 80%R clear to around 25%R and then back out again.

It was all taken care of with room treatment, mostly absorptive material under the movie screen in the front of the room (but there's more, hee hee). The result was an integrated sound that did not move around at all.

Will elaborate on the supposed explanation for the wandering effect.
 
#123 ·
Different frequencies do relate with room differences and not always in a nice way. For example, for awhile I found the lower mid range of some songs tended to be a bit shouty, particularly in voices that hit the lower registers like Nora Jones for example or even some bass guitars reaching up into their upper levels. Moving the speakers a bit did ameliorate this issue so I know what you mean.

I am sorry to get this off track.
 
#124 ·
The Spatial Hologram M1 speakers were invaluable tools for the amp evaluation weekend. Once set up and fine tuned, they gave us a very wide soundstage with pinpoint imaging, for the most part.

It was using the M1 that we first noticed the "wandering guitar" issue. The problem was worse with the Hologram M1 than with the ESL. The M1 is dipole at low frequencies, with widening rear dispersion as frequencies go lower, and the ESL crosses over to monopole below 500 Hz, not leaking as much toward the front wall. Still, the issue needed resolution for both speaker types. Room treatment took care of it.
 
#125 ·
While I was not overwhelmed with the M1 it was a very useful and revealing speaker for the amp comparisons. It created a very large soundstage so any variance in imaging would be apparent. I found the bass to be a bit fat and the treble unforgiving, which makes it much easier to notice issues in either area.

My preferfence would be for the ESLs with a sub, but if I were not going to use a sub and had the space to set up the M1 optimally, it would be a very pleasing speaker to own.
 
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