Saturday 3 December 2016

MEASUREMENTS: What does a US$500/watt stereo amplifier sound like? (Vitus Audio SS-010)

Behold!


That white item on my floor my friends is a Vitus Audio "Signature Series" SS-010 25Wpc solid state Class A into 8-ohms stereo integrated amplifier. It came out circa 2007 and had a suggested price of US$13,000 at the time (hence the ~$500/W stereo channel calculation in the title). Of course, the audiophile press had a crack at reviewing it. For example, here's the Stereo Times review from June 2007 and here's one from HiFi+ presumably from around then. I have seen no measurement results on this device and in fact the printed manual has this as a statement of their philosophy:
Vitus Audio is dedicated to musical performance rather than technical details and high performance measures. We believe that many manufacturers are blinded by the current available theory, instead of looking for new answers. At Vitus Audio everything works until proven not to. This way we always try to push the limits and explore the unexplored. As a result of this many of the solutions we use today are considered to be "impossible to ever get working", however they have convinced many people and reviewers world wide of the opposite. 
Before any of our new topologies are implemented in our products, they are carefully reviewed by our dedicated listening panel. This way we can guarantee the correct level of musically (sic) performance and robustness.
I added the bold highlighting as I thought this statement was rather surprising (worrisome?). Seemed a bit backwards from the orthodox concept of science driven by hypotheses that are supported by experimentation rather than just believing "everything works"! Suppose nobody bothered to test or measure... Does that mean it still "works" as a default position? By default, are theories then "true" until proven otherwise? Hmmmmm.... Let's just agree to disagree and move on.

At this price, it would be unusual if the reviewers did not like the device and the whole back-story around the company and designers. Interesting nuggets I got from reading the reviews are that internally this device is wired with VA's supposedly special "Andromeda" wiring (you can read more about this here) and the designer has a thing for beefy non-toroidal transformers. Thanks to my friend who was moving and needed a place to "store" the audio system, I borrowed this "handmade" amp for 2 months to try out. Let's just say my friend did not purchase at the manufacturer's suggested retail price.

Since 2007, Vitus Audio, the Danish company that makes this amp has upgraded and released a few newer models of course. This model according to HifiEngine was produced up to 2011. The Vitus Audio SS-010 will output 25W Class A into 8-ohms. There is also a Class AB setting which is also limited to 25W. The main difference is that in Class A it sucks ~250W and in AB ~50W (no surprise, Class A is inefficient). I didn't bother spending much time listening to Class AB mode which sounded fine. There's also the typical vague specs: SNR >110dB, THD+N <0.01% - presumable these are at rated power.

Vitus Audio SS-010 Rear panel. Two inputs - one set of RCA unbalanced, and one XLR balanced.
Perhaps most "impressive" is the fact that this baby is around 80lbs in weight. That's a heck of a lot of metal, much of it is the very solid enclosure and heat sinks (the dark stripes on each side - good dissipation of heat given Class A). It gets only slightly warm after a couple hours of use so it's clearly more than adequate to dissipate the heat provided that ambient temperature and airflow is adequate. Just as impressive is a hunk of metal called the remote control that can double as a police officer's baton in its ability to inflict physical damage. The remote is rechargeable.


When turned on it "thunks" and if you use the volume control, it also emits a short "thunk" with each step up (of which there are 47) probably due to the resistor relay system used. You can change the setting to be a power amp and defeat the volume control (it warns you before doing so and there's a pass code to do this - good safety feature). Unfortunately, I noticed the amplifier does produce a mild but audible transformer hum when turned on. Not loud enough to distract when playing music but audible from my listening position about 10' away on those quiet nights in the sound room.

As you can imagine, I listened to a number of albums on my system with this amplifier in place. Here's the equipment chain for reference:
Windows Server 2012 R2 computer --> gigabit ethernet system --> Logitech Transporter --> balanced XLR --> Emotiva XSP-1 preamp --> balanced XLR --> amplifier (my Emotiva XPA-1L monoblocks or this Vitus Audio as power amp) --> 4' Canare 4S11 speaker cable --> Paradigm Reference Signature S8v3 speakers
The amplifier comes with its own generic-looking black 16 AWG IEC power cable (I guess VA sees this as adequate for a very expensive amp). All bass management turned off from the preamp. Subwoofer disabled.


The AV system circa late-November 2016: Vizio P75-C1 up on the wall now :-).
Remember that using a 25Wpc amplifier means you're going to need efficient speakers! My Paradigm S8's being rated around 92dB/W isn't the most sensitive by far but was able to play loud enough for my typical listening levels (note though that I'm talking about typical music reproduction like from CD's; highly dynamic audio like home theater soundtracks would not be this amp's forte). From the moment I turned the system on with this amplifier in place, it was obvious that this amplifier's gain is lower than my Emotiva XPA-1L Gen 1 monoblocks ($700 x 2 MSRP back in 2013) given the same pre-amp input (by about 8dB). I also noticed marginally more hiss from the speakers when using the Vitus Audio than the Emotiva and I wondered whether internally it's designed with "true" balanced topology despite using XLR inputs.

So, what does $500/W sound like?

Let's start with the easy part... Subjectively I had fun listening to the amplifier in my system. It looks great, the weight and construction is very "solid" and the control buttons are easy to use. The amber LED display is small, simple, but functional. It's good that the display can also be dimmed. There's a nice illuminated "VA" logo that can be switched on/off for taste.

I ran the amp through a number of albums I've been listening to lately for comparison with the Emotivas. As you can imagine, with significant difference in sensitivity, switching cables then trying to match volume means there was no easy way to A/B compare with good confidence. My impression when listening to Sting's 57th and 9th (2016, DR7 - I like the track "50,000") suggested that it has enough dynamic ability to handle typical modern compressed masterings at adequate playback levels through my system. My impression was that there was indeed a "smooth" quality to the sound which IMO is not necessarily a "good" thing... I guess I appreciate a more "clinical" sound which in my mind speaks to the ability for a sound system to resolve details present in the recording (the HiFi+ review admitted that this amp wasn't the highest resolution amp reviewed - I agree). Listening to Leonard Cohen's You Want It Darker (2016, DR13!) demonstrated very good channel balance with Cohen's voice presented solidly "front and center" with nice layering of the instrumentation and separation from the background singers. On a synth-driven album like the new Yello Toy (2016, DR11!), the "surround" effects were presented nicely with an impression of 360-degree envelopment sitting in the sweetspot (eg. have a listen to the track "Limbo").

Acoustic music like Lucie Horsch's Vivaldi: Recorder Concertos (2016, DR12, Decca) likewise was presented nicely. However, with the average lower volume of classical recordings compared to rock/pop, I did wonder whether there was a bit more strain in reproducing the orchestral dynamic peaks. Also, as suggested above with the increased background hiss, the noise floor wasn't as good compared to the Emotivas. I'm sure many "serious" audiophiles are interested in playing classical music with elite amplifiers like this, so honestly, my impression suggests these should be paired with very sensitive speakers (like 100+dB/W horns and the like) in order to allow full dynamic expression and not to push the power too far to the limits. The noise floor remains an issue however.

What about objective measures?

Pulling out my 8-ohm power resistor rated to 300W then, let's run a few measurements through the dummy load and have a look at how these amplifiers perform... First, I wanted to have a look at the noise floor during silence (the Transporter was streaming a track full of digital "0"s):
As you can see, the Vitus Audio is indeed a bit noisier than the Emotiva overall. There's also an unfortunate noise peak out near 50kHz with the Vitus Audio amp.

How about the overall frequency response using a sweep from 20Hz to 48kHz (24/96 test signal)?

Interesting and impressive flat frequency response for the Vitus Audio amp - only -0.5dB way up at 40kHz. You see the Emotiva drops down to -0.5dB at both extremes of human audibility at 20Hz and 20kHz. Realize of course that in the big scheme of things, this isn't a problem because speaker-room interactions will have a huge impact on the sound in ways much more profound... Check this out:

Previously, I have written articles on room measurements and correction filters and applying these filters to Logitech Media Server. What you see in the light blue tracing above is the frequency response the amplifier has to produce to "equalize" for the room at the listening sweet spot (as processed with BrutefirDRC/LMS on the server computer and sent to my Logitech Transporter)! Remember folks just how much "imperfection" there is in the frequency domain when that sound emanates from the speakers and bounces around the room by the time it reaches the listener. Needless to say, this is hopefully a poignant and concrete reminder of the importance of speakers and the room you listen in, plus how you manage the room acoustics...

As for basic distortion measurements, let's start with having a look at a 1kHz 0dBFS 24/96 signal passed through an 8-ohm power resistor at 1W:

As you can see, I've overlaid the Emotiva XPA-1L's graph over the Vitus Audio and slightly offset it to the right so we can see the relative levels of the harmonics. It's obvious again that the Emotiva is quieter and the harmonic distortion is significantly lower as per the THD measurements.

Now, let's give it a bit more juice and look at 5W:

Notice that in both instances, the odd order harmonics (3kHz, 5kHz, 7kHz, 9kHz) are more prominent than the even order harmonics. This is the typical pattern with solid state amplifiers as opposed to tube amps where even order harmonics tend to be more prominent and said to be a type of "euphonic" distortion. Since I am one who prefers to achieve "high fidelity" rather than subjective "euphonia", personally I'm happier when distortions are lower or absent; in this regard, obviously the Emotiva is much cleaner...

Since the graphs above were all done with the right channel, I wanted to make sure the left channel for the Vitus Audio and my left Emotiva monoblock wasn't much different:

I plotted the graph above in log scale as well to have a look at the lower frequencies. This graph is a direct overlay without any shifting. As with the right channel comparison graphs, the Emotiva clearly achieved a lower noise floor overall with less harmonic distortion. The ~51kHz noise is still present through the Vitus Audio amp's left channel.

Here's another comparison but using a more complex 19 & 20kHz intermodulation signal:

Again, the previous observations and relationships remain. On the whole, the Emotiva amplifier has a lower noise floor. Harmonics and intermodulation products are not as pronounced as the Vitus Audio. The ~51kHz noise obviously still there with the Vitus Audio (circled) and easily examined when plotted with linear frequency scale.

Finally, for completeness, since Vitus Audio makes a big deal about Class A sounding much better than Class AB, I thought it would be interesting to run it in AB mode and see what the noise floor and distortion results look like at 5W:

IMO insignificant difference. Marginally higher value on the THD in Class AB mode but nothing to be excited or concerned about. Baseline noise level and general harmonic structure with higher odd-order harmonics also retained as expected. As I noted above, I didn't really spend much time listening to this amp in AB mode. I did play a couple of songs and didn't think there was much if any difference. We don't know how much bias is used in the amplifier design though. If it uses a high bias, we could still be operating in Class A mode at 5W I suppose. Although not shown in the spectrum from 20Hz-20kHz above, the Class AB FFT still had that 51kHz ultrasonic noise present.

Note that I did not go higher than just 5W in these comparisons. I really did not feel like pushing the borrowed amplifier and I also wanted to keep it simple when analyzing the FFT using my Focusrite Forte ADC. Even though I'm not pushing the amps to the limit, I do believe it's really those first few watts that's important when it comes to sound quality. At 1 and 5 watts, we can at least compare apples-to-apples measurements at typical power output when playing music. Refer to sites like Audioholics for full bandwidth tests, dynamic bursts (the Emotiva monoblocks are said to have 90,000uF storage capacitance - not sure about the Vitus Audio), damping factor, etc... Also, worth watching the video here for discussion of how much power you might need. Finally, I do recommend reading this article from them about the sound of amplifiers; many good points and thoughtful discussion items to consider. Remember that although the discussion can be complex, when it comes to "real world" listening, just be mindful that we don't want to overly trivialize nor magnify the sonic differences that might exist between reasonably spec'ed amps (as in general the audiophile press IMO are apt to do).

By the way, out of interest, I used a couple Audio-Technica AT2035 microphones to record the sound in my room playing segments from Eiji Oue & Minnesota SO's Rachmaninoff: Symphonic Dances... (Reference Recordings, 24/96) and Eva Cassidy's Songbird ("Fields of Gold") using the Vitus Audio and the Emotivas playing at the same amplitude level. Despite the relatively high noise (not the best microphones), the recordings did sound slightly different between the two amps when flipping back and forth using foobar's ABX comparator. A bit more "warmth" with the Vitus Audio, more "clear" with the Emotiva... Far from a definitive test, but interesting data point for me since there's no way to easily A/B compare directly without fumbling with switching cables and volume readjustments.

In conclusion...
So what does this $500/W amplifier sound like? Well, not bad of course (it would take gross incompetence for an amplifier >$500 to sound bad these days!). But from listening and in the objective measurements, I can say definitively that the Vitus Audio's noise level is not as good as the much less expensive Emotiva monoblocks which MSRP at 1/9 the price. And at the measured conditions of 1W and 5W into a dummy 8-ohm load, the harmonic distortion is likewise higher with the Vitus Audio.

For me, they both provide enjoyable listening experiences but obviously for higher volumes and "aggressive" music, hitting those peaks was effortless with the Emotivas and my speakers. Likewise, on extremely dynamic material typically with lower average volume (especially movie soundtracks), the two Emotiva monoblocks capable of packing 250W into 8-ohms each really fill the room with clean sound (especially bass frequencies with the subwoofer turned off).

The real question is the usual one when it comes to audiophilia and price. What is the value of a "handmade", heavy, solid metal, boutique device of this type to you? Compared to the Emotiva monoblocks, to imply higher value to a device with 1/10th the output power and 9 times the price makes no sense from the perspective of "sound quality" as defined by distortionless high power output and lower noise floor based on objective measurements (and just putting one's ears to the speakers).

As I see it, a luxury item like an amplifier with an audacious asking price >$10,000 is about those "non-utilitarian functions". Like the aspiration to achieve "pride of ownership" (or more bluntly "bragging rights") when it comes to a luxury car, fancy watch, expensive handbag, designer coat, etc... It's important to realize that these luxury items might not run faster, tell time any better, hold more things, keep you warmer, or in this case amplify an electrical signal cleaner and with less distortion. How these things are "valued" is based on socioeconomic status and psychological factors, not the underlying "utilitarian" quality (ie. "better sound") - no matter how some folks seem to confound or miss this rather obvious fact.

PS: I wasn't initially going to bring this up, but it just kept nagging at me as I was writing up this post. Have a look at this "Pictures" page from the printed user manual:

Notice where the images come from. Still copyrighted HiFi+ magazine pictures! I'm not saying there's anything terribly wrong with this, but I am concerned about the obviously poor "optics". Over the years, I have expressed concerns about the mainstream audiophile press and the intertwined relationship with the Industry. Already I think for many of us, glossy magazines like HiFi+ appear to be nothing more than the advertising arm of the Industry. What then should the consumer think about a situation like this where HiFi+ not only writes a long review on this product, the review is linked to on the Vitus Audio website as advertising testimony (see review link above), and the company even uses the magazine's pictures in the product's manual sent to each owner. So where are the boundaries? What does journalistic independence (and perhaps integrity) look like in this hobby? When a magazine prominently provides images in the user manual, does that already imply that the magazine endorses the product before consumers get their hands on one?

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Wow! December is here already? Where did this year go?! It really is amazing as I get older how quickly time just flies by. Looking around this past week, it doesn't look like much is happening in the audio world. As you can see in the picture above of my sound room, I did get that 75" Vizio P75-C1 4K TV and have it all set-up in my media room.

Early impression - impressive :-). In a dark room, black is black with the Full Array Local Dimming (FALD) lighting system. Gamma looks nice (as compared to the Sharp a few weeks ago). Good to have both HDR10 and Dolby Vision HDR standards supported although Dolby Vision material remains lacking (I hope they'll start embedding DV metadata in UHD Blu-Rays at some point, DV streaming on Netflix looks great despite limited bitrate). I'm running the beta firmware (3.0.6.4) at this time which works well for HDR10 playback off an inexpensive Amlogic S905X-based TV box using a custom LibreELEC/Kodi OS build. I figure I'll wait until the next formal firmware release before I spend time with more detailed calibration. The 10-bit panel looks great for gradients when displaying high bitdepth HEVC material. If Vizio continues to release high quality but reasonably priced TVs like this, they'll be like the Oppo of the video world. I guess Christmas has come early in my household!

I remain impressed by the real advancements happening in the world of video display. It has been a good year I think for the proliferation of 4K and HDR technology primarily... This is as opposed to stereo audio technology which clearly has matured for many years now and what we're IMO seeing is primarily maintenance of high quality at lower price points (like the Raspberry Pi streamers) and what I believe are needless "pseudo-solutions" like MQA with little potential.

Have a wonderful week ahead folks as we run into the final stretch of 2016. Hope you're all enjoying the music (and video!)...

30 comments:

  1. The result is sobering. In reality, the picture is even more dramatic if you use the 2x350 watt Yamaha p3500s that sells for just over US$500 for comparison, tested/measured here:
    http://www.homecinema-fr.com/forum/amplificateurs-de-puissance-haute-fidelite/mesures-ampli-yamaha-p3500s-mise-a-jour-t30056383.html Build quality and measurements are impeccable.

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    1. Yup. Have to always be mindful of that concept of value. An amp like that Yamaha looks impressive!

      Boutique equipment one often see at audio shows could be great I'm sure. The problem is that so few companies actually publish meaningful objective measurements to demonstrate that they at least get the *basics* right. Made worse when some companies like this Vitus Audio even take shots against objective measures in their intro. Even if they have a specs section, it's shameful that the specialty audiophile press are so often unable to verify or at least comment on whether even the most basic performance characteristics pass muster...

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  2. Hi Archimago,

    Your friend didn't pay the full, normal, price for this but he still paid a lot, I'm sure. Why did he do this? Does he think it really sounds better than other, less expensive (and mostly more powerful*) amps? Have the both of you ever got together to compare amps, in either his or your systems? If so, do you hear things differently?

    *It's worth repeating that people often forget that the relationship between power and perceived loudness ("volume") is logarithmic, e.g., 50W doesn't sound twice as loud as 25W; you need 250W (x10) for that. Factor in the fact that some amps are far better than others at delivering power into some "difficult" speakers and it can make a mockery of the usual power ratings.

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    1. Hi Otto.

      Yup. Indeed an important reminder of the fact that hearing/volume is a logarithmic property.

      My friend did pay a fair amount for the amp but all things considered, much less than the $>10k. Alas with his busy job we haven't spent time A/B'ing yet but I have had other "audiophile" folks come for a visit. We'll do this in the next 2 weeks before Christmas when we meet up. Basically everyone generally liked the sound of the Vitus but have the same impression that it's not as resolving as the dual monoblocks. Yes, everyone can hear the difference in hiss from the speakers and the soft transformer hum with the Vitus when pointed out.

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  3. When we moved to a much larger house and when shortly afterwards I also replaced my Quad ELS 57 speakers by the less sensitive Quad 2805's, it became obvious that my beloved 2x45 watt Quad 303 did not have enough power. The refurbished 2x140 watt Quad 606-2 was an audible improvement at higher levels and with more dynamic music. I now even wonder if I should not get some Quad 260 watt monoblocks.

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    1. Hi Willem.

      Man, electrostatic speakers... And with a larger place, definitely go with clean high power :-).

      Just don't go deaf!

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  4. Hi Archimago,

    Great article on the potential pitfalls of equating price with performance in the world of audio.

    I noticed that you're using a Logitech Transporter instead of your usual Teac UD-501. Does the Transporter sound better?

    Regarding network streaming into the Transporter, are you using Logitech Media Server or a DLNA solution like JRiver? Does the Transporter support gapless playback properly?

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    1. Hey Nerd Killer!
      I would say that the Transporter and UD-501 are essentially equivalent in sound quality. I use them interchangeably and when both set to a sharp antialiasing filter, the frequency response is almost interchangeable. In fact, I can use the same FIR room correction filter with both and achieve a very similar measured frequency and time domain response at the sweet spot!

      For the Transporter, I use LMS with Brutefir room correction. I reserve DLNA streaming for my Raspberry Pi 3 --> TEAC UD-501 using JRiver. Normally LMS supports gapless no problem. But if using DSP room correction, unfortunately no gapless...

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  5. Hello Archi. Enjoyed your review as usual. I was intrigued by your comments about the Amlogic tv box. What does it do exactly? Is it different than a Roku Stick? Any clarifications and/or extensions of your description would be appreciated.
    Guy

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    1. Hey man.
      I'll perhaps write about this more in another post.

      Basically it's like the Roku but these boxes typically run Android. I find that Android is great for the number of apps, but I like the stability of LibreElec (which replaces the Android OS) and just running Kodi to stream my movies and TV shows I have on the video server computer - the same machine as all my music. It's also a great way to get all my multichannel 5.1 FLAC's to play over HDMI.

      Currently the Amlogic S905X SOC is I believe the cheapest way to run a simple video player that can handle hardware decoding of 4K HEVC including 10-bit color, 60Hz and HDR output. I use the el-cheapo Sunvell T95X with the LibreElec firmware - stable for weeks...

      Delete
  6. I'd be really interested to see the class A comparison at 1W. My understanding is that the crossover distortion effects low power output more so than higher outputs. Also, any reason why you didn't include the class A vs AB measurements for the Emotiva? (Which also has that feature)

    I'm sharing this article with everyone I know, some great level headed writing here. Love your blog, thank you so much for your hard work!

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    1. Hi John, thanks!

      Yup, I have made measurements of the XPA-1L also Class A vs. AB... I'll post that for completeness in the next couple weeks. Haven't run the signal through my oscilloscope yet to have a look at the crossover distortion. Will see if I can find time to do that also :-).

      Delete
  7. I'd love to see the Benchmark AHB2 Power Amplifier compared to these. My understanding is that this is the amp to beat when it comes to a low noise at low power. And it is "only" $3000.

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    1. Hey, I suspect the Benchmark will be great... I certainly respect John Siau for his balls being in the Industry to take positions on DSD and his recent post about MQA.

      As Willem suggest below though, perhaps more power is what one needs in one's home with one's speakers... And depending on the ambient noise level, one has to think hard about whether >130dB dynamic range is needed - as impressive as that spec is! The great thing is that $3000 is indeed a very "good" price compared to so many questionable other devices out there!

      Delete
  8. The Benchmark is probably the amplifier that measures best right now. The question is, however, if the better measured performance is actually audible, compared to, say, the Yamaha amplifier that I linked to. My hunch is that the Yamaha may even come out on top, given its much higher power output.

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  9. A note for your interest. I am involved in the consumer audio industry and have been for many years. A product I designed was reviewed in hifi + in recent years, the review process was conducted at arms length with no possibility of influence over what was written. There was no advertising spend involved either. This has also been my experience with many other publications. The only publication that has ever requested an advertising spend was a web based one which itself is full of advertising.

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    1. Good to hear of your experience Audio.

      I'm just concerned about what I saw looking at this device and the apparent "fingerprints" from HiFi+ everywhere. As in other domains where there are potential conflicts, it's useful to have clear disclosures given the optics...

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    2. It is possible, after the event, to purchase the review in a high res pdf format for subsequent promotional reprint purposes. However it is not cheap to do so. The online review can be linked to for free. It is also possible I guess to "steal" the images from a review and use those for other materials. More often in my experience the manufacturer will supply the images to the reviewer which can be an advantage as that ensures the quality of the pictures.

      Delete
  10. Since the subject of advertising has been raised, some say the same about the blog here and the adverts.

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    1. Hi Matt. Happy to address this.

      Other than the ad banner for Mitch's book on DSP on the right panel (which I personally found of great value and makes a huge difference for sound quality), the rest is just Amazon ads pointing to the things I mention (both for good and bad) and standard AdSense ads which basically follows your browsing patterns like pretty well any other blog out there using AdSense.

      As I mentioned before, I do get a few bucks from the writing to let me buy CD's here and there mainly through Amazon.

      The main thing is that in all these years, I have never had any companies let me borrow anything. Other than friends loaning me stuff, everything else I write about I *own*, purchased in the "open market" with whatever deal I can find just like everyone else... This is why I also want to focus on the importance of *value* and the obvious *lack of value* in so much of what is advertised in the audiophile space. I am happy to bring my opinions up without any concern around relationships with the Industry.

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  11. Pretty lively thread about this blog post @ computeraudiophile.com some are questioning the measurements as inconclusive especially since they are purely resistive loads.

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    1. Sure. It is what it is. Measurements off an 8-ohm power resistor. Not much different from almost any other reviewer measurements.

      However. Notice the noise level with the Vitus Audio. No matter how you think the speaker load may change things in terms of component matching, this expensive amp is *noisier*. The difference is audible. However one wants to see it, I cannot consider this fact a positive for the device.

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  12. Just an update:
    I had my friend who owns the amp come over for a listening comparison. Using the same tracks played initially on the Vitus Audio and then Emotiva - vocal tracks, jazz, rock, trying my best to keep the volume the same, he thought:
    1. He liked the midrange better on the Vitus Audio.
    2. But the Emotiva seems to have better high and low frequency extension especially with dynamic transients.

    Realize of course that this is all sighted listening and it takes about 30-60 seconds for me to switch cables between the 2 amps.

    Another data point: My friend's wife sat in on the whole listening session. When asked if she heard any difference: "No difference". Interesting I guess considering she's younger than myself and her husband (we're in our mid-40's), presumably has better hearing as a woman, and since she's not into the gear (music lover of course), doesn't particularly have any preference either way.

    Go figure :-).

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  13. Bob Carver started the low cost high watt price catagory in the early 70's with his 300wpc Phase Linear amps.
    He continued that trend at Carver Corp and at Sunfire. The Audio world is full of mega buck junk...I blame Mark Levison (the man) for starting this trend of charging way too much.

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  14. Thank you for an insightful analysis into amplifier performance. I appreciate the objective data and the conservative subjective interpretation. As there are many different ways to build an amp, I was wondering if you had the opportunity to look at the amps built by Roger Sanders (sanderssound.com) These are high current designs for high load planar speakers (jaggies, electrostatics, etc)

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  15. What an awesome post, I just read it from start to end. Learned something new after a long time. Its extremely good and very helpful for me.Thanks for sharing this great post.
    Magic Xpa

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  16. I have enjoyed this post immensely, despite the fact I question a good bit of it. I suppose that having a PhD in electrical engineering would generally put me in full agreement with measurements, but after having been in the audio hobby for 23 years and having owned approximately 150 pieces of hifi equipment, I can say that the implicit relationship between sound quality and measurements is shaky to nonexistent. I have some amps that measure terribly (my Kora Aries monoblocks for example), but they sound ridiculously good. Then I've had some that have WAY better performance on paper, but in practice just fell totally flat on their face (a McIntosh MC202 thuds to mind).

    Not to mention the standard-industry-practice metrics you have shown have practically no bearing on the metrics we use when listening. We are so far off the right path that I'm not sure we will ever get back on the right one. Your 3rd plot showing the room effects does a great job of demonstrating one facet of this, so I know you and I have common ground. I've been doing research as a hobby in this field for many years and it's a fascinating rabbit hole of biological interactions and electromechanical wave theory. But I'd better digress....

    Are measurements useless? No. Do I like seeing them? Yes. Do I feel they matter when it comes to musical sound enjoyment? No. In my stereo I currently have 8 tube amplifiers and 4 solid-state amplifiers. They each have their own personality and character, each their favorite kinds of music, and I love them all. They remind me of my friends - not all of them are technically adept, but they are all wonderful people.

    Thank you for the post. Keep up the good work!

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  17. Interesting review. I demoed a bunch of amps last year (Vitus, Luxman, Devialet, Naim, Mackintosh). The Vitus integrated, to my ears, was the overwhelming best by some considerable margin. It seemed to serve music 'just right' which is not a measurable variable, I do admit.

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