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Everything posted by etc6849

  1. I would compare the waterfall plots to see the differences. It is much easier to see things that way if you are only looking at the bass region. You will see a faster decay of 20-80Hz. Time aligning sub drivers with sub drivers is much easier. Just use the impulse/etc plot to time align them. Start with one sub, then align another to it, then align another to one of the first two subs, etc... After that, you hook all the subs up to a common output, pick a filter, measure, then align each woofer with all the subs going at once.
  2. I do level, then set the crossovers, then do time alignment as I described. Things should be done in this order. Even setting level later will impact the crossover point (it sounds like you already are aware of this, but I'm putting it here for others). The slope at the crossover region is seldom a brick wall, so there is plenty of overlap for the time alignment method I describe. Technically, FIR filters don't impact phase (using them for woofer to midrange and midrange to tweeter), so really I could go back and adjust things out of order, but for the low order bessel filter I use for my woofers and subs I definitely can't do that obviously.
  3. @Chris A My step response looks very different than yours. I think mine might look more ideal, but honestly, I have never looked at my step response so I am curious what you think. I have never used psy smoothing either, but seems like a good idea so here is what things look like for SPL and phase. Note I intentionally tilted levels when I set them up, and I'm not using any PEQ or Dirac. Perhaps if I point the mic at the speaker as you suggest it would look nicer. I'm definitely capturing more of the room effects the way I've been measuring. One thing that is confusing is the phase shift that appears at 6kHz and 13kHz when I unwrap phase. This only appears in my front two speakers and not my rear speakers.
  4. I have a small room, so I just did all measurements at the listening position, with the mic pointed toward the ceiling and the tip at ear height. For the time alignment, I also did something different. My thinking was for time alignment, the primary concern would be around the crossover region. So I performed band limited measurements for the drivers over a reasonable overlapping region, then compared the impulse/ETC plots. For example, to align a sub to a woofer with a 110Hz crossover, I would do measurements covering 20-200Hz for both my sub and the woofer. I then compare the two ETC plots, and get the time delay that way. I did similar method for the woofer and midrange, etc... What is interesting is that this seemed to produce decent results after looking at the peak energy curve on the spectrogram (something I didn't think about using for time alignment).
  5. @Chris A Music itself can mask THD too. However, it seems some instruments are better than this than others such as pianos that don't mask amp distortion as well (since they produce overtones that are not perfectly harmonic per this link). Here are some calculations I did for matching an amp to my bookshelf speakers. I should have probably done this prior to tri-amping my main speakers, but the driver data was not readily available. For most though, driver with horn sensitivity is likely available, so they can follow the same methods as below provided they have data for their amp (I used actual measurement data from the links below to ensure accuracy instead of the manufacturer's data). Klipsch P-17b speakers: http://e994010f48279d85b5d7-a0bc3fbf1884fc0965506ae2b946e1cd.r57.cf2.rackcdn.com/legacy-files/p17b_-_Spec_Sheet_635738650125214000.pdf Emotiva XPR-1 amp measurements: https://hometheaterhifi.com/reviews/amplifier/power-amplifier/emotiva-xpr-1-monoblock-power-amplifier/ Benchmark AHB-2 amp measurements: https://benchmarkmedia.com/blogs/application_notes/interpreting-thd-measurements-think-db-not-percent For the XPR-1 amp, I calculate that it will have a worst case 34 dB SPL of distortion at a 80dB SPL listening level (assuming 20 dB peak, giving a 100dB SPL peak). Also, using the XPR-1, my speakers would reach an SPL of 121dB, and have 54dB SPL coming from the amps distortion. Since this exceeds the speakers max recommended output, likely the distortion at 121dB SPL would be greater than 54dB (amps + speakers)... Don't worry, I don't plan to ever have them that loud. If I use an AHB-2 amp with the bookshelf speakers, I'd see a peak level of 113.6dB (fine for any volume I'm going to use them at), and the distortion would be below 0dB SPL at -6.4dB SPL, so it would be impossible for it to ever be audible. I'm ignoring the Benchmark DAC 3 DX (DAC I'm using), but it's not the limiting component for the XPR-1 amp case. If both amps were played back at 80dB SPL with a 100dB SPL peak level, we'd see the AHB-2 contributes -20dB SPL (not audible) while the Emotiva XPR-1 contributes 34dB SPL (might be audible depending on room). This surprises me some as the Emotiva XPR-1 measures as good as amps costing a lot more. Based on the used market though, AHB-2 versus two XPR-1's seems fair based on used prices. Given that the bookshelf speakers are in my living room, I am fine with 34dB SPL of noise from the amps as it is a noisier room and I doubt I will hear a difference. I have less in the XPR-1's anyways as I bought them off craigslist Bechmark AHB-2 case: (I only calculated noise from the amp for max level below, but obviously any level below that will be even lower) For fun, I re-did the max SPL from the AHB-2 amp using Pascals, then converted to SPL after cross-multiplying to obtain the new Pascal value... Of course it is the same: Application Notes I studied: https://benchmarkmedia.com/blogs/application_notes/interpreting-thd-measurements-think-db-not-percent https://benchmarkmedia.com/blogs/application_notes/speaker-efficiency-and-amplifier-power https://benchmarkmedia.com/blogs/application_notes/audio-rules-of-thumb
  6. I guess it depends on space. To be totally honest, if I can fit two horn loaded subs or 5 well engineered direct subs like I have now (9 sub drivers in total), I think my current setup would win in terms of measurable distortion at the MLP as my room is on the small side. What really surprised me was the performance I gained by going with 5 subs, especially considering I have three woofers in each speaker crossing to the 9 sub drivers (for example, there are 12 drivers working for a 100Hz tone). This has led to a setup with measurements like .363% THD at 29 Hz at 90dB and .239% at 80 Hz at 92dB: I did measure my room as you rightly point out. With my lights off (LED lights buzz just a tiny bit), I get this RTA result: I see plenty of places where less capable amps would make hiss depending on the spectrum of the noise content (and they did, which is why I spent so much to replace them). This was the case with the old Emotiva XPR amps I had, and I think their SNR was around 92dB at 1 watt, but they had a lot of hiss when I tri-amped. Yep. I have reached that. I do hear a very faint hiss when my head in the the horn. However, I still may buy several 8 channel DACs at some point and do all the DSP work on the PC. I haven't yet, mainly because I'm not sure I'd hear a difference.
  7. Here are some more measurements to consider. I've owned several of these in the past before I found the path to audio nirvana 😀 It seems one can gain 30dB of dynamic range or more by using digital out from a PC and using a well measuring DAC and feeding an amp (even without tri or bi-amping). Combining everything possible to reduce overall distortion (room treatments, signal chain, multiple subs, actively tri-amping) has created a system that most will never hear the clarity of. Well worth the expense for the performance I'm getting. I know I could be driving a nice car instead, but most of my gear will hold it's value better than a car. Some AVR measurements: Some AVP measurements:
  8. Indeed. It is very hard to measure that low from what I understand. Amir has at least $50k in test equipment (his Audio Precision APx555 alone is over $25k?). I definitely don't think most reviewers (unless they are technicians or test engineers) and many manufacturers (sad but true) have the necessary test equipment to measure that low.
  9. What I found was that eliminating the extra unnecessary DAC improved performance. I'm not sure if this is because the ADC was the limiting factor (which also gets eliminated when you send digital straight to your DSP), but likely. Just in case anyone says all DACs sound the same: it depends on your entire signal chain and even the noise in your room. When your amps are no longer the limiting component affecting overall dynamic range, the extra DAC and ADC can be the remaining factor needing improvement. I bet most of the blue DAC measurements below are from DACs that will sound the same (all are very well engineered), but many of Amir's SINAD measurements of AVRs and even expensive DACs look so horrible, that for sure those using sensitive speakers with a consumer grade AVR/AVP or poorly designed DACs are missing dynamic range if they use a leading amp like the Hypex nCore NC400 or Benchmark AHB2. I wouldn't have believed how much dynamic range people are missing, but the measurements don't lie: https://www.audiosciencereview.com/forum/index.php?threads/master-sinad-distortion-comparison-graph-for-dacs.4814/ Amps are even worse too. Compared to the best known measurements of the Benchmark AHB2:
  10. I'm glad to finally see measurements of the hypex ncore modules. These measurements look really really good, and the amps are very small. ATI also makes an 8 channel amp that uses OEM ncore modules... now I see why. https://www.audiosciencereview.com/forum/index.php?threads/review-and-measurements-of-hypex-nc400-diy-amp.5907/
  11. ATI makes some 8 channel amps that use the hypex n-core modules: http://www.ati-amp.com/AT54XNC.php. I have a feeling these would make great amps for tri-amping, and you could fit 16 channels in 8 rack units and have much lower noise floor than other consumer brands. They are likely the best bang for your buck, and the only amps that measure better are the Benchmark amps, but they are very expensive even if you buy them in bulk like I did. I would probably call ATI and see if they have some B-stock units. They have gave me a 50% discount 8 years ago, but I'm not sure what they are doing now days. As for ease of use here's a video of some of the controls and display in action: https://drive.google.com/open?id=19DguWj0G3R-7xSj7UBlGWrW507STXZSA And here is some of the code I had to create to get everything working: http://cocoontech.com/forums/topic/30996-new-modules-matrix-orbital-vk-displays-vfd-rme-totalmix-osc-jriver-and-mce-controller/ You can get a PC to act like an appliance, but it does take a lot of setup. Even when I use the keyboard volume control, RME TotalMix changes level (instead of the Windows volume mixer). The JRiver apps make it very easy to play a movie or music though using an iPad or Android tablet too.
  12. Some pics of my new PC case. I'm using this rack for tri-amping my C, FL and FR, and also crossing to 5 subs that are individually time aligned and level matched. The PC case didn't do anything for sound, but sure looks nice. I highly recommend everything else in the rack though because the amps and processors did improve my sound and measurements over the consumer gear I had before.
  13. If you can find a used XD4080, I would go for it over the XP4080. I would also try calling Acoustic Frontiers and haggling on a new one too. The one's I bought from him were well below retail (somewhere between 1400-1600), but he is a nice guy and gave me a decent price compared to any pro audio online place I tried. I use the Xilica XD's FIR feature for the LF/MF/HF and wouldn't go back. You are limited on taps (they change the slope of the FIR), but there are plenty of taps for my speakers and keeping distortion below .2% at the listening position and at 90dB. This compares with some of the worlds best headphones in terms of distortion, but magically my speakers are 7 feet away where as Focal beryllium driver is an inch from your ear. It is 100 times easier to get great sound when setting up FIR filters. I played with a lot of different filter types, but FIR won hands down and I really believe I hear a difference. Not distorting phase is a huge plus for FIR filters. Someone really experienced like Chris can no doubt get a setup sounding great without FIR filters and get a very nice looking phase, but he has read a lot and spent a lot of time to get there and is one smart dude. I was immediately happy with FIR and the results measured very well with less phase wrapping in the REW plot versus what I could do with IIR filters.
  14. etc6849

    What I Got Today!

    True. They are Benchmark AHB2 amps and the speaker processors are Xilica XD4080s. I'm doing FIR filtering for actively tri-amping some P-39f's, and also cross to 5 subs. It is like any hobby... I could have bought a sports car, but instead buy used cars with cash and finance my audio gear.
  15. etc6849

    What I Got Today!

    A custom PC case to match my amps.
  16. This is a great option if you want to experiment with a digital solution with AES out: https://www.amazon.com/GUSTARD-32Bit-384KHz-Digital-Interface/dp/B00PU3R6KY/ It is what convinced me to buy the RME AES32 PCI-E 16 channel input/16 channel out card. The driver support and quality of the RME cards are top notch. Although it was expensive, it is very flexible (can show up as a 16 channel device to a DAW/JRiver and also a 8 channel device to Windows at the same time so Netflix still works), and you can even control the RME mixer over the network which is how I control the volume (via my home automation system). Having a 5.1 setup that uses AES out from my PC, three Xilica XD4080 processors with FIR filters and 10 Benchmark AHB2 amps is incredible. I can literally turn the volume down 85 dBU and still understand the words being spoken. Some of this is attributed to the AHB2 amps, but I could never get there with having my XMC-1 processor in the mix. It is the clearest most life-like system I have ever heard. There is zero hiss unless you put your ear into the horns. I also added 3 more subs, giving a total of 5 subs running off one of the Xilica units. These 5 subs are all time aligned and level matched, and the performance is incredible. Although it took a good day to align all 15 drivers and the subs, it was well worth it. I've had the full 5.1 system setup for 6 months now, and I am 100% satisfied with it. I don't think there are any additional changes I can make to the system to improve quality, it is simply the best sounding setup I have ever heard at any price. I did end up making my own custom racks (Middle Atantic CFR series cabinet frame units) and cables using Canare star quad cable too so the system looks nice too. Using AES makes so much sense; you can locate a rack with more Xilica XD4080's in other parts of the house (or even your neighbors down the street), with no signal loss. This is my ultimate plan for my permanent home as JRiver supports multiple zones, and I am only using 6 channels out of the 16 channel card. JRiver also has some very nice looking iOS and Android remote app options. Plus, I'm now using MadVR to playback 4k HDR content from within JRiver; this gives me a world class video option if you buy a higher end graphics card. Some pics and older measurements: https://drive.google.com/open?id=0B1J0a4OV_WGLQndldFAtZXMxdVk
  17. Tri-amping aside, I would read the rest of my post (like the bottom 3/4 of it) that talks about how poorly consumer grade gear is designed, and provides a verifiable example on the Marantz AV8801 and 8802. The article I quoted explains why AVR's are technically inferior to higher end pro grade DACs (such as Benchmark's DAC2), although I agree it is pretty technical and most aren't going to read and study it. Yes, on my sensitive speakers and setup, even before tri-amping, a DAC made a noticeable difference (cause I bypassed the XMC-1 processor entirely when I tried it). However, as you state, once you put consumer grade inferior audio circuits in the chain, of course it will affect S/N ratio, so you would be right if one just inputs into an AVR from a DAC (the article also talks about this with an Oppo 105 example). I didn't read "standalone DAC" the way you did in the OP, I hope plugging on into the Denon is not their plan. One does need to look at the entire signal chain and the room too. No doubt my goals are different from the OP and I have spared no middle class expense getting there. I still standby that AVR's absolutely cannot get me there (or anyone wanting world class fidelity), trust me I tried several, and even expensive processors like the XMC-1 and AV8801. All the consumer gear is just marketing hype. My system sounds many times better now using 100% pro gear. I also don't care what boutique consumer brands people try, because the combination I am using is better overall (as you said it lets me tri-amp with FIR filters which is a huge benefit). The Xilica XD4080 is as good as the best boutique brands if you just use it as a 8 channel DAC and feed it AES while keeping the passive crossovers in your speakers, let alone comparing it to D&M receivers. You sincerely do have to hear it to believe it though, so I don't blame you for your skepticism if implied; good quality to have.
  18. Consumer grade AVR's and processors are a waste of money if you are in search of ultimate sound quality. You cannot get there with an AVR. The smartest thing I did (and most expensive) was listen to DrWho and ChrisA and go with full active tri-amping. The next smartest thing was to use an all pro gear signal chain with a single DAC at the end. My basic signal chain: RME HDSPe soundcard outputs digital AES into a Xilica XD4080 speaker processor that has FIR filters for W/MR/TW and then feeds an analog signal to Benchmark AHB2 amps. My setup is a little more complex as it involves 5.1 system that is fully tri-amped with 5 subs individually DSP'd, but the results are absolutely world class and like nothing you will ever hear in any hifi store (no matter the price point). Here's some quotes from the technical article I linked to discussing the Marantz AV8801 and 8802: https://benchmarkmedia.com/blogs/application_notes/19947905-the-audio-path-in-consumer-grade-audio-products Low-Voltage Signal Path It appears that internal audio signals are kept small, normally 1 V rms (1.4 V peak) or less. The low signal levels allow the use of low-cost low-voltage integrated circuits, but these low signal levels affects the signal to noise ratio (SNR) of these units. The SNR is also affected by many other design decisions, but low voltages always make it more difficult to achieve a high SNR. For example, if the level of noise in a circuit stays constant, but the signal level is reduced, then the SNR will be reduced. The 1 V rms internal signal level also makes attenuation necessary at the analog inputs. Volume Control ICs Cannot Handle High Voltages In the AV8802 and the AV8801, the balanced inputs are attenuated by at least 6 dB (perhaps even 12 dB) as they enter the unit and are converted to single-ended signals. This means that balanced analog signals are reduced by a factor of 2 or by a factor of 4 before they reach the internal signal path. This attenuation reduces the SNR of the audio system, but it is necessary to prevent overloading of the volume-control IC. ... The volume-control IC will handle 2 V rms signals, given the 5 V to 7 V supply rails used in these products. But, the volume control IC delivers its best distortion performance when signals are 1 V rms or less, with distortion rising rapidly over that level. I don't know if the single-ended inputs are reduced in level. There may be a 2:1 (6 dB) attenuation on the single-ended inputs, but it is hard to tell without a full schematic. ... The output of the AV8802 is rated at 1.2 V rms single ended, and 2.4 V rms balanced. The higher output of the balanced circuit is achieved by an inversion of the single-ended signal, to provide a non-inverted and inverted signal to the balanced output connector. Curiously, the buffer has 12 V rails, but the active circuitry won’t see input signals close to those levels because of the limitations of the the volume-control IC. Driving a Power Amplifier Marantz rates the balanced outputs of the AV8802 at 2.4 V rms. This limit makes sense when examining the internal components, but it is a fairly low signal level for a balanced output. The single-ended outputs provide 1.2 V rms. 1.0 V rms will drive a typical power amplifier that has a gain of 29 dB to an output level of 100 watts into 8 ohms. If the balanced output of the AV8802 is used to drive the Benchmark AHB2 amplifier at the high-gain setting (23 dB), or say a Bryston amplifier at its lower gain setting (also 23 dB) the pre-pro will be very near its 2.4 V limit. At an amplifier gain of 23 dB, it takes 2 V rms at the amplifier input to deliver 100 watts into an 8 ohm load at the amplifier output. The noise levels of the amplifiers will be very good at this level, but the system noise performance will be limited by the noise performance of the Marantz pre-pro. Hybrid Approach to Volume Control A DAC like the ESS ES9018 provides an excellent internal 32-bit digital volume control, but an analog control would still be required for the analog inputs. Providing separate volume control systems for digital and analog inputs is a path to good audio quality. This technique is used in the Benchmark DAC2 HGC. Analog inputs are controlled by a variable resistor tied to the motorized volume control knob. Analog inputs do not pass through a performance-limiting volume control IC. Digital inputs only use the 32-bit digital control. The position of the volume control knob sets the gain of the 32-bit digital processor. This hybrid approach is too expensive a solution for mid-range consumer AV products such as the Marantz and Emotiva pre-pros.
  19. There are many technical advantages: https://benchmarkmedia.com/blogs/application_notes/19947905-the-audio-path-in-consumer-grade-audio-products I sold off my XMC-1 and Emotiva amps, and went for a 5.1 actively tri-amped setup (DAC is inside Xilica XD4080 speaker crossover units). My speaker crossovers are fed AES digital off a 16 channel RME card. If you can get a high quality speaker crossover 8x8 and feed it AES, I bet it sounds better than an AVR. My setup is like nothing I have ever heard (it wasn't cheap though). If you just want stereo, USB is going to be your simplest/cheapest DAC input option, but this is limited as you can't crossover your front speakers to your subs. I personally will never go back to wasting money on processors or AVRs that quickly get outdated, limit you on crossover filters for your subs, etc...
  20. I haven't tried or bought it yet, but if you end up using only a PC, someone recommended I try http://www.audiovero.de/en/acourate.php, which would simplify a PC only setup and let you use FIR filters combined with room correction filters (or any custom filter you can think of) for all drivers. EDIT: This would make great use of 16 channels of AES out I also forgot to mention that JRiver has a virtual sound device, so other programs can use the filters even when they are external to JRiver. If you load the generated filters into JRiver, JRiver can account for the added audio delay by delaying the video (nice depending on how many taps the FIR filters have). This would mean you could freely use any DAC you'd like for even greater fidelity, while all processing is done on your PC using 64 bit floating point. This is the book for setting up Acourate and JRiver that someone was recommending to me: https://www.amazon.com/dp/B01FURPS40 I doubt you would need it knowing how tech saavy you are, but maybe someone here might find it useful. As for ease of use, JRiver has a really easy to use remote apps for Android and iOS too, so it should be very easy for people to pick a song or movie. I ripped all of my bluray movies to mkv files using Makemkv. It is bit perfect and works great for 3D and 2D movies. Absolutely no problems at all, and eliminates all the menus and trailers so it saves hard drive space.
  21. Hi Chris, A month ago, I re-setup my 5.1 system in another room without the sloped ceilings, plus I wall mounted my TV. The system uses 3 Xilica XD4080's, 15 channels of amplification for tri-amping all 5 speakers, and 5 powered subs (each sub having their own DSP channel and summed to mono using one of the Xilica XD4080's); and of course a PC running JRiver Media Center and the RME HDSPe AES PCI-E card (16 in/out). HDMI is used for 4k video playback by running a short cable from the display to the PC's onboard video. Netflix, PowerDVD for UHD bluray playback, 3D blurays via JRiver, etc all work and send AES out via the RME card. With lots of treatments, the TV setup back several feet from the front speakers, and 5 elevated subs that are each time aligned and level matched, Dirac is no longer necessary for me and likely not worth the 8dB headroom loss. I can't believe I lived with the sloped ceilings for so long when the room next door is much easier to deal with. The RME card I use can be bought from the US distributor cheaper than retail if they have any open box units: https://synthaxshop.com/collections/open-box-deals I can turn songs down below -89dBU using the RME's TotalMix FX volume control and hear every word of what is said. For me, AES resulted in less cable clutter too as it lets me have a second rack for tri-amping the rear speakers that is fed off a single AES cable from the front rack (that doubles as a center stand). I do however, run another cable from the rear rack to the front to carry the mono sub signal back to my front rack. It is like having a new system with all drivers and subs time aligned and level matched for the main seat. Honestly, consumer grade gear has too many technical limitations like lower peak voltage, poorly implemented volume controls, etc... I don't think it has any place in systems like ours if you already use and/or don't mind using a PC for everything. I would seriously consider eliminating the AVP as it is a bottleneck in your system. Even if someone wants analog input, there are reasonable pro audio ADC's that could send AES into the RME card, and you can redirect the input signals however you want within TotalMix FX.
  22. Just seeing this. Feel free to call me if you are interested.
  23. I think there is less perceived loss on a system that has the best possible S/N ratios in the signal chain (e.g. a lot more dynamic range) for the reasons @DrWho describes in his two posts. I know in 2013 after I bought the squashed album "Daft Punk - Random Access Memories" when it came out, I was using a much less expensive signal chain, and the album sounded very squashed (La Scala II's fed by ATI AT2007 amp and an Onkyo TX-NR905 receiver). On my new setup capable of ~119dB+ of dynamic range (limited by D/A of the Xilica XD4080 when fed using AES), the album sounds noticeably better. I think the improvement comes from tri-amping using amps with a S/N of ~132dB and having much lower IMD (from the amps themselves as well as tri-amping); also the D/A stages of the Xilica are far better than the Onkyo (plus I'm not using an AVR for volume control anymore). It would appear as you increase the S/N ratio and improve IMD, it makes the hidden stuff much easier to hear on these types of tracks (e.g. background instruments and the little details still present even on the loud tracks). I'm not saying these are the only parameters, but it would seem they are far more important than I previously thought if your goal is to get every last detail out of a so called "squashed" track. As DrWho pointed out, since our ears operate in the time domain, but can differentiate frequencies at the same time, our minds can pick out quieter details even with a loud electric guitar playing in the foreground. Further, even over the same mid-range frequencies, somehow our minds can pick out conversations in a crowded restaurant even though there could be 20 people talking at once; no SPL meter can do that.
  24. This is very insightful, and explains something I've been noticing in JRiver. A lot of tracks I've been listening too lately have a measured dynamic range of 4.4dB or less, but they obviously sound much better and are very dynamic on my system. After reading this post, I found this link: https://wiki.jriver.com/index.php/Dynamic_Range "Which one is more accurate? It depends on what your criteria are. If you consider extremely narrow dynamic peaks to be an important part of the picture, then R128 may sometimes give you a misleadingly narrow impression. If you instead want to get a sense of how dynamic "most of the song" is, crest factor DR may give you a misleadingly good impression (in the example above because of a handful of clipped peaks). It's best to look at both and try to understand why when they disagree. Dynamic Range (either one) is not the be all end all of musical quality. You may find you prefer some tracks that are more compressed than others. Dynamic Range isn't a perfect test, it's just more information."
  25. The ATI amps (using hypex ncore modules) have excellent measurements at lower wattages, although I'd like to see the first watt expanded cause there looks like a dip thereafter: https://www.soundandvision.com/content/ati-at527nc-and-at524nc-amplifiers-review-test-bench But still, this beats most measurements I've seen except for the Benchmark AHB2. https://www.stereophile.com/content/benchmark-media-systems-ahb2-power-amplifier-measurements Some more good looking measurements from the NAD M22 (scroll to bottom for IMD), I'm thinking they also use hypex ncores: http://hometheaterhifi.com/reviews/amplifier/power-amplifier/nad-masters-series-m12-preamp-and-m22-stereo-power-amplifier-review/
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