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Everything posted by Shadders

  1. Hi, It is going to happen - Microsoft have stopped access to the e-books : https://www.bbc.co.uk/news/technology-48829661 Will happen to other services and purchases, such as games etc. I always purchase the CD or DVD/Blu-ray, and have never downloaded. There will always be a glitch, dispute, or cessation of service, affecting the customers. Regards, Shadders.
  2. Hi, Farnell has the same issue - despite the transistor being in the system as i could locate it through narrowing the filter criteria, it could never return the device through a search. I noticed that when i completed a search, then "bing" was in the search URL that flashed up. Maybe the target system has moved across to a Microsoft solution ? Regards, Shadders.
  3. Hi, @The Computer Audiophile , if possible, can you move the relevant posts from #15088 onwards, in this thread to the new one created : Thanks and regards, Shadders.
  4. This is the discussion on whether Red Book CD (RBCD) is all we need fro audio reproduction given that amplifiers may or may not have a lower noise floor.
  5. Hi, Not sure how he calculated - the Rane article states : Required Conditions. In order for the published figure to have any meaning, it must include the measurement bandwidth, including any weighting filters and the reference signal level. Stating that a unit has a “S/N = 90 dB” is meaningless without knowing what the signal level is, and over what bandwidth the noise was measured. For example if one product references S/N to their maximum output level of, say, +20 dBu, and another product has the same stated 90 dB S/N, but their reference level is + 4 dBu, then the second product is, in fact, 16 dB quieter. The 130dB has to be referenced to a specific output level. The ASR review is not clear on what output signal level is being used. Regards, Shadders.
  6. Hi, If we assume 200watts in 8ohms specification for the amplifier (i think it is specified at 100watts), then 200watts is 23dB. The SPL 120dB - 23dB = 97dB sensitivity speaker. Not many speakers in that range. I quoted 86dB as this is more probable. Even a 90dB sensitivity speaker requires 1kW amplifier. Is it not the issue that, the lower sensitive speaker requires the amplifier to provide a greater power, increasing THD and hence the stated 120dB SPL etc. statement is not relevant ??? The issue is also, the 130dB figure measured - what were the parameters for this measurement ? If 1watt into 4ohms is -106dB due to THD, then how is -130dB S/N achieved in the test - what were the parameters ? I think the relevance to MQA here is that the noise floor of CD is sufficient, and high resolution is not needed - since any music will mask any noise artefacts, especially at -106dB noise floor, making -130dB a nice figure, but irrelevant ??. Regards, Shadders.
  7. Hi, i do not know - does ASR measure to 1Watt into 8ohms? for all its S/N ? It is not specified for the Benchmark. The review states : "Wow, assuming you play at peak of 120 dBSPL, your noise floor will be at -10 dBSPL! That is absolute silence." If you play at this level, then THD rises, so not sure -10dB SPL is accurate. The 120dB SPL refers to 34dB power (2.5kWatts) for a 86dB sensitivity speaker. This exceeds the Benchmark capability. The RANE site is good for the explanations - the parameters need to be stated for any S/N figure ; https://www.rane.com/note145.html Stereophile specification list for the Benchmark AHB2 does not list the parameters for the 130dB S/N except that it is A weighted. Regards, Shadders.
  8. Hi, Sandyk can confirm this, but the specification for the SC200 was measured for the completed amplifier - not simulation. The ULD was also the measured performance. If you purchase the kits/PCB, and follow the article instructions, then you will achieve the measured performance. Regards, Shadders.
  9. They do all look old, scruffy, and lardy.
  10. Hi sandyk, Yes, there are many excellent DIY designs, which can be built for the fraction of the price. It is a shame that DIY is not more popular. Regards, Shadders.
  11. Hi, If you buy Bob Cordell's new book, there is an example design in chapter 4, with all required ancillary circuits, which has 125watts in 8ohms, and 1kHz THD is 0.0008%, and 20kHz THD is 0.004%, close to the Benchmark. Although the S/N is 100dB A-weighted. Regards, Shadders.
  12. Hi, The specification is A-weighted, so please correct if wrong, removes noise due to the filter. The ASR review probably does not use A-weighting. Regards, Shadders.
  13. Hi, I am not bothered about the ads - i like the ads - seeing other equipment and brands. Regards, Shadders.
  14. Hi, I noticed this about 3 weeks ago - if i have ublock ad blocker turned on, i see the ad at the top and those at the side. If i turn it off, i am prompted to turn it off, and still see the ads at the top and side. I turn it back on, no prompt to turn it off, and still see the ads. So, not sure where the logic problem resides. Regards, Shadders.
  15. Hi, Your subjective listening neither confirms or refutes the objective measurements. You will not know whether you can hear 20kHz+ or not. Again, if you are happy that the manufacturer decides for you regarding your hearing, or that 20kHz+ has no effect in the system reproduction, then ok. The issue is that they present measurements that make their amplifier look better than the usual class A/B amplifier. They restrict the measurements to make their product look better, then claim no other amplifier can be better. I do not think class D should be given such preferential treatment - we should therefore be asking all reviewers to use the 22kHz measurement bandwidth, to level the playing field. Another aspect is the very low output impedance of the unit. I think the performance of the Purifi module is excellent in this regard, but this is at 1amp output current (rms assumed) which equates to 6.83volts peak output into 4ohms. If we have a transient of 20.5volts peak, which is 3amps (rms) into 4ohms, is the output impedance the same ?. At 1amp, the damping factor is 12,000 which is vastly greater than any other amp. The objective measurements are used to present an expectation of performance, and subsequently the listener will hear accordingly. I do not think our hearing is as good as we believe it is. Regards, Shadders.
  16. Hi, The point is, Purifi make exotic claims, and these should be scrutinised - stating theirs is better than anyone elses whatever the amplifier, is more than promoting a specific attribute the amplifier has. What class D sellers/manufacturers say regarding THD, is purely based on their desire to ignore the usual measurement bandwidth because it makes their product look worse. We have people selling RF absorbent materials stating that they are beneficial when placed inside or near an amplifier, yet for some reason, the 20kHz+ mush from class D which is always there regardless whether a signal is being amplified, seems to be irrelevant. For the sub-harmonic, this was relating to tweeter mechanical - i have seen discussion on it - but i would not know if it occurs. The nCore tests showed the IMD signals repeated at 40kHz and was quite high in energy. What this means is that does IMD occur with lower frequencies causing the IMD to be inband - such as 5kHz+6kHz ? Does the IMD in the mid 20kHz cause metal dome tweeters to ring ? since they have resonances here ? I agree, that it is really the subjective listening that matters - do you like it, but we cannot pick and choose which measurements matter, because the ignored set make the product look worse, yet still apply the ignored set to other amplifiers. Regards. Shadders.
  17. Hi, The measurement bandwidth is 22kHz in some cases, and 40kHz in others for THD versus frequency, and 61kHz in others. For the 61kHz measurement bandwidth (the last graph) shows that the amplifier THD is 0.1% to 0.2% at 20kHz, yet the specification states 0.001% typical for 20Hz to 20kHz, using a the IMD test. The specification for the Hypex NC500 states : "Note 2: At higher audio frequencies there are not enough harmonics left in the audio band to make a meaningful THD measurement. High frequency distortion is therefore determined using an 18.5kHz+19.5kHz 1:1 two-tone IMD test." So, do you accept that class D manufacturers are right and decide for you that 20kHz+ frequencies are meaningless, or is this just to make their numbers look better ?. They certainly claim the superiority when it suits them (Purifi "exotic" statement). The graph with the full spectrum without any filter (3rd from last), shows that for an 80mV input signal. There is significant noise from 20kHz to 100kHz, hence the poor THD with 61kHz measurement bandwidth (100x worse than IMD). Does this energy from 20kHz to 100kHz affect the tweeter ?. What about the higher frequencies 100kHz to 400kHz ? Is there such a thing as sub harmonic distortion in tweeters ? EDIT : To add - the intermodulation distortion graph, second from last - the 35kHz to 45kHz intermods are 40dB worse than the benchmark amplifier. Is it possible that the tweeter is affected by these intermods at the level that they appear ? What about lower intermods, such as 9kHz+10kHz tests ?, or 12kHz+13kHz tests ? Regards, Shadders.
  18. Hi, Do you believe that the output of class D is solely the music input replicated with the specified THD, and a 500kHz switching frequency ? Regards, Shadders.
  19. Hi, I am not disputing anyones experience. In fact, their experience has shown that frequency bandwidth above 20kHz is not required. I think this fact, is a definitive reason to claim that high resolution in respect to sampling frequency, really is not required. It is Purifi who have made the "exotic" claim that their amplifier is the best ever (my summary). They, through their measurements and "exotic" claim have made the decision for you, that you cannot hear anything above 20kHz, nor can the class D noise above 20kHz affect the in band performance. So, for class D and class A/B comparison, class D gets preferential treatment for the measurement bandwidth. In addition, the module specifications is a standalone measurement, such that enclosure, power supply (to some extent), wiring, placement, are optimal in every case. A class A/B amplifier is always measured based on the manufacturers offering which include the aforementioned, and its distortion mechanisms. Regards, Shadders.
  20. Hi, This is an open forum where all views are allowed. The fact that you have no interest, does not make the points being discussed irrelevant. Questions to the designer whether technical or other are pertinent, since they claim : "This corresponds to an unprecedented 110MHz Gain-Bandwidth Product and produces consistent ultra-high performance across the audio spectrum unmatched by audio ampliers of any technology or operating class." I do not think we should let such a designer tell everyone what to think. For your statement on "weird thought process" : The class D modules are measured with a measurement bandwidth of 22kHz. Why ? (i have answered this). No reviewer or audio enthusiast has ever complained about the excess noise above 20kHz Class A/B amplifiers are regularly reviewed with measurement bandwidth of 80kHz. Essentially, class D amplifiers are getting preferential treatment, else the performance of the two cannot be compared, and given that there is excessive noise above 20kHz which no one has ever complained about - means you just cannot hear it. The "golden ears" reviewers and enthusiasts, quite simply, do not have "golden ears". Not sure where you are getting the non-real world from - Purifi quote real world figures, make exotic claims regarding those measurements, and these are being discussed. Would you prefer it that we just accept what the manufacturers, reviewers, sellers, and fanbois say without critical discussion ? Regards, Shadders.
  21. Hi, This is about performance, not whether the tweeter can or cannot reproduce the signal. The performance of a class A/B amplifier exceeds the class D amplifier. The issue is that the extra noise in the audio band 22kHz+ for class D, exceeds class A/B amplifiers noise. Regards, Shadders.
  22. Hi, Due to the excessive noise on a class D output which is present permanently, the measurement of the THD uses a 22kHz bandwidth filter. The class A/B amplifiers use 80kHz in the measurements. A class A/B amplifier output is a continuous function of the input. Your reference to "Crossover notch distortion" is a continuous function in a correctly biased class A/B amplifier - it is non-linear, but the feedback reduces this to a minimum, as does multiple transistors in the output stage. The transistor is not a discontinuous device, as it operates entirely with a continuous non-linear function when forward biased. Please see : https://linearaudio.nl/cyril-batemans-capacitor-sound-articles All ceramic capacitors have inherent distortion which exceeds all others. Polyester capacitors have significant distortion. Polypropylene and polystyrene capacitors have the lowest distortion. Regards, Shadders.
  23. Hi, As an example the following tweeter : http://www.sbacoustics.com/index.php/products/tweeters/ring-dome/satori-tw29rn-b-8/ Extends to 40kHz in frequency. This tweeter will reproduce the signal if it is there. There are many others just as capable or better. Regards, Shadders.
  24. Hi Alex, Thanks - the problem is that my Media player will limit the data rate on the optical to 48kHz. I have a Peter Gabriel 24/48 download from B&W which is excellent. I have some blu-ray discs which over HDMI allow for 96kHz, but i found these discs sound no different from a good RBCD. So, i have listened to high resolution - the increased bit depth seems to make the difference for myself. Regards, Richard.
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