Shadders Posted June 19, 2019 Share Posted June 19, 2019 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. pkane2001 1 Link to comment
Shadders Posted June 19, 2019 Share Posted June 19, 2019 22 minutes ago, psjug said: I agree that my numbers might not make sense. I meant more to make the general point. I don't worry about it so much myself. If I could afford the benchmark I would buy it, just because it is a great amp not because I think I need 130dB. And if I owned that amp I wouldn't then go out and seek 24 bit audio; I'd still be happy with 16-bit. 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. Link to comment
Shadders Posted June 19, 2019 Share Posted June 19, 2019 2 minutes ago, sandyk said: Hi Richard The Benchmark is not alone in giving decent Unweighted and Weighted noise figures these days , with even many kit amplifiers performing very well at a cost, typically including metalwork , transformers etc. of <Au $1,000 Even the recent less ambitious Silicon Chip magazine designed 200W SC200 Amplifier specifies Signal-to-Noise Ratio: -116dB unweighted with respect to 135W into 8Ω(20Hz-20kHz) I have attached the specs for the previous more ambitious SC ULD3 amplifier from March 2012, as well as their DAC from way back in Sept.2009 which is capable of further improvement using more recent voltage regulators etc. Undoubtedly there are numerous commercially available amplifiers and DACs that easily surpass the performance of these older designs these days. Regards Alex 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. rando 1 Link to comment
Shadders Posted June 20, 2019 Share Posted June 20, 2019 1 minute ago, psjug said: Just out of curiosity, have you or @Shadders seen measurements of finished amplifiers made from these kinds of kits? I'm not sure I've seen measurements of any amplifier other than the AHB2 that meets the 96dB SNR+N at 1W. Maybe nCore is right on the edge of meeting this with a 22KHz filter. Maybe there are a few others, but I bet they are rare. 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. Link to comment
Shadders Posted June 20, 2019 Share Posted June 20, 2019 50 minutes ago, psjug said: I can't find any numbers or curves showing THD+N at 1W for that amp. The neuorochrome modulus stuff also looks like it may meet the 96dB at 1W, but the unit reviewed on ASR is not quite there. Edit: The ASR test of the neurochrome amp is only slightly worse than the manufacturer curve (apparently due to intentional enclosure compromise), and this is into 4 ohms. THD+N into 8 ohms is better for this amp - I think it may meet the 96dB at 1W mark. 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. Link to comment
Shadders Posted June 20, 2019 Share Posted June 20, 2019 2 minutes ago, esldude said: https://www.audiosciencereview.com/forum/index.php?threads/review-and-measurements-of-benchmark-ahb2-amp.7628/ If you look at the chart graphing THD+N for all power levels you see it around .0005% for 1 watt for 4 ohm load. This would be - 106 db at 1 watt, and is almost fully noise. The comment about playing at 120 db SPL would of course require a better than 86 db speaker. Meaning with any less efficient speaker at a lower SPL the noise and distortion of the amp are going to be well below 0 db SPL in the listening area. 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. Link to comment
Popular Post Shadders Posted June 20, 2019 Popular Post Share Posted June 20, 2019 2 hours ago, esldude said: Well the statement about 130 db and noise level being -10 db SPL comes after the SNR measurement. He basically used the definition in the Rane link posted up thread. Max power/noise with no input signal. So at max power THD+N would be about -116 db, but vs silence the ratio measured is 130 db. Those harmonics of distortion well below -110 db are going to be masked if you were playing music. As the level of the music varies noise is always going to be below being heard right down to silence as the input. So the statement is accurate. 22 khz bandwidth, I think a 4 ohm load. 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. The Computer Audiophile and crenca 1 1 Link to comment
Shadders Posted June 20, 2019 Share Posted June 20, 2019 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. Link to comment
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