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ServerBaboon View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ServerBaboon Quote  Post ReplyReply Direct Link To This Post Posted: 29 Apr 2022 at 1:57pm
Here is recent and interesting video on test only approaches for reviews, I am intrigued as to why he felt the need to post it now Smile

https://www.youtube.com/watch?v=Fa1y9JRip68

Just as a bit background, this guy is the one who did research on critique on MQA and then fell out with MQA/Tidal when Tidal removed his uploaded 'test' clips which may or may not colour your view.


Forgot this one posted in comments section of the above video, I have not watched this one its an hour long and by someone from Audio Precision

https://www.youtube.com/watch?v=J6d14cTiCjI


[edited to remove some gibberish]


Edited by ServerBaboon - 29 Apr 2022 at 6:13pm
Steve

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Graham Slee Quote  Post ReplyReply Direct Link To This Post Posted: 30 Apr 2022 at 5:23pm
Now, not being crowd funded and being shunned by just about everybody in the arrogant world (for not sounding posh maybe, or not having a Oxbridge education), I bought my own AP525x, and not an AP550, and it runs on V3.? instead on V7.? (can't remember everything...).

But it has the advanced signal gen, and the FFT spans 1MHz if I just use one channel.

You can look up the prices of this gear, and it's somewhere between £10K and £20K.

As for the "cheat" setups I can show you my entire screen too, but I don't have the clever video manipulations and you have to put up with photographs. I think it might be something to do with me having to make things for a living, rather than me being a you tuber.

The sinad thing is a bit alien to "old pros" like me, as in my day we used Neutrik, Wayne Kerr, and Lindos analysers, which were big boxes (apart from Lindos) with meters and such, and the FFT was called a spectrum analyser and cost the earth - and was a separate rather big box with a CRT as display.

So, when I show you the FFT and harmonics it's relative to the output power (or voltage, depending on what it's measuring), and that might be plus several dBs above 0dB.

So when you see a second harmonic at -75dB at 1 watt then the 1 watt is a few dBs higher up than the 0dB shown in that video.

If I had the time to adjust the top of the signal down by x dBs, then the -75dB would be those x dBs lower, and I could look good too!

But, (recently - the past 2-3 years) I'm using the FFT while tweaking the workings of half wave currents on the 0V rail of a single HT AC amplifier. I wish I could explain all this in simple language that trips off the tongue in a you tube video (and get the advertising revenue!) but I'm just a hard working Yorkshire lad in my late 60's by now, and not savvy with stuff like that (disadvantaged?).

So, we (John C has my old ATS-1 - cost over £7K in its day) do our best to show you honest specifications that may look worse than those published by others, because that was the way we were told to measure things for the broadcasting industry where we once worked.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Fatmangolf Quote  Post ReplyReply Direct Link To This Post Posted: 30 Apr 2022 at 5:27pm
Thank you Graham for explaining why your specs are understated and honest.
Jon

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Post Options Post Options   Thanks (0) Thanks(0)   Quote ServerBaboon Quote  Post ReplyReply Direct Link To This Post Posted: 30 Apr 2022 at 6:40pm
I saw this video more as comment on the use of measurements as the only method of reviewing,  scoring and comparing products rather than actually listening.  That when viewing these reviews you cannot not make accurate judgements when you see these test figures as you would not know all the settings used in the testing never mind whether they are relevant or not. This chimed with your previous comment about methodology  testing of phono stages used in a phono stage review on the ASR site.

While the almost mythical SINAD figures quoted by some far east dac makers, and praised as a target by at least one magazine and particular reviewer (120dB or nothing) and some youtube review channels, is the subject of several youtube videos I felt the the comment about manufacturers in this video was more a question of 'BBC' balance and was not expecting it would imply a required response so I will be more careful with the links next time as this was certainly not my intention.

There is another video by the Headphone show if you search for SINAD on youtube discussing the fruitlessness of judging a product based on a single value as used by some review sites/channels.








Steve

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Graham Slee Quote  Post ReplyReply Direct Link To This Post Posted: 30 Apr 2022 at 10:38pm
My reply wasn't meant as a dig at you Steve.

To me it wasn't a "fact check" type video at all. It was more of a "look at me" type video from somebody sounding young enough to have very little experience in the real world.


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Post Options Post Options   Thanks (1) Thanks(1)   Quote Graham Slee Quote  Post ReplyReply Direct Link To This Post Posted: 02 May 2022 at 6:18am
Thought I'd best do my homework by looking at the two pages in the APx500 users manual - that's two pages out of more than 500!

S/NAD - signal to noise and distortion - now called SINAD, is the reciprocal of THD+N (1/THD+N) and the unit is dB (the decibel).

It's related to ENOB (hahahLOL) - Equivalent Number Of Bits.

120dB S/NAD is 20 bit. 20 bits containing 6dB of audio information = 120dB.

Never heard of 20 bit? It's known as 24 bit. Four of the 24 are non-audio bits for something else. I guess 24 looks a lot larger than 16, whereas 20 might not?

But S/NAD was intended as a quick "all in one" test for radio communications - where there is a lot of noise and distortion - to give an indication of clarity.

There is no SINE in S/NAD, so why they have to show the sine wave so large, when all we in test know the stimulus is a sine wave anyway, I don't know.

The other display is the FFT (used to be called a spectrum analyser), and if you shorten the FFT (reduce the resolution) can look quite phallic! NADs and NOBs, hey!LOL

Getting that low in the digital domain is easy - just select the right chip. But getting that low in analogue means trading off "speed" (or slew rate) to slow down the Brownian motion, to reduce the noise. But then, just use an enhanced slew-rate op-amp to boast ultra-fast slew.

So, does that sound natural? DIF! So what sounds natural? Well, a natural slew rate of course! And how do you obtain a natural slew rate? By trading off some of the noise! But that won't do 120dB... 

Exactly!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Aussie Mick Quote  Post ReplyReply Direct Link To This Post Posted: 03 May 2022 at 2:15pm
1. Measurements tell designers when they get something wrong, not how something sounds
2. Things like “SINAD” working their way into the common parlance (typically head-fi types with too much time) is an awful development. A little knowledge…
3. Just bloody listen to the thing and try to find the internal strength to trust yourself and what you hear
4. Stay of social media and listen to music
5. ASR is full of forum posts that clearly indicate it’s okay culturally there to criticise and outright dismiss products even when said posters declare they have no intention of hearing those products
6. The forum there is like the Colusseum, where the spectators hope the next “overpriced hifi ripoff” will get killed by the lions. 
7. I need a cup of tea…  
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