[maverickronin]

Quote:

Like you said, why would he do that?

Maybe he's a deep cover subjectivist out to discredit science and evidence in this hobby...somehow or other... 

 

[Willakan]

It's unfair to assume that an amp design that does not supply comprehensive measurements is automatically crap - unless of course the publicity literature places emphasis on the number of ways they compromised the design (surprisingly common) to meet some strange "audiophile" rules.
So when someone provides full and entirely reasonable looking measurements, has no real motive to fake them and appears to have invested huge amounts of time into the design, it appears strange that he is met with more skepticism that usual.

 

[Modo]

Quote:

So when someone provides full and entirely reasonable looking measurements, has no real motive to fake them and appears to have invested huge amounts of time into the design, it appears strange that he is met with more skepticism that usual.

It's called successfull propaganda.
 

 

[mikeaj]

Music is a series of tones and silences.....
 
If something does well at reproducing test tones, it will do well with music....
 

That would pretty much be my position too. But there's always the question of "sure, THD was really low, but what about with multiple tones together?" And even if one IMD test reveals nothing wrong, another with different tones may produce a different result. You can't test every combination of everything.

But with a large body of measurements across many situations, seems unlikely that these tests--which are designed to show the extent of nonlinearities--would somehow overlook something important. i.e. performance with a large set of benches is good, but in some real-world scenario, not so good

 

[rroseperry]

Whoa, where's the suggestion that the measurements could be faked coming from? Did I miss something?

That just makes no sense.

 

[mikeaj]

Whoa, where's the suggestion that the measurements could be faked coming from? Did I miss something?

That just makes no sense.

I think that's a hypothetical more than anything. Too many objectivists playing devil's advocate to try to appease the holdouts.

Actually there was one guy who thought the noise measurements were faked because of the kind of weird noise in dB referenced to 400 mV signal level. Noise is -115 dBV A-weighted, which is of course a better number than if you reference it to 400 mV.

 

[purrin]

Quote:

 That would pretty much be my position too. But there's always the question of "sure, THD was really low, but what about with multiple tones together?" And even if one IMD test reveals nothing wrong, another with different tones may produce a different result. You can't test every combination of everything.

But with a large body of measurements across many situations, seems unlikely that these tests--which are designed to show the extent of nonlinearities--would somehow overlook something important. i.e. performance with a large set of benches is good, but in some real-world scenario, not so good

 
Hehe. I believe LFF was being sarcastic.
 
When we examine non-linear distortion tests that display the entire spectrum, the multi-tone (three to five) approach tends to create a lot more "garbage" than single tone tests. Two tone tests start to create IMD which is more audible than THD. Here's a visual example. 
 
As far as measurements for the O2, the best approach is to develop a comprehensive suite of tests, have someone independent perform them on the O2, and then perform the exact same tests on other amps. The comparison aspect is crucial.
 
 

 

[upstateguy]

Quote:

<snip>
As far as measurements for the O2, the best approach is to develop a comprehensive suite of tests, have someone independent perform them on the O2, and then perform the exact same tests on other amps. The comparison aspect is crucial.
 
 

Good idea.  Too bad no one does that for anything.
 

 

[purrin]

 
Quote:

Good idea.  Too bad no one does that for anything.

That's really the sad part. I'm going through Stereophile amp reviews, and when they do provide measurements, they don't provide meaningful information. 
 
For example, they have nice graphs on THD and IMD. But examining a graph and noting that there 0.5% THD at 100Hz really does not tell me anything. Is that distortion mostly 2nd harmonic, 3rd harmonic, a series of nasty odd harmonics, etc. Full spectrum graphs of non-linear distortion at 100Hz?" Those typically look the same. Industry standard" IMD full spectrum measuring at 19kHz and 20kHz? C'mon! When does music ever contain 19kHz + 20kHz tones at 0db?
 
Let's run a comprehensive series of 3-5 tone tests (throughout the audio band) at reasonably loud listen levels into realistic loads to show us how messed up the entire spectrum really looks like. These tests aren't perfect, but they are better than the typical stuff we see now.
 
I'd also like to see tests that measure dynamic compression and ability to accurately reproduce low level signals during loud passages. I don't think anyone's invented these types of tests yet. These are two major aspects which I subjectively feel separate the good amps from the bad.

 

[maverickronin]

Quote:

Whoa, where's the suggestion that the measurements could be faked coming from? Did I miss something?

That just makes no sense.

 
I don't think its been seriously proposed in this thread specifically, but some other people have been suggesting conspiracy theories elsewhere.  I think they're silly but there's no end to the sort of silly stuff that needs to be argued against.
 
Quote:

Industry standard" IMD full spectrum measuring at 19kHz and 20kHz? C'mon! When does music ever contain 19kHz + 20kHz tones at 0db?

From what I understand, the point of that test is that those high frequencies are where negative feedback is least effective so its sort of a worst case scenario kind of thing.

 

[estreeter]

Quote:

That's really the sad part. I'm going through Stereophile amp reviews, and when they do provide measurements, they don't provide meaningful information. 
 

 
Stereophile's measurements are debated up hill and down dale each and every time that John Atkinson or one of the other staff members dares to question the performance of a highly-regarded piece of kit, particularly when there is a big sticker on said gear. While I admit to being a subjectivist (I'll drink the tube amp Kool-Aid no matter how much distortion nwavguy tells me they produce), surely there's room for both listener emotion and objective measurement in audio ?
 
As I said before, love him or loathe him, he had the guts to put this out there for dissection. Not broad theory to be endlessly debated in Weird, er, Sound Science, not some half-baked ideas for an amp - a flesh-and-blood product that most of us can afford to buy. If nwavguy took his bat and ball and went home tomorrow, I *believe* he has left enough detail in the public domain for someone else to produce the amp (happy to hear otherwise) or, even better, to refine and improve his design.
 
I know there are plenty here who have built impressive DiY projects, and I'm sure that some have design ideas of their own, but how many can take something to the point where its a reality for others to build their amp ? I look back on various fiascos (Mikael, you out there ? Stanley, come back - all is forgiven) in the world of headphone amps, and its clear that tying your $500 deposit to a lone gunslinger can be a minefield - to his credit, nwavguy has distanced himself from that side of the Objective2.
 
To his more vocal opposition, can you swallow your pride long enough to buy one and post your impressions ?
 

 

[khaos974]

Stereophile's measurements are debated up hill and down dale each and every time that John Atkinson or one of the other staff members dares to question the performance of a highly-regarded piece of kit, particularly when there is a big sticker on said gear. While I admit to being a subjectivist (I'll drink the tube amp Kool-Aid no matter how much distortion nwavguy tells me they produce), surely there's room for both listener emotion and objective measurement in audio ?
 
As I said before, love him or loathe him, he had the guts to put this out there for dissection. Not broad theory to be endlessly debated in Weird, er, Sound Science, not some half-baked ideas for an amp - a flesh-and-blood product that most of us can afford to buy. If nwavguy took his bat and ball and went home tomorrow, I *believe* he has left enough detail in the public domain for someone else to produce the amp (happy to hear otherwise) or, even better, to refine and improve his design.
 
I know there are plenty here who have built impressive DiY projects, and I'm sure that some have design ideas of their own, but how many can take something to the point where its a reality for others to build their amp ? I look back on various fiascos (Mikael, you out there ? Stanley, come back - all is forgiven) in the world of headphone amps, and its clear that tying your $500 deposit to a lone gunslinger can be a minefield - to his credit, nwavguy has distanced himself from that side of the Objective2.
 
To his more vocal opposition, can you swallow your pride long enough to buy one and post your impressions ?
 

Plenty?

The Dynalo, dynahi, the Cavalli designs, the Pete Millett designs, the AMB designs, the Pimeta, the Cmoy, the Bottlehead, the Wire ... plenty of of in the sea. Not all of them are as thorough measured as the O2, but the schematics are out there.

And I have not doubt at least one of the performs better than the O2. What's cool with the O2 is that it's cheap and a through hole design.

 

[estreeter]

Which board member can take credit for designing the CMOY ? 

 

[khaos974]

Which board member can take credit for designing the CMOY ? 

Sorry for the CMoy and probably one or to of the others, but assuredly, Kevin Gilmore and AMB are members of HF, I'm sure I could find a few other designs where whose authors are also members of HF.

 

[purrin]

There are maybe one or two more who are no longer active on HF. There were other contributors on HeadWize too (which I knew about before HF.) Besides, last time I checked, nwavguy was technically not a member of HF.