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Posts posted by ray-dude

  1. This is very true.  I experience a very abrupt phase transition where some recordings suddenly seem very real.  Some recordings never get there, others get on the "good side" of reality mountain after some significant effort or enhancement.  I've attributed this to my brain getting better at fabricating the illusion for me, once appropriate auditory cues are there.  Conversely, for recordings on edge of that transition, it is a very sensitive "tell" when I've done something to disrupt some aspect of music reproduction.   In a way, much of my audio optimization journey has been about getting more and more of my music library to feel like it is "real" and in the room.



    The head vice would be fabricated out of panzeholz ;)  For the spirit of this anecdote, I was trying to share what is detectable, (thankfully) not how I listen.  FWIW, it is angular distance from the driver.  That is a LOT of lateral head position to have 1mm impact on distance to driver (at 9' listening distance, ~3" if I did my math right?).   My head twist variance is absolutely more than 1mm, agreed.  Interestingly, I find that my head position naturally gravitates to where the soundstage is most expansive and natural (or in the case of the pink noise scenario, where the null is more pronounced)


    To the ITD, you are certainly better read on this than I am, but isn't that related to localization of sound source by the time difference it takes for sound to get to each ear?  With stereo music reproduction, we actually don't want to hear the speaker driver, we want a sound stage projected before us.  My phase analogies were related to that sound stage projection, not localizing where a speaker may be.  


    That being said, I am google-level ignorant on the ITD measures.  I have no idea if the psycho acoustics are the same mechanism between ITD for sound source localization, and reconstructing a sound scape from the aggregate phases of the sounds we are hearing.  I suspect our brains are doing a lot of interpolation/projection for the later functions, just because our brains are really good at casting things in a way where it is easier to digest/interpret (Coltrane obviously isn't standing in front of me, but damn does my brain gets a lot of juice when it sounds like he is...sign me up for more of that kind of self-delusion!).



  3. I'm with you on filters.  I'm still trying to get my arms around what the various filters in HQP are doing on various recordings.


    I'm talking more about our brain's ability to detect and process phase/timing differences, esp. for spatial placement.  For better or worse, our brains have evolved to give us the sense of spatial placement and space, based in part on these sort of phase cues (at least for naturally occurring signal scenarios)


    To Chris' original ask about "threshold of human" hearing, there are certainly multiple thresholds for different types of information that we hear. 


    As a practical example of phase vs frequency thresholds, I typically phase align my speakers with mono pink noise.  I drive both speakers with the same signal.  My speakers are single driver high efficiency speakers (no cross overs, no multiple driver phase alignment issues, basically point sources).  As the speakers become phase aligned to my listening position, the image converges to a dot.  The tighter the dot, the better the phase alignment and the fewer spurious paths/reflections.  If I invert the signal to one speaker, it becomes even easier to fine tune, since I'm now sitting in an effective null. Even very small phase differences between the speakers becomes audible as a buddy is tweaking a speaker position.  As a practical matter, in my room, ~1mm changes in speaker position is audible for me in this (very) artificial scenario (and since this is an objective forum, distance from my listening position to the same position on speaker drivers confirmed to be identical to within the ~2mm resolution of my laser measure ;) 


    If we were to naively translate that to frequency, at the speed of sound that implies ~340kHz hearing resolution.  My 53 year old ears tap out around 15kHz and clearly can not hear >300kHz tones.  However, I can hear phase timing differences with that level of signal timing resolution, in this (very) artificial scenario.  With a better treated room, I'm sure things would be much better still.


    This is akin to interferometry.  In optics, resolution is limited to wavelength of light you're using to "see" divided by two.  If you want to see smaller things, you need to use smaller and smaller wavelengths.  However, you can us phase information to get arbitrary resolution, if you have a coherent enough light source and you're able to integrate the signal long enough to overcome any noise in the measurement.  Way back in the day, this allowed me to monitor etch depth in semiconductor structures to essentially the atomic level, clearly WAY beyond the resolution of the light I was using to do the etch depth measurement.


    For me, higher resolution sources (whether natively recorded or reconstructed with a sinc reconstruction function) has been about phase timing accuracy, not audibility of the ultra high frequencies.  Depending on the recording chain and performance of the components, that phase resolution may or may not matter obviously.


    (Chris, sorry for the long detour into phase land...I suspect your original question was more related to limited of audibility in distortion and noise measurements than timing accuracy)



  4. 1 hour ago, pkane2001 said:

    But then, the question is what is it?


    I suspect it is differing levels of phase/timing sensitivity.  I'm definitely a phase/point source guy (on steroids) and have optimized my system around same. I've noted that when folks come over, some people are definitely more WOW for phase-related optimizations, and others barely hear them at all.  The later group seems to be more power/amplitude focused.  Some folks fall somewhere in between.



  5. 47 minutes ago, jabbr said:

    This has a list of SFP/SFP(+) and QSFP(+) modules with the type of laser in https://www.finisar.com/sites/default/files/resources/finisar_optical_transceiver_product_guide_3_2015_web.pdf

    As you can see the SFP multimode modules tend to be VCSEL and the single mode modules tend to be DFB ... as of 2015 



    Fantastic, thank you!  My (currently) preferred FTLF1324P2BTL is a Fabry-Perot laser, which seems to be operated like a laser diode? (direct modulation, limited to lower bandwidth channels)  Alas, I'm not finding more modern reference designs (yet), but the older ones I've found all have Vcc direct to the laser diode or driver in the block diagrams.


    If the 10G modules have a constant power load to go with their tighter operating tolerances, that certainly makes them even more interesting.



  6. The presumption I've been working with is that signal integrity is effectively a given with these devices, which is why I've been paying more attention to possible impact on power/ground planes (other candidate is radiated RF, but that seems a stretch as well)  I most certainly was not expecting to hear differences between SFPs (pretty stunning actually, for all the reasons you cite, as is anything on the network having an impact on SQ)  


    I should give the caveat that my only experience has been wth 1 gigabit SFPs.  Do you (or others) happen to know the type of laser typically used in these devices?  At a $20-30 price target, I was presuming these low cost modules wouldn't be using more advanced photonics (I'm a geezer...it's been almost 30 years since I've done work on DFB lasers, and back then, we were delighted just to get them to work).  


    I spent a little bit of time looking for a published reference design for a 1G SFP module, but didn't (yet) find anything current.  What I did find had a simple driver on the LED laser module, with the differential signal switching the laser on and off:




    If someone has a pointer to a more modern published reference design for a 1G SFP module (with presumably more advanced photonics than an LED laser), it would be very helpful to understanding what is going on inside of these beasts.


    If 10G modules have more advanced photonics switching, that could be an argument for making the investment in 10G network gear (I have not had access to this sort of kit to test, although it is definitely on the list). 




    Such an amazing album, and an amazing performance (and format) in a dire time.  "Dreamsicle" is an instant American classic (when Jason Isbell writes a song, it stays wrote)






  8. I remember looking at this page when I first heard differences.  On pins 15 and 16, the laser is actually turning on and off (even if fed with a differential signal).  Unless the power is getting dumped into an offsetting load when laser is off, that will create a correlated pulsing load on the power lines, no? My (very) naive assumption was that the power driver circuit biases the laser to the critical voltage, and the differential signal switches it on and off.


    All that being said, I'm obviously not familiar with how the driver circuits in these modules are typically implemented nor the compliance requirements for noise on ground plane or power plane, so above is an honest question, not a belligerent one (I'm honestly delighted to toss wrong hypotheses on the "Oh Well" pile...life's too short to chase dead ends)


  9. 1 hour ago, wwc said:

     If "vivid" translates to more natural and dynamic, that's good, but I am a little cautious going into this upcoming change.


    If it is any reassurance, my system is a bit unforgiving of glare and aggressiveness in the treble range (one interpretation of "vivid")  What I am hearing is more of the glorious sense of speed and precision which I love with the Extreme, which for me translates to a more tangible presence for the performers in the room.  Vivid is less about tonal response, and more about tangibility of the experience of the music.  Looking forward to hearing your impressions after you hear it!




    As proof that reviewers do not get special treatment, I have not yet gotten the beta of Taiko Audio Server on my machine (I'm eagerly waiting though).  Above are my impressions post Great Disruption (aka, the Roon upgrade we no longer talk about)


    I have not tried the KVM trick yet.  I want to hear how much I'm giving up with TAS on the network, then see if the hassle is worthwhile.  Having the machine on its own network certainly cut traffic way down already.  I'll definitely report back once I have some time with the new player.

  11. I have to concur on the gap between Roon and other players.  I am still waiting for the beta of Taiko Audio Server, but based on what I'm hearing as possible with players like Euphony Stylus or HQPlayer direct (no Roon), there is a pretty massive benefit to be had over Roon.  With Roon's focus on every more features and orchestration across multiple rooms and devices, this will only get worse (I suspect it is the network chattiness of Roon that has been at the core of the SQ degradation).  


    I know it is difficult to say so with a straight face, but I think the Extreme is extremely fairly priced for what it is (there is no price gouging or inflated dealer margins here).  Taiko isn't making a huge amount of margin on these boxes.  


    The bigger question is whether what it is is necessary or needed for most folks, or if 90% of what is there can be had for 10% of the cost.  (FWIW, a big motivation for the deep dive I did was the hope that some of the design choices in the Extreme could have a nice impact for folks in their own systems).  For folks that want every bit of that last 10%, the Extreme is an incredibly expensive, but high value option.


    I am looking forward to hearing the Extreme Mini, and seeing what Emile and team can do with a more constrained BOM and price point.

  12. Chord DACs do require Vbus, but only for the USB handshake.  A cool trick with the USPCB (which I adore) is to switch off Vbus to the Chord DAC after the handshake is established (I played with this a bit when I was experimenting with isolation approaches between server and DAC)  Just remember to switch it back on if things seem not to be working later!



  13. 1 hour ago, cat6man said:

    So let me put down a friendly challenge.  In the interest of being 'objective' and not 'subjective' in this sub-forum, how about a sub-sub-group interested in getting to the bottom of this technically and not just acting like my old 'arrogant PhD' colleagues who already knew all the answers (but had oversimplified the situation and therefore hadn't formulated the problem accurately)?


    This is the fun stuff!!  If PhD's are allowed in, count me in!


    (FYI, I put my hypothesis out there in part 1 of my Extreme review...reference voltage, ground plane, and reference timing are the father/son/holy ghost of digital audio, I think, and everything always seems to come back to those fundamentals)

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