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Topic: arduino audio controller in *stereophile* magazine (Read 6289 times) previous topic - next topic

retrolefty

#15
Jan 19, 2011, 05:24 am Last Edit: Jan 19, 2011, 08:13 am by retrolefty Reason: 1
Quote
lets put both of them on the same test harness and see what the computer says.


You seem to keep missing my main point. If something measures better, but is undetectable with normal human hearing, is it really 'better'. Does it need to be better?

Your preamp might have a flat response out to 10Mhz, but does that make it sound better or even different from a preamp that is flat only out to 40khz? You got noise down to -130db, that's impressive. But can you hear a difference between a -90db and -130db noise floor in a normal listening environment, again under double blind testing? Color me skeptical. I understand electronics and I understand that -130db is an impressive specification to meet. I just don't think it has anything to do with listening to quality Hi-Fi music. Your just testing your test equipment.  ;) Electronic measurement masturbation perhaps.  ;D

Your preamp may have nice .5db level steps, but can you hear a difference in +.5, -.5, or 0 db change in a double blind hearing test? You know what Mr. Bell was trying to come up with when he came up with the decibel scale? A unit of hearing measurement of just detectable levels of amplitude change by the average person.

It should really be about ones enjoyment of music. The vast popularity of portable MP3 players, with their less then state of the art audio specifications,  suggest that people like to listen to the music, not the equipment.

I love nice stereo music played on well designed and constructed equipment. But I have long ago lost faith is specmanship, and spending excess money on parts that don't improve the end product.

Have you ever looked at the real world frequency response specifications (verified and measured by 3rd party) of even expensive high end loudspeakers? Do you think a better then good enough preamp will improve such a system? Hi-fi is a system, and the final results can be no better then it's weakest links, speakers and human hearing. The electronics has been 'good enough' for many decades.
Now show me some new digital controlled servo operated loudspeaker with flat 20-20khz response and maybe I would be interested in checking it out or up for a serious 'showdown' test.

Rambling I know, but what say you?  ;)

Lefty

linux-works

addressing some of your points:

- noise level and being audible: yes, in headphones and good speakers, you can hear these things.  as each stage improves (the dac, the pre and the final amp) you do hear more of the recording (which most people do consider a good thing).  and yes, 130db down is still audible in headphones on classical music that has good dynamic range.  its not flat 130db either, that's a best-case null point.  on average, things that are 'good' these days tend to be 100db or better but that's a real honest 100db, not some marketing specs.

- upper frequence response matters.  you need a few times the audio passband worth of FR to pass the audio band *cleanly*.  modern pre's tend to want to have good response up to 50khz, 100khz and beyond just so that the '20-20k' gets thru easier.  send a square wave thru at even 10k and watch it as it goes thru a high bandwidth amp vs one that is 'just enough' to pass 20k.  the fidelity of that wave is visible on any scope.

- 0.5db steps, it matters to get you a smooth transition as you vary the knob.  I tried single db steps (for almost a year, on one of my protos) and thought 1db was pretty ok for daily use.  then I built a half db stepper and liked it a lot more.  costed 1 more relay and a few more resistors.  was worth it.  and for a subwoofer box, I built one that uses 8 relays and only gives 25.5db for total range but it moves in 0.1db steps.  yes, for a subwoofer level control, you *do* want that level of granularity.  try getting that from your sony ;)

- re, high end spkrs; yes, I have looked at the FR graphs.  some of the modern tweeters are truly amazing.  you can buy tweeters for $50 or less that are flat out to 30k.  modern tech is WAY beyond what we had even 10 yrs ago (its a good thing, btw).  along the same lines, if you use good headphones (my ref pair is sennnheiser hd580 and hd650) you will hear every little detail and it will be quite flat sounding.  cheap speakers and phones are limiting but modern systems are not.

- servo speakers; not necessary.  even conventional cone (boring) spkrs are very high fidelity these days.  I think you're just quite out of touch and not willing to update your world view, sorry to say.  a LOT has changed since the days the dinosaurs walked the earth.  old classic gear can be treasured for its 'sound signature' but performance wise, its usually not competitive.  there are a lot of exceptions but I would not consider a mass market sony box of any kind - no matter what the company claims - to be competitive with custom made DIY audiophile gear.  for lots of reasons.

retrolefty

#17
Jan 19, 2011, 05:53 pm Last Edit: Jan 19, 2011, 06:09 pm by retrolefty Reason: 1
- noise level and being audible: yes, in headphones and good speakers, you can hear these things.  as each stage improves (the dac, the pre and the final amp) you do hear more of the recording (which most people do consider a good thing).  and yes, 130db down is still audible in headphones on classical music that has good dynamic range.  its not flat 130db either, that's a best-case null point.  on average, things that are 'good' these days tend to be 100db or better but that's a real honest 100db, not some marketing specs.

You say -130 down is audible, I say it's not under any conditions. Only an independent double blind testing protocol could determine which of us is correct. Your opinion, or any one's opinion, even mine, is not fact and should not be stated as such. Your making the claims, so the burden is on you to prove those claims if you wish. Otherwise you have posted your opinions well, but they remain just opinions. Measurement is not listening, and opinions are not provable repeatable facts.


- upper frequence response matters.  you need a few times the audio passband worth of FR to pass the audio band *cleanly*.  modern pre's tend to want to have good response up to 50khz, 100khz and beyond just so that the '20-20k' gets thru easier.  send a square wave thru at even 10k and watch it as it goes thru a high bandwidth amp vs one that is 'just enough' to pass 20k.  the fidelity of that wave is visible on any scope.

That sir is rubbish. You can see extended FR with a scope, but you can't hear a difference past the upper FR of human hearing. Content above a given hearable upper limit does not modify the content below that limit. Plus, what audio media do consumers use that have content past normal human hearing frequency response. Most don't listen to frequency generators!


- 0.5db steps, it matters to get you a smooth transition as you vary the knob.  I tried single db steps (for almost a year, on one of my protos) and thought 1db was pretty ok for daily use.  then I built a half db stepper and liked it a lot more.  costed 1 more relay and a few more resistors.  was worth it.  and for a subwoofer box, I built one that uses 8 relays and only gives 25.5db for total range but it moves in 0.1db steps.  yes, for a subwoofer level control, you *do* want that level of granularity.  try getting that from your sony

Again I'm sceptical, but as stated before only double blind testing is capable of separating fact from opinion. My current Sony component setup is just one of a large number of systems that have passed through my hands. I'm not even sure it has the best specifications of the stuff I've owned, just the system I enjoyed using the most.

- re, high end spkrs; yes, I have looked at the FR graphs.  some of the modern tweeters are truly amazing.  you can buy tweeters for $50 or less that are flat out to 30k.  modern tech is WAY beyond what we had even 10 yrs ago (its a good thing, btw).  along the same lines, if you use good headphones (my ref pair is sennnheiser hd580 and hd650) you will hear every little detail and it will be quite flat sounding.  cheap speakers and phones are limiting but modern systems are not.

I too enjoy owning a pair of Sennheiser HD580 cans. And of course a tweeter does not a complete loudspeaker make, it's just one of many parts that comprise a modern loudspeaker, including crossover, other drivers, cab design, etc.  I'm sure some speakers have improved over time, but I'm also still sure that speakers,normal human hearing and listening room properties, are still the ultimate limits or FR and distortion and further improvements in up stream electronic components is just gilding the Lilly.

- servo speakers; not necessary.  even conventional cone (boring) spkrs are very high fidelity these days.  I think you're just quite out of touch and not willing to update your world view, sorry to say.  a LOT has changed since the days the dinosaurs walked the earth.  old classic gear can be treasured for its 'sound signature' but performance wise, its usually not competitive.  there are a lot of exceptions but I would not consider a mass market sony box of any kind - no matter what the company claims - to be competitive with custom made DIY audiophile gear.  for lots of reasons.

I'm still a member of a popular audio forum and I think I have tried to keep up with audio evolution. However I'm still of the opinion that the vast majority of audiophile 'golden ear' equipment is designed only to separate dollars from their gullible customers. That is OK, if they can afford it, it is their privilege to waste their discretionary money anyway they wish, just don't tell me all the claims are fact. I love those Lexus TV commercial showing a audiophile staring at his tube audio amplifier and saying "there is real gas in those tubes".  ;)

Lefty  

linux-works

too much stuff to address point by point, but in general, I think you are painting with too broad a brush.  the audio field is truly filled with the spectrum from non-science to real science.  and when you buy commercial stuff, you often have little idea where in that spectrum your gear's design and implementation fit.

otoh, with DIY gear you can verify its design and performance (like the whole open source thing).  and so, I'll leave it there.  if people want to do their own builds and then compare the sound of this kind of system vs their existing one, they're more than welcome.  I do believe that if given a fair chance, the sonic clarity of the relay attenuator vs the typical $1 dual gang volume pot will justify the cost to the DIYer.  what does a typical preamp (decent one) cost these days?  then how much would it cost to build a DIY relay attenuator?  the relay thing is in the $100 range, give or take what you want to do to it (PSU wise and buffer/gain stage wise).  you can build it quite cheap (passive, just relays and resistors in the audio path) and nothing commercial can even come close in price or performance.

and finally, you get control over your UI when you go the DIY route.  this is a non-audio side of the project but you'll never be able to modify or customize a sony UI, for example.  and often, the commercial gear is very crass and raw in how its UI works.

I did used to think genuine analog pots were fine for audio use.  after I did tests on typical pots and saw the tracking errors and crosstalk as the frequency went up - I changed my 'world view' on attenuators in the audio path.   if you opened your mind and gave a new system a fair chance, maybe you'd see things in a new way as well.

the only downside, really, is that the relay attenuators are clicky as you turn the volume knob or run up/down the volume range.  it runs a binary sequence and so each time you cross a binary boundary (31db to 32db, etc) you get a massive click via a bunch of relays being pulsed to 'roll over' the count.  a few binary boundaries are noisy (lol) but not noisy in the speakers (I mute the relays during volume-change events).  the relay chatter, physically, is noisy though.  that's the only down side I can think of.  all the rest are positives compared to conventional volume controls.

retrolefty

Well stated. I, in any of my points wished in no way to discredit the quality or craftsmanship of your posted work. It really is nice looking product and I'm sure it meets your posted specifications. Besides it has an Arduino inside, which I would assume both of us approve of.

We can part friends and leave the rest to rest.  ;)

Lefty

childofthehorn

#20
Jan 20, 2011, 07:05 pm Last Edit: Jan 20, 2011, 08:36 pm by Childofthehorn Reason: 1
Nicely done Brian!

Yeah, AMB's workmanship are top notch! I know he likes FrontPanelExpress  and it looks like he used one of the Chinese enclosures for the base instead of a Pars. Very Clean! Been really meaning to ask where he gets his boards done because they seem to be reasonably priced and fantastic quality. I have been using the SeeedStudio or BatchPCB service ad while nice are no comparison to the beauty of those AMB boards.

You might want to seriously look into using one of the I/O expander ports and connecting in to the TPA Buffalo or Opus to enable the digital filters. The code is simple enough, but an easy connection module would likely do a lot to make it easy on the non-coders.

If you want to do an android app that controls over Wifi, let me know. I can certainly get a good start on that since I have been wanting to do it for AMPs?DAC's to converge everything.

Another possibility of a cool module is a set of digital potentiometers that could snap in for the trim pots in the AMB designs. Use an A/D tied in with voltage tolerance so that you could have a dynamically adjusting amplifier. This would be VERY cool for the Beta22 for those of use using it as a low-imp, high-imp, and speaker amp - plus it could account for drift. This board could have helped when my left amp board blew and caught fire (same spot as a few other people). It would be insurance that also ensured the best possible SQ.

All the Best man! You certainly do keep up the good work!

The Spec issue.... yes I understand. Most of the time, audio is not limited by the hardware, but by the software. You need to remember that every bit of mastering takes something out, especially in the digital game.  God forbid though to many audiophiles that you use software to your advantage to fix something. I mean, do you think that PSA or Meridian is NOT using software to make it sound better? C'mon.

There really is no need to use the 0.1% or 0.5% resistors in many cases and a LOT of the audio game is all about overkill. I can see how someone may really want an R-2R ladder if you want to make a custom set of impedances, but why not just go with one of the REALLY nice digital pots from TI or Maxim? Most are SPI and the ones that use digital serial are pretty easy to make your own interacting protocol (done it). If your amp draws 2A, why always make PSU's with 50 filters and running up to 15A? There are a Million headphone amps doing this right now and someone put it in their heads that because a headphone amp that only needs to drive at most 100mA/channel should be using an 1amp or more of power. Some have also forgotten that simple is sometimes the best and that a clean, accurate simple circuit will beat an overly complicated design any day (tube and hybrid designs show this all the time).  

Headphones do show the details, much better than speakers do. I have the Stax, CD3K, and the AKG's (had the HD580's - just were not my favorites). in those cases, headphones are extremely sensitive to noise floors and ground loops (however small) because of the sensitivity and well, just how intimate your head is with the transducers. Only really use them at work now though...

Still, keep working at it!


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