So, you aren't going to tell PMA he is fooling himself if he thinks he can hear opamps? Or that his test setup must be oscillating or something because he is hearing something he shouldn't?
Do we need to quote Bruce Hofer as a reposte? You've cherry picked what supports your view (and clearly reinforces it).
I didn't recommend using any equipment made where Bruce Hofer works. I was merely reporting on the opinion of a manufacturer of test equipment who's name you mentioned yesterday(?) along side AP. Does the expressed opinion of dScope's manufacturer change your opinion of the dScope itself? Is it now disreputable?
Moreover, whatever Mr. Hofer may say, I already mentioned that most of Pass HPA-1 was designed by ear, and using a DVM and scope. An AP was only used at the end of the process. It can be done, and it can result in an SOA sound quality design (as 'sound quality' relates to human perception). Its already been done, its reality, so get used to the fact, is all I'm saying.
It wasn't that long ago, in the BT thread of the time, that the old guard in the thread insisted that opamps can't possibly be differentiated by ear. Ed Simon made up a test box of opamps for a listening comparison in response, and then never reported results. Now PMA comes along and says opamps have a sound alright, and nobody bats an eyelash.
If PMA keeps up with his self-taught listening training, before long he will be saying that wire has a sound too. What are you going to do then?
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The difference here Mark is I respect PMA's technical abilities - please visit his website.
Separately, you've missed the point. He said he had nearly two 'perfect opamps' which to my mind does not seem to indicate a guy who is blindly swapping these things out. I certainly look at a range of devices when I'm designing stuff, so yes there are always alternatives. But do I put an LF356 in place of an NE5534 in a phono stage? or a 741 as a DAC I-V? I'm sure you'll hear a difference in those instances. That's opamp rolling - not selecting one from a handful the designer has ascertained will do the job properly.
Something from the crypt (2012) 12 point checklist for anyone using opamps in an audio design
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Yes, understood. Exactly my point. If you respect his technical abilities then you accept his listening claims. That seems very incongruous to me, since hearing is a human perception and it is human perception that is so distrusted here, but apparently only in people who are not 'technically respected.' As if you know everyone's technical background.
All old news. Anything else, hopefully something we don't already know?
No, he makes sure he can pass foobar ABX in a run of 10 trials, the limit of his concentration for ABX, before announcing a result here.
He already stated to the effect that its true that ABX taxes concentration in a way that makes it much harder than merely hearing a true difference in simple listening. People here used to insist that ABX couldn't be hard, either you hear something or you don't. They insisted the concentration claim was 'pure bs.'
Is it still pure bs that ABX is hard and requires great concentration, and bs that ABX is biased towards false negatives on account of those factors?
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No signs of virus in Da Nang. Did I miss anything good here.... I mean besides the usual slapping each other around?
-RNM
-RNM
Glad you didn't deny it, thanks anyway, I'll probably be dead of old age before you provide any real evidence, or even any useful pointers on what to listen out for. Remember Goop? We never did find out anything new.
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I was not sure whether Lucky's 50G peak acceleration was in m/sec2 or indeed meant with a capital G.
Peak velocity for a mono signal at 1Khz@0dB is sqrt(2)*5.6cm/sec=8cm/sec. Peak acceleration will then be 2Pi*f*(peak velocity) = 502 Nm/sec2 or 51G.
So force on a 1mg tip in that case is not the 5mg as mentioned in the above posting but 51mg peak force.
This 51mg peak is 4% the 1,4g force on the wall. If the walls would be rigid, it would have no impact at all.
But It will certainly have some minor impact on distortion, because the "footprints" on the groove walls will slightly change their shape, a so called "Scanning Loss" named by Bastiaans.
At higher frequencies, the acceleration will increase dramatically.
What I can find is that 10cm/sec is about the maximum a cutter uses at 10Khz, corresponding to a level of ca -8dB when riaa corrected. So 1000G will theoretically be possible.
That would mean a 1gram peak force on a 1mg tip. Still below the 1.4 gram of the 2 gram stylus force, but substantially changing the pressure and because of that a much larger effect on footprint and distortion as at 1Khz.
Fortunately, many carts are having an effective mass between 0,1mg and 0,5mg that will help to decrease the negative effects of peak acceleration
On the other hand, distortion because of the pinch effect, i.e. pushing the needle tip out towards the middle of the groove because of the radius of the needle, is quite substantial at 10Khz at his modulation level.
See image below for a -10dB signal and a 7um elliptical needle. This effect will of course contribute to increased crosstalk. For a 17um spherical needle it would even be much worse.
So the deeper you go, the more worms are escaping the can and the more complex it becomes.
Crosstalk measurements to get a better insight in the elastic/plastic surface behaviour will be hard to separate from other contributors like Cart motor imperfections and Pinch effects.
And to come back on the Bastiaans paper: In no way attention was paid to the aspect of a cooling down time to let the surface stabilise from the plastic into the solid phase
The amount of times an LP was played was also no part of his review.
Hans
Attachments
Do you have more than one dac? If so, have you learned how to hear a difference in IMD by listening for audible effects on vocal groups? Have you learned how to hear differences in cymbals? (Do they sound like noise bursts or real? Do different cymbals in a drum kit sound different from each other?)
If you have two or more dacs and can discern those things as sounding different between dacs, then we can take it from there. If not, keep working on listening carefully, would be my pointer for now.
Yes, of course it can be done optimizing topologies comprising of fully debugged subcircuits, but very difficult to do for less explored or critical topologies.
True. Building and listening to many different circuits is part of preparing to be an audio designer who works largely by ear.
No matter what design methodology is used, there is a lot of preparation needed in advance of getting good at it.
No. Is the filter the source of IMD in a dac? What would be the effects of IMD in that case?
Bill,
TI/Burr Brown have product lines such as "Sound Plus" and "Premium Sound!"
Also forgot he LM833, Almost all of the That Corporation chips, Phillips TDA1034, and with a bit of google you might get up to 100 fingers!
When the design goal was low noise, low distortion and 600 ohm output drive capability it would seem the design intent was audio use.
"All old news. Anything else, hopefully something we don't already know?"
Its just an example of some of the pitfalls 'rollers' fall into. That it still goes on 12 years later should be cause for concern.
Clearly not something I'd expect people who have selected 'nearly perfect' devices to fall into. Hopefully you know about this stuff, so your comment is pretty disingenuous I'd say given some of the OPA rolling that around on some of the threads here on diyaudio.
Its just an example of some of the pitfalls 'rollers' fall into. That it still goes on 12 years later should be cause for concern.
Clearly not something I'd expect people who have selected 'nearly perfect' devices to fall into. Hopefully you know about this stuff, so your comment is pretty disingenuous I'd say given some of the OPA rolling that around on some of the threads here on diyaudio.
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