@counter culture, I can assure you there's virtually no energy above the audio band, let alone at true RF frequencies, related to the O2's power supply. Ferrites are useless. You have to have sharp corners to create lots of harmonics at RF frequencies, and a linear power supply operating off of 50/60 hz sine waves doesn't have any such sharp corners.
I've looked at the spectrum on the dScope out to 96,000 hz and 99% of the energy is below 121 hz. I've also used a 350 Mhz 2 GS/sec scope and there's even less above 96 Khz. This isn't an RF issue at all. It's just good old fashioned electromagnetic hum. And it's solved.
I've looked at the spectrum on the dScope out to 96,000 hz and 99% of the energy is below 121 hz. I've also used a 350 Mhz 2 GS/sec scope and there's even less above 96 Khz. This isn't an RF issue at all. It's just good old fashioned electromagnetic hum. And it's solved.
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I realize this is off topic, but if I was able to find someone who would send you a Twisted Pear Buffalo DAC, would you be willing to measure it? If you agree, I will see if Russ and Brian might be willing to send one out for measurements. If they aren't, a DIYer might be willing to send one, especially if they bought a new Buffalo III and have a spare II. I only have one and I use it all the time, so I wouldn't want to be without it for the measurement period, but I could contribute an output stage if needed. It would be very interesting to see how a Buffalo measures on your expensive measuring setup.
Thank you for your time.
Aaron.
Great! I'll ask around and see if anyone is willing to send you one. I'll start with the designers themselves. I doubt they have the measuring equipment you do, and they might be curious to see what you measure.
Hope it works out!
Aaron.
DAC's don't need a sweeping THD vs power output measurement. I mean a 24bit ADC in a good soundcard is the worst load you could give a DAC, I guess I don't see how your equipment is going to "properly" measure a DAC any better than a CS ADC that nearly everyone who builds their own DAC owns in their soundcard, are you proclaiming the ability to measure jitter with some NIST standard ? Maybe you should start a new topic in the correct forum
Yeah I agree. This word in scare quotes "properly" definitely belongs in them because its a weasel word, giving the appearance of being science. Who says what's a "proper" suite of tests for a DAC?
If it were me I'd say a proper test suite would be one that correlated with how it sounds. Does anyone know such? Instead we are more likely to get the currently fashionable tests (multiple averaged FFTs included because they're provided by most equipment vendors) - who's to say they are the "proper" ones?
Many years back Stereophile tried introducing a noise modulation test but that didn't catch on. Its definitely an interesting avenue of measurement for DACs, particularly sigma-delta ones.
It will always boil down to the question of "What do you want?".
If you want something that "sounds awesome"... go ahead and buy whatever sounds "awesome".
But I prefer the electrons to my speakers unaltered and as pure as possible.
That means the way the was meant to sound by whomever made it.
And if I want any coloration to my music, there's plenty of opportunity to get it from the speakers.
'Sounded' equipment can only provide a good listening experience if the entire system is matched.
If everything is just a 'wire', you can mix and match anything you'd like.
And don't put every single word like 'properly' on the gold scale.
We should all be able to agree that a DMM and Rightmark are not suitable to measure anything high-end.
If you want something that "sounds awesome"... go ahead and buy whatever sounds "awesome".
But I prefer the electrons to my speakers unaltered and as pure as possible.
That means the way the was meant to sound by whomever made it.
And if I want any coloration to my music, there's plenty of opportunity to get it from the speakers.
'Sounded' equipment can only provide a good listening experience if the entire system is matched.
If everything is just a 'wire', you can mix and match anything you'd like.
And don't put every single word like 'properly' on the gold scale.
We should all be able to agree that a DMM and Rightmark are not suitable to measure anything high-end.
But your speaker are an iron core inductore, they are part of the amp! You can't take a cartesian dissection of audio chain, especially when it comes to the temporal membrane of our ears that transfers the physics to perception and consciousness. Your thinking is very, well 17th century Descart. Just about 3 centuries proved wrong by everything from quantum mechanics to the theory of relativity. Anyone who knows even the basics of electrons knows that newtonian physics and cartesian philosophy don't apply.
Measurements are a tool, interpretation of them is completly subjective unless you have have a working model of how perception, the mind , and consiousness work. Let me know when you work that out.
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Jokener's basically right though. Even amb wrote that he uses RMAA just to check if it "works" or something is screwed up. Even for that RMAA is only partly useful.
Maybe you should start a new topic with your attempts to invalidate measurements / objectivity. Good luck.
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I don't use "properly" as a "weasel world" but merely to indicate few audio engineers would consider RMAA "proper". Audio Precision, Prism Sound, AES papers, and even Stereophile have established guidelines for testing DACs. AP, in particular, has some excellent "white papers" on the subject. A lot of those tests cannot be done at all with RMAA, or at least cannot be done properly with RMAA with a high level of confidence in the results. I have written an entire article on the topic. It's a very sketchy bit of free unsupported software.
As for jitter, one of the employees of Prism Sound (makers of the dScope), developed the Jtest signal and test methodology that I use. There's an AES paper on the topic and it's been widely adopted by many others--even their main competitor Audio Precision. RMAA cannot make the measurement.
RMAA also doesn't do low level DAC linearity tests, digital carrier tests (jitter, stability, eye pattern, etc.), test at known output levels, conduct CCIF IMD tests, the noise tests use an unknown bandwidth and unknown weighting, you cannot view distortion residual, you can't create known amounts of jitter on a digital output and measure how well a DAC deals with it, etc. For a partial list of what the dScope performs see: Prism Sound
As for jitter, one of the employees of Prism Sound (makers of the dScope), developed the Jtest signal and test methodology that I use. There's an AES paper on the topic and it's been widely adopted by many others--even their main competitor Audio Precision. RMAA cannot make the measurement.
RMAA also doesn't do low level DAC linearity tests, digital carrier tests (jitter, stability, eye pattern, etc.), test at known output levels, conduct CCIF IMD tests, the noise tests use an unknown bandwidth and unknown weighting, you cannot view distortion residual, you can't create known amounts of jitter on a digital output and measure how well a DAC deals with it, etc. For a partial list of what the dScope performs see: Prism Sound
Clarification appreciated
So 'properly' is more here about using kit designed for purpose rather than pressing a soundcard into service as a measurement tool. Yet the list of tests you've mentioned still bears little relevance to how a DAC sounds IME. Do you have any experience of correlating sound to measurements? Otherwise what meaning can potential purchasers ascribe to the figures that come out of the dScope, other than that the designer probably checked his or her design on that piece of kit too?
If you want to open up the entire subjective vs objective debate that's getting well off topic. But the short answer, supported by several well conducted blind listening tests, is that DACs that measure sufficiently well are sufficiently transparent and thus don't have a "sound" once you remove the usual sighted listening bias. Lots of people don't want to believe that, but they've never managed to demonstrate significant audible differences exist between DACs that measure reasonably well when the listener doesn't know which is which.
The most extensive example of DAC transparency is probably the year long 500+ trials done by Meyer & Moran. They inserted an extra 16/44 A/D and D/A after an SACD player playing hi-res material and nobody could tell it was there under realistic listening conditions. For another example see the Matrix Audio blind test where a high-end Wadia CD player was compared to a very low end Sony--two extremely different DACs. There have also been tests where an A/D D/A pair are inserted after a phono stage playing vinyl and are undetectable.
There have been significant efforts to corroborate measurements with sound such as this AES paper. There are many other articles.
Measurements provide a level playing field and solid basis for comparison. Subjective impressions do not. Once you start talking about the "sound" of a DAC it's like trying to say Wine A tastes better than Wine B. The next person might have the opposite opinion.
You've stated your beliefs, no surprises there. So what would you say to the guy who posted this about the Muse DAC over on Head-fi? Would you tell him that he can't fix his DAC noises because they don't show up in dScope's measurements or that if he could only listen blind then what he thinks he's hearing would go away?
Mini Dac TDA1543 X 4 NOS
When listening to music through my Dell laptop, I get interference when scrolling via my touch pad in Firefox. I know this sounds bizarre, but I can't replicate the interference under any other conditions. The interference is like clicking and hisses, it almost sounds like a CD skipping. Scrolling through word documents or Chrome with the touch pad seems fine. It also seems diminished even in Firefox when running off my laptops battery.
To my way of thinking this is obviously a common-mode noise issue (because it improves on battery power) and tests could be devised to check it on DACs. Haven't seen anyone actively doing this though - which is odd because its not an uncommon occurrence in practice to find such effects.
They're not just my "beliefs" they're supported by lots of objective peer reviewed credible evidence. The subjective camp, however, has very little similar evidence supporting their views.
Extraneous noises from DACs inside PCs or running on USB power are not uncommon. The dScope can detect such noises at levels much lower than a human ear. It can trigger, much like an oscilloscope, on any threshold above a certain value to capture random noise events. Unlike an oscilloscope, that threshold can be down around a few microvolts if desired. And it can display the noise spectrum when the noise event occurred.
Most, however, don't consider weird background noises to be a typical DAC sound quality issue. Obviously you don't need a $10,000 piece of test equipment to tell you there are weird clicks and chirps in your headphones. But the test equipment is very useful for helping determine how transparent your hardware is in many other ways. Your example doesn't negate all the other data.
As someone previously suggested, if this goes further it should really be in a different thread. Feel free to start one if you'd like.
Getting back on topic, I'll be publishing some DAC tests soon and I'm still looking into an internal (single box) solution for the upcoming desktop version of the O2.
@Shamharoth, the irony of your question is I have far more experience with amps for speakers than headphone gear. I've designed many audio power amps from minimalist modest designs to excessive ones that dim the lights when played loudly and require two men and a boy to move around.
Unfortunately, relatively few seem to care about driving speakers beyond using a halfway decent AV receiver, iPod docked boom box, or powered desktop speakers. And for the few who want a serious amp, it's hard to compete with the likes of Emotiva.
There's a bit of a niche market for high quality desktop audio that companies like Peachtree Audio are trying to cash in on. But Peachtree is doing it with tube-distorted snake oil and I'm not sure there's sufficient interest in genuinely high quality amplification for desktop speakers.
For those who want accuracy just buy some powered Mackie monitors like the MR5's or better and call it good. They'll put anything Audioengine or Peachtree offers to shame.
And if you want a DIY speaker amp, there's also some stiff competition. They're over 25 watts, but I can't say enough good things about Bruno Putzeys' UcD amplifier modules. He's a brilliant guy I've met personally on multiple occasions and his amp designs are more than impressive and very reasonably priced. His designs are big on real engineering and low on snake oil. It's hard to compete with what he's done.
There are also the National Semi (and other) chip amp reference designs.
So while speaker amps are a nice idea it's a problem that's already well solved. Headphone gear seems to be a far more popular current topic where there really is a much bigger need for improvement.
Unfortunately, relatively few seem to care about driving speakers beyond using a halfway decent AV receiver, iPod docked boom box, or powered desktop speakers. And for the few who want a serious amp, it's hard to compete with the likes of Emotiva.
There's a bit of a niche market for high quality desktop audio that companies like Peachtree Audio are trying to cash in on. But Peachtree is doing it with tube-distorted snake oil and I'm not sure there's sufficient interest in genuinely high quality amplification for desktop speakers.
For those who want accuracy just buy some powered Mackie monitors like the MR5's or better and call it good. They'll put anything Audioengine or Peachtree offers to shame.
And if you want a DIY speaker amp, there's also some stiff competition. They're over 25 watts, but I can't say enough good things about Bruno Putzeys' UcD amplifier modules. He's a brilliant guy I've met personally on multiple occasions and his amp designs are more than impressive and very reasonably priced. His designs are big on real engineering and low on snake oil. It's hard to compete with what he's done.
There are also the National Semi (and other) chip amp reference designs.
So while speaker amps are a nice idea it's a problem that's already well solved. Headphone gear seems to be a far more popular current topic where there really is a much bigger need for improvement.
First, let me thank you, RocketScientist, for all your work on the O2.
I have a question : have you ever thought about making a full-sized speaker amp ? Like 2x25w ? It would be really great.
Thank you again.
You might find this: http://www.diyaudio.com/forums/soli...sed-lme49830-lateral-mosfets.html#post2717110 interesting, although it looks like Opc has already cut off the group buy on it.. Scalable from 6-400 watts..
Finally, my friend has finished his wood case
Similar to the design
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Similar to the design
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An externally hosted image should be here but it was not working when we last tested it.
RocketScientist, I think you are confusing soundcard measurements with RMAA, soundcards with good software and a low noise buffered input can take very meaniful measurements..
The hardware of the dscope looks to me like an ADC with a low noise floor (what you find on $200+ soundcards). What's new is some brilliant software and buffers/interfaces to adjust power and input to the ADC, which I think is great but certainly not to the level of this holy war of objectivism, its basically a USB soundcard taken to a new level. What are they charging for a dScope? As an engineer myself I appreciate the new tools this software provides, but lets face it when you correlate measurements to human perception science just isn't there yet. I do look foward to building your little O2 as I have an open mind about things, but until you can answer the basic question whether an electron is a particle or a wave, I think we all need to keep an open mind and understand the limits of science Peace and thanks for what you are sharing.
The hardware of the dscope looks to me like an ADC with a low noise floor (what you find on $200+ soundcards). What's new is some brilliant software and buffers/interfaces to adjust power and input to the ADC, which I think is great but certainly not to the level of this holy war of objectivism, its basically a USB soundcard taken to a new level. What are they charging for a dScope? As an engineer myself I appreciate the new tools this software provides, but lets face it when you correlate measurements to human perception science just isn't there yet. I do look foward to building your little O2 as I have an open mind about things, but until you can answer the basic question whether an electron is a particle or a wave, I think we all need to keep an open mind and understand the limits of science
Peace and thanks for what you are sharing.