That sounds like a good idea on its face. It certainly breaks the ground loops, but I don't know much else about it. I wonder if there's a Toslink think I could get for my laptop? I'll have to look.
Demian, in case anyone is interested, I needed DC response for some non-audio experiments and found it trivial to pull up the HPF enable pin on the A/D in the EMU 0204 and connect it to DGND. It works like a DC coupled scope now (op-amp offsets are problematic at high G but eventually I will bypass them).
Thank you to all who have replied thus far. Although, I have to say that much of the abbreviated parts don't really make a great deal of sense. I am looking for some means of measuring frequency response, phase, impedance, waveform analysis and several types of distortion and noise in audio electronics with reasonably reliable results. I am not sure what equipment does this, what probes are needed or anything. It seems like if I go asking people for advice the next thing they say is to mortgage the house and buy a single analyzer, because USB analyzers were said to be...what is the term..."useless" above typical audio frequencies. The thing is that I am not in a position to know otherwise. However, I do think it is important to be able to measure things with residual PWM noise and oscillation, too. You gentlemen have been really good, because most people elsewhere on the net simply play snob and don't answer, or they give cryptic answers send the thread creator running in circles.
I kind of settled on USB types at first because some people on the web claimed they were as good as the high priced analyzers. Then I was told about the important limitations and lower frequency barring. You see, I don't know, there is no real point-shoot guide out there for new people getting into testing electronics. There is tons of material to be read online, but much of it is unnecessarily verbose, much less concise or complete. I see designs all the time that I know are incorrect or can be unsafe. That is great, but what about the ones in everyday use that may have a problem or performance issue that is no immediately evident? That is where the testing comes into my picture. I am really looking for people to guide me to something that serves the purpose. My need may be a bit different, but I can guess that the tools industry is as competitive as any other. Again, thank you for the suggestions.
Maybe there are even some slightly older analyzers that serve these functions and can be bought used at reasonable prices? I once read that after Dan D'Agostino moved on from Krell, he bought some $500 retired Audio Precision or HP analyzers to build his new line of (gulp) $50,000 amplifiers. I simply do not know what models to seek out. And let us say that someone was looking at a scope like the Rigol DS1052E 50 MHz Digital type with FFT, 8bit vertical resolution, dual channel 250MSa/s 8kpts, 2 mV/div - 10V/div. In layman's terms, what limits does this impose on measuring, graphing and interpreting results? Here is what I am looking for:
Impedance analysis
Frequency response
Waveform analysis (scope)
Harmonic and intermodulation analysis
Wide bandwidth for oscillation and PWM testing
Reasonably reliable results again higher priced units
Low self-noise
I kind of settled on USB types at first because some people on the web claimed they were as good as the high priced analyzers. Then I was told about the important limitations and lower frequency barring. You see, I don't know, there is no real point-shoot guide out there for new people getting into testing electronics. There is tons of material to be read online, but much of it is unnecessarily verbose, much less concise or complete. I see designs all the time that I know are incorrect or can be unsafe. That is great, but what about the ones in everyday use that may have a problem or performance issue that is no immediately evident? That is where the testing comes into my picture. I am really looking for people to guide me to something that serves the purpose. My need may be a bit different, but I can guess that the tools industry is as competitive as any other. Again, thank you for the suggestions.
Maybe there are even some slightly older analyzers that serve these functions and can be bought used at reasonable prices? I once read that after Dan D'Agostino moved on from Krell, he bought some $500 retired Audio Precision or HP analyzers to build his new line of (gulp) $50,000 amplifiers. I simply do not know what models to seek out. And let us say that someone was looking at a scope like the Rigol DS1052E 50 MHz Digital type with FFT, 8bit vertical resolution, dual channel 250MSa/s 8kpts, 2 mV/div - 10V/div. In layman's terms, what limits does this impose on measuring, graphing and interpreting results? Here is what I am looking for:
Impedance analysis
Frequency response
Waveform analysis (scope)
Harmonic and intermodulation analysis
Wide bandwidth for oscillation and PWM testing
Reasonably reliable results again higher priced units
Low self-noise
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The scope is great for general purpose testing and has the bandwidth to see problems. It won't tell you directly distortion, SNR etc.
You can get a traditional distortion analyzer for around $300 on ebay. A Sound Tech, HP, Boonton, Krohn Hite or others can do the audio measurements pretty easily and won't break without an effort on your part so they really are still a first stop. Combined with a scope, especially a scope with spectrum analysis would address most audio needs pretty well.
Its important to understand at a pretty deep level what you are measuring, what you are looking for and what you will do about what you find. Only then will the measurements be useful. Measuring for measuring's sake is kind of pointless.
You can get a traditional distortion analyzer for around $300 on ebay. A Sound Tech, HP, Boonton, Krohn Hite or others can do the audio measurements pretty easily and won't break without an effort on your part so they really are still a first stop. Combined with a scope, especially a scope with spectrum analysis would address most audio needs pretty well.
Its important to understand at a pretty deep level what you are measuring, what you are looking for and what you will do about what you find. Only then will the measurements be useful. Measuring for measuring's sake is kind of pointless.
I'm having fits with my Tracker Pre. It works but not well in duplex mode. I keep dropping samples that creae a mess and the EMU software has no tools for tweaking it. I can get really good measurements from an external source but not from the internal dac. Do you have this issue?
It may be worth documenting the EMU input and output circuit to better understand the limits. I think the general form is common to all their products and the ADC/DAC are what change.
I have used the scope in Visual Analyzer and I find it to be pretty good for free software. Of course you are limited to the sampling rate of your A-to-D converter and what the software itself supports. These days you can get cards or outboard units with 192kHz rates but I am not sure that this is supported by VA. Even with 96kHZ you have room for the audio bandwidth plus some. It's definitely not a "real" scope, e.g. 10MHz+, etc.
For distortion measurements I have been less than happy with VA. For that purpose I have been using Room EQ Wizard, which has some nice features and gives distortion products up to 9th order. It's very easy to use as a distortion analyzer. Don't use it for much else, however, I haven't really fully explored it. For example, here is a distortion spectrum obtained with REW. The distortion percentages listed in the small inset box:
.
For distortion measurements I have been less than happy with VA. For that purpose I have been using Room EQ Wizard, which has some nice features and gives distortion products up to 9th order. It's very easy to use as a distortion analyzer. Don't use it for much else, however, I haven't really fully explored it. For example, here is a distortion spectrum obtained with REW. The distortion percentages listed in the small inset box:
.
Some (not all) computers now come with toslink built into the headphone jack, so that's what I'll be using with PCM4222-evm and Frex's ADC.
I've got zero experience with taking measurements using soundcards, but what is the point of duplex mode in this case? Is there a specific problem with two independent devices other than clutter on the workbench?
Toslink in the headphone jack is going to be an output (an LED)- you might want to double check this. Toslink inputs don't seem to be so common.
Hmmm on a quick search it is rare as you suggest. I'm lucky - my mid 2011 iMac does have it but none of the newer iMacs do. Current mac mini does have it though, very few PCs do though, I hadn't looked until today had only been researching based on my own needs with the computer I'm using.
Toslink in the headphone jack is gone on new stuff. No one is making them anymore. Not many pc's have toslink it or even coax in capabilities. They see in as meaning a Skype microphone. new laptops come with stereo headphone out and single mike in like a cell phone.
You may need to get a soundcard addon. Today its USB. My tracker pre runs fine on ASIO but not using the internal windows sound engine (I confirmed today).
You may need to get a soundcard addon. Today its USB. My tracker pre runs fine on ASIO but not using the internal windows sound engine (I confirmed today).
I was not able to find a toslink Express Card adapter, or any other kind of toslink adapter, for my laptop. I read somewhere that toslink has more jitter than S/PDIF, but that it provides galvanic isolation, which is good. I suppose S/PDIF with a really good coupling transformer might be a good choice instead.
I now have my EMU tracker pre working pretty well. It works much better with ASIO and is not usable on WDM at 192. only certain ports on my computer work with it. Their driver does not like the USB3 ports.
Great performance at 48K.
At 192K even though the harmonics are the same ARTA adds in the HF stuff that starts at 20 KHz and takes .00035% and turns it into .25%.
Both the DAC and the ADC have the HF issue but the ADC is still quite good (image 3)
I need to find my EMU 0404. It should not have that HF issue.
Great performance at 48K.
At 192K even though the harmonics are the same ARTA adds in the HF stuff that starts at 20 KHz and takes .00035% and turns it into .25%.
Both the DAC and the ADC have the HF issue but the ADC is still quite good (image 3)
I need to find my EMU 0404. It should not have that HF issue.
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Does anyone have any experience with the now-twelve year old Audio Precision System One G Revision Audio Analyzer? Stereophile uses one of these. Or, am I better off with something else?
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Transport jitter isn't really important in this context though is it? Sampling clock is the only place we would care about jitter in an ADC for measurements, right?
That's correct. For the transport the data can withstand a whole lot of jitter without errors. The transport jitter is only an issue for the DAC. And contrary to common knowledge the current generation of SPDIF receivers are really good with very low jitter.
Here is an interesting blog Blog! ... one man deals with the AP limitations 🙄 and may look also on this special DAC implementation 😀 😀
Hp
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