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Old 6th May 2010, 10:04 AM   #11
SY is offline SY  United States
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I've had excellent experience with the M-Audio Delta 192 PCI card. Reliable and repeatable distortion measurements down to better than 0.002%. I've been playing with an external unit, the Echo Audiofire 2, which connects through the Firewire port.

Both have balanced inputs and outputs (which I find useful). The M-Audio does 192kHz sampling, the Audiofire 2 is a 96kHz unit. The Audiofire seems to have worse power supply noise rejection (spurs at 180 and 300 Hz), which could probably be dealt with by using a separate power supply. The M-Audio PCI card seems to have no significant problems with noise pickup, and when I'm not using it to measure, it serves as my music source.

Both also have SPDIF in and out.

No matter your choice, you'll want an analog interface box, and I heartily recommend Pete Millett's design.
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Old 6th May 2010, 01:58 PM   #12
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Most 24 bit sound cards can do heaps of precise analyses with their own or even free software. It may be obvious and just repetitition, but what isn't in the print on these cards is John Cordell's point in Steevos last thread - the necessary bandwith.

If the card ADC is limited to 22 or even 50kHz as most audio cards seem to be, you won't read too many harmonics of 20kHz. Ever wonder why so many DIY builders plots have falling THD above 5kHz?
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Last edited by Ian Finch; 6th May 2010 at 02:00 PM. Reason: grammar
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Old 27th February 2012, 08:42 AM   #13
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I have a EMU0404 and a MacBook Pro. I would like to do some distortion measurements, do I need anything else (e.g. to limit input voltage?). Or do I just hook up a CD-player or Amp to the soundcard (doesnt sound like a bright idea )
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Old 27th February 2012, 08:49 AM   #14
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I've been trying to use an external EMU 0404 but have been unable to make it work due to driver issues. I'm using W7 64bit.
There's a 'beta' driver on the EMU website for W7 but as said, I've not been able to make it work.
Might be particular to me or my system, but you'd probably want to check before buying.

jan didden
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Old 27th February 2012, 08:57 AM   #15
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I got it to work on my mac for measuring speakers (with the mic). It was a bit of a hassle I remember choosing the right . I believe 24bits doesnt work (although this was an issue with the Mac driver and should not be there on Windows)...

Would like to measure equipment, just need to know if I need an ARTA box (or so) or a Voltage Divider on the input...
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Old 27th February 2012, 09:30 AM   #16
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Hello Jan,

you said:I've been trying to use an external EMU 0404 but have been unable to make it work due to driver issues. I'm using W7 64bit.
There's a 'beta' driver on the EMU website for W7 but as said, I've not been able to make it work.
Might be particular to me or my system, but you'd probably want to check before buying.


I use EMU0404 USB with win7 x64 and had similar issue. I had to remove the integrated soundcard's driver to make it work. After that it work with spectraplus 5 but i have to set the sample rate manualy in the driver and in spectraplus. And still have an issue when i use it in 96k-192k/24 bit loopback.
So my soundgenerator is external and i use emu only for adc.
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Old 27th February 2012, 09:46 AM   #17
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Quote:
Originally Posted by Gordy View Post
For software I think that ARTA and RightMark are popular:
ARTA Home
Latest News. Audio Rightmark
Big thumbs up for ARTA from me.

Although I use it mainly for speaker / room / crossover measurement and it has a lot of acoustic measurement features you wouldn't use when measuring an amplifier, (RT60, CSD, etc) its possibly the best low-mid price package you'll find anywhere with an extensive feature set, good usability and excellent accuracy. It also has a time unlimited nearly full featured free demo which only has saving disabled, making it very easy to tell if it will do what you want.

Definitely check out the demo.
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Old 27th February 2012, 10:12 AM   #18
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Quote:
Originally Posted by Ian Finch View Post
Most 24 bit sound cards can do heaps of precise analyses with their own or even free software. It may be obvious and just repetitition, but what isn't in the print on these cards is John Cordell's point in Steevos last thread - the necessary bandwith.

If the card ADC is limited to 22 or even 50kHz as most audio cards seem to be, you won't read too many harmonics of 20kHz. Ever wonder why so many DIY builders plots have falling THD above 5kHz? regards
Excellent point.

My sound card can do 96Khz 24bit and I take all my measurements (in ARTA) in this mode and never use 48Khz or lower. It's not just about being able to measure supersonic distortion products, its also about staying well clear of the inevitable digital brick wall filter that most sound cards have, and the attendant phase shift and droop/ripple at the top end.

If you have a brick wall filter at 22 / 24Khz it's inevitably going to affect treble measurements, but a brick wall filter at 48Khz is well clear of the frequencies of interest. Anyone wanting to take serious measurements should be using a minimum of 96Khz, 24bit, or 192Khz if you're really serious. 48Khz just isn't enough.

Just a small warning to those starting out to beware of sound cards which claim modes that they don't really support - most consumer cards will claim they support 96Khz etc in software but really the hardware is sampling at a much lower rate and doing on the fly resampling in software, and the quality is usually worse than actually just using the cards native sample rate. (Many cards only have one or two native sample rates, and you should always stick to a native sample rate to avoid on the fly resampling)

Always perform an analog loopback measurement to verify that the card genuinely supports the claimed sample rate. For example if you have 96Khz selected yet a loopback test shows a steep rolloff at 22-24Khz you know the card is really upsampling from 44.1/48Khz...

Some cards will even switch between resampling or not with very tiny changes in the sound card settings, which can be a trap waiting for you to fall into.

For example my Audigy 2ZS is capable of genuine 96Khz 24bit operation (although analog SNR in 24 bit mode is only about 10dB better than 16 bit mode) but if you set the bass and treble sliders in windows anywhere other than exactly at zero, it will switch to 48Khz sampling with software upsampling to 96Khz. (Since bass and treble adjustment is done by the EMU engine which only internally processes at 48Khz)

Likewise if any sound effects are enabled or even any other applications have the sound device open at the same time at a different sample rate (I'm looking at you iTunes!) it will do the same thing. With such sound cards its important to be aware of the sound card settings and perform an analog loopback test at the start of a measurement session to verify that windows or some app hasn't mucked with your sound card settings...

Any change to sample rate settings in the measurement application, any volume control panel changes etc would require you to re-verify calibration through analog loopback.

It's not a nice feeling to know that a couple of hours of measurements need to be done again just because some app you ran the day before fiddled with your windows sound settings

Setting your default sound device to your onboard sound (if you have one) and manually selecting the measurement sound card in your measurement software can be a way to minimize a lot of these problems, in fact with Vista and Windows 7 its necessary with some measurement software as even a windows sound effect from a dialog message popping up can cause measurement issues like clipping or making the sound card revert to upsampling.
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Last edited by DBMandrake; 27th February 2012 at 10:25 AM.
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Old 24th March 2012, 11:01 AM   #19
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I've given up on the EMU0404 - there's lots of posts online and everybody seems to have issues and the last support post from EMU days 'we're working on it'- that was 2 years ago...

I'm now looking to buy a 24/196 2-channel Dr DAC prime. Has anybody experience with this external USB sound card for measurement purposes?

thanks,

jan didden
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Old 24th March 2012, 11:25 AM   #20
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What about building a nice distorsion analyzer built upon nowdays high sampling rate 16-18 bit ADC's. Mate it to Bob Cordell's DM would be a powerfull tool to measure THD up to 20kHz.
It would be nice if a skilled diyer in the digital domain showed us a nice project based on it.
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