With the soundcard you still need and interface and a lot of effort with the calibrations.
The QA400 + a laptop/notebook computer and you are very portable. USB soundcards are notoriously troublesome for measurements since one delayed or dropped frame will wreck the measurement.
I have both so I don't need to decide, but if only one it would be the QA400.
The QA400 + a laptop/notebook computer and you are very portable. USB soundcards are notoriously troublesome for measurements since one delayed or dropped frame will wreck the measurement.
I have both so I don't need to decide, but if only one it would be the QA400.
I agree QA400 is a better choice. It's design for that specific purpose. Unless you have a special need for a good sound card, that you have use other than this, it's not worth the effort unless you like to deal with computers.
For me, even I have the Personus USB, I still lean towards buying the QA400 as I have to be at the mercy of other software to make the Personus work. Things never that smooth when you try to use a piece of equipment out of it's original intentions. Then the digitize rate of the Personus is only 48KHz, that, there is nothing you can do to make it 196KHz of the QA400.
For me, even I have the Personus USB, I still lean towards buying the QA400 as I have to be at the mercy of other software to make the Personus work. Things never that smooth when you try to use a piece of equipment out of it's original intentions. Then the digitize rate of the Personus is only 48KHz, that, there is nothing you can do to make it 196KHz of the QA400.
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I have the QA190, and have found it to be a little troublesome. Do note, that I am a complete neophyte, and as such may be using the tool wrong.
Issue #1: The /10 /100 switch is sloppy(on mine), and it's easy to accidentally have it not seated. It took FOREVER for me to discover that this was a major source of my initial frustration in use.
Issue #2: The 190 seems to be an excellent antenna, making measurements very much harder. It's so much of an issue, that I run naked (no input protection/buffer) when testing my 8W tube amp (peak amp power is below the QA400 max input limit).
Issue #3: Despite many back to back tests, I've never been able to get a QA190 reading with a noise floor close to a reading without (same amp, same testing session).
Thanks
Good to know. I was going to do a simple voltage divider to feed to the QA400. I guess I'll save the $79 and make my own.
NP electrolytics with a higher voltage rating tend to have lower distortion Nichicon NP electrolytics designed for loudspeaker crossovers are quite good and available in very reasonably-sized radial packages, especially for low values like 10uF.
Cheers,
Bob
😕
Sorry I don't understand. You mean driving a sound card with QA400?
I am getting close to buying. I just build the OPS, so I'll be bringing it up in the next few days. Any word of wisdom, please give it to me.
Thanks
Alan the QA400 is a sound card which has is purposely designed as a test instrument. The software bypasses Win audio API to avoid the the calibration being from being messed with by other software running or other users changing win audio settings with out the other users knowing.
It uses different methods for signal generation to obtain the distortion measurement. This was done to avoid settling time of the mesurement.
Richard's comment is he would choose the QA400 over using a common sound card for doing the same. Any of the available software like ARTA can be used with commercial sound cards to obtain a decent distortion measurement. This can be enhanced by using an external notch filter before the sound card. But one still needs to build a front end for a sound card for it to be really useful. Same holds true for the QA400.
This is where QA400 and sound cards separate from distortion analyzers and will never meet a analog analyzer's performance. Big difference in price though even for used gear.
A $200.00 instrument can't compare to a $ 25,000.00 one.
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Thanks for the reply and clarification. I don't quite get why the QA400 can't compare to the real analog analyzer( I take that you mean spectrum analyzer). I thought the reason QA400 is cheap because it only run up to 192K sampling rate. But at audio frequencies, it is as good as any spectrum analyzer.
I understand it's a single end and have no attenuator to protect the input stage. But from my understanding, I only need to build an attenuator for the input. I corresponded with QuantAsylum, in my case, only interested in testing power amp, no high gain small signal circuits. I told them I am planning to just build a voltage divider that is switch selectable attenuation to drive the QA400, they said it's find.
I don't see there is a need of any fancy frontend. Can you explain?
Thanks
What is a distortion analyzer? I thought spectrum analyzer is all you ever need to look at distortion. You mean something like this:http://www.ebay.com/itm/HP-Agilent-...471?pt=LH_DefaultDomain_0&hash=item2ee1df1a47
How can this be better?
No. I mean something more like this.
https://www.google.ca/url?sa=t&rct=...PTeiWCHGQ67MEqQ&bvm=bv.98197061,d.cWw&cad=rja
https://www.google.ca/url?sa=t&rct=...PTeiWCHGQ67MEqQ&bvm=bv.98197061,d.cWw&cad=rja
That's more like fancy instrument. But the basic spectrum analyzer can do just as good a job. All you are looking for is the height of the harmonics from distortion like what LTSpice FFT shows. You don't need anything more than that. QA400 might not give the fancy reading or automation, but it should do the job.
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Being PC-based and capable of FFT, the QA400 can function both as a distortion analyzer and a spectrum analyzer. Moreover, it can provide readings of either THD or THD+N.
Most other PC/software-based soundcard+PC analyzers can also provide both THD and spectrum analyzer functions.
Cheers,
Bob
It looks like the ShibaSoku is specified to have a distortion residual down by 115dB at 1kH, but only 102dB up to 16kHz. The real unit is probably better by 5dB or so, so that comes out to 120dB at 1kHz and 107dB at 16kHz (or about 0.0004%), not as good at 20kHz. I assume this residual spec is THD, not THD+N residual.
So it is probably good to a bit better than 0.001% THD at 20kHz.
Cheers,
Bob
If it's just for power amplifiers, you might want to consider getting an HP350C attenuator. It's 600 ohm, DC to 1 MHz and usually go for $50 to $70.
Hi Bob Shibasoku was ridiculously conservative with the specs in the Brochure.
There are no tracking notch circuits in the Shibaloku 725B/C and D. It's all done with relays based on frequency measurement. The gains are also switched with relays based on input level. The residual tends to be a lot lower than most audio analyzers.
I think you need to add some zeros to your quotes.
I'll put some measurements of my oscillator on a 725C and 725D later today.
Thanks David. Did you mean to say my quote of -107dB did not correspond to about 0.0004%?
Cheers,
Bob