QA Software?
"Based on AK5397 and AK4490. These are flagship products from AKM, with sample rates up to 768Ksps. We’re still locking down final sample rate options, but it appears we’ll settle on 192Ksps and 384Ksps. The 192Ksps sample rate will provide compatibility with existing software and the 384Ksps will only work with QA software. In our measurements, we haven’t seen much difference between the 48 and 192Ksps sample rates."
I can't find anything on QA's web about this sw. Anyone using it? Actually I found the dowloads and the release history. Would be nice if someone reviewed it 🙂
Regards
"Based on AK5397 and AK4490. These are flagship products from AKM, with sample rates up to 768Ksps. We’re still locking down final sample rate options, but it appears we’ll settle on 192Ksps and 384Ksps. The 192Ksps sample rate will provide compatibility with existing software and the 384Ksps will only work with QA software. In our measurements, we haven’t seen much difference between the 48 and 192Ksps sample rates."
I can't find anything on QA's web about this sw. Anyone using it? Actually I found the dowloads and the release history. Would be nice if someone reviewed it 🙂
Regards
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Hi, i have just received the QA400, i'm a bit unsure how to connect my amp to the QA400. Do i need to buy a female BNC connect to and wire it to my amp then connect to the input of the QA400. And also for the input signal to the amp, we will use the output of the QA400, is that right?
You will need an attenuator for the amp output since it will be much more than the QA400 can handle. You also need a load resistor for the amp.
Sent from my SGH-M919 using Tapatalk
Sent from my SGH-M919 using Tapatalk
To measure a 2VRMS DAC output into 10k ohm load, should i make a resistor devider of two 5k resistor to get 1VRMS input into the QA400? Thanks!
Is the DAC output balanced?
Is it with or without DC offset?
Is the instrument input unbalanced?
Is it with or without DC offset?
Is the instrument input unbalanced?
I'm trying to measure ODAC, it has SE output, the DC offset is 1-2mv. I set up like this: two 5k resistor (two 10k in parrarel) in series from output to ground then connect a cheap BNC to crocodile clip to the output ground (white wire) and the output of the divider. A 44.1k 16bit 1Khz WAV file is generate by audacity then i use Jriver to play this file with max window volume and get this result. The measurment looks so bad, much worse than an Odac should normaly measured. The QA400 is fine, i try the loop back test and get result very close to the offcial spec, the ODAC is also work well. I also tried to measure on a Laptop and also get the result like this. Anyone have an idea?
That actually looks pretty good. Some of the spurs may be from grounding between the PC and the DAC. Ideally the PC should be running on batteries and well away from the QA400.
To check for clipping increase the level until the harmonics shoot up. Its usually pretty obvious. Try measuring with the DAC at -6 dBFS. You may even be clipping the digital in Jriver if its gain is set too high.
To check for clipping increase the level until the harmonics shoot up. Its usually pretty obvious. Try measuring with the DAC at -6 dBFS. You may even be clipping the digital in Jriver if its gain is set too high.
the highest harmonic and the highest hum are both at ~-90dB ref signal.
Try to find why the hum+buzz is that high.
You need to get your test set up arranged that this is at least 10db lower and preferably better than -120dB. That could take a lot of time for experimentation and re-wiring.
Then you can look again at the harmonics.
-90dB is not far away from 16bit performance.
Try to find why the hum+buzz is that high.
You need to get your test set up arranged that this is at least 10db lower and preferably better than -120dB. That could take a lot of time for experimentation and re-wiring.
Then you can look again at the harmonics.
-90dB is not far away from 16bit performance.
Further to Demian's point -- use the shortest test leads you find convenient, and when you're down to the subatomic level the probes from Pomona, or those you fashion yourself will work far better than alligator clips.
This application note by Jim Williams discusses probing techniques in detail:
http://cds.linear.com/docs/en/application-note/an47fa.pdf
Jack
This application note by Jim Williams discusses probing techniques in detail:
http://cds.linear.com/docs/en/application-note/an47fa.pdf
Jack
I've had the QA405 on the Christmas list for awhile! 😀 But... I just read through that status blog post. Urk. I agree with several of the things they dropped but...not using the +/-15Vdc power rails with an external power adaptor, in lieu of staying with being fully USB powered, seems like a major error to me in several ways. Having the QA400 run on USB did seem to make a lot of sense. The QA401, not so much in my view. Combine that with the lack of guaranteed ASIO support makes the thing seem a little "rushed out the door for the holidays".
In their words-
"The optimal distortion point on the QA401 is shown below. This could be improved with higher supply rails..."
"As you’d expect, the performance is improved over the QA400. Roughly, we closed about half the gap between an AKM reference board and a QA400. In other words, there’s some AKM performance left on the table that couldn’t be had due to the reduced supply rails. "
"Wide supply range. Ideally you’d want to the input and output amps at +/-15V rails to maximize your THD. Right now we’re tipping the scales at 600 mA from a USB connection while running our internal rails at +/-6.5V. This isn’t ideal, but it’s one of the biggest tradeoffs we had to make to get the power consumption and form factor we wanted. On some machines, the 600 mA current will cause the port to shut down gracefully. The solution there is to power the QA401 from a powered hub or to power it from a Y power splitter, which are common today." Seriously? That seems acceptable to QA to ship?
Trade the power supply issue off over the nice differential inputs/outputs and attenuator, etc. Hmmm...
On price they say: Our feeling at this stage is that we can hit $429/$439. The QA405 was headed north of $600, so you can hopefully understand the rational. No, I really can't understand the rationale. This is a targeted to be a piece of better-than-average test equipment. $439 vs.$600, $160 more, is virtually the same number in my view of things. If it were $439 vs. $6,000, or $1,000, or even $800, well there is a difference to write home about. But $160 more, a 27% increase, for worthwhile performance improvements and additional useful features in a piece of test equipment? When the QA400 will presumably still be around to cover the the "lower" price-point end of the market?
I would be curious what thoughts other folks have about QA's power supply decision. Maybe it will make more sense to me after some holiday egg nog!
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I would be curious what thoughts other folks have about QA's power supply decision. Maybe it will make more sense to me after some holiday egg nog!
There will be a busy market for modified units...I recall that one of the folks in this thread had an Audio Precision unit modified such that the power transformer was placed outside the chassis.
Dats right Jack. If there is a trade off, something that QA didn't want
to do because of cost or other problems with running the rails hotter
than USB likes. It would be nice if QA would put out a modification
plan for DIYers to do them selves. Maybe if you go down that road
and you try to go back it has USB problems.
I don't know. Just thinking out loud.
Cheers,
Sync
While there may be some small benifit to raising the rails its probably in the 3 dB range on distortion. I think the reality of the QA405 with the input ranging with a lot of relays and a lot of other stuff would make it more like $1000 and the China market that is actually paying for this would be too small. My guess is that QA needs to sell at least 500 to make the numbers work. China assembly lines can be adapted to the QA401 easily and its already orders of magnitude better than any BT speaker or most cell phones on the market. Our best hope is the over the top cell phones with 192/24 playback using ESS or AKM DAC's take off even more so they need higher performance audio test for production. Then there is a market.
Could we separate the USB power/signal wiring?
Tap into the USB plug/cable and connect an external 5Vdc, 1Adc low noise isolated PSU?
Ideal project for a 1A Salas Shunt regulator.
Once we have some, it may be that 700mA, or 500mA, would be sufficient.
Tap into the USB plug/cable and connect an external 5Vdc, 1Adc low noise isolated PSU?
Ideal project for a 1A Salas Shunt regulator.
Once we have some, it may be that 700mA, or 500mA, would be sufficient.
Some questionning on QA400 from a newbie..
Hi,
I just discovered this QA400 forum some days ago.
I'm about to buy a QA400 but have some questionning
and Quantasylum support is SLOW to answer my requests so I'm asking you guys
who seem to know well this test device:
- Should I wait for another device (QA405) to be released soon
before buying the QA400 ? (New one would be much expensive than $200 ????)
About the QA400:
- Is-it possible to use it without frontend added circuitry ?
or with GOOD resistor divider (when testing a power amp) ?
Doing it safely, measuring the signals amplitudes before
connecting them to the QA400 I/O ?
- Is-it possible to view more than 2 spectrum curves at the same time
on the graph window ?
(ex: display some separate freq responses on the graph
after their saved acquisition like RMAA)
- Possible to save acquisitions for later uses ?
- Any issue with Windows 8.1 compatibility ?
- Working on both USB2.0 or USB 3.0 standards ?
Thanks for your help !
J-Pierre
Quebec, Canada
Hi,
I just discovered this QA400 forum some days ago.
I'm about to buy a QA400 but have some questionning
and Quantasylum support is SLOW to answer my requests so I'm asking you guys
who seem to know well this test device:
- Should I wait for another device (QA405) to be released soon
before buying the QA400 ? (New one would be much expensive than $200 ????)
About the QA400:
- Is-it possible to use it without frontend added circuitry ?
or with GOOD resistor divider (when testing a power amp) ?
Doing it safely, measuring the signals amplitudes before
connecting them to the QA400 I/O ?
- Is-it possible to view more than 2 spectrum curves at the same time
on the graph window ?
(ex: display some separate freq responses on the graph
after their saved acquisition like RMAA)
- Possible to save acquisitions for later uses ?
- Any issue with Windows 8.1 compatibility ?
- Working on both USB2.0 or USB 3.0 standards ?
Thanks for your help !
J-Pierre
Quebec, Canada
I agree! I wish QA would at least qualify the performance at +/-15Vdc to make sure raising the rails doesn't break something else, or introduce other noise/distortion gremlins.
I'm going to have to take a closer look at JensH's ongoing creation.
Well...maybe I'm looking at the QA401 wrong (my post 1770 above), after thinking about it some more. Rather than compare it to "what the QA405 could have been" at a less-than-$1000 mark, what I was expecting to happen, I probably should just be looking at the QA401 as "a slightly better Q400" for just a couple of hundred bucks more.
If someone was thinking of getting a QA400 for the first time it would be worthwhile to save up a bit more and get the QA401. Since the QA401 will presumably be a superset of the QA400 with no QA400 functionality lost (it runs the same software anyway, according to their blog), if someone already has a Q400 sell it and get the QA401. Which is probably what I will do. 🙂
As for the QA401's crazy-**** power supply (IMHO, lol), an alternative to a USB 2.0 Y-cable may be to get a powered USB 3.0 hub. At least there is the *potential* for up to 900mA per port, but with the mysteries of USB version inter-compatibility I'm not sure if the 2.0 device (QA401) would have access to all 900mA. Or get a powered USB 2.0 hub and use the Y-cable with that. At least the cable doesn't suck up USB ports on the computer that way.
If someone was thinking of getting a QA400 for the first time it would be worthwhile to save up a bit more and get the QA401. Since the QA401 will presumably be a superset of the QA400 with no QA400 functionality lost (it runs the same software anyway, according to their blog), if someone already has a Q400 sell it and get the QA401. Which is probably what I will do. 🙂
As for the QA401's crazy-**** power supply (IMHO, lol), an alternative to a USB 2.0 Y-cable may be to get a powered USB 3.0 hub. At least there is the *potential* for up to 900mA per port, but with the mysteries of USB version inter-compatibility I'm not sure if the 2.0 device (QA401) would have access to all 900mA. Or get a powered USB 2.0 hub and use the Y-cable with that. At least the cable doesn't suck up USB ports on the computer that way.
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USB doesn't have to powered from the USB port. A simple adapter can be made up at a small cost that allows an external power supply. This can be a regulated battery supply.
As for kick up the rail voltages for the op amps this depend on the dc to dc converter QA used. I don't get QA's reasoning for keeping the rails lower. We're talking about a few mA.
The current doesn't go up with rail voltage much unless load is considered.
I think it is more a cost thing.
As for kick up the rail voltages for the op amps this depend on the dc to dc converter QA used. I don't get QA's reasoning for keeping the rails lower. We're talking about a few mA.
The current doesn't go up with rail voltage much unless load is considered.
I think it is more a cost thing.
While the current may not increase significantly on the load side, that same current or slightly greater current is now delivered at a higher voltage which means the power consumed increases, and more importantly that increased power requires much more current on the USB side of the equation.