To quote the brief specs for QA403:
"The maximum AC input to the QA403 is +32 dBV = 40Vrms.
The maximum DC is ±40V, and the maximum ACPEAK + DC =
±56V"
Measuments of tube amplifiers may involve high voltages e.g. when measuring the ripple or noise on B+. Pete Millett's soundcard interface is not an audio analyzer. It just scales the input voltage to suite the soundcard inputs so it is similar to Autoranger or E1DA Scaler. E.g. it could be used with QA403 to make that usable for tube amplifier measurements.
I'm currently reviewing it for AudioXpress, and can confirm that it needs basically 1A at 5V. It runs fine on a PC USB port or a powered hub but I had issues with a passive hub.
The screen shows the actual USB voltage it receives and it runs fine as long that stays above 4.6V or so. A fat USB power cable also helps.
Ideally, for lowest noise, you'd run it from a power bank.
Jan
How would you stack up a QA403 against an audio precision SYS-2522? I know you are also a very in-depth user of AP systems.
I was just about to purchase the QA but then came across AP system and now I am about to get one in the next couple of days, so your thoughts before I purchase sir, will be very appreciated as they might spare me from getting the wrong product.
Thanks!
I was just about to purchase the QA but then came across AP system and now I am about to get one in the next couple of days, so your thoughts before I purchase sir, will be very appreciated as they might spare me from getting the wrong product.
Thanks!
For almost any (diy) audio measurement the QA has great performance and a short learning curve. The AP is much more flexible if you want to do special things, but it has a longer learning curve and you really, really need to know what you are doing. It's easy to get a great AP graph that's totally wrong.
Performance wise there's very little difference in practical use. It would be unwise to take a purchase decision on the difference between -120 and -125dB.
For 99.999% of diyaudio projects I would recommend the QA.
Jan
Performance wise there's very little difference in practical use. It would be unwise to take a purchase decision on the difference between -120 and -125dB.
For 99.999% of diyaudio projects I would recommend the QA.
Jan
Thank you! I am trying to add an instrument that will allow me to make reliable and repeatable measurements. What you told me deserves some extra consideration from my side. 5/7dB increment can be quite useful but as comes at a price. Sound cards have come a very long way.
I don’t have issue with longer learning curve, right now I just don’t grasp entirely the meaning of more flexible instrument. Would you be so kind to give one or two examples where the AP and it’s flexibility would come into play?
I don’t have issue with longer learning curve, right now I just don’t grasp entirely the meaning of more flexible instrument. Would you be so kind to give one or two examples where the AP and it’s flexibility would come into play?
A good place to start is the AP user guide. Look at all the numourous settings for the generator and the analyser, the analog and digital panels, the sweep and settling panel.
Ask yourself if you would ever need all of that.
For freq response and distortion measurements, even the QA can be overqualified.
Do you ever, ever expect to build or buy anything that has lower than -120dB distortion ??
Jan
Ask yourself if you would ever need all of that.
For freq response and distortion measurements, even the QA can be overqualified.
Do you ever, ever expect to build or buy anything that has lower than -120dB distortion ??
Jan
The best reason to buy an AP is the option to show AP-plots to your customers imho.
For non professional use I would avoid a closed system, that may depend on windows.
A program like REW combined with a good usb sound card offers all I need..
And that's it.
Just my 2c
For non professional use I would avoid a closed system, that may depend on windows.
A program like REW combined with a good usb sound card offers all I need..
And that's it.
Just my 2c
I fully agree with all the comments here. Mostly it is to show customers and truly the measurable range for audio equipment is certainly less than 120dB. Also, I know about the Clio, it is a great tool that I believe the magazine Suono used to have many years ago, not sure if now they converted to AP or not.
In the end, due to the great price I found the AP2522, if it operates properly, I will go test the unit today and perform all the self-tests, if it pans out, I will go for the AP system.
On the side note, I also have the soundcard-based system as well so if needed I can always use both.
In the end, due to the great price I found the AP2522, if it operates properly, I will go test the unit today and perform all the self-tests, if it pans out, I will go for the AP system.
On the side note, I also have the soundcard-based system as well so if needed I can always use both.
Hi,
I want to measure amps up to 800W at 8 ohm (included bridged amps), that means, the input has to withstand > 90V RMS.
The QA403 needs an attentutor, that means, the Pete Millet Box would be ok in front of a good usb interface (I just bought the UAD Volt 2).
But before I spend a lot of money, I will test the whole measurement chain with cheaper equipment.
I want to measure amps up to 800W at 8 ohm (included bridged amps), that means, the input has to withstand > 90V RMS.
The QA403 needs an attentutor, that means, the Pete Millet Box would be ok in front of a good usb interface (I just bought the UAD Volt 2).
But before I spend a lot of money, I will test the whole measurement chain with cheaper equipment.
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For understanding the Pete Millet device:
The display shows the input RMS voltage? In which frequency range does it measure whith good accuracy?
The display shows the input RMS voltage? In which frequency range does it measure whith good accuracy?
I think I will play it safe and use a powered USB hub, rather than trusting to the capability of one of the USB ports on my computer.
I would recommend the same percentage amount for most professionals as well.
There are also plenty of cases where you can just simply rent one, or just simply send your design to someone doing it for you.
For that amount you can do that pretty often.
These days there are also other interfaces that come pretty close for a fraction of the price.
The QA403 isn‘t able to measure output voltages of powerfull amps up to 800-1000W at 4 or 8 ohm, a pity.
Which more devices are availible?
Which more devices are availible?
