QuantAsylum QA400 and QA401

Jump to Latest
#2,083
jan.didden said:
Yes when I am ready I can see if there is interest in a Group Buy. If I can get say 50 or so made that would make the price much more friendly!
Especially for the box and PCBs, and a few relatively expensive items like the AD536 AC-to-RMS converter.

Jan
Click to expand...

You're getting the level of a sine waveform. Do you really need to use an RMS detector.
I'm not familiar with this particular pic.Most of them come with at least a 10bit ADC.
You can sample the peak of the sine and convert to equivalent RMS.
Even a cheap peak detector would work for this. Or generate a quadrature from the fundamental and zero crossing detector to trigger ADC.
 
#2,086
#2,087
jan.didden said:
Yes, the numbers.
The max input is 100V RMS (140V peak) so you can directly measure power amp output. Min. input around 150mV. Between those levels the autoranger will deliver around 1V to your soundcard. Fully automatically.

Freq response is flat to 100 kHz at +/- 0.1dB. Distortion -120dB. That should be OK for all those sound cards out there.

To help with setup, the display shows the actual level going into the soundcard and the autoranger input level and attenuation or gain setting applied.
Atten/gain ranges from -40dB to +16dB.

Jan
Click to expand...
Dare I ask how fast this thing switches between levels? What will a soundcard see if the input goes from 0V to a 140Vp 20KHz sinewave?
 
#2,091
Another milestone in the development of the autoranger!
Finalised and tested the cal procedure.
Especially calibrating the freq response for 0.1dB flatness out to 100kHz is a challenge if you don't have a fully equipped lab 😱

I now have a procedure that needs only an AC DMM with reasonable performance and a signal generator that can output 10kHz and 100kHz, preferably up to 10V or more but that's not critical.

The procedure directs you to do some measurements and enter values in a small spreadsheet and the spreadsheet then tells you what to adjust (cap trimmer) for which DMM indication.
For -20dB and -40dB settting, in both SE and BAL mode.

It's done faster than described!

Jan
 

Attachments

  • ar cal.png
    ar cal.png
    416 KB · Views: 445
Last edited:
#2,093
RNMarsh said:
I gather it is all done... designed and built. Now what is next? schematic/bom/pcb ?


THx-RNMarsh
Click to expand...

I have to decide how to get this out to people who want it. Probably as a kit, PCBs, box and a BoM. Or maybe complete units.

I have to count all the bits and parts see how much it will actually cost. As a complete unit it will be close to $300 for sure. The box and PCBs as a kit will be much lower of course.

The box I have now is not painted and not labelled and I am thinking about getting in an order of painted and labelled boxes.

There are a lot of SMD parts but I have made sure the smallest is 0805 so still easy to solder.

Maybe Group Buy, maybe Kickstarter? If I get 100 made prices will drop considerably.
This is new territory for me,

Jan
 
#2,096
Waly said:
Nope, still a big delta. No triggering features (think synchronous averaging), limited LF extension, no reference channel, etc...
Click to expand...

Yes. An AP does all that. And is also about 40dB more expensive 😎

I did a write-up this afternoon, it's here.
The power supply I developed for the AR is really a nifty little stand-alone unit and is described here.

I will add more detail over time.

Jan
 
#2,099
jan.didden said:
Yes. An AP does all that. And is also about 40dB more expensive 😎
Click to expand...

Really?

Audio Precision System One | eBay

Audio Precision Portable One Plus P1P 10612 with Probe Self Test Passed | eBay

Audio Precision ATS 1 Audio Test System | eBay

Prices for second hand lab equipment dropped well under 50% (more like 70% on average) in the last 12 months.

Of course, the fun of building something yourself is priceless.

P.S. And still available:

http://www.ebay.com/itm/Audio-Preci...425967?hash=item3d225b7c2f:g:cDAAAOSwRgJXiPzH

http://www.ebay.com/itm/Audio-Preci...252066?hash=item4d496b52a2:g:xU0AAOSw0UdXqibU
 
Last edited:
You must log in or register to reply here.
Top Bottom