QuantAsylum QA400

[dchisholm]

Originally Posted by gk7

Demian,

would you mind to post the schematic as some graphic file,
to have a look at it without installing software ?
Looks (or rather reads currently ;-) ) like a very useful project,
thanks for sharing it.

Please don't think I am the least bit ungrateful, lazy, or nit-picking . . . but I support this request.

I know it takes a little extra work to export a CAD file in another format, and usually requires some thought to select the best set of options for the translation. (Thinking makes my brain hurt!) However, *.pdf, *.jpg, and *.png, file formats are more accessible to the Forum community than native CAD formats. You will almost certainly reap the benefits of more reviewers' comments on your work. (Even *.html, *.ps, or Gerber-format files are more likely to be reviewed than native CAD files.)

{My machine has 4 different installed programs that use the " *.sch " file extension, and at least that many using " *.pcb ". Two of them are commercial-grade, professional, CAD/EDA programs that were installed for compatibility with employers' software. (I.e., if I don't use the program specified by the client then he finds somebody else to do the job.) On a good day it is annoying to keep track of which project uses which program . . . and then there are not-so-good days.

I will not give any opinions about the capabilities or quality of the ExpressPCB software compared to what I currently use, nor do I have any prejudice against ExpressPCB per se and would learn their software if requested (I am currently out of work) - but none of my recent employers have requested that I work in ExpressPCB. I am not inclined to install yet another program using those file extensions. I don't want to risk upsetting my registry and file-type definitions. At best, I envision wading through a bunch of installation options in hopes of preventing the new software from changing my current work environment; at worst, the new installation will simply make the changes without even telling me what has been changed.}

Dale

[1audio]

No real problem. I hope the two conversion stages don't degrade the content too much.

I suspect a lot of DIY'ers use expressPCB because its simple and cheap. I would not use it for a major project but this is little more of a "G job".

[dchisholm]

Thanks for the drawings. Yeah, the circuit looks a lot like Pete Millett's sound card interface without the metering, protection, and range-switching circuitry. Since this will be used with a high-performance measuring instrument there will undoubtedly be some discussion about the choice of active devices - e.g., INA134/DRV134 versus offerings from THAT Corp ( http://www.thatcorp.com/THAT_IC_Selection_Guide.shtml ), etc.

Looks like there may be a typo on the power converter chip's part number. I think you meant to call out the " DSP1N5D12 " sted " DSP1N5D17 ".

Dale

[1audio]

The THAT parts (impossible name, just try to Google them) are interchangeable with the TI (and I think (ADI) parts. The receiver has the caps for the THAT but they aren't used in the other devices. I have samples of TI and THAT to try. I'll see what works.

The 17V is intentional. I need enough voltage to get 10V RMS out. I'll know very soon if it works and what the downsides are. The converter is expensive so lets see if it works right for this.

[dchisholm]

Originally Posted by 1audio

. . . The 17V is intentional. I need enough voltage to get 10V RMS out. . . .

That makes sense. I was confused because +/-17V is a rather unusual choice for supply rails, and the other two diagrams showed +/-12V rails. I'm sure you have verified all of the absolute max voltage ratings - there are a few "full voltage" IC's where +/-17V rails are right at, or over, the rated capability.

Dale

[dchisholm]

Originally Posted by 1audio

The THAT parts (impossible name, just try to Google them) . . .

Yeah, I know. That's one of the reasons I included the link in my reply. I can't imagine anybody in the advertising or PR business would agree with it for a corporate name.

Dale

[Telstar]

I also have samples of THAT30** and MAT 1*. Very curious to see how they perform.

[1audio]

Originally Posted by dchisholm

That makes sense. I was confused because +/-17V is a rather unusual choice for supply rails, and the other two diagrams showed +/-12V rails. I'm sure you have verified all of the absolute max voltage ratings - there are a few "full voltage" IC's where +/-17V rails are right at, or over, the rated capability.

Dale

Me being lazy with the cad software. 12V rails are included so i hijacked them. the +/-17V supply is a stock part. i will be going though datasheets some more. Many pro market IC's run on +/- 24V.

[1audio]

I got the boards and parts in finally. One mistake- the holes for the minijack pins are too small. I'll note the other errors we find and post an updated version once its all working.

[1audio]

Here is a great note on expanding the QA400 performance through coherent averaging Melt the noise away…. - QuantAsylum Home Page