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Old 17th January 2013, 02:11 AM   #251
gootee is offline gootee  United States
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Quote:
Originally Posted by bcmbob View Post
gootee,

Your spreadsheet is exactly what I was hinting at in post #233. That's is excellent (pun intended) work. I haven't figured everything out yet but it is fantastic for those of us who are just learning the subject.

Thanks Bunches

BTW: I'm running it on OpenOffice and it appears to translate perfectly.
Thanks, Bob. Thre's also a PDF of a paper I wrote about it, which describes the analysis and the methods used, and also includes more about how to use the spreadsheet. It's at:

Power Supply Resevoir Size

It turns out that analyzing a simple transformer/rectifier/capacitor circuit is surprisingly complex, and there is no closed-form mathematical solution.

It was actually my first Excel macro and my first VBA programming experience (but I've programmed plenty, in other languages). The only code that I lifted from someone else is the mouse-drag zooming of the plots. But I came up with the mouse-cursor waveform measurement functionality and programmed that myself.

Still, if you really want to simulate that type of stuff (and any other circuits), I strongly recommend taking the plunge and downloading LT-Spice, from linear.com (It's free!). It's much easier in the long run, and much more powerful and flexible right away.

Regards,

Tom
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Old 17th January 2013, 03:23 PM   #252
bcmbob is offline bcmbob  United States
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Hey Tom,

I was going to ask for a walk through of the spreadsheet but as usual you were a step (several steps) ahead. I'm re-reading all the Rod Elliot PS related pages, but this time I'm taking the advice from that old book "Dinetics". Mr. Hubbard says you will never understand what you are reading if you skip over a single word you don't understand. Well, my Google finger is getting sore, but I'm having a lot of those "Oh, that's what they were talking about" moments.

Keantoken's tutorial on LT-Spice is also something many of us have needed. I have had the program installed for months but was very intimidated at jumping in.

Thanks again to all on the diyAudio Forum for such useful direction, patience and understanding to bring we less informed/experienced up to speed.
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Last edited by bcmbob; 17th January 2013 at 03:25 PM.
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Old 18th January 2013, 07:16 PM   #253
KSTR is offline KSTR  Germany
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Not much going on (too busy) but some progress in the supply evaluation (the planned local decoupling scheme), see here : Network Analyser Measurements. I hope I'll finally build the full proto this weekend....
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Old 18th January 2013, 10:08 PM   #254
gootee is offline gootee  United States
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Those measurements are very encouraging and an array on a real PCB might measure even better.

I'm guessing that the exact feed and measurement point locations might have a significant effect. I think that Terry Given guessed that the mid-points of opposite sides of a square array would be good, for the input and output points, based on trying to get the current to spread across the board so that the caps shared it more-equally (although with a square array I can't understand it very well). I would have guessed that a circular or octagonal array would be good.
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Old 20th January 2013, 02:55 AM   #255
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On a simpler note, I had a thought:
5x 100u per rail, as close as possible to pins 7 and 8
Rail to rail cap, tiny bypass caps and power cable at pins 13 and 15
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Old 21st January 2013, 02:35 AM   #256
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Default Board came in

I really like like Kean's idea, post 240, and will try it as soon as I get a 50 ohm multi-turn trimmer (to use as variable resistor).

The TDA7294 ebay kit, same board that Bob is using, has arrived in the mail.
My first first steps included, simplify the mute circuit for power/midrange quality, use audiometric size NFB cap for bass quality, increase the 22u bootstrap cap to 47u for bass quality, and. . .

At first, it looked possible to set the feedback resistor closer (as in the photo below); however, this is still out on the end of a long thin trace shared by the bootstrap cap, the long thin trace is inductive and running maximum gain for non-audio signal is poor design. So, actually, the feedback resistor needs moved trackside, to directly under the chip from pin 2 to pin 14.
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File Type: jpg TDA7294-SS-Board.jpg (95.2 KB, 258 views)
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Old 21st January 2013, 07:27 AM   #257
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Quote:
Originally Posted by danielwritesbac View Post
Here's some options that don't have a bass blocker effect:
150u with 3k3 fs and 68k fb, 22x gain

220u with 2k7 fs and 75k fb, 29x gain
220u with 2k7 fs and 68k fb, 26x gain
220u with 3k3 fs and 75k fb, 24x gain
220u with 2k7 fs and 56k fb, 22x gain

270u with 2k2 fs and 68k fb, 32x gain
270u with 2k2 fs and 56k fb, 27x gain
270u with 2k7 fs and 68k fb, 26x gain
270u with 2k2 fs and 47k fb, 22x gain

330u with 1k8 fs and 56k fb, 32x gain
330u with 1k8 fs and 47k fb, 27x gain
330u with 2k2 fs and 56k fb, 26x gain
330u with 1k8 fs and 39k fb, 23x gain

470u with 1k2 fs and 33k fb, 29x gain
470u with 1k2 fs and 27k fb, 24x gain
470u with 1k5 fs and 33k fb, 23x gain
How,which formula you are calculating,
At 1K,22k,what value will be for cap? ,At 220uf,1K,,what will be feedback R?
Thanks.

Last edited by simply14prem; 21st January 2013 at 07:31 AM.
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Old 21st January 2013, 10:35 AM   #258
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This schematic looks awesome
michel.terrier.pagesperso-orange.fr/radiocol/detail/tda7294.htm

Last edited by simply14prem; 21st January 2013 at 10:39 AM.
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Old 21st January 2013, 11:21 AM   #259
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Quote:
Originally Posted by simply14prem View Post
This schematic looks awesome
michel.terrier.pagesperso-orange.fr/radiocol/detail/tda7294.htm
Isn't that just extracts from the datasheet translated into French? Or am I missing something?
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Old 21st January 2013, 11:41 AM   #260
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Quote:
Originally Posted by geoffcooper View Post
Isn't that just extracts from the datasheet translated into French? Or am I missing something?
there is a diagram near the default pic.just that.unable to reproduce the full image.
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File Type: jpg SC201301c21-182020.jpg (17.6 KB, 214 views)

Last edited by simply14prem; 21st January 2013 at 11:55 AM.
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