Build Thread for TPA BIII + Ian Async I2S FIFO + OPC NTD1 + Salas SSLV - Page 31 - diyAudio
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Old 28th November 2012, 02:42 AM   #301
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Quote:
Originally Posted by hochopeper View Post
I agree.


bigpandahk, The calcs I did above were to show how easy it would have been to calculate the temps expected before just trying it and waiting to see what would happen.




Also, what were you planning to use as an input to these regs?
I will simply use capacitor (6800uf) filter for the input to these regs.
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Old 28th November 2012, 02:44 AM   #302
qusp is offline qusp  Australia
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Quote:
Originally Posted by bigpandahk View Post
I will simply use capacitor (6800uf) filter for the input to these regs.
I think he means what voltage...
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Old 28th November 2012, 02:51 AM   #303
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Patient and planning are things I don't have. It I have implemented changes step by step with planning ahead, I wouldn't burnt the BIII

Thanks for your words and will remind myself to be patient and plan for all works.
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Old 28th November 2012, 02:52 AM   #304
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Originally Posted by qusp View Post
I think he means what voltage...
12Vac
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Old 28th November 2012, 02:59 AM   #305
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Originally Posted by bigpandahk View Post
12Vac
With 12V AC you can calculate the average and max/min ripple voltage after your rectifier.

Then you know the voltage input on your regulator and you already know the current draw and voltage out and power is easily determined. Spending a few minutes scratching on a piece of paper or in a spreadsheet to work these things out is very much worthwhile. You really should do this anyway so that you know your ripple voltage won't drop below the regulator's output voltage. This will allow you to select the correct transformer. You may then find that you would be better with a 5, 7 or 9V AC secondary. You also might want to calculate full load and no load voltage on your transformer, considering your actual loads not just the max/min voltage that is based on the transformer rating.

If you have that many transformers to include in one case then I'd really start thinking about getting a custom toroid made. I have one that has 6 secondaries. qusp's have how many secondaries? More than that again though. They don't come cheap but save you on enclosure space...

Last edited by hochopeper; 28th November 2012 at 03:02 AM.
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Old 28th November 2012, 03:01 AM   #306
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way too high, thats an LDO, it can probably survive on 100mV drop at these currents (look it up) it will die instantly being asked to supply 100mA and swallow what 7V? with NO heatsink?

hey we all rush ahead sometimes with new toys, but you need to make sure the system is locked down before you add something new, its much easier to predict and notice problems if you know what to expect under normal operation.

the NTD1 is going to be a test, not a complicated build really, but if malfunctioning....
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Old 28th November 2012, 03:10 AM   #307
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Quote:
Originally Posted by hochopeper View Post
If you have that many transformers to include in one case then I'd really start thinking about getting a custom toroid made. I have one that has 6 secondaries. qusp's have how many secondaries? More than that again though. They don't come cheap but save you on enclosure space...
10 secondaries, I have 2 hehe. each secondary current is different, designed to feed a specific pre-regulator for a specific regulator for a specific dac pin.... $140 ea for high quality potted custom toroids, saving this much space and taking the place of 4-5 transformers it works out not too bad
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Old 28th November 2012, 03:49 AM   #308
AR2 is offline AR2  United States
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All wise advices. I think with these digital circuits, power supply is the biggest task one has in construction. Separating power lines for analog, digital and clock, for DAC, than add FIFO, than add separate lines for source, in my case USB to I2S with separate, again, clock 7.5 V and 5V supply, than Arduino supply, and again in my case separate supply for VCF display...

If I was starting now, it would be much easier and I would definitely go for custom Tr. since I could forsee all of the elements. Problem is when things evolve during construction, and plans change.

As for the LDO regulators, I like Linear Systems LT3080. If space allows, sometimes having pre regulation and than another regulator is a good way of solving higher step down voltage. By all means, it is better to have the right transformer, but if you are stuck for some reason, having two regulators is not bad ether. And that is before it hits boards, that in almost all cases have their own on board regulators. That is definitely better than burning one reg with too high voltage dropout.

One reason why this TI TPS7A4700 is so attractive is because selecting voltage is so easy. I could see a nice project - board with several of these regs where user could select voltages with terminator blocks. One bigger board, but still smaller than if all is done separately. And by following very important advice from Hochopeper, heat calculation before hand will save a lots of agony.
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Old 28th November 2012, 05:23 AM   #309
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I have to seriously consider custom made transformer but I don't have a good source for high quality potted custom toroids
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Old 28th November 2012, 05:34 AM   #310
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sumr magnetics, avel lindberg, tortech and harbuch may also do it I think. That's a few off the top of my head just now. There are certainly others, though if you go that route you'll certainly need to have all your requirements calculated and regulator choices bedded down first.
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