Rough draft, modified SOZ with CCS pull-ups & CPU biasing, need advice. - Page 2 - diyAudio
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Old 28th October 2003, 02:40 PM   #11
moe29 is offline moe29  United States
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i don't understand half of this... but i think i'm inpressed?

i'd never heard of CPU biasing... a little more explanation for the
neophytes out here?

can't wait to see pics!

m.
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Old 28th October 2003, 03:07 PM   #12
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The processor basically does 2 things.

1) it acts like a volt meter. eg: in the main amp section, it will measure the voltage over the 2 speaker outputs.

2) after measurements are made, it will adjust the bias voltage sent to the 2 gates on Q1 & Q2 so that my output is 50% of the supply voltage & the DC voltage difference sent to the speaker is under a microvolt.

In the processor module, there is the potential to store the 2 bias voltages being sent to the Q1 & Q2 gates which will move slightly with amp temperature & age. Downloading this to a PC would give you a graph of your Amps consistency. Sort of like the little diagnostic memory capability in some car's fuel injection system microprocessor.

This concept is not completely new, there are some microcontroler biased tube amps which corect for drift as the tube ages.
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Old 28th October 2003, 03:10 PM   #13
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And why so many bits in the ADC/DAC parts? Seems to me a simple microcontroller with integrated ADC/DAC will do the job. Well, maybe not grow lemons at the same time
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Old 28th October 2003, 03:15 PM   #14
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Default here is the psp...

Nothing special...


Here is the link to my pre-amp / attenuator PCBs.

http://www.diyaudio.com/forums/showt...002#post249002

Only the Balanced Zen Line Stage left, then I'll have made a complete system.
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Old 28th October 2003, 05:35 PM   #15
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Quote:
Originally posted by analog_sa
And why so many bits in the ADC/DAC parts? Seems to me a simple microcontroller with integrated ADC/DAC will do the job. Well, maybe not grow lemons at the same time
Microcontroller ADC are usually sufficient when taking multiple samples, however, I donít like their accuracy & drift factors. Compare this 4$ 4 channel switchable device: ADS1242

http://focus.ti.com/docs/prod/produc...Number=ADS1242

NOTE: my 2 audio in's go through a 1 Hz low pass filter.

For the dac, I figure 16 bit should be good enough. Something like this:

http://focus.ti.com/docs/prod/produc...Number=DAC8571

Can't use any dacs that need a maintained master clock since I want the processor board to shut down once the calibration is finished.

Now, the cheapest TI processor with 12bit internal AD = 3$, 14 bit internal AD = 7$. Cheapest processor is under 1$. None with a real DAC.

Now, from microchip, cheapest processor is < 1$, with 12bit AD = 2$, no 14 bit or above. None with a real DAC.

I figure using an 8 pin PIC12C508 with the 3$ 24bit ADC, and, 2 x 16 bit dacs (3$), for a total of 10$, it will kill the 7$ ti processor with the 14 bit AD before finding a 2 DACs for it.
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Old 31st October 2003, 10:21 PM   #16
Arx is offline Arx  Canada
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Might want to have a peek at atmel.
Typically a tad bit more expensive than Microchip, but a lot nicer IMO. Much nicer instruction set, lots of registers, less funny issues with memory allocation and tables and stuff.

I'm definately far from being an expert on the things, but from the little bit I've done, I've found my favourite.

l8r.
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Old 31st October 2003, 10:44 PM   #17
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Quote:
Originally posted by Arx
Might want to have a peek at atmel.
Typically a tad bit more expensive than Microchip, but a lot nicer IMO. Much nicer instruction set, lots of registers, less funny issues with memory allocation and tables and stuff.

I'm definately far from being an expert on the things, but from the little bit I've done, I've found my favourite.

l8r.

Too later, the design is finished, look here:

http://www.diyaudio.com/forums/showt...957#post257957
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