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Volume control for M3 - Page 2

post #16 of 19
12/8/09 at 9:00pm
Quote:
Originally Posted by nkk View Post
Any idea on when it will be done? As in, before spring break time this year, or after?
I have a mostly-working solution for PGA right now (just no board; but a working schematic and code). I'm debugging some code to make it work with the relay atten but that may be weeks off. hopefully not more than that and the relay project is my current focus. its also the most 'purist' way to go, at least compared to the op-amp based PGA solution.

otoh, if someone was looking for a surround 5.1 vol control, I would NOT suggest relays (lol).
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post #17 of 19
12/8/09 at 9:03pm
Quote:
Originally Posted by linuxworks View Post
if you feed a low noise power supply into this circuit, you should get good results
What power supplies have you tried that worked well, versus worked poorly?
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post #18 of 19
12/8/09 at 9:31pm
when I used a 10v chip (5v for digital and 5/-5 for analog; instead of the 12/-12 version of the chip) I used a tread feeding an rail splitter TLE chip. in one config, I was able to be just about *at* the noise floor of the gear we tested with (m-audio RME firewire box). and I remember in that config (months ago) that I was not able to hear any objectionable noise. it was a great setup! which is why I tore it down and was not able to get that level of quiet since ;( but I will, I just need to find all the right tricks to running this chip in the best light.

it could also be that I had more luck with the DIP 5/-5 version of the chip vs the SMD 12/-12v version. and fwiw, you can run the 12/-12 chip at 5v dual and it works just fine, in a pinch.

I might also have had a separate 5v logic supply for the PGA back then and now I'm sharing with the arduino. probably not a good idea.

I have some dc-dc converters that I bought as black box modules that I intend to try. I have one that creates dual 5 from single 5 and that might be useful on the DIP version. I realize that everyone hates dc-dc's but these chips do need isolated supplies (or they seem to benefit a lot from it, at least).
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post #19 of 19
12/8/09 at 9:46pm
Fair enough. I ask because I am helping prototype a... shall we say... competing solution?
I was going to power it initially with a LM317/LM337 regulator (LCBPS from Twisted Pear), but was also considering using their Placid BP shunt regulator if I have the funds.
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