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Old 5th September 2012, 08:47 PM   #311
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Quote:
Originally Posted by dirkwright View Post
Walt Jung's article on current sources shows the LM317 + MOSFET as a good choice for up to 40mA. I don't know how it performs for noise.
I just ordered the parts for figure 13C from his part II article in Audio Express on current sources. I'm going to either remove or bypass the 100 ohm resistors on Victor's board.
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Old 5th September 2012, 09:29 PM   #312
richiem is offline richiem  United States
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For me, those hairs being split are distortion components below -120dBu, so some things matter more than others. For recording or listening to music, I'd happily use the EMU 0204.
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Old 5th September 2012, 09:33 PM   #313
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For me, those hairs being split are distortion components below -120dBu, so some things matter more than others. For recording or listening to music, I'd happily use the EMU 0204.
Well, reading the spec's on these things isn't always helpful, since I don't recall seeing one rated for better than -120dB at all yet some seem to measure better than that. So, I'm wading in a swamp trying to figure out which to get.
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Old 5th September 2012, 11:01 PM   #314
richiem is offline richiem  United States
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I understand, Dirk, I'm wading in there too. For my purposes -- measuring oscillator distortion in the 0.0001% area and less (sometimes much less), the SNR of these cards is not the ultimate spec, although more is always better. I can live with SNRs of 110dB just fine -- spectrum analyzer averaging helps clean that up to give noise floors of -130dBu and more.

The Gearslutz site has a nice comparo of the "transparency" of sound cards and modules that you'll find interesting. I've lost the link, but if you go there I think you can find it. Nice methodology, and very interesting results.

Larry Burk sent my some plots of an old EMU 1212M (PCI card) and the noise floor is relatively flat out to the 90kHz Nyquist limit. So I may look into one of those. Larry says it's a bear to use, tho'.
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Old 5th September 2012, 11:54 PM   #315
dimitri is offline dimitri  United States
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this Gearslutz link is not working
this might be helpful:
Audio interfaces and their AD/DA chips

Last edited by dimitri; 6th September 2012 at 12:10 AM.
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Old 6th September 2012, 01:40 AM   #316
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If I see another sound card that screams "7.1 channels! 24 bits! only 17.99$!!", I will scream.

I'm still convinced that the PCM4222EVM is a pretty good choice for me, since I can put it in a separate RFI and EMI proof box (that I am going to make myself), and it has balanced inputs.

Last edited by dirkwright; 6th September 2012 at 01:52 AM.
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Old 6th September 2012, 07:00 AM   #317
1audio is offline 1audio  United States
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1) The current noise of an LM317 won't be an issue with the shunt regulators and parallel caps. It would be if you were dealing with high impedances.
2) I suspect the interface circuit may be limiting the ADC's, The TI should be pretty adequate for most applications. The demo board is finicky and mine sometimes seems to stick in 16 bit mode.
3) A Lynx card is a good alternative but big bucks. I like the ESI card a lot. The HF noise is only an issue in a few cases. I also like the driver and mixer interface. Unlike most of the cards in this class the Juli supports 176.4.
4) The Juli can connect directly to the I2S interface of an ADC and DAC. Its a bit of a hack but it would be possible to hatch a replacement for the on board chips since the analog board is removable. But you are still hooked to a PCI interface.
5) The ESI Waveterminals were discontinued years ago.
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Last edited by 1audio; 6th September 2012 at 07:02 AM.
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Old 6th September 2012, 12:51 PM   #318
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OK, thanks 1audio. When I get the TI board, can I bug you about settings? I suspect it would perform pretty well in a good box with a quiet power supply.
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Old 6th September 2012, 04:31 PM   #319
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Please bug me about the TI board settings. They are a real PITA to get right. Also the changes to support external clocking. There is a problem on the board.
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Old 6th September 2012, 06:30 PM   #320
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I've found the 4222EVM rather easy to configure

The external clock thing is kinda less straightforward. It takes the external clock, divides it by 2, and works with it as internal oscillator. To get the 1x/2x/4x sampling frequencies, you'll have to stick to 22/24MHz oscillators. The "multipliers" actually are dividers built inside the PCM4222 ADC - for 1x (44.1kHz sampling) it divides the MCLK by 4 (4x - 1/4), 2x - 1/2, 4x - 1/1. You'll have to stick to 128Fs/256Fs/512Fs oscillators as the board won't support 192Fs/384Fs modes (limitation of DIT).

My spreadsheet with configuration settings - for PCM mode + it's sampling rates:
http://s3t.it/data/uploads/pcm4222evm_v0.1b.xls
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