EMU0204 mods for FFT measurements - Page 2 - diyAudio
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Old 5th March 2013, 11:13 PM   #11
davada is offline davada  Canada
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Quote:
Originally Posted by soundchaser001 View Post
Hi;

Can you tell me what OS and aproximately what kind of PC you are using?

Thanks

Matt
Sure.

I'm running XP on i5-2500 3.3GHzwith 3.17GB ram. Gigabyte board.

Cheers,
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Old 5th March 2013, 11:15 PM   #12
davada is offline davada  Canada
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Originally Posted by Ervins View Post
Also let us know your hardware, OS and signal generator.

Hi Ervins.

The generator is a 339A osc.
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Old 5th March 2013, 11:17 PM   #13
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Thanks;

Reason I asked was that there are forum posts (not in DIYAudio) indicating that E-MU driver for WIN 7 (what I'll be using) are not the best but the 0404/0204 both look ideal from a performance perspective. I haven't selected a soundcard yet.

Matt
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Old 5th March 2013, 11:19 PM   #14
davada is offline davada  Canada
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Originally Posted by RNMarsh View Post
Sunstantial development! Everyone on the planet will benefit from this spin-off project.
can such be applied to other ADC? Such as, the QA400?

Thx-RNMarsh
Hi RIck,

The QA400 is about 3dB below FS as it is. I don't think there is much that can be done with it. The input impedance can be brought down by replacing the 100k resistors with lower value
R's on the VCOM bias circuit to the buffer amps. I did observe lower noise from doing this but not that much.

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Old 5th March 2013, 11:32 PM   #15
davada is offline davada  Canada
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Quote:
Originally Posted by Bob Cordell View Post
David,

These are very nice results. Thanks for starting a separate thread on this. I look forward to seeing the details. I have a Juli@ that I really like, and will be interested to see if these mods may be applicable in some way.

Cheers,
Bob
Hi Bob,

I think these mods should be applicable to any sound card. I don't have a Juli@ or 0404 to play with but if you look at the chip set you can see what ADC or codec ESI used then get the data sheet for it.

The manufactures of the cards stick very closely to the IC's data sheet recommended input. If a high input Z is not needed then the noise can be brought down by lowering the input Z. But think the key here is to utilize the full input range.

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Old 6th March 2013, 12:00 AM   #16
davada is offline davada  Canada
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Quote:
Originally Posted by soundchaser001 View Post
Thanks;

Reason I asked was that there are forum posts (not in DIYAudio) indicating that E-MU driver for WIN 7 (what I'll be using) are not the best but the 0404/0204 both look ideal from a performance perspective. I haven't selected a soundcard yet.

Matt
Hi Matt,

I've heard that too. There is problem with the XP driver at 192ksps as well. I get some jumping of the noise floor every now and then. This same problem came up with beta version of SW for the QA400. It turned out to be a timing problem with one of the XP API. IIRC, QuantAsylum fixed the problem by increasing the delay time for sending the data packets.

I would think Creative would give the win7 issues more attention since the 0204 is still a current product. XP has it own issues and the reason for ASIO.

Cheers,
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Last edited by davada; 6th March 2013 at 12:02 AM.
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Old 6th March 2013, 12:06 AM   #17
glt is offline glt  United States
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Quote:
Originally Posted by davada View Post
...

Looking at EMU's input circuit I noticed that the full range of the ADC is not being used efficiently for our purpose. What is better for us is to use the full scale of the ADC for our measurement range. For me that is 0dB (1Vrms) reference.

...

Cheers,
What is the original full range? The spec says 6.5 dBv maximum input. Is this the original full scale?
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Last edited by glt; 6th March 2013 at 12:08 AM.
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Old 6th March 2013, 12:13 AM   #18
davada is offline davada  Canada
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Originally Posted by glt View Post
What is the original full range? The spec says 6.5 dBv maximum input. Is this the original full scale?
Hi glt,

I have only modded the one channel. I'll check the other later tonight. What you quoted sounds about right. When I post the schematic it will be clear.

Cheers,
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Last edited by davada; 6th March 2013 at 12:16 AM.
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Old 6th March 2013, 12:39 AM   #19
glt is offline glt  United States
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Hi David,
Thank you. Perhaps it is a good idea to just mod one channel in order to accommodate higher level sources in the other channel...
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Old 6th March 2013, 01:01 AM   #20
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Quote:
Originally Posted by glt View Post
Hi David,
Thank you. Perhaps it is a good idea to just mod one channel in order to accommodate higher level sources in the other channel...
Not a bad idea but if you want a reference channel for component measurement or corrected speaker measurements don't they have to be the same?
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