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Old 20th May 2013, 09:36 PM   #121
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There are some mention of the Juli@ soundcard in this thread have anybody done any modifications to it?

Or have the schematics or traced some of the analog sections?

I though I would start looking a little closer on how its implemented tomorrow, and it would be nice to have a headstart.

I have noticed there is a pads for a 5x7mm oscillator right under the 22.579Mhz crystal with some luck that turns out to be a very convenient way to improve the x44.1K rates.
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Old 20th May 2013, 10:00 PM   #122
davada is offline davada  Canada
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The trouble with the EMUs and other sound cards is there are no schematics for them.
The best that can be done is to trace everything out and document it. This is difficult with SMT and getting values in circuit is a chore.

Good luck.
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Old 20th May 2013, 10:02 PM   #123
davada is offline davada  Canada
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Quote:
Originally Posted by RNMarsh View Post
Thanks -- as you can tell, i am unlikely to redo from scratch what others already did without details... too time consuming. Too many projects and trying to sell a house as well. So, i'll get back to this mod when i have more time. meanwhile, i'll try the eMu-0404 that i did a mod and use ARTA with it. I want to see if either e-Mu model is better than the QA400 in accuracy at low distortion levels.

Thx-RNMarsh

One EMU0204 may not be the same as another. Things do go through revision and the part designators maybe different. I'm too busy to do anything myself right now.
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Old 21st May 2013, 08:26 PM   #124
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Quote:
The trouble with the EMUs and other sound cards is there are no schematics for them.
The best that can be done is to trace everything out and document it. This is difficult with SMT and getting values in circuit is a chore.

Good luck.
Indeed but alteast the components are numbered..

To make matters worse the Juli@ PCB is covered in some thick white surface counting making following surface traces almost impossible, even under a microscope. Luckily they are only using 0603 components so most of the resistors values are readily readable.

Anyway I mounted a pair of 0402 47ohms across the ADC inputs to get some sense of the analogue parts influence on the noisefloor, I will try to improve the decoupling and the Vref filtering tomorrow to see what effect that gives.
Attached Images
File Type: png 47R_Left_88k2.png (132.2 KB, 320 views)
File Type: png 47R_Left_96k.png (82.6 KB, 270 views)
File Type: png 47R_Right_88k2.png (82.6 KB, 267 views)
File Type: png 47R_Right_96k.png (82.4 KB, 263 views)

Last edited by Tazzz; 21st May 2013 at 08:29 PM.
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Old 22nd May 2013, 12:28 AM   #125
RNMarsh is offline RNMarsh  United States
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to what extent is the ADC distortion characteristtics/dynamic range attributed to the operational range limitation of dropping down to 3v operating level?

-RNM
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Old 22nd May 2013, 02:41 PM   #126
1audio is offline 1audio  United States
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Quote:
Originally Posted by Tazzz View Post
There are some mention of the Juli@ soundcard in this thread have anybody done any modifications to it?

Or have the schematics or traced some of the analog sections?

I though I would start looking a little closer on how its implemented tomorrow, and it would be nice to have a headstart.

I have noticed there is a pads for a 5x7mm oscillator right under the 22.579Mhz crystal with some luck that turns out to be a very convenient way to improve the x44.1K rates.
There is a bunch of stuff on the web for the Juli card but its mostly focused on digital playback. The pads for the oscillator on the back I think are misleading. The card as is is pretty free of jitter. I measured less that 20 pS wideband. On a JTest its also very clean It does have other noises. You can see them in the attached plots.

The opamps are a limitation since nothing else uses that footprint. I have not done measurements with the balanced interface.

I would use (and do use) an external capture card connected with SPDIF. You get isolation and can run it 50' away if needed.
Attached Images
File Type: png Juli -3 dBV distortion.PNG (65.1 KB, 255 views)
File Type: png Juli -3 dBV distortion wide band.PNG (64.0 KB, 70 views)
File Type: png Juli -3 dBV distortion and jitter.PNG (56.8 KB, 74 views)
File Type: png Juli Jtest.PNG (59.8 KB, 77 views)
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Old 22nd May 2013, 02:55 PM   #127
HpW is offline HpW  Switzerland
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Quote:
Originally Posted by 1audio View Post
The card as is is pretty free of jitter. I measured less that 20 pS wideband. On a JTest its also very clean It does have other noises. You can see them in the attached plots.
Currently I do not see the real JTest....

The test is based on a 16 Bit source with a LSB toggle, the strong signal is Fs/4 signal (level may -6 dBFS or else) & LSB Toggle at Fs/192.

Then you will see low level & low freq. square wave (with its fourrier compnents) abr. at -96dBFS and a strong signal at fs/4. The fs/4 signal should be zoomed in to get the phase noise or to see symmetric signals (not a periode of the LSB toggle)...

Or visite my home page and naviagte to Support\HpW Tech
my 2 cents on this

Hp
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Old 22nd May 2013, 03:52 PM   #128
1audio is offline 1audio  United States
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You are right, it isn't a standard Jtest. Its a measurement I made some time ago and I didn't document all the details. Its a measurement of the capture side. The 8 KHz bandwidth comes from the presentation at Stereophile. When I get my shop back up and running I'll redo it.

I'm not sure that a low level signal on top of a main carrier will show anything on a capture system. Is there a better method of verifying jitter on the ADC side? Do you have a JTest file that you can share as a source? I have several but I'm not sure of their freedom from errors.
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Old 22nd May 2013, 07:08 PM   #129
HpW is offline HpW  Switzerland
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Quote:
Originally Posted by 1audio View Post
I'm not sure that a low level signal on top of a main carrier will show anything on a capture system.
16 Bit LSB toggle = a square wave should be clearly visible on a 24 bit DAC & ADC.

Quote:
Originally Posted by 1audio View Post
Is there a better method of verifying jitter on the ADC side?
The best so far if the source master clock is 100% in think with the ADC, then you do a coherent measurement and any FFT Window may will be not required.

Quote:
Originally Posted by 1audio View Post
Do you have a JTest file that you can share as a source? I have several but I'm not sure of their freedom from errors.
this is nicely integrated within my wave generator with various D-Jitter alike signals.

hp
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Old 1st June 2013, 10:00 AM   #130
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Here is what I get with the following small changes:

Two LT1117 replaced with LT1763 (one of these is 5V analog supply and the other general 3.3V digital)
Addition of 680uF/4V poscaps on the ADC Vref decoupling
100nF//10uF (0603) decoupling around the ADC
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