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Old 22nd March 2014, 06:48 PM   #1
mravlca is offline mravlca  Slovenia
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Default USB isolator with shunt regulator

Hi guys! I just wanted to share with you my project. I came up with the idea to supply my ODAC with shunt regulator, I know this isn't anything new and that this has tried somebody before me.
Schematic for regulator was taken from salas and modified a bit, instead of 2SK170 I used BF862 and also power mosfets have been changed. The board is designed so that the isolator part and regulator can be separated if needed, I managed to make it to fit dimensions 75mm*43mm.
I made some measurements on scope and I couldn't see any unusual behavior, I hope I will source better scope and then post measurements.
With this device I have gained even better sound, now I have more dynamics and details have become more clear.

BR,
Ales
Attached Images
File Type: jpg usb isolator (7).JPG (415.9 KB, 575 views)
File Type: jpg usb isolator (8).JPG (391.7 KB, 555 views)
File Type: jpg usb isolator (9).JPG (388.2 KB, 541 views)
File Type: jpg usb isolator (10).JPG (467.3 KB, 534 views)
File Type: jpg usb isolator (11).JPG (417.2 KB, 518 views)
File Type: jpg usb isolator (12).JPG (416.4 KB, 205 views)
File Type: jpg usb isolator (13).JPG (391.4 KB, 215 views)
Attached Files
File Type: pdf sense_shunt_and_isolatr_scheme.pdf (27.6 KB, 194 views)
File Type: pdf sense_shunt_and_isolatr_pcb_top.pdf (38.5 KB, 55 views)
File Type: pdf sense_shunt_and_isolatr_pcb_bottom.pdf (25.0 KB, 48 views)
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Old 27th March 2014, 09:05 AM   #2
mravlca is offline mravlca  Slovenia
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Default Iccs measurments

I did some measurements to determine Iccs from IRF9610, maybe somebody will find this info useful.

Rccs (ohm) Iccs(mA)
8,2 248
6,8 288
5,6 339
5,1 360
4,7 388
3,8 452
3,2 509

I didn't go any further than this as USB devices shouldn't use more than 500mA.

BR,
Ales
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Old 5th April 2014, 01:12 PM   #3
mravlca is offline mravlca  Slovenia
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Hi guys!
In the file attached you'll find BOM and some other useful info.

BR,
Ales
Attached Images
File Type: jpg TOP.jpg (860.4 KB, 175 views)
File Type: jpg bottom.jpg (579.4 KB, 152 views)
Attached Files
File Type: zip UBS_shunt_BOM.zip (64.7 KB, 48 views)
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Old 6th April 2014, 05:51 PM   #4
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Hi mravlca

Could you provide some informations about :
1 - Electrolytics caps lead spacing
2 - P1 trimmer value, 500R ?
3 - Values for 3.3 & 5.0V Output
4 - SMD 100nF (1206) : mlcc type ?

I've noticed that R11 (Rccs) value sets current amount (Iccs).
Thank you for your answers, sorry for my noob questions

Regards

Phil

Last edited by korben69; 6th April 2014 at 06:01 PM.
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Old 6th April 2014, 05:59 PM   #5
maxw is offline maxw  United Kingdom
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Nice job!

Do you have a line input on your PC? Any chance of posting RMAA measurements comparing with and without the isolation?
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Old 7th April 2014, 12:27 PM   #6
mravlca is offline mravlca  Slovenia
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Quote:
Originally Posted by korben69 View Post
Hi mravlca

Could you provide some informations about :
1 - Electrolytics caps lead spacing
2 - P1 trimmer value, 500R ?
3 - Values for 3.3 & 5.0V Output
4 - SMD 100nF (1206) : mlcc type ?

I've noticed that R11 (Rccs) value sets current amount (Iccs).
Thank you for your answers, sorry for my noob questions

Regards

Phil
Hi Phil,

1 C9 7.5mm*16mm Panasonic FC 4700uF 16V can fit here, C6 & C10 5mm*10.5mm these two caps are a bit overkill in size
2 P1 has a value of 500ohm
3 I will test with my board and report it
4 X7R 50V

Quote:
Originally Posted by maxw View Post
Nice job!

Do you have a line input on your PC? Any chance of posting RMAA measurements comparing with and without the isolation?
Thanks! I hope I will be able to do that today.
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Old 7th April 2014, 01:46 PM   #7
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Thank for your reply.
I need more informations about :
1 - Q3/4/5/6 : SOT23 ?
2 - D5/6/7/8 Green Led 1206 : Voltage / mA / mcd ?
Thanks

Regards

Phil

Last edited by korben69; 7th April 2014 at 01:49 PM.
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Old 7th April 2014, 03:09 PM   #8
mravlca is offline mravlca  Slovenia
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Quote:
Originally Posted by korben69 View Post
Thank for your reply.
I need more informations about :
1 - Q3/4/5/6 : SOT23 ?
2 - D5/6/7/8 Green Led 1206 : Voltage / mA / mcd ?
Thanks

Regards

Phil
1 Yes, SOT-23.
2 2.1V/ 20mA/ mcd->birghtness isn't important

BR,
Ales
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Old 7th April 2014, 03:16 PM   #9
mravlca is offline mravlca  Slovenia
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Default RMAA test

I did some tests. As you can see there is difference between two measurements. 2nd picture is THD using USB isolator and 3rd picture is ODAC only. I believe that with better sound card we could see even bigger difference.

BR,
Ales
Attached Images
File Type: png Rmaa_test.PNG (38.5 KB, 82 views)
File Type: png USB_isolator_ODAC.png (5.4 KB, 79 views)
File Type: png ODAC.png (6.5 KB, 71 views)
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Old 7th April 2014, 03:55 PM   #10
maxw is offline maxw  United Kingdom
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Quote:
Originally Posted by mravlca View Post
I believe that with better sound card we could see even bigger difference.
Definitely. I'm guessing you are using an onboard line input with these measurements?
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