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Old 7th March 2013, 12:40 PM   #321
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"In my experience SMD X7R are very poor when it comes to current handling capability, you have to parallel them almost 30X in order to ensure trouble free operation when pumping multikilowatt into 2 ohms load.You haven't seen them blasting and evaporating in the air."

What about using this foil cap series?

http://www.paktron.com/pdf/Capstick_CB4.pdf
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Old 9th March 2013, 08:02 PM   #322
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...looking good, but hard to get.
Do you know a source, where private people can order them?
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Old 9th March 2013, 09:43 PM   #323
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If you want I can try to get you some. We once built them into a power supply, but then they got replaced by many parallelled ceramics for cost reason.
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Old 9th March 2013, 10:29 PM   #324
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That's a nice offer, but not necessary.
I am generally avoiding to design in components, which I cannot get easily by regular shopping. ...so I will stick my paralleled X7R and go for double stacked in order to gain margin for reliability ...
Even without double stacking they are handling the hottrodding well up to now.
Also while working on the OCP adjustment with output currents up to 60A, they did not complain.
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Old 10th March 2013, 08:22 AM   #325
Baldin is offline Baldin  Denmark
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Quote:
Originally Posted by ChocoHolic View Post
...sudden silence?
I guess you want to say: Stop optimizing, but release the builders package.
Ok, understood. And since the over current protection is working now as well, I think the design is mature enough to go for the builders package.
This week and coming week will be very busy in work, so I cannot promise a schedule for the builders package - but I am starting to prepare the data for V1.3.
It's a very impressive design, with impressive performance.
If I could just get my small (low watt) designs to work as good

Super work, Choco
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Old 10th March 2013, 06:19 PM   #326
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Default Builders Package

The attached builders package already include a fundamental EMI improvement.
Earlier I mounted all Mosfets and diodes with a ceramic isolator to the heat sinks. Q309, D311 and D313 carry the jumping voltage of the switching node at their back plane and spread the RFI across the entire heat sink. Not clever.
I introduced a grounded shield between the heat sinks and Q309, D311 and D313. The shields are directly connected to GND close the switching stage.
The heat sinks are now connected by a RC to GND, 1Meg parallel 100nF.
With this improvement the disturbances of the proto open on the workbench are low enough to have just medium disturbances on my FM alarm clock while the amp is playing music at full power.

Have fun with the attached builders package.
The PCB is intended to be with 70um copper. 35um will still work, but most likely stressing some of the tracks close to melt down when running the amp in heavy duty.
Please note that this is an advanced project and employs high voltages, which can cause lethal injury.
Also regarding assembly and getting it running it is not the right project for beginners.

Looking forward to see your builds coming. I will support you in case of questions.
Attached Files
File Type: pdf SystemD_2k4_Supply.pdf (74.6 KB, 232 views)
File Type: pdf SystemD_2k4_Modulator.pdf (118.4 KB, 226 views)
File Type: pdf SystemD_2k4_Power.pdf (150.1 KB, 246 views)
File Type: pdf PCB_V1_Front.pdf (206.9 KB, 186 views)
File Type: pdf PCB_V1_Back_seethroughfromtop.pdf (131.1 KB, 146 views)
File Type: pdf PCB_V1_Back_viewfromback.pdf (131.4 KB, 135 views)
File Type: pdf SystemD_2k4_BOM_V1dot3_2013March10th.pdf (482.6 KB, 179 views)
File Type: zip SystemD_2k4_PcbVendorFiles.zip (152.5 KB, 123 views)
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Old 10th March 2013, 07:13 PM   #327
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Some more information.

The +/-82V should be in the range +/-65V....+/-83V. It also plays at lower voltages, but it does not really make sense to run such an amp at low rails.

The +/-12V must be within +/-11V...+/-14V (can be a wall plug).

The Drv must be a floating 15V...22V connected with its minus to the -82V (can be a wall plug). For higher voltages R403 must be increased. For voltages above 25V R403 and the heat sink of Q401 must be increased.

Last edited by ChocoHolic; 10th March 2013 at 07:14 PM. Reason: ...to many typos...
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Old 16th March 2013, 03:32 PM   #328
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Default Towers of X7R

V1.3 already includes the double stacked rail caps right at the switching stage.
But I didn't have a proper picture in the Excel sheet, so I highlighted this in the BOM and the verbal description - but had to use the unstacked picture.

Now two pictures which show the double stacked caps.
Also the construction of the CuBars between MosFets and series diodes is shown. Ensure that the distance between the CuBars and any cap is at least 1mm.
Using the dual pin rows is making life easier during assembly and service.
If you use pin rows with a 2.54mm spacing make sure that you pull out the unused pins - not just lazzy cutting.
Needless metal parts in a high power switching stage are always a unnecessary risk.
Attached Images
File Type: jpg Doublestack1.jpg (131.6 KB, 504 views)
File Type: jpg doublestack2.jpg (117.0 KB, 492 views)
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Old 16th March 2013, 10:44 PM   #329
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Besides the picture, I noticed a critical thing missing in the GetItGoing part.
For the 12V operation I advise to put additional resistors of 1k8 and 3k3.
Later at higher rails I just told to remove the 3k3... Of course also the 1k8 has to be removed as well !
If you miss this, most likely the IRS20957 will be fried.
Sorry for this, hope there are no accidents so far.

I am attaching again the full updated package.
The BOM-file now contains the new picture and removal of both resistors.
All other files are unchanged.
Attached Files
File Type: pdf SystemD_2k4_Modulator.pdf (118.4 KB, 108 views)
File Type: pdf SystemD_2k4_Power.pdf (150.1 KB, 87 views)
File Type: pdf SystemD_2k4_Supply.pdf (74.6 KB, 78 views)
File Type: pdf SystemD_2k4_BOM_V1dot3_2013March16th.pdf (521.1 KB, 103 views)
File Type: pdf PCB_V1_Front.pdf (206.9 KB, 86 views)
File Type: pdf PCB_V1_Back_seethroughfromtop.pdf (131.1 KB, 83 views)
File Type: pdf PCB_V1_Back_viewfromback.pdf (131.4 KB, 79 views)
File Type: zip SystemD_2k4_PcbVendorFiles.zip (152.5 KB, 59 views)
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Old 17th March 2013, 03:30 AM   #330
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Nice & Easy builder's package Choco

I like those mighty X7R towers standing in authority over the rails looking for any potential HF ripple escaping from the shackles of command which forces them to go to GND.
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