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Old 25th April 2012, 04:26 PM   #1061
Siberia is offline Siberia  Lithuania
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sure thing, Salas, just wanted to know I've understood the logic behind the calcs
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Old 25th April 2012, 04:30 PM   #1062
Salas is offline Salas  Greece
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If you look back, I had posted a graphical method for projecting R1. It must be many posts before.
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Old 25th April 2012, 04:32 PM   #1063
Salas is offline Salas  Greece
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Located it: http://www.diyaudio.com/forums/power...ml#post2746266
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Old 25th April 2012, 04:45 PM   #1064
AndrewT is offline AndrewT  Scotland
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If you start with a 33r or 30r resistor and measure the CCS current from it's Vdrop, you can add as many more similar resistors until you reach the CCS current you require.

As each extra resistor is added you will find that the Vdrop changes slightly. This is due to the Vgs of the FET increasing with each increase in Id.
eg.
with one 30r fitted you may measure 1950mVdrop indicating 65mA
with two fitted it may be ~1930 indicating 64mA through each for a total of 128mA
for three, maybe 1920 showing a total of 192mA.
If you want exactly 200mA then you require an extra 8mA.
This would need a fourth resistor whose value would be ~1920/0.008 ~=240r
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Old 25th April 2012, 05:05 PM   #1065
Siberia is offline Siberia  Lithuania
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I see my main mistake, again. While looking at the graph I've mixed ID value of 0.2A with 2A. Thus high VGS. It explains why I was mediocre at maths in school and why I need double checking. Thanks.
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Old 25th April 2012, 07:36 PM   #1066
Murdoc is offline Murdoc  Germany
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Hi!
First of all thanks for the perfect boards and the work on the regs, too!
A few have been working in my buffalo for a longer time now, and now I'm going to complete a BA-3b build. This is why I have read many hours about star grounding and about preventing ground loop issues.

My questions is, what is the best practice on wiring the SSLV with a (pre)amplifier, in my case the BA-3.
a) As the SSLV uses remote sensing, the (twisted) cables should meet as close to the terminal of the BA-3 board as possible.
b) If it was an unregulated supply, I would set here a star ground, and wire it to the earth connector (seperated with a bridge rectifier || 10R || 100nf). Can I do the same with SSLV--BA3?
Is this the best way to get "perfect" ground, would this be a best practice?

Thank you for your help!

Best regards,
Matthias
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Old 26th April 2012, 12:05 AM   #1067
Salas is offline Salas  Greece
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There was a nice member posting here nicknamed ''backbones'' who has experience on BA-2 & BA-3 regarding SSLV1.1, maybe he can give you specifics if he will read your questions.

In general:
a) Correct
b) SSLV can be earthed centrally from the (-) pin of its smoothing capacitor (C105). Being a double rectifier symmetric system in your case, it can be tempting to try use it floating. Which is what you do with your bridge lifted plan (excluding fault condition) anyway.
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Old 26th April 2012, 10:29 AM   #1068
Murdoc is offline Murdoc  Germany
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Thank you Salas!

Hm, I think I'll try to "audio-ground" it shortly before it goes into the preamp. What pros and cons do you see for floating vs. grounding?

PS:
The buffalo had a floating supply all the time, but now I know. And how I'll do it if I place it in its new case. Here I see that I've learned a lot but by far not enough!
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Old 26th April 2012, 10:36 AM   #1069
AndrewT is offline AndrewT  Scotland
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Build it up in stages without a chassis. Keep the "mains" end well insulated for safety.
Get it all working with just a Main Audio Ground. At this stage there is no Safety Earth and no connection to PE.
Connect to the Power amp. And get that working properly.


Second to final.
Add in temporary "chassis" and make the PE connection and then the MAG to SE connection.
finally.
If it is still operating properly then you can work out how to package it with identical electrical connections.

There is no point in assembling inside a chassis and trying to experiment with grounding inside that chassis with the added complication of the PE & SE connections.
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Old 26th April 2012, 11:14 AM   #1070
Murdoc is offline Murdoc  Germany
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Hi Andrew!
You guided me in the right direction, I think I knew what I was aiming for but didn't exactly know how to get there. Thank you for this good advice, Andrew!

Best regards,
Matthias
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