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Old 28th March 2013, 02:36 PM   #1861
AndrewT is offline AndrewT  Scotland
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22degrees is much more realistic.
60 degrees is not what we use/find.
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Old 28th March 2013, 03:51 PM   #1862
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Hi all,
sorry if it is already answered.
I don't want to read the whole thread
Is there any difference ideal capacitors size between dual secondary dual diode bridge
and center tap transformer with single diode bridge?


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Old 28th March 2013, 04:45 PM   #1863
DF96 is offline DF96  England
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It depends. An extra diode drop may or may not make a big difference, depending on how much spare voltage you have. To understand the issue you will need to read the thread. Sorry!
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Old 28th March 2013, 07:10 PM   #1864
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I did promise some pictures.

The first is a 24 VCT flatpack transformer driven two diodes into a capacitor (10,000 uf) and 50 ohm resistor. Note the unbalanced peaks which can indicate diode mismatch or unbalanced windings.

The second is the same circuit with only a 470 uf Capacitor doing the filtering and a toroid transformer with more than 10 times more current capability.

So you can get an idea of the maximum and minimum charging times. Note on the toroid it is the back side that lingers!
Attached Images
File Type: jpg Current Pulse 8 V Flatpak 10000 .1.JPG (91.4 KB, 176 views)
File Type: jpg Current Pulse Torroid 12V 470 uF Filter.JPG (93.1 KB, 172 views)
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Old 28th March 2013, 10:48 PM   #1865
DF96 is offline DF96  England
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First one dominated by transformer resistance; second one dominated by transformer inductance? One could imagine some ringing superimposed on the charging pulse in the second one. Just a guess.
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Old 29th March 2013, 07:44 AM   #1866
alayn91 is offline alayn91  France
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Hello,

Why is the scale voltage only 20mV ??

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Old 29th March 2013, 08:18 AM   #1867
Fob is offline Fob  Bulgaria
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I think the question is more complicated than it looks. Depends of PA topology, PS type and so on. I'll give an example.
There was japanese patent from '70s that prevent voltage drop to driver stages. The sound quality improvement is significant.
There is more issues. No one rectifier 'love' big capacitors. The diode recovery can inject significant spikes in the rails. Sometimes the 'shunt 100nF' to the main electrolytes are crucial ... so on.
Other things. If you have 'magnificent' sound in 75% from rated power is beter that 'good' sound in all power range ....
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Old 29th March 2013, 10:34 AM   #1868
AndrewT is offline AndrewT  Scotland
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I have an apology.
I was considering only 50Hz supplies.
Simon has shown the data for a 60Hz supply.
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Old 29th March 2013, 12:49 PM   #1869
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Quote:
Originally Posted by alayn91 View Post
Hello,

Why is the scale voltage only 20mV ??

Regards.
We are measuring current! The scope is calibrated in voltage it is a small resistor of .1 ohms in the ground leg we are viewing.
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Old 29th March 2013, 11:07 PM   #1870
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Gootee I didn't mean to drive you off. I was impressed by your math. Keep up the good work.
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