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Old 24th July 2012, 12:24 PM   #251
tsiros is offline tsiros  Greece
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so you mean that while electrolytics (not electrolytes) are a good way to stabilize the voltage, they are not the best source of power when the amplifier stages need it? and that for that purpose you need smaller but faster responding capacitors?

frankly i doubt electrolytics are "slower" to respond. they are pretty much as fast as electrons can respond.
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Old 24th July 2012, 12:45 PM   #252
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Electrons can be the same, but the road can be short and smooth, or long and bumpy.
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Old 24th July 2012, 01:44 PM   #253
MiiB is offline MiiB  Denmark
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I think what you see on the scope shots is the charging and de-charging slopes. if you cap bank was faster or bigger the rising slope would be steeper, the de-charging follows the current pull through the load resistor and would as such resemble at DC current pull through the amplifier. For me this looks like the two things that the caps needs to do, one: to get charged and hold the charge, two. to supply the current to the music load. I still see a separation of these two events as a positive. So the supply must could/must then be divided in two...One crude and big for the charging and one smaller faster for the signal.. the two banks is separated by a resistor or a coil to ensure a smallish voltage drop to the Signal-bank
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Old 24th July 2012, 01:52 PM   #254
PChi is offline PChi  United Kingdom
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Quote:
Originally Posted by forr View Post
Hi,

Here is a symetrical power supply 2*10000 F.
Each rail is loaded by a 39 Ohm resistor connected to ground.
Mains was provided through a Variac transformer with a slow increase
in voltage at start-up to avoid current peaks.

Click the image to open in full size.
A power supply using 2*10000 F,
voltage mains adjuted to get 2*29V DC voltage.


Click the image to open in full size.
Voltage and waveform on each rail.

Click the image to open in full size.
Details on the ripple waveforms.


Click the image to open in full size.
Addition of 44000F in parallel with the positive rail 10000 F cap.

Click the image to open in full size.
Details of the ripple waveform with 54000 F.

As expected, the ripple is reduced, however its shape is not
the familiar almost triangular waveform and should content
more high frequencies components than with 10000 F.
More or less current does not change much this shape.
I wonder what is the cause of this "distorsion".

I have done these experiences with two power supplies from amp
manufacturers, B&O (3300 F for a 2*20W) and Marantz
(2*10000F for 2*100W shown here). With these values,
they certainly did not want oversize the size of their reservoir.

Could the preservation of the neat triangular waveform of ripple
be a criterion to choose the optimal value of caps of a power supply ?
I think that your waveform distortion on the positive supply is voltage drop caused by the rectifier current.
It's either due to where the Oscilloscope probe is connected when the extra voltage drop is due to the resistance of the wire and connections (What does the waveform look like when the Oscilloscope probe tip and ground are connected directly to the capacitor terminals).
Or the electrolytic capacitor ESR is rather high. The capacitors suggested in post #54 look good.
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Old 24th July 2012, 01:52 PM   #255
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Quote:
Originally Posted by MiiB View Post
the two banks separated by a resistor
Why settle for a fixed resistor value.
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Old 24th July 2012, 03:56 PM   #256
MiiB is offline MiiB  Denmark
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could also be a coil....or an active device probing the current draw...
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Old 24th July 2012, 04:05 PM   #257
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Next stage would be such a setup for each individual output device.
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Old 24th July 2012, 04:37 PM   #258
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Quote:
Originally Posted by jacco vermeulen View Post
Omega power amp, Class.
I miss the larger main caps with screw terminals (e. g. Sprague etc.)
as usual to find by older models like this:
AudiogoN Forums: Review: Classe Audio 70 Amplifier
Quote:
Originally Posted by forr View Post
Hi,

Here is a symetrical power supply 2*10000 F.
Each rail is loaded by a 39 Ohm resistor connected to ground.
Mains was provided through a Variac transformer with a slow increase
in voltage at start-up to avoid current peaks. ?
thank you for this detailled report.
actually you need an additional test with an amp and tone bursts at various level and various amplifier loads similar like this about
http://www.marklev.com/IMF/TLS80/tls80tonburstbass.jpg. Then more differences there occurs.
There are to find several amplifier tests in this kind in the German test magazine "Production Partner" - go to
http://www.quoka.de/unterricht-liter...neuwertig.html
As load will be used impedances from 16, 8, 4 and 2 ohms.
the increase in output power nearly inversely proportional to the reduce of the load impedance down to 2 ohms, one can be sure, a strong power supply was installed.
Unfortunately you will not find such investigations in typical audio magazines (i. e. for home audio and car hifi)

Last edited by tiefbassuebertr; 24th July 2012 at 04:56 PM.
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Old 24th July 2012, 05:00 PM   #259
MiiB is offline MiiB  Denmark
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Jacco. that part I'm not so sure off...but to separate the voltage from the current would be nice...
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Old 24th July 2012, 05:08 PM   #260
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Quote:
Originally Posted by tsiros View Post
so you mean that while electrolytics (not electrolytes) are a good way to stabilize the voltage, they are not the best source of power when the amplifier stages need it? and that for that purpose you need smaller but faster responding capacitors?

frankly i doubt electrolytics are "slower" to respond. they are pretty much as fast as electrons can respond.
Elcos have a much higher ESR/Z ratio than metal films and they have a higher ESR/Z ratio again over ceramics.
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