glennb said:
One resistor per rail, and 2 rails, means that the total number of resistors is 2.
That is a very slight added noise, so I think it goes close to the other noise--the rectifier.
So, was the 1/2w of 2.2k resistors within workable specs? I was aiming for a lighter than usual, but still workable, value. I've got some on my TDA7294 and they've never turned brown.
sneih said:
In my opinion, that answer is "no."
Nordic gave us the maximum figure of 22nF for use at the diode bridge--so 100nF is too big.
You can use (recycle) a pair of those 100nF at the opposite end, the "output" end, of the power supply (just one per rail), but they're not for use at the diode bridge.
Something different goes on the diode bridge:
(Mark Houston's photograph)
See the right hand side of this photo.
Those are Ten Nanofareds
Notice that they are printed with "103" and do please click the attached photo (below) so you can print out the capacitor values chart.
You may omit the caps from the diode bridge.
Term: "Diode Bridge" = Bridge Rectifier
P.S. Thanks for the "workout." That tells me that I should probably eliminate (omit) the 10nF caps from my beginner's power supply thread--the number ten is on the rectifier and the number one-hundred is on the power supply board, and they're getting confused. Please don't take offense. I'm very grateful to have this information.
EDIT: OH!! I see how this happened! My power supply photo doesn't specify which end is input or output (although it does show a rectifier). Will fix!
Attachments
danielwritesbac said:
The noise of the resistor is totally swapped by the overall low impedance of the power supply. I suggest you read up on noise theory....
Yes, 2.2k 1/2W is fine up to about 40 volts. It will get hot on higher voltages.
]danielwritesbac said:
In my opinion, that answer is "no."
Nordic gave us the maximum figure of 22nF for use at the diode bridge--so 100nF is too big.
You can use (recycle) a pair of those 100nF at the opposite end, the "output" end, of the power supply (just one per rail), but they're not for use at the diode bridge.
Something different goes on the diode bridge:
(Mark Houston's photograph)
See the right hand side of this photo.
Those are Ten Nanofareds
Notice that they are printed with "103" and do please click the attached photo (below) so you can print out the capacitor values chart.
You may omit the caps from the diode bridge.
Term: "Diode Bridge" = Bridge Rectifier
P.S. Thanks for the "workout." That tells me that I should probably eliminate (omit) the 10nF caps from my beginner's power supply thread--the number ten is on the rectifier and the number one-hundred is on the power supply board, and they're getting confused. Please don't take offense. I'm very grateful to have this information.
EDIT: OH!! I see how this happened! My power supply photo doesn't specify which end is input or output (although it does show a rectifier). Will fix!
@daniel
btw i already finish my first power supply.
the power show as:
AC : 21 - 0 - 21
DC : 28.8 - 0 - 28.8
that is right?
btw my friend hand over this transformer but i don't know what ampere this transformer? can u guess for me?
thx u so much
Sneih, you may get a rough idea of the VA of your transformer by weighing it and comparing it to a list of different transformers (with the same voltages) for sale at somewhere like Farnell.
AndrewT said:
MJL21193 said:
My educated estimate is 156.32A.
sorry forget to attached picture...
hehe
sneih said:
Imagine a fully-charged capacitor value C farads connected in parallel with a resistor value R ohms; the capacitor discharges in an exponential decay curve such that after a time R x C seconds it's lost 63% of its charge
R x C is known as the 'time constant' of the circuit, symbol tau or 't' for ease, and if start =100V it's down to 37V after 1t, 13.7V after 2t, 5V after 3t, after 5t the capacitor has lost 99.9% of its charge and is effectively "flat".
Conversely, if you have an empty capacitor C charged through a resistor R the charge time follows an exponential curve such that the capacitor is 63% full after time R x C, 86.3% full after 2t, 95% full after 3t.
I should have just posted a link... 😱
what are the benefits of dual secondary vs CT vs dual transformer configuration, other than higher amps on the dual tranformer.
I use 24-0-24 CT standard transformer rated at 3A. it produce about +/- 32volts.
but a slight hum still audible if i stick my ears to the speaker. I already implement star ground configuration to the chipamp build.
or, maybe... just maybe, my mains doesnt have any earth connection. and maybe i should make an earth mains connection by sticking a 2meter copper rod to the ground.
I use 24-0-24 CT standard transformer rated at 3A. it produce about +/- 32volts.
but a slight hum still audible if i stick my ears to the speaker. I already implement star ground configuration to the chipamp build.
or, maybe... just maybe, my mains doesnt have any earth connection. and maybe i should make an earth mains connection by sticking a 2meter copper rod to the ground.
Check if moveing transformers, affects the hum, make sure RCA jacks are isulated from the case, make sure high power wires are not next to signal wires etc...
The only difference between dual secondary and CT is that with the dual secondary the coil at the center tab is cut in two halves. By connecting the two wires you basically have the same configuration.
The advantage of dual secondary is that you can also parallel the secondaries to get the double current.
I see no advantage of dual transformer, it is tricky to set them in parallel, both transformers need to have the same specs. If you set them in series, also both transformers needs to have the same specs. Maybe this can have some advantage on the shape.
+/- 32V and you use the TDA2050??
This is way to high, this can cause the hum....
Regards, Rolf
The advantage of dual secondary is that you can also parallel the secondaries to get the double current.
I see no advantage of dual transformer, it is tricky to set them in parallel, both transformers need to have the same specs. If you set them in series, also both transformers needs to have the same specs. Maybe this can have some advantage on the shape.
+/- 32V and you use the TDA2050??
This is way to high, this can cause the hum.... Regards, Rolf
IceCube said:
A probable advantage of the single transformer of double the VA is better regulation (a lower rise in voltage at low load).
As an example, for Clairtronic toroids my catalogue quotes regulation%:
- 30VA - 13.7%
- 50VA - 11.8%
- 100VA - 10%
- 160VA - 7%
- 300VA - 6.4%
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