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Old 15th October 2012, 03:45 AM   #1451
AJT is offline AJT  Philippines
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Quote:
Originally Posted by danielwritesbac View Post
Q: Why does extra large power supply capacitance make my amp sound dull?
A: The power supply board to amplifier board umbilical cable is too short.

P.S.
In extreme circumstances or for compact layouts that don't have an umbilical cable at all, Diode//Capacitor (like MR//3n3) can substitute instead of the long cable.
in my super leach amp i used 2 x 56,000ufd/100volt nichicon computer grade caps, the sound is fantastic to those who heard the amp play.....no dullness at all, whatever that means....
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Old 15th October 2012, 04:28 AM   #1452
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Quote:
Originally Posted by Tony View Post
in my super leach amp i used 2 x 56,000ufd/100volt nichicon computer grade caps, the sound is fantastic to those who heard the amp play.....no dullness at all, whatever that means....
That means good power circuit layout. Kudos! Not all amplifiers have fortunate power circuit layout.
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Old 15th October 2012, 04:43 AM   #1453
AJT is offline AJT  Philippines
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thanks, that amp is more than 20 years old now and is up for refurbishing, i am going to use new trannies from On semi and a pair of 68,000ufd/100vdc 105*C Hitachi computer grade caps purchsed from Apex Jr. for about U$25 each....
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Old 15th October 2012, 04:49 AM   #1454
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Daniel, I have to agree that the the constant string of abstract terms you seem to pluck out of the air is extremely frustrating to follow. Instead of blasting away at the keyboard, pouring out your own internal dialogue, consider others who are trying to communicate with you. You must try to remember that you write for forum readers, not just to mirror your own abstracted thoughts. I realise that your peer groups may follow you perfectly but most here will have no clue what you refer to, however widely accepted you consider your notation or terminology to be.

We are real and individual people out here and we also have our ruminations and silly thoughts too but unless you are a good comedian this will all be lost and leave everyone, including yourself, with a string of question marks hovering overhead. Please, slow down, compose, reread and edit your message as if you were writing to a distant cousin or explaining a crystal radio to a 10 year old.

I'm also actually interested in what you have to say but do please indulge us in a little more common English and standard terminology.
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Old 15th October 2012, 05:10 AM   #1455
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OT: i guess that is his style.....but there are many here who write in an easy to understand manner, i specially like PRR, learned a lot from him.....nanana, BudP, smoking-amp, tubelab and a lot more ..... ...
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Old 15th October 2012, 08:39 AM   #1456
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Thanks Ian. Thanks Tony.
I really do try.
Perhaps a couple of photos?
The length of the umbilical cable can be as short as 1mm.
Attached Images
File Type: gif Power_Monobloc_D-C.gif (6.5 KB, 122 views)
File Type: gif Power_Virtural Dual Mono_D-C.gif (13.9 KB, 121 views)
File Type: gif CRC_Power_Virtural Dual Mono_D-C.gif (16.0 KB, 126 views)
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Last edited by danielwritesbac; 15th October 2012 at 09:04 AM.
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Old 15th October 2012, 10:39 AM   #1457
DF96 is offline DF96  England
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Quote:
Originally Posted by danielwritesbac
D//C is exactly as it says, 1 diode paralleled with 1 capacitor.
No, a diode paralleled with a capacitor could perhaps be written D||C, provided your readers knew that you always write D for diode. I guessed that the C mean capacitor, but I had no idea what a double division meant. Please don't try to invent new symbolism as it just inhibits communication. Just learn existing symbolism.

Your apparent concern about charge or signal flowing back to the reservoir cap seems to me to be entirely misplaced, and based on an incorrect mental model of how PSUs work. I find circuit theory is usually the best option. It has the merit of being based on sound science.
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Old 15th October 2012, 12:31 PM   #1458
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Daniel has a very fertile imagination....he sees electrons and currents flowing every which way it seems........

what i know up to this time is that current flows from a higher source of potential to the lower one......
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Old 15th October 2012, 05:46 PM   #1459
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Quote:
Originally Posted by danielwritesbac View Post
Thanks Ian. Thanks Tony.
I really do try.
Perhaps a couple of photos?
The length of the umbilical cable can be as short as 1mm.
Your implementation of the diodes does NOT seem to be a practical approach, and I believe that the diode drop is reducing the PS rail voltage. Did you ever simulate the performance of the circuit with and without the paralleled diode and cap??? Remember, this is just the power supply. There is a tenuous connection to what you would actually "hear" from the amplifier, so do not do listening tests to "proof" your tweaks!!!

Out of the three you presented, the right most one has the most merit. I have recently realized that a single pair of caps can't offer the advantages of two banks of caps with a resistor in series with the rail in between to create a low-pass RC filter. Choose the resistor value so that the corner (-3dB) frequency is about 15 Hz and the mains noise and ripple harmonics will be strongly attenuated. In the figure, I am referring to the 0.22R resistor and the 10,000 uF caps. By the way, this is a pretty small capacitance for a PS unless the amp is only putting out something like 20WPC (for a class AB amplifier). If you are not sure what I am talking about, read up on RC low-pass filters, etc...

So taking your PS schematic:
Click the image to open in full size.

Here are my suggestions:
  1. GET RID OF THE DIODES (to the right of the bridge rectifer... you might need those)!!!
  2. Where there was a cap in parallel with the diode, get rid of that too
  3. Don't bother with the snubbers on the diode bridge. The single series resistor in between the two banks of caps attenuates any diode ringing.
  4. Increase the 0.22R resistor to 1 ohm and use a wire-wound 5W or larger ceramic/sandstone power resistor. When used in conjunction with the 10,000uF cap, this gives you the 15Hz corner frequency I mentioned.
  5. Eliminate the 2.2n+1R snubber
  6. Do you really need LEDs for your rails? A PS is not a christmas tree.. but do use a 1k ohm 3W resistor to bleed the caps at turn off (or omit, they will bleed themselves eventually).

NOTE:the star as you have drawn it is OK with the dual bridges off of dual secondaries as shown. If a center tapped transformer with a single diode bridge is used DO NOT use a single star as shown. Instead, the first pair of caps must be connected with the transformer secondary at a single point, then a WIRE must connect this point to the point in between the second pair of caps, and that is where the earth ground should be connected and all grounds should return. This will restrict the strong current pulses coming from the diode bridge to the first pair of caps. I'm not sure why the other espousers of this practice (AndrewT, Sreten, etc.) have not made this more clear. It is important to note that you absolutely can not pull that off if there is only a single pair of reservoir capacitors.

So, attached are the two topologies I am suggesting.

-Charlie

.
Attached Images
File Type: jpg dual_secondary_PS.jpg (25.5 KB, 107 views)
File Type: jpg center-tapped_secondary_PS.jpg (18.9 KB, 45 views)
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Old 16th October 2012, 03:11 AM   #1460
gootee is offline gootee  United States
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Quote:
Originally Posted by CharlieLaub View Post
<snipped>
Remember, this is just the power supply. There is a tenuous connection to what you would actually "hear" from the amplifier, so do not do listening tests to "proof" your tweaks!!!
<snipped>
-Charlie

.
Actually, almost always, the power supply capacitor current is exactly the signal that you hear. For very-convincing "proof", see the image from an LT-Spice simulation that I attached to post # 372 of this thread:

Power Supply Resevoir Size

Cheers,

Tom

Last edited by gootee; 16th October 2012 at 03:15 AM.
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