Bob Cordell's Power amplifier book

[Mark Johnson]

Why not buy it? Then you can read whatever sections you desire, without having to depend upon the kindness of strangers



YouTube link

 

[AndrewT]

I have it but I don't have the fourth edition, so I can't look at 4th figures 5.39 & 5.40 to see what is required.

 

[stuartmp]

Hi all. On page 383 of Bob's book he talks about film type snubber capacitors. I was just wondering are tantalum capacitor ok to use or are film type capacitors better. If so please provide a explanation and details so I can understand.

Thanks.

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[AndrewT]

tantalum are polar, film are non-polar
tantalum are low voltage usually <=50Vdc, film are higher voltage usually >=50Vdc, 35Vac

That bag of small yellow possibly 0.2" pin pitch look like Hi-K ceramic.

 

[stuartmp]

Thanks Andrew. I did not realise that they were Hi-K ceramic. Thank you for your explanation

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[AndrewT]

if the ceramic have a black cap then that usually means NP0/C0G
Those size of beads in 100pF and with a black cap would be NP0/C0G

Ask the Members that control these posts to move these last four posts to a new, or old Thread.

 

[stuartmp]

What is the best type of capactors for bridge rectifier capacitors.. part numbers would be a great help so I can read the datasheet.

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[AndrewT]

You don't have capacitors in a bridge rectifier.
Do you mean what type of capacitors do you need to create a damping Zobel across the transformer inductance?
The resistor absorbs the energy of the ringing and the capacitor helps prevent the resistor from blowing up.

 

[stuartmp]

Do you have a example part number of a actual capacitor that is used as a snubber in a power supply as per Bob's book o page 383?

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[AndrewT]

go to the quasimodo thread and it's offshoot.

page 383 is headed Part4: Simulation and Measurement

 

[stuartmp]

Sorry my mistake. Page 350.

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[AndrewT]

Having read the paragraph in the lower half of page350, I suggest you ignore the figure 16.7b and go to the quasimodo Thread as stated earlier.

 

[Johno]

Hey Stu, snubber caps are best metalised film or film foil with low resistive losses. At the mains frequency the relatively high Xc protects the snubber resistor from too much continuous current and at the much higher secondary resonance frequencies the much lower impedance allows the resistor to dissipate all the ringing energy. For a short time the resonant current could be quite high so the cap needs to have a reasonable pulse current rating.

Capacitors with an X or Y rating for direct connection to mains are very reliable for connection across transformer secondary, are readily available and fairly low cost although they are fairly large.
See RS Stock No. 869-7469
This is 250Vac, 100n X2 with pitch of 15mm

Cheers
John

 

[stuartmp]

I read a bit of that thread awhile ago I will re vist it and look into this further. However I fine it very puzzling that nobody can offer a single part number of a snubber capacitor that they have actual used in an actual amplifier build....

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[stuartmp]

Thanks for your input.

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[Mark Johnson]

I used this exact capacitor in a CRC snubber connected across the transformer secondary, of an actual amplifier build. Carefully note: the capacitor was NOT connected in parallel with a diode; it was connected in parallel with the transformer secondary. This particular capacitor was mentioned by name in the Quasimodo design note, shown below.

_

 

[stuartmp]

Thank you for that Mark and Johno very much appreciated now I have a starting point to work from.

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[SGK]

Just wondering if there is any update on when the 2nd edition of Bob's book will be available for purchase....

 

[Bob Cordell]

Just wondering if there is any update on when the 2nd edition of Bob's book will be available for purchase....

Its been delayed significantly because I am in the middle of down-sizing from my house into a town home. Probably looking at sometime in 2018.

Cheers,
Bob

 

[SGK]

Understood. I know what that feels like. I am in the midst of moving the family from London to Miami and having to do a stint in New Zealand while my immigration visa is processed.

As a guy stuck with balanced sources I'm still hoping the second edition devotes space to fully balanced input stages etc so I can save the space required by my implementation of Self's balanced to single-ended input board....