Phono Pre-amp

Notes on Power Supply Construction...

Check out this book
http://www.amazon.com/Fundamentals-Electronics-Second-Robert-Erickson/dp/0792372700/ref=sr_11_1?ie=UTF8&qid=1202702014&sr=11-1

Advanced text on power supplies. Contains chapter on line conditioning.
LC Catalog is: TK7881.15 .E75 1997 (First Edition)
In Seattle University and UW Engineering libraries.

Note on blocking DC from toroidal transformers.

Notes referenced in diyaudio...
http://www.tnt-audio.com/clinica/mains_e.html
Low capacitor unit consisting of 8uf cap, MOV, and 220K 2 watt resistor. Nice.

Common mode choke.

L2 is a common mode toroid choke. C 2 and C4 are filter/load capacitors between the DC rails. These are polypro, AC, "refridgerator" style caps with low ESR.

C4 and C5 are good quality bypass caps.

A common mode choke is used after the transformer to limit 120 hz and 60 hz hum on the line. The filter also helps eliminate high frequency noise and EMI.

With carefully chosen values, this could be viewed as an LC Pi filter.

Part maker is CWS Coils. http://www.coilws.com/toroidal/CM_Series_toroidal_c_choke.php

Design notes are at: http://www.metglas.com/design/d2.asp?download=cmc.exe
From the metglas design site, it appears that a 1" diameter size core made of K series finemet
(part number K2313D in the FT-3km series) would do well without about 20-25 turns per side.
Wire size can be AWG22 or 24.
The schematic is from a Nemic-Lambda article. http://www.nemic.co.il/doc/PS4.pdf