N-channel Amp

There have been questions time and again in these pages regarding Anthony Holton's N-channel amplifier. I have just completed the second PCB of this amplifier and have found the sound to be really good.

Since there have been repeated requests for the PCB design, in a couple of days I will post the PCB design and a picture of a populated board. Only I need to know if I can send these as attachments to the Web Administrator (Jason).

I have a question in this regard. I plan to use about 70,000uf of capacitance per rail for a stereo pair. My transformers (1.1 KVa) produce about 85volts per rail off-load. I would like to insert inductors to form a pi-filter. What are suggestions to make inductors using EI core, either CRGO or CRNGO laminations. These would be cheap to make where I live.

What should the core rating be (to handle >10 Amps), the guage of wire and the number of turns? Any suggestions, including using torroidal cores would be much appreciated.



2001-02-04 4:23 am
With a +/- 85V rail the chokes need to be rated at 20A for a dual mono supply or (40A) for a mono supply feeding a stereo amp.These are peak amperage values.Tell the coil designers that you need a 'swinging choke' rated at 5A(10A) continuous and 20A(40A) peak.Pick the largest core size you can stand.Find out how much wattage this will dissipate and at what temperature rise.Pick a sensible temperature rise, say 30*C.Take the wattage figure and divide by the square of the continuous current.This will give you the maximum DCR of the wire.Select wire length based on DCR requirements.Balance gauge size/length vs maximum inductor volume.Whatever the inductance is, is whatever the inductance is (not critical).