Field Coils for Audio Systems

[dcathro]

As requested by @GroovySauce I will list the components that I bought to make the Coleman power supplies.

Chassis - Kesper bamboo box from amazon.
Transformer - 300VA 2 x 12Vac from ebay
Power Supply caps - Mundorf MLytic 22000uf @ 40V
Power Supply resistors - Mundorf Mresist 10W
I used speaker binding posts for the +/- outlets which were pure copper from ebay
The heatsinks were made from 2mm (150 x 100 mm) copper plate and a 10mm aluminium block (50 x 100 mm)
I made the power cord captive (no IEC socket) and connected everything up using ceramic terminal blocks bought locally. I also incorporated a slow blow 5 amp fuse before the transformer as recommended.
I replaced the electrolytic caps supplied for the regulator with AN Kasai 50uf @ 63v and most of the resistors with Takman non magnetic carbons. There are a few that Rod says need to be as supplied.
One important thing when building these is that you can hear everything, especially the orientation of the power transformer. There is one orientation or the AC inputs and AC outputs that sounds optimal.

 

[GroovySauce]

@dcathro Thank you much! That is very helpful.

 

[dcathro]

In Hi-End audio we all know that we have to spend a fortune to get improvements in sound!

Well I just got a huge improvement from 12 wooden clothes pegs.

Let me explain. When I built my power amp, 15 years ago, I did a lot of experiments with the chassis and the heatsink. I found that I could hear the fins of the heatsink ringing and ended up using a large thick (6mm) copper plate. Even then, the number of connections/supports of the heatsink could be heard.

Then a few months ago when visiting a friend, I noticed he had a new piece of kit - a turntable motor controller for his Garrard sourced from Hong Kong. What caught my eye was that he had all these clothes pegs attached to the heatsink of this device. We then listened with the pegs on and off, and the difference was profound.

So although my FC PS heatsinks don't have fins, I thought I should try wooden clothes pegs on the thin (2mm) copper plate. I was blown away at the difference, much better tone and texture without loosing anything else.

It just goes to show just how EVERYTHING is important in the Field Coil power supply.

 

[Superchunk]

There's a pair of the Lowther field coils, which never really came to fruition as a driver for sale, for sale in England for a long while that I keep considering to try. Has anyone here had experience with them?