Where to get a certain power transformer??
« on: December 28, 2016, 01:32:48 PM »
Hi,

I'm trying to get a power supply for the D-EF47 microphone build in a smaller case.  I'm hoping to find a power transformer, preferably Toriodal, with an input of 2 x 115V and an output of 220V and 20V.  2 x 115V is important to me (for dual voltage) because I want to be able to travel with it and not have to worry about the country voltage.

At the moment the build calls for one power transformer for the 220V, one for the 20V and there's that C-40X Choke... a lot of stuff to put into one box.  I've searched online all day but I'm just not getting anywhere.    Any suggestions would be very welcome!
Thanks in advance :)

Dennis


Khron

Re: Where to get a certain power transformer??
« Reply #1 on: December 28, 2016, 02:10:52 PM »
Assuming price is no object, you could always go for a custom-wound one, but it won't be (too) cheap.
But then again, fortunately, tube mics don't require hundreds of watts, so the whole thing shouldn't end up too huge and/or pricey :)

http://www.audiophonics.fr/en/electronic-components-toroidal-transformers/toroidal-transformer-custom-made-p-3675.html

In your case, you'll need to look at the "4" column, since you need 4 windings (2x 115v primary, 220v & 20v secondary).

PS: Is the 20v for the heater? Seems awfully wasteful, if/since most tubes "only" require 6.3v; but then again, i'm not yet too familiar with the tube used in that mic / project :)

Also, are those voltages RMS? If that's the case, do keep in mind that the resulting rectified DC is the RMS multiplied by 1.4 (so about 308v and 28v respectively).

Another choice would be these guys:
http://sklep.toroidy.pl/en_US/c/Mains-Transformers/143

On the other hand, chances are good there might be other better choices in your area, assuming you're on the other side of the pond (ie. the Americas) :P

TLRT

Re: Where to get a certain power transformer??
« Reply #2 on: December 28, 2016, 05:10:36 PM »
I can make to you any kind of custom wounded toroid, I'm using these in my builds also,(it has CE markings) this has optional primary(2x115 or 230V only, and 230V / 20V secondaries(rated to 25VA)

Whoops

Re: Where to get a certain power transformer??
« Reply #3 on: January 02, 2017, 10:48:40 PM »
How many mA do you need on the 20V secondary?

TLRT

Re: Where to get a certain power transformer??
« Reply #4 on: January 03, 2017, 01:34:17 AM »
min 0.5A for EF86

Whoops

Re: Where to get a certain power transformer??
« Reply #5 on: January 03, 2017, 07:47:44 AM »
Ok,
I would use 2 toroid transformers also,

P: 2x115v -  S: 1x220v (or 2x115V)

and the other transformer

2x115V - 2x10V (20VA)

TLRT

Re: Where to get a certain power transformer??
« Reply #6 on: January 03, 2017, 07:54:31 AM »
Ok,
I would use 2 toroid transformers also,

P: 2x115v -  S: 1x220v (or 2x115V)

and the other transformer

2x115V - 2x10V (20VA)

We already arranged this with the thread starter, we have a good dual design, it has stable output, mounting kit,and statically shielded, I used dozens of these trannies in my builds without any problem.