A newbie question

prooptiki · 15th October 2008, 08:08 PM

I am owner of two transformers.

2xTR400

250VA double isolation.
Dimensions: d=126mm h=65mm
Primary: 2x115 Vac
Sec. main: 2 x 0-40 Vac
Sec. aux1: 13-0-13 Vac
Weight: 2.9kg
Transformer is Audio Graded, fully potted, and with electrostatic screen between primary and secondary windings.

So my question is, I want to make a clone of firstwatt F3 amplifier, can I use these transformers or the vac of 2*40 is too much for these amplifiers?

Thank you

Nelson Pass · 15th October 2008, 10:31 PM

A 40V secondary will give you about 55 volts, and since the F3 regulates
that down, you will have a nice range of voltage adjustment, and you can
use one secondary per channel. It will probably run a little hot, but you also
have the option of dropping the voltages by putting an inductor in series with
the windings, which will also improve the power factor of the supply.

prooptiki · 16th October 2008, 02:21 PM

And the last question!!
Which is the best value of dropping the voltages?
Thank you

hifimaker · 16th October 2008, 05:30 PM

Consider trying Duncan's freeware PSU Designer II emulation software. It's a superb tool to design and emulate power supplies with almost any combination of chokes, resistors, and caps.

A lot of DIYer's use it on this site.

http://www.duncanamps.com/psud2/index.html

-David

prooptiki · 20th October 2008, 05:27 PM

My quetion is not for the way to do it, but for the best voltage for the amplifier, for example the circuit says 18V.
Thank you

15th October 2008, 08:08 PM	#1
prooptiki diyAudio Member Join Date: Feb 2006 Location: Ioannina	A newbie question I am owner of two transformers. 2xTR400 250VA double isolation. Dimensions: d=126mm h=65mm Primary: 2x115 Vac Sec. main: 2 x 0-40 Vac Sec. aux1: 13-0-13 Vac Weight: 2.9kg Transformer is Audio Graded, fully potted, and with electrostatic screen between primary and secondary windings. So my question is, I want to make a clone of firstwatt F3 amplifier, can I use these transformers or the vac of 2*40 is too much for these amplifiers? Thank you

20th October 2008, 05:27 PM	#5
prooptiki diyAudio Member Join Date: Feb 2006 Location: Ioannina	Thanks for the responce My quetion is not for the way to do it, but for the best voltage for the amplifier, for example the circuit says 18V. Thank you

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15th October 2008, 10:31 PM	#2
Nelson Pass The one and only Join Date: Mar 2001	A 40V secondary will give you about 55 volts, and since the F3 regulates that down, you will have a nice range of voltage adjustment, and you can use one secondary per channel. It will probably run a little hot, but you also have the option of dropping the voltages by putting an inductor in series with the windings, which will also improve the power factor of the supply.

16th October 2008, 02:21 PM	#3
prooptiki diyAudio Member Join Date: Feb 2006 Location: Ioannina	And the last question!! Which is the best value of dropping the voltages? Thank you

16th October 2008, 05:30 PM	#4
hifimaker diyAudio Member Join Date: Oct 2003 Location: San Jose	Consider trying Duncan's freeware PSU Designer II emulation software. It's a superb tool to design and emulate power supplies with almost any combination of chokes, resistors, and caps. A lot of DIYer's use it on this site. http://www.duncanamps.com/psud2/index.html -David

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