Hello Brian, Jim, Nigel, Alan, Vasile, Peter etc :)

Brian wrote:
>    If you're looking for actual transformer design information,
>you might want to search for a copy of "Audio Transformer
>Design Manual" by Robert G. Wolpert.
>At one time, he was selling this book from a website, but I'm
>not sure any more.  Might be worth looking for.

    I've searched on the net, and found that this book is a very usefull
source of reference. Althought, I cannot find it to sell anywhere on the
net. The writer's address is "Robert G. Wolpert, 5200 Irvine Blvd. #107,
Irvine CA 92720" and the book seens to cost about US$36.00. He also wrote
"Transformer Design & Manufacturing Manual".

    The book is available at: http://www.nuenergy.org/orderform.htm for
US$49.00.

    If someone knows another place on the web where I can buy it, or the
writer's email address, please tell.

Jim and Nigel wrote:
>> It's commonly used in the music field, for example connecting guitars
>> directly to the PA system.
>But the original author of this post *may* have had
>another application in mind ...

    No, that's exactly the application I want. I'm a musician and want to
build my own DIs designing the transformers myself. As I'm doing some
research about inductors and transformers, it's all usefull informations
with practical applications for me.

>>>There might be other ways of 'driving' a low impedance load
>>>(like 150 Ohms) other than through the use of a transformer,
>>>such using an op-amp (or two). If the transformer is to
>>>provide some amount of common-mode isolation even this can be
>>>accomplished to degree using op-amps.
>>
>> That's not the main point, it's isolation to prevent earth loops, a
>Been there/seen that/done that.

    An active direct box can be made using op-amps and also is a very
usefull tool. But I like the ground isolation that can be achieved with
transformers. When you're using electronics on stage (like guitar effect
processors, sequencers, computers, keyboards, sound-modules etc), the gro=
und
isolation between your rig and the mixing consoles is an important safety.

Alan wrote:
>For information on designing transformers see if you can find a copy of =
the
>"AWV Radiotron Designers Handbook". This book has its origins pre second
>world war in Australia and contains all sorts of necessary information. =
I
>believe it has been re-issued recently on CD ROM, and is well worth gett=
ing
>if you can track it down.

    It seens to be a very usefull book. I'll buy one (paper) available at
www.bh.com with the title "Radio Designer's Handbook Fourth Edition" for
=A335.00 plus postage.

    The CD-ROM is available at http://www.ultranet.com/biz/raddev/#CDROM =
for
US$29.95 plus postage.

Peter wrote:
>A pair of better stage line transformers will set you back $150 or more
>now.

    Yes, Jensen direct box transformers costs about US$70.00 each.

> imho expect to spend four times that much until you have a working
>prototype that satisfies your special needs (I assume that if there woul=
d
>be an off the shelf one you would buy it).

    In Brazil the costs to import electronic components (and everything
else) is very high. Our currency (real) is about US$0.40 and the tributat=
ion
is very high (above 60% plus internal taxes) so I preffer doing the
transformers here as there's a very good transformer manufacturer on my
city.

> Testing small signal
>transformers requires a lot of uncommon test equipment but you can
>improvise most of it.

    What uncommon test equipment do you reffer? Anyway, I do have some go=
od
audio tools to make some tests on my computer. Also, I have my ears and t=
he
ears from some friends that works as musician and/or audio tecnician. :)

    Any more infos anyone???

    Thanks,

    Brusque

-----------------------------------
Edson Brusque
Research and Development
C.I.Tronics Lighting Designers Ltda
(47) 323-2138
Blumenau  -  SC  -  Brazil
www.citronics.com.br
-----------------------------------

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