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Old 5th October 2006, 09:31 PM   #1031
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Default Toroid Audio transformer

Sheldon,

I believe is 2:1

0-50 0-50, 0-24.5 0-24.5


with the primary in series, centre to GND and secondary in series for 8 Ohm load should do the job.


Alfonso
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Old 5th October 2006, 10:24 PM   #1032
Sheldon is offline Sheldon  United States
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Quote:
Originally posted by Wavebourn
I propose further development of the same idea. It is up to her to discuss it, or not to discuss.
She did discuss those issues in the first few pages of the thread:

" 1. In the event of a device failure substantial DC could be placed across the speaker - which lets the magic smoke out.

2. With two sectioned secondaries I can match for the loudspaker impedance by series or parrallel switching, whereas this is not possible using the center tapped choke method.

And with the options of the secondary windings I can even reconfigure to drive sub ohm impedance loudspeakers.

Q. Okay, why would I want to do that?

A. Line arrays.

My amplifier can drive line array speakers with ALL the drive units wired in parrallel. A line array with 16 off 2" full range 8 ohm drivers become a 0.5 ohm impedance loudspeaker.

Try driving that with any solid state amplifier!"

And:

"Also I have put in a lot of design effort into this amplifier and then been constantly pooh pooed by "those that know" so I must admit to have been a bit anxious about airing it publicaly on the forum.

Most people tell me to ditch the transformers - totally missing the point - and use conventional circuits. What is the point of that sort of comment? It then just becomes another "me too" design and I wouldn't have started on this path in the first place if what was available worked properly."

There's plenty more in the tread available for minimal effort.


Sheldon
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Old 5th October 2006, 10:32 PM   #1033
Sheldon is offline Sheldon  United States
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Default Re: Toroid Audio transformer

Quote:
Originally posted by apelizzo
Sheldon,

I believe is 2:1

0-50 0-50, 0-24.5 0-24.5


with the primary in series, centre to GND and secondary in series for 8 Ohm load should do the job.


Alfonso
Should work ok for 1:1 (parallel primaries) or 2:1. Susan recommended that the OPT use exact same number of turns on each of the secondaries. I would think that most good toroids are wound this way, but might be worth checking. If they are, the voltages on each secondary should be identical. Also check the resistance and add a bit of series resistance to equalize, if needed.

Sheldon
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Old 7th October 2006, 10:28 AM   #1034
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Hi Sheldon,

Thank you for covering the points raised.

I have been very busy getting a consumer product (DVB DTT STB) that I have been working on since Easter through EMC compliance testing - pleased to say it has passed on first submission and the client received a nice shiny new test house certificate on Friday afternoon.

Still got to finish off all the production information etc. but at least I am now able to sleep at nights.

Best wishes,
Susan.
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Old 7th October 2006, 01:12 PM   #1035
EUVL is offline EUVL  Europe
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Susan,

Good to hear you are doing well.

Cheers,
Patrick
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Old 7th October 2006, 03:22 PM   #1036
Sheldon is offline Sheldon  United States
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Quote:
Originally posted by Susan-Parker
Thank you for covering the points raised.
Just trying to save you the trouble, and hoping that I quoted your words in an appropriate fashion. Though I have to admit to some self serving intent here. I've been participating in the forum for a couple of years now, and have seen too many examples of knowledgeable contributors drop out in frustration at having to contend with argumentative intrusions that contribute nothing to the discussion at hand. I'm enjoying this thread and value your participation. I don't want to see things start down that road.

Quote:
Originally posted by Susan-Parker

have been very busy getting a consumer product (DVB DTT STB) that I have been working on since Easter through EMC compliance testing - pleased to say it has passed on first submission and the client received a nice shiny new test house certificate on Friday afternoon.

Still got to finish off all the production information etc. but at least I am now able to sleep at nights.

Best wishes,
Susan.
Always nice to finish up a big project. Trust you have a chance to listen to some music before hitting the pillow.

I should get the Jfet's soon. My pre amp (DEQX) has 75 ohm output impedence and can be set at several levels from about 0.8 to 4Vrms. So with a 10V DC supply and and 1:2 input transformer, I can drive it directly from the pre. I'll give that a shot first, then try driving it with the tube amp. Have to wind a transformer first, so I'll keep that simple too. Just four parallel windings on a single bobbin.

Sheldon
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Old 8th October 2006, 08:31 PM   #1037
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Quote:
Originally posted by EUVL
Susan,

Good to hear you are doing well.

Cheers,
Patrick
Hi Patrick, thanks. Yourself?


Quote:
Originally posted by Sheldon


Just trying to save you the trouble, and hoping that I quoted your words in an appropriate fashion...

(snip)

Sheldon
Much appreciated.

Hope all goes well for you.

Look forward to hearing how things progress with the JFETs.

Best wishes,
Susan.
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Old 10th October 2006, 03:25 PM   #1038
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Hi Susan,

I put together Zeus on my bench last Saturday and on Sunday I spent all afternoon listening music. I could not leave my room. It's FANTASTIC!!!
I first start experimenting with unmatched pair of IRF540 with a 12V 2A battery as power source. Adjusting quiescent current slowly up to 50mA after that my meter showed ~2000mA. I found out that they were very unmatched
The problem went away after I got a matched pair of IRF540.
Then I start beeing more confident about switching to higher DC and I installed a pair of IXFH58N20. WOW!!
I would like to post some pictures and spectrum shots.
I'm impressed how the 100V 100W PA output toroidal transformer works for the entire spectrum as the EI is not ready yet.
Input transformer:Claritronic toroidal 30VA 2x115-0, 2x12-0
Output Transformer:Powertran (Altronics) toroidal 2x50-0, 2x24.5-0 8Ohm
Mosfet: 2 x IXFH58N20
Bias: 7805
Power supply: 25VAC 80VA toroidal, bridge, Aerovox 10.000uF 100V

Best regards,

Alfonso
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Old 10th October 2006, 10:11 PM   #1039
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Hi Alfonso,

Thank you for your post

Great to hear of your progress.

Quote:
Originally posted by apelizzo
Hi Susan,

I put together Zeus on my bench last Saturday and on Sunday I spent all afternoon listening music. I could not leave my room. It's FANTASTIC!!!

(snip)

I would like to post some pictures and spectrum shots.

(snip)

Alfonso
Look forward to the pics and info.

Very pleasing.

Thanks.

Best wishes,
Susan.
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Old 10th October 2006, 10:35 PM   #1040
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Susan,

I've sent pictures of Zeus to your email address while I'm working out where to upload them on the net.

Best Regards,

Alfonso
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