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niss_man

250/400w Zeus Audio, Class AB Diy Design/Build

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Just thought I'd put up my amplifier build. This amp was up and running around 6 months ago, but I've just put the final touch in it. Replaced my 1000va Nuvotem transformer to a Torroidy "Supreme audio grade" transformer. I'll post some pics of the process here. I have called this the "Zeus Audio - Simamp". I had some cast silver "Zeus Audio" name plates made for my Tsunami speakers so I thought to carry on the tradition with the other projects I build.

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Original speaker Logo. 3d printed wax, then cast in silver. Expensive logo.

 

I started by reading the Bob Cordell book "Designing Audio Power Amplifiers".

I produced a schematic using the best bits of the book.

Image result for designing audio power amplifiers bob cordell

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Decided to use a nice symetrical layout. Not because it sounds better, but because of my psychological tendancies.

 

The amplifier was also tsimulated using the same "Ltspice" program learned by reading the book..and google.

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Voltage out (green). Power across 8ohm load (blue)

 

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simulated power acros 8ohm load

 

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Current though 8ohm load at max power before clipping.

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FFT plot @ max power 1000hz

 

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THD @max power 1000hz

 

To be continued

 

Cheers

 

Simon

 

 

 

 

 

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58b64f83cbdd2_originalpcb.thumb.png.a291ed5b2d15973db7533812abecddca.png

Here is the original pcb layout. I say original because this one had some mistakes which made the amp oscilate and destroy some transistors. Always the first batch has something wrong!

 

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The original boards arrived from pcb manufacturing (PCB Way) in China. Don't let the C word sway you, these are great quality boards.

 

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Boards showing back side as well. Note the power section has thick traces on the top and bottom layers for extra current capability. I have to give a thank you to "ostripper" from diyaudio forums for letting me copy techniques he used on some of his amp board designs.

 

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Not great photo I know. This shows the original boards populated and sitting on a large heat sink.  Electrolytic caps are Nichicon Fine Gold and Panasonic FC. You will also note the transistors aren't the usual 3 leg BCE type. Those are Onsemi NJL1302D/NJL3281D. The D at the end means they have an embedded diode in the package. The diodes for 2 of the transistors are  then used in the bias circuit for what is meant to make it have greater stability.

 

 

 

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DSC_0745.thumb.jpg.8ce2ee077bdb28b146eb0d82e244b4c7.jpg

Picture says everything. 22000uf 100v. Have 8 in total crammed in the chassis for  176000uF total for the power supply.

 

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Custom made Toroidy transformer. Highly recomended. 50v secondaries x sqrt2 =  70V positive and negative rails.

 

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Earth wire for shielding between windings.

 

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Encapsulated in resin and put in a polished stainless enclosure for even better shielding from stray emi.

 

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Here it is with my old nuvotem transformer. Cant be seen as it's under my diy emi shield of a cooking pot with nice copper bottom. Also note the amplifier boards are different. This is my second version with separate input boards and power supply boards. You will also see a soft start board on the side of the pot/transformer. That is definitely needed when dealing with a large transformer and copius capacitance.

   You will note the use of copper bus bar as the power supply rails and gnd . Overkill but it looks great.

 

 

 

 

 

 

Edited by niss_man

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58b65a0d9be3f_inputpcb1.thumb.png.6a8e874076042139903f419991685156.png

Updated input board. No mistake this time.

 

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Updated power stage board.

 

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Now we're getting somewhere!

  Final boards, transformer and box. Notice the extra shielding over the input modules. 

 

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Had to shorten up the bus bars a bit to fit the larger Toroidy transformer.

 

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That is Spalted Rainbow Sassafras from the forgotten state Tasmania. Some gorgeous wood comes from that gorgeous state. Thanks Tassie.

 

 

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Thats about it. Except my new logo's which have to be attached.

 

 

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No MOSFETs this time Simon?

 

I would also like to express my interest in an integrated version of this product.  

Edited by Cafad

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1 hour ago, Cafad said:

No MOSFETs this time Simon?

 

I would also like to express my interest in an integrated version of this product.  

No mosfets this time. The last amps I made were SKA GB150D diy modules designed by Greg ball. This design is a bit more involved.

 

I would love to build you an amplifier Jeff. It would be quite a long process though. Would have to redesign or add some boards for the preamp section. I would like to use a lightspeed attenuator as the preamp( or maybe a clone note as @robmiddid) as I am using except mine is in another preamp box. The box would have to be upgraded in size from an already large box as well. Give me a pm or call.

     

Edited by niss_man

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Guest

WOW love your work COPPER BUS BAR, excellent, nothing like current on tap

Can see some big hours in the work there

Toroidy make lovely potted and encapsulated transformers, they always come in the blue wrapper and are actually polished steel, you can tell by the darker hew the steel colour has to SS

Harbuch make some nice transformers as well. Ordered 4 yesterday after a listening test India vrs Australia Transformers in a little amp project. The ferite core means a lot to the final listening am finding (EDIT and hand founded for audio in SA apparently) .

Please keep posting your wears excellent stuff !! 

Edited by Guest

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I can live with a long process.  I'll have my people call your people so we can talk.

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1 hour ago, 125dBmonster said:

WOW love your work COPPER BUS BAR, excellent, nothing like current on tap

Can see some big hours in the work there

Toroidy make lovely potted and encapsulated transformers, they always come in the blue wrapper and are actually polished steel, you can tell by the darker hew the steel colour has to SS

Harbuch make some nice transformers as well. Ordered 4 yesterday after a listening test India vrs Australia Transformers in a little amp project. The ferite core means a lot to the final listening am finding.

Please keep posting your wears excellent stuff !! 

Thanks

 

I was wondering if it was steel and not stainless. With this transformer I can put my head very close and there is no hum or noise. A supremely quiet transformer. Not cheap at around $600 delivered by sea mail but I'm glad I tried them. I will use Toroidy again for sure.

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Cool, wack on a magnet if in doubt

Locals make some nice ones too particularly if you know what to get, but the Toroidy is supreme and addictive :D when the need comes to build again .

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I love an over the top build Simon.  Nice stuff!  I wonder how many people look at those photos and have a comprehension of just how much planning and effort actually goes into building from scratch like that.  Awesome work...and your own circuit to boot...that's hardcore DIY right there.

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2 hours ago, acg said:

I love an over the top build Simon.  Nice stuff!  I wonder how many people look at those photos and have a comprehension of just how much planning and effort actually goes into building from scratch like that.  Awesome work...and your own circuit to boot...that's hardcore DIY right there.

Thanks Anthony

I would like to have added up the hours I spent in planning, reading, sitting on the computer designing, buying and building, testing, finding mistakes and building again. I think it would have shocked me as well. As you know half the fun is in the learning in the process and the other half is the sastisfaction at the end of it.

This is "Deep end DIY" :D:D

 

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6 minutes ago, niss_man said:

I would like to have added up the hours I spent in planning, reading, sitting on the computer designing, buying and building, testing, finding mistakes and building again. I think it would have shocked me as well. As you know half the fun is in the learning in the process and the other half

 

Nah, you probably wouldn't...or at least I probably wouldn't...the answer would be a little disturbing.  I just hope we can both eventually listen to this stuff for more time than we spent researching and building it...that would be a good outcome. 

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This amps a keeper. I will definitely listen to it for longer than I spent building it.

 

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1 hour ago, Boris Karlof said:

Ha!

I love it when art meets science.

Shine on & keep on keeping on. Audio needs more souls driven by passion

Nice one.

Thanks Mark.  :)

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