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


niss_man
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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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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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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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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.

     

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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 !! 

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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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Fantastic work @niss_man. :) 

What a daunting project to take on.

You definitely deserve to be commended for your efforts. :thumb:

 

What about the sound?  

You mentioned it's a keeper but what more can you tell us about its sound and performance?

 

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23 hours ago, Martykt said:

Fantastic work @niss_man. :) 

What a daunting project to take on.

You definitely deserve to be commended for your efforts. :thumb:

 

What about the sound?  

You mentioned it's a keeper but what more can you tell us about its sound and performance?

 

I won't write a review of my amp as I would be totally biased of course. I do however like an amp that is there to do it's job and do it's job well. To me that is something that acts as a conduit between cd/pre/dac etc and the speakers. Something that can deliver grunt when needed and also be delicate when needed. Something that can play quick dynamic music as well as it can laid back music. In other words what I'm saying is, I want my amp to sound like nothing. In my eyes if you want to change the sound then change the source components and cables. I know all amps do have there own sound and if I were to say something about the amp I would maybe use words like "detailed, fast, powerfull, finess" or maybe even the word "nothing".

                      I am sure other more unbiased people would have much more to say about the amplifier in more detail but only once it is in there own system at home. Comparing this amplifier to my SKA GB150D amplifier I would have to say this has more detail (less mossfet midrange fuzz), finess, power and neutrality.

 

Cheers

 

Simon

       

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1 hour ago, niss_man said:

I won't write a review of my amp as I would be totally biased of course. I do however like an amp that is there to do it's job and do it's job well. To me that is something that acts as a conduit between cd/pre/dac etc and the speakers. Something that can deliver grunt when needed and also be delicate when needed. Something that can play quick dynamic music as well as it can laid back music. In other words what I'm saying is, I want my amp to sound like nothing. In my eyes if you want to change the sound then change the source components and cables. I know all amps do have there own sound and if I were to say something about the amp I would maybe use words like "detailed, fast, powerfull, finess" or maybe even the word "nothing".

                      I am sure other more unbiased people would have much more to say about the amplifier in more detail but only once it is in there own system at home. Comparing this amplifier to my SKA GB150D amplifier I would have to say this has more detail (less mossfet midrange fuzz), finess, power and neutrality.

 

Cheers

 

Simon

       

 

It's okay you're allowed to be a little bit biased !!! :D 

 

It sounds like your amp is good at exactly what you like, can't ask more than that. :) 

 

Slightly off topic but if you ever get the chance to listen to a Halcro amp (the high end class AB models) you definitely should. :offtopic:

By the description of what you like in an amp I reckon they would be exactly what you like in a really extreme version.

To describe them they are pretty much invisible.

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1 hour ago, Martykt said:

 

It's okay you're allowed to be a little bit biased !!! :D 

 

It sounds like your amp is good at exactly what you like, can't ask more than that. :) 

 

Slightly off topic but if you ever get the chance to listen to a Halcro amp (the high end class AB models) you definitely should. :offtopic:

By the description of what you like in an amp I reckon they would be exactly what you like in a really extreme version.

To describe them they are pretty much invisible.

Yes I have been lucky enough to hear the Halcro Star wars Tie Fighter ones a few times. Mike Lenehan's, @Cafad 's place and at a QAC meet as well. 

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Well I don't usually do reviews on power amps but I could certainly give the Simamp a run against my Halcro if Simon was willing to let it out of his sight for long enough.

 

We have yet to seriously discuss the possibility of a Sim-Int amp though and that would be my preference.

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