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Old 13th September 2011, 09:37 PM   #1
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Default The high slew rate design that time forgot?

I found this design in an old magazine. It is by Yuri Ezhkov and was published in Electronics World of September 1999 under the title "Fast Audio Power." The circuit diagram is attached to this post. If there is any interest I can post the other two pages.

The design is quite complicated. I have to admit that I have yet to get my mind into high gear to figure it all out.

The specifications given includes output power is 90W into 4 ohm with a slew rate better than 50V/us. Although the author gives some detail of construction in the text, there was no PCB design.

I don't know if any of the ideas presented went any further. The design uses a bewildering number of different transistors. The author does give alternative type numbers for most of them, but it does not help much as they are not familiar to me. What makes it worse is that I do not have a SPICE model for even one of them. Simulating this design will therefore be quite undertaking.
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Last edited by ingenieus; 13th September 2011 at 09:42 PM.
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Old 13th September 2011, 10:01 PM   #2
kaos is offline kaos  United States
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50 V/uS isnít that fast. Donít care for some of the design choices either.
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Old 13th September 2011, 10:10 PM   #3
jcx is offline jcx  United States
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Self, Cordell both manage better SR in their audio amp design books
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Old 14th September 2011, 05:57 AM   #4
Bonsai is offline Bonsai  Taiwan
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This is not a SOTA design.

I'd skip it and take the advice above on Cordell and Self. For more practical and closer to home examples, see OStripper's work on this forum (at the top of the page). This will deliver high slew rates, ultra low distortion in a very practical and down to earth design and uses many of Self and Cordell's techniques.
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Old 14th September 2011, 10:28 AM   #5
wahab is offline wahab  Algeria
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50V/uS is a good value..
Higher slew rate will inherently reduce stability in any classical design,
be it the ubiquitous single differential based topology ala blameless ,
or more refined symetrical differential siblings..
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Old 14th September 2011, 10:35 AM   #6
Bonsai is offline Bonsai  Taiwan
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Yes, agree Wahab, there are some nice fully balanced designs ot there as well ;-D

BTW, its perfectly possible to get 100V/uS and still be stable on an FBS design.
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Old 14th September 2011, 10:48 AM   #7
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For a trully high slew rate design try the Stochino amp. 300Vus, is fast enough I should think.

BTW the Stochino sounds terrific, about the best sounding DIY design I have seen published and built but be aware its not newby builder material.
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Old 14th September 2011, 10:54 AM   #8
wahab is offline wahab  Algeria
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Hi, Bonsai , that s quite right, but with some limitations.
The usual LR output circuit almost invariably save the day with most
designs that are instable as soon as some capacitive loading is added,
and it will be more than mandatory in those so called high slew rate designs,
partly reducing the expected SR...

As for full symetrical circuits , unfortunately they dont work as easily
as the single differentials , but they have the advantage of better stabilty
as well as symetrical slewing.
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Old 14th September 2011, 12:07 PM   #9
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Thanks for all of the input, guys. To advance the state of the art, we have to keep looking at all the alternatives out there.

The Blameless design is certainly the one to go for if you want something that will work, and work well. I have one on the back burner at the moment.

I will look at the Stochino design. Is this the definitive version?

Click the image to open in full size.
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Old 14th September 2011, 12:22 PM   #10
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Yes, be sure to upgrade the output mosfets, those are not really capable for the power rating of that amp. When pushed hard into 4 ohm loads those will go up in smoke.
Youll need a very good pcb design too, if you dont get it right, those mosfets will go up in smoke too.

BTW, ingenious where you from??
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