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Old 18th November 2012, 09:23 PM   #11
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Originally Posted by GregH2 View Post
Meanman, You will find a circuit which nearly meets your requirements here: Simple 85W amplifier However, if you wait a few weeks I will be posting a 70W quasi BJT version which I think will be the best sounding... Cheers, Greg.
I'm very curious
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Old 18th November 2012, 09:26 PM   #12
GregH2 is offline GregH2  Australia
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Originally Posted by meanman1964 View Post
I've the FetZilla a while now and was thinking myself it wouldn't be easy cause it's realy a special amp.Many whom has hear this amp were impressed.
Yes, more power is possible, but it the beautifully simple circuit topology of the lower power version which makes it sound so good I think. Everything just comes together - the device dissipations, the circuit simplicity and the actual devices themselves. More power needs more parts and/or different devices.

I think a version with a cascoded input JFET, an IRF610 VAS running at 20mA or more, and paralleled lateral outputs would do quite well. Hopefully someone will give it a go. I am trying to avoid building amplifiers with rare or specialised parts these days.

The other option is to replace the input with a small mosfet such as the ZVN2110G which also sounds pretty good. The problem is the high input capacitance, though the sonic effect of this isn't as bad as one might think.

Last edited by GregH2; 18th November 2012 at 09:30 PM.
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Old 18th November 2012, 09:31 PM   #13
Bigun is offline Bigun  Canada
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Hi Lineup,

I like this general topology, the way you draw it makes it look very simple.

Reminds me of the JLH Class AB published in 1970, [http://sound.au.com/tcaas/jlhab2.htm]which of course was all BJT.


I do like the use of Laterals in the output for simplifying the thermal stability of the bias. I suppose this is the only output device that we can use without adding some temperature compensation ?
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Old 18th November 2012, 09:35 PM   #14
GregH2 is offline GregH2  Australia
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Originally Posted by Bigun View Post
Hi Lineup,

I like this general topology, the way you draw it makes it look very simple.

Reminds me of the JLH Class AB published in 1970, [http://sound.au.com/tcaas/jlhab2.htm]which of course was all BJT.


I do like the use of Laterals in the output for simplifying the thermal stability of the bias. I suppose this is the only output device that we can use without adding some temperature compensation ?
Yes, and I can promise you the laterals sound better and probably load the VAS a lot less than undriven BJTs. Unless you want to run very high VAS currents which in turn requires a buffered or darlington VAS.
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Old 18th November 2012, 09:40 PM   #15
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Greg,Maybe it's better for me to give your Simple 85watt amp a go
For my own use I don't need a more powerfull FetZilla
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Old 18th November 2012, 09:54 PM   #16
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The FetZilla I've build is realy a special amp with nice mids good staging and detailed hights and very strong tight bass.If we need power it is only for the bass region.Is it possible to design a kind of a Fetzilla topology that goes to max 200Hz wouldn't this make things easier to design?
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Old 18th November 2012, 10:39 PM   #17
Bigun is offline Bigun  Canada
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meanman, how would you compare your FetZilla with your DX blame ?
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Old 19th November 2012, 12:25 AM   #18
Jay is offline Jay  Indonesia
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Quote:
Originally Posted by GregH2 View Post
I will be posting a 70W quasi BJT version which I think will be the best sounding...
Quasi! And good sounding! That will be my vote for the best circuit of the year

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meanman, how would you compare your FetZilla with your DX blame ?
What a teaser!
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Old 19th November 2012, 05:34 AM   #19
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meanman, how would you compare your FetZilla with your DX blame ?
The Fetzilla is more open more detail crispy hights and controlled bass but I also like the Blame ST.
Will get back on that after I compaired them together on the same speakers.
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Old 19th November 2012, 06:51 AM   #20
lineup is offline lineup  Sweden
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Originally Posted by GregH2 View Post
More power needs more parts and/or different devices.

I think a version with a cascoded input JFET, an IRF610 VAS running at 20mA or more, and paralleled lateral outputs would do quite well. Hopefully someone will give it a go. I am trying to avoid building amplifiers with rare or specialised parts these days.
Cascoded input, IRF610 VAS and Laterals parallelled at output.
Sounds as the way to go.
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