to me liberal is open minded....free.. to others liberalism is something different...one must be very careful in communication...
Apart form that...this thread is surely very very good...a lot different than the best spec. threads around...so many good points, so many good reasons for the steps this little circuit goes through..all is done for a reason..to minimize compromises, to maximize performance and simplicity..I like...!!
Apart form that...this thread is surely very very good...a lot different than the best spec. threads around...so many good points, so many good reasons for the steps this little circuit goes through..all is done for a reason..to minimize compromises, to maximize performance and simplicity..I like...!!
Your talking to a guy who is happy with a 0.1 or even 0.22 res on the o/p of his amps, so I know where your coming from on this.
MiiB
You sum it up good.
There is not one amplifier Fetzilla.
Each contributor has at least 3 suggestions or way to build.
To be open for different ways to make.
I guess it will never end.
Myself, I am open for any request.
The latest was a Fetzilla with IRFP240/9240 outputs.
So I made and published such a version: http://www.diyaudio.com/forums/soli...as-lateral-output-perfect-11.html#post2588935
Most any way to build Fetzilla is interesting.
New issues and new solutions.
There are clever boys reading.
I love when they jump in with a new idea.
The only thing is to keep Fetzilla fairly simple.
This will attract the constructors the most.
THis is my favourite version of JLH Class A.
Called JLH Update: The Class-A Amplifier Site - JLH Class-A Update
JLH UPdate does very good in SPICE simulation.
It is close to HIFI
And yet so simple!!
An externally hosted image should be here but it was not working when we last tested it.
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Fetzilla Ultimate - low distortion
This version is the ultimate Fetzilla.
It has very low distortion THD 0.001% at 1 Watt
It is when you want really good HIFI.
This version will probably not colour the sound so much.
It will be a clean and faithful reproduction.
Your speakers will have a chance to dominate the sound.
Enjoy
This version is the ultimate Fetzilla.
It has very low distortion THD 0.001% at 1 Watt
It is when you want really good HIFI.
This version will probably not colour the sound so much.
It will be a clean and faithful reproduction.
Your speakers will have a chance to dominate the sound.
Enjoy
Attachments
This version is the ultimate Fetzilla.
It has very low distortion THD 0.001% at 1 Watt
It is when you want really good HIFI.
This version will probably not colour the sound so much.
It will be a clean and faithful reproduction.
Your speakers will have a chance to dominate the sound.
Enjoy
How much is the quiescent current of this schematic ?...
Making some sims at Iq 0.6A, i.e class A , it appears that THD is not exceptionnal
at high frequencies while being good enough at 1KHZ.
Global linearity is very dependant of the output stage linearity , that s
why a relatively high Iq is better.
Attachments
This sounds good...bass is better
Currently my favourite version.
Differences are:
1) Increased Bootstrap capacitance to 660u.
2) Decreased bootstrap resistance to allow a full 20mA of VAS current.
3) Decreased output fet gate stoppers to 200R.
Overall sound at all frequencies is vastly better. Bass is quite good, bigger bootstrap cap might do even better.
I also tried halving the VAS degeneration, but I don't think it really helped much, in fact it possibly made things worse so I will stick with the 51R for now.
Currently my favourite version.
Differences are:
1) Increased Bootstrap capacitance to 660u.
2) Decreased bootstrap resistance to allow a full 20mA of VAS current.
3) Decreased output fet gate stoppers to 200R.
Overall sound at all frequencies is vastly better. Bass is quite good, bigger bootstrap cap might do even better.
I also tried halving the VAS degeneration, but I don't think it really helped much, in fact it possibly made things worse so I will stick with the 51R for now.
Attachments
SWF,
Most of this change would come from the gate stopper change. This has profound influence on bass for mosfets, even with verticals. Hint: try 220R on one, and 150R on the other.
You could reduce your bootstrap cap to 470uF with no ill effects.
I suspect that 12mA at the VAS would be fine, too.
ONE THING AT A TIME!!
You really do have too much energy!! But that's terrific, at the end of the day we all wish we had your energy.....
Cheers,
Hugh
Most of this change would come from the gate stopper change. This has profound influence on bass for mosfets, even with verticals. Hint: try 220R on one, and 150R on the other.
You could reduce your bootstrap cap to 470uF with no ill effects.
I suspect that 12mA at the VAS would be fine, too.
ONE THING AT A TIME!!
You really do have too much energy!! But that's terrific, at the end of the day we all wish we had your energy.....
Cheers,
Hugh
DC offset stability of this amp seems awfull , while distorsion
is three times higher than with Lineup s fetzilla.
Such CFB amps are somewhat out of date in their ancient form
and will provide no great perfs according to current standards.
Hugh, all modifications were done one at a time with a brief listening session in between. The bass improvement does not require much listening time to identify.
I simply posted the cumulative changes. Both the bootstrap and the gate stopper mod made an improvement.
As I said, I also tried halving the vas degeneration for more OLG. Didn't help so I left it as it was.
I have upped the current in the vas because I like the sound more, not for any technical reason. Don't you agree that fets sound better at high currents?
If I had to pick whether to use a bootstrap or ccs for the final version it would be tough. Bass performance of the ccs is better, but there's something very pure about the mids with the bootstrap. For pure vocal music I would pick the bootstrap without hesitation. For rock the CCS. If only I didn't listen to both.
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