I'm quite interested in post 2299 and wondering if I should build that instead of the wolverine 😀 And I just finished up the PCB design for the wolverine too. Hmm.
Mine is not going to be modular as it needs to be compact.
Mine is not going to be modular as it needs to be compact.
Some nice looking IPS here. Just watch out for cascode oscillation. 220 to 470 R in the cascode bases cures the problem. Same for Hawksford as well.
http://hifisonix.com/wordpress/wp-c.../Cascode-Oscillation-in-Audio-Amplifiers1.pdf
http://hifisonix.com/wordpress/wp-c.../Cascode-Oscillation-in-Audio-Amplifiers1.pdf
Don't count out the "wolverine" NOTHING can beat it's PSRR. (-120db+)
(below) , I went all the way with Miib's idea. The mirrors increase
PSRR to -100db. Best of the symmetrical designs.
THD is still 2ppm ... I'm using the input cap and am trying for a "realistic
simulation". And running it into the "slewmonster" OPS.
The circuit below does have the lowest THD 20 of all - winner !
Would we hear this (12ppm to 2 ppm ??)
Is this worth a 18 device IPS ? Hmmmm.
OS
(below) , I went all the way with Miib's idea. The mirrors increase
PSRR to -100db. Best of the symmetrical designs.
THD is still 2ppm ... I'm using the input cap and am trying for a "realistic
simulation". And running it into the "slewmonster" OPS.
The circuit below does have the lowest THD 20 of all - winner !
Would we hear this (12ppm to 2 ppm ??)
Is this worth a 18 device IPS ? Hmmmm.
OS
Attachments
Thanks Bonsai for the practical hints regarding cascode oscillations, I have ofthen worked with cascodes in some of my phono-stage designs, and had to debug a lot due to these kind of issues, a gate/base stoppers are commonly used and why not here as well.
Makes sense..
O-stripper, why not make the input-cascodes driven..??
Makes sense..
O-stripper, why not make the input-cascodes driven..??
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SORRY SORRY.
Please don't look at these measurements!!!
These are even better!
This time, test based on digital oscilloscope measurements.
-3db high
NAD V1.2=1.2MHz(with high filter present)
the rest later....
Thimios.
Yes, it is strange that amp can produce good 200kHz square wave but have 400k Hz -3dB? 😀
Thimios, I wait measurement of your CFA with 1K/33 feedback.
aside from simulations, do you have a set up for testing open loop gains/bandwidth for a prototype amp?
Ok bimo all measurements must be repeated .It's a stupid way measuring 400KHz with digital voltmeters
Thimios.🙁
Yes, but there must be a reason for the input cap. I can't really hear any difference with or without it. Even on the scope I don't see any difference below 20khz. So, why is that cap there and what determines the value?
An input cap is shielding the amplifier from source components with DC offset.
With an input cap and careful thermal design you can build amplifiers without DC servos.
With an input cap and careful thermal design you can build amplifiers without DC servos.
I think my CFA-XH redraw has passed my check, check, and re-check. I think I will be outputting the Gerbers and ordering some shortly. If anyone sees a gross error I managed to miss please let me know. I'm also going to order more OPS. Since there are already OPS out in the wild I will likely order more IPS than OPS to allow those already with the OPS on hand to have an opportunity to get this IPS if they so choose.
In order to keep the thread here clean please hold any requests until I open a thread in the GroupBuy section for the purpose.
In order to keep the thread here clean please hold any requests until I open a thread in the GroupBuy section for the purpose.
-3db high
all tested 10VRMS/4R
Gnome........1.72MHz😱
Nad ........1.2MHz
Spooky.......850MHz
Symasui......830MHz
CFA-X V1.3...530KHz
CFA-X V1.2...520KHz
All these mesurments low pass filter on board.
Thimios.
all tested 10VRMS/4R
Gnome........1.72MHz😱
Nad ........1.2MHz
Spooky.......850MHz
Symasui......830MHz
CFA-X V1.3...530KHz
CFA-X V1.2...520KHz
All these mesurments low pass filter on board.
Thimios.
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Hi thimios,
For us novices would you please explain how you are conducting these tests and what the results mean?
Thanks, Terry
For us novices would you please explain how you are conducting these tests and what the results mean?
Thanks, Terry
With simple words ,an amplifier can't have a stable amplification over all frequencies.
Speaking for audio amplifiers these must cover the band 20hz up to 20khz.
If we want to examine this ,a generator fitted at amplifier input.
An oscilloscope connected across dummy load at amplifier output.
Putting generators frequen.. at 1KHz we see Vout on oscilloscope.
There are two points were this V out comes ....V=Vout*0.707 (-3db).
One at low frec. and the other at high frec.
Suppose we see 10vRMS at 1khz ,then we adj frequencies up to see 10*0,707=7,07v on scope.This is -3db point.
As an amplifier has this point at high freq that means this amplifier have linear amp. up to this point.
The same for low freq.
I hope this can help a little.
Thimios.
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Thought about why (especially the gnome), might have such a high F3.
Gnome ... w/ diamond , has the highest Z.
VFA's also are High Z input.
"Current on demand" , would lower the Z for the other CFA's.
So, the F3's seem to back this up.
The IPS's slew rate is independent of this , almost the reverse of the F3's ?
OS
Now that the CFA-XH boards have almost reached fruition thanks to the efforts of OS and JK, I have a question about transistor selection.
The SA992/SC1845 are impossible to source locally from RS or Farnell and international shipping is pretty expensive from Mouser and Digikey for these few components. I really don't have much choice in the way of high Vceo small signal transistors apart from the 2n5401/5551.
OS, are you able to simulate the schematic with the 2n5401/5551 and let me know what the performance is like? I'd like to use these parts if possible, but I'm worried that it will significantly compromise performance.
The SA992/SC1845 are impossible to source locally from RS or Farnell and international shipping is pretty expensive from Mouser and Digikey for these few components. I really don't have much choice in the way of high Vceo small signal transistors apart from the 2n5401/5551.
OS, are you able to simulate the schematic with the 2n5401/5551 and let me know what the performance is like? I'd like to use these parts if possible, but I'm worried that it will significantly compromise performance.