Nelson Pass said:
This means we are all on the wrong track!!??
/Hugo - likes his little creation anyway 🙂 but wants SuperS.
I believe the circuits using current feedback op amps are not the problem here, only the ones using ordinary op amps with the output boosters.
The following circuit using conventional op amps should work. Those of you who have been working with this need only reverse the inputs and attach the feedback from the other side.
By the way, I have only looked at it with balanced input signal - it may not work with a single-ended input.
The following circuit using conventional op amps should work. Those of you who have been working with this need only reverse the inputs and attach the feedback from the other side.
By the way, I have only looked at it with balanced input signal - it may not work with a single-ended input.
Attachments
Nelson Pass said:
😎
With the CF-version, grounding the 2 resistor halves between the OP’s outputs did the most important improvement. No need to ground the left hand speaker terminal, all voltages more symmetric, running balanced or SE.
/Hugo
I got rid of the DC offset.
In this circuit is less then 10mV DC from output to ground.
Independent of any adjustment.
The circuit works under all conditions.
The OP does it
The two 100ohm resistors R10/11 are only cosmetic decoration 😎 , they can be 0ohm, makes no difference.
Could that also be supersymmetric ?
By the way, I tried a circuit very similar to Nelsons new circuit.
It did not work, the only difference was feedback from OP out to OP -input via voltage divider network.
Did anybody try Nelsons circuit ? I dont doubt that it works...
P.S. I tried to post my new circuit and to download Nelsons design, but my internet connection always failed, could not go online for more than one hour
Nelson Pass said:
I tried more to remove the oscillation and xover distortion, again in vain. If any offset voltage appears at the output node in idling condition, it acts as a positive feedback to the inverting input so that non-zero voltage to the inverting input happens and amplified. This is my finding through the experiments. In order to get rid of this effect, I could use feedback from the op output. Then, X principle disappears. Drinking morning coffee...
JH
I run the circuit from unbalanced source.
In my old design the sound became just a little more silent when I tied both inputs together to the unbalanced preamp output.
Now in my new circuit, when doing this, it is total silence.
I think this is a good sign... 🙄
The perfect differential amp 😀
Also it makes no difference if I leave the second input open or connect it to ground.
Could it be that my new design happens to be supersymmetric ?
Or if not supersymmetric, is it at least a good amp
At least it sounds so.
In my old design the sound became just a little more silent when I tied both inputs together to the unbalanced preamp output.
Now in my new circuit, when doing this, it is total silence.
I think this is a good sign... 🙄
The perfect differential amp 😀
Also it makes no difference if I leave the second input open or connect it to ground.
Could it be that my new design happens to be supersymmetric ?
Or if not supersymmetric, is it at least a good amp
At least it sounds so.
When the CDP is on stop, and I hold my ear direct close to the speaker, I can not hear anything.
101% silence.
No hum or noise.
Not possible to decide wether the amp is on or off.
3mV DC across the speaker.
101% silence.
No hum or noise.
Not possible to decide wether the amp is on or off.
3mV DC across the speaker.
Certainly it doesn't have to be SuperSymmetric to be a good amp, so congratulations.
Keep in mind that I came up with my contributions to this thread using only pencil and paper. None have been simulated, none have been built. If you build them and they don't work, don't assume that I never make mistakes.
Keep in mind that I came up with my contributions to this thread using only pencil and paper. None have been simulated, none have been built. If you build them and they don't work, don't assume that I never make mistakes.
Was that referred to my circuit ? 🙄
So I guess it is not supersymmetric...
No matter, I listened to headphones and it sounds very good to me.
Thanks a lot, Nelson !
By getting a little knowledge from your very good tutorial about DIY OP amps I was able to adapt the schematics of this thread within a few sleepless nights to get my own first classA amp going without any previous experience. 😀
Nothing can supersede a real master...
Now as it even works with reduced bias, I like to proceed to ( no matter if Nelsons design or my own ) a circuit that
> runs from 24V rails and paralleled transistors
> provides 30-40Watts minimum
> can be switched to different bias currents so that power consumption can be reduced while listening to room level.
I need 8 channels for my 4-way active speakers...
Supersymmetric now ?
This circuit behaves different.
Only left input connected to source, right input open: Normal operation.
Left input connected to source, right input connected to ground: Seems to be -6 dB.
Both inputs tied together to source: Silence.
R10/11 could be 0 ohm, did not try...
This circuit behaves different.
Only left input connected to source, right input open: Normal operation.
Left input connected to source, right input connected to ground: Seems to be -6 dB.
Both inputs tied together to source: Silence.
R10/11 could be 0 ohm, did not try...
R10/11 are not necessary.
Next things to try:
Connect OP -inputs direct to ground or to OP output.
Next things to try:
Connect OP -inputs direct to ground or to OP output.
jh6you said:
Jh, and maybe others,
Why not give the current-feedback version a try?
I'm not sure its SuperSymmetry, but at least it works.
And the sound is plain good!
This would take some frustration away, and give you something
to rely on for further improvements.
As far as I understand Nelson, this CF-amp is the best version for the moment.
(I'm not saying this because I succeeded).
It was you, Jh, who did the most work on thinking and drawing...
Bernhard,
You seem quite happy with your 'special' version.
You don't give a damn about conventions but you made it.
And that's the nicest part.
Let us know if you build the 100 Watter. 😉
/Hugo
Netlist,
how is your progress ? Do you still have offset ?
Honestly, this is the the way, I got to my design:
In final desperation I just tried every kind of feedback, I could imagine... Without thinking...
One with a 10myF + 10k in series gave me heavy low frequency oszillations
New questions:
What about bipolar or mosfet half or full bridges in a package ?
What makes the offset disappear in Nelsons design ? I got sme ideas but I am not shure.
What is the output power of this amp ? I also got ideas about that, and also I am not shure.
JH,
I admire your ambition to find your own design, but as the master has posted a working design, why not just be happy ?
how is your progress ? Do you still have offset ?
Honestly, this is the the way, I got to my design:
In final desperation I just tried every kind of feedback, I could imagine... Without thinking...
One with a 10myF + 10k in series gave me heavy low frequency oszillations
New questions:
What about bipolar or mosfet half or full bridges in a package ?
What makes the offset disappear in Nelsons design ? I got sme ideas but I am not shure.
What is the output power of this amp ? I also got ideas about that, and also I am not shure.
JH,
I admire your ambition to find your own design, but as the master has posted a working design, why not just be happy ?
Bernhard,
You’re most amazing in experimenting without thinking.
Fine thing is that you have a working amp and nobody till now is able to tell what you build!! 😉
For the moment my amp is no more.
I disassembled it; it became too crappie after all that tweaking.
I don’t have the need to keep my experiments for the moment.
Now and then I make some progress on my AlephX.
But!!!
I ordered a few parts to make a mosfet version.
If all is well, I’ll have them tomorrow.
I've got one working Mos-version on the sim, and as I said I'll post results when results are there. There will be a small ‘speciality’ on it. 😀
I think the offset was due to great tolerances from all the parts.
Don't understand the question about Mosfets and Bipolars in a package???
The power of 'what I made' was about 15/18Vpp on a scope.
But I never really measured the current.
When I compare to ZenV4 it was audible almost equal in power.
You’re most amazing in experimenting without thinking.
Fine thing is that you have a working amp and nobody till now is able to tell what you build!! 😉
For the moment my amp is no more.
I disassembled it; it became too crappie after all that tweaking.
I don’t have the need to keep my experiments for the moment.
Now and then I make some progress on my AlephX.
But!!!
I ordered a few parts to make a mosfet version.
If all is well, I’ll have them tomorrow.
I've got one working Mos-version on the sim, and as I said I'll post results when results are there. There will be a small ‘speciality’ on it. 😀
I think the offset was due to great tolerances from all the parts.
Don't understand the question about Mosfets and Bipolars in a package???
The power of 'what I made' was about 15/18Vpp on a scope.
But I never really measured the current.
When I compare to ZenV4 it was audible almost equal in power.
Netlist,
I am looking forward to Nelsons comment, wether my design with crossed feedback in post 252 qualifies as X or not. 🙄
I think - no.
In my new circuit, whatever the adjustments are, the offset remains 0,003V across the speaker.
I put a 47ohm pot in series to a 270ohm, and to this arrangement a 270ohm parallel.
0,003V in all positions of the pot.
I mean modules: 2 NPN and 2 PNP in one case.
Very good idea
I wonder if its possible to built this with 4 N-Mosfets.
This is sometimes a very helpful strategy:
If you cant find it, yust search everywhere.
I am looking forward to Nelsons comment, wether my design with crossed feedback in post 252 qualifies as X or not. 🙄
I think - no.
In my new circuit, whatever the adjustments are, the offset remains 0,003V across the speaker.
I put a 47ohm pot in series to a 270ohm, and to this arrangement a 270ohm parallel.
0,003V in all positions of the pot.
I mean modules: 2 NPN and 2 PNP in one case.
Very good idea
I wonder if its possible to built this with 4 N-Mosfets.
This is sometimes a very helpful strategy:
If you cant find it, yust search everywhere.
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