♫♪ My little cheap Circlophone© ♫♪

[Elvee]

Originally Posted by danielwritesbac

Here it is attached.
It looks like this sim is useful to explore quite a few different options of refining the sensor behavior.
Personally, I was never able to figure out which mods were best, except that the integrated buffer always looked pretty good.

Using C2 without series resistor will probably upset the non-switching behavior above several KHz.
In addition, the lead-compensation schemme might look attractive in sim, but I fear it would cause minor instabilities (HF or even VHF) in a real circuit.

That said, a darlington input like this one will raise the input impedance and eliminate the bias current modulation effects, practically without drawback.

[krokkenoster]

Originally Posted by Elvee

Including the input capacitor to balance the input LTP results in an offset of 7µV (that's in sim, obviously).

The offset current falls to 3.68mA, but this means this is incorrect:

These values yield a primary resistance of ~2mΩ

Elvee
I am just wondering here on my own how many "Circlophones" were already built. It makes me think of the "Texan" of the late sixties. If everybody that built it would have had to pay you royalties like it used to be for Radio in the early twenties that Marconi had to be paid for every radio receiver even crystal sets that were constructed! I think that you would then be able to spend much more time on "improved" amps and be able to afford doing it! The engineers that did design the "Texan" complained about this in 1972. I think that this is becoming a "Classic" like the Williamson, Bailey,Lindsley Hood , Douglas Self and other classic amps that were ever published! Everybody's building it because it works and works well

[Elvee]

Originally Posted by krokkenoster

Elvee
I am just wondering here on my own how many "Circlophones" were already built. It makes me think of the "Texan" of the late sixties. If everybody that built it would have had to pay you royalties like it used to be for Radio in the early twenties that Marconi had to be paid for every radio receiver even crystal sets that were constructed!

From the beginning of the Circlophone project, I deliberately made the choice to share the design completely freely, with no strings attached. Therefore, I feel no resentment towards people using it, that would be silly and illogical.

I think that you would then be able to spend much more time on "improved" amps and be able to afford doing it! The engineers that did design the "Texan" complained about this in 1972. I think that this is becoming a "Classic" like the Williamson, Bailey,Lindsley Hood , Douglas Self and other classic amps that were ever published! Everybody's building it because it works and works well

I am not a professional audio designer (or just only marginally, since I work in the telecoms), it is just a "violon d'Ingres", and I do not have to rely on it to earn a living.
I have enough time to make other research, and I have to admit I am not (yet) disclosing my best, most valuable ideas.
I have some hope (when I am in a very optimistic mood, especially after two or three glasses of dry sherry) that in some distant future, I will be able to valorize and exploit some of them.... But realistically, I think they will end up on this forum or another.

[ersa191]

Question resistors R8/R11/R24 must be 3W or they can be 0.6/1/2W? thanks

[Elvee]

Originally Posted by ersa191

Question resistors R8/R11/R24 must be 3W or they can be 0.6/1/2W? thanks

The Circlophone is designed to allow the use of 0.25W resistors throughout, including R8/R11/R24.
However, for output power > 50W, I recommend a larger size for the main feedback resistor (R17). It is not compulsory, but it will ensure an optimum linearity, even with normal quality resistors.

[ersa191]

Originally Posted by Elvee

The Circlophone is designed to allow the use of 0.25W resistors throughout, including R8/R11/R24.
However, for output power > 50W, I recommend a larger size for the main feedback resistor (R17). It is not compulsory, but it will ensure an optimum linearity, even with normal quality resistors.

Thanks!

[danielwritesbac]

Originally Posted by Elvee

That said, a darlington input like this one will raise the input impedance and eliminate the bias current modulation effects, practically without drawback.

There's a lot that could be done in a sim and I tried many varieties to get the sensor behavior more regular or at least easier to play with and get away with it. Only one thing helped those tolerances albeit perhaps indirectly and it was Kean's BC550C/BC560C buffered input shown. If you were looking for options to get more control over the sensor, the good news is that an answer really does exist. That particular input is apparently the path forward that allows further refinements.

It needs proofed. And after that input is installed, you could then play with the sensor a bit to then proof that the tolerances are slightly easier. The sims all say so, but it is time for some measuring that is beyond my abilities.

[danielwritesbac]

Here it is

[terranigma]

Originally Posted by danielwritesbac

It needs proofed. And after that input is installed, you could then play with the sensor a bit to then proof that the tolerances are slightly easier. The sims all say so, but it is time for some measuring that is beyond my abilities.

I'm also curious about that if it is the thing the sensor really need for or something to preserve more room for sensor to make it performing more freely. I'm watching for good news here.

[danielwritesbac]

Well, that input mod is indirectly helpful to the sensor because of generally overall improved tolerances. I hope that Elvee can find some time to proof that input.