• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Drawbacks of Parafeed?

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High permeability cores saturate pretty quickly, produce plenty of nasty resonant, high frequency spikes and easily generate DC from AC or from signal voltage. Push-pull operation exacerbates the already precarious situation. According to the standard measure of inductor Q factor defined in terms of loss, and signal integrity left out of consideration, the toroidal transformer ranks the highest.
I really don't really understand why you keep talking about saturation......it has nothing to do with good design and appropriate use. It doesn't happen.
Not all of Hi perm cores are like that. Radiometal saturates at 1.5T and is pretty much usable in an extremely linear and trouble free manner up to 1T. Its only drawback is availability....
So for applications where the power rating is not exaggerate this material doesn't require a big size. For DIYers it only comes in EI laminations but that's not a problem at all as 100KHz bandwidth is possible without compromises. And small natural air gap provides minimal DC handling.
The balance of the amplifier with signal can be fixed without running into troubles or if one is paranoid :D there are other electronic solutions like servo-bias that allow the use of truly un-gapped transformers without issues.
 
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Depanatoru,
you are commenting on things you don't know. The reason to manufacture amorphous, noncrystalline transformer cores is to achieve low density. An amorphous structure generally has high resistivity. In order to be purposeful, the toroidal core has high density, low resistivity and small physical size. You read too many marketing pamphlets.
 
The reason to manufacture amorphous, noncrystalline transformer cores is to achieve low density. An amorphous structure generally has high resistivity. In order to be purposeful, the toroidal core has high density, low resistivity and small physical size. You read too many marketing pamphlets.
What are you talking about? Toroidal cores have been available in amorphous and nanocrystalline for years. For example Vacuumschmelze has cores up to 194x155x25 as standard size and will make at the size you require if you meet their minimum custom order size. Here is the link to the datasheet https://www.vacuumschmelze.com/Assets-Web/L2194-W908_en_de.pdf.
 
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I really don't really understand why you keep talking about saturation......it has nothing to do with good design and appropriate use. It doesn't happen.

It happens all the time. What`s more, the ferromagnetic disorders afflict paramagnetism as well. The magnetic environment is not a nice place to be if you are an electron.

For DIYers it only comes in EI laminations but that's not a problem at all as 100KHz bandwidth is possible without compromises.

Transformer capacity and performance strongly depend on loading. Measurements carried out under no load conditions are more or less meaningless numbers. Specifying distortion figures for transformers is an utterly unserious conduct.

bucks bunny,
put forward your own opinion, how else would I know you are not ignorant.
 
It happens all the time. What`s more, the ferromagnetic disorders afflict paramagnetism as well. The magnetic environment is not a nice place to be if you are an electron.
Your comment really doesn't make any sense.

Transformer capacity and performance strongly depend on loading. Measurements carried out under no load conditions are more or less meaningless numbers. Specifying distortion figures for transformers is an utterly unserious conduct.
Who said no load conditions? You are struggling now.....
 
The ungapped toroidal transformer is designed for maximum efficiency, hence exhibits minimum resistance, minimum bandwidth, maximum amplitude and maximum distortion.


Toroidal transformers have maximum bandwidth and low distortion, even very poorly designed toroidals will have wider bandwidth than many EI transformers. If you can get this basic detail wrong what else are you getting wrong ?

Shoog
 
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