This would require modulation, because it wouldn't be practicable in baseband.
It is difficult to achieve extreme levels of linearity in this process: it is a kind of multiplication, and doing it with a carrier or a DC doesn't change fundamentally that aspect.
Yes, but one that remains perfectly linear would also be difficult to find, unless you have an idea?
Otherwise, a variable capacitor as suggested above, or a Hall element.
I have no idea about the linearity of Hall element's materials.
Kudos Elvee! That's creative!
What audio features does it do differently than a potentiometer? For example, dulling with a 10k pot or distortion/noise with a 200k pot, and in-between those values is compromise between the two extremes? Does the new volume control do differently or in some way reduce the compromise?
What audio features does it do differently than a potentiometer? For example, dulling with a 10k pot or distortion/noise with a 200k pot, and in-between those values is compromise between the two extremes? Does the new volume control do differently or in some way reduce the compromise?
Most important points are shown on the schematic.
To summarize: compared to a conventional pot, it has no contact noise and more subtly, no noise modulation.
Compared to all "electronic" methods, the variation does not rely on any non-linear component of any sort, be it analog switches, non-linear resistors or variable transconductance cells.
The only sources of possible distortion are the input and output amplifiers, and we are on safe grounds there, because the input amp is basically a high quality headphone amplifier, and the output amp, a simplified variation of RIAA preamp, both of which are well-known, and can be made to very high quality standards without too many problems
As I mentioned above, a differential variable capacitor (not this one) could be used for the same function.could an adjustable air capacitor be substituted for the field coils?
I have heaps of these lying around...
But the supporting circuitry would have nothing in common, that's an entirely different project.
A good shielding from both inside and outside stray fields would indeed be essential.
However in real usable unit, the size would be very much reduced, making shielding and separation easier.
Also, the coil arrangement shown on the demo unit may be conceptually straightforward, but it isn't necessarily optimal.
One could think of different arrangements, giving more than 180° rotation range for instance.
However in real usable unit, the size would be very much reduced, making shielding and separation easier.
Also, the coil arrangement shown on the demo unit may be conceptually straightforward, but it isn't necessarily optimal.
One could think of different arrangements, giving more than 180° rotation range for instance.
Nothing in common with this project: with a 50dB control range, you are going to need an additional, conventional volume control, and just looking at the spacing of the curves, the THD must be of the order of several %.
A world apart.
Some modulator tubes for SSB can do better than that (but they will remain far from the Vari-M in terms of performance).
Elves, an absolute cracker!
It ticks all the right boxes for "mad scientist" idea:
- it works
- it works in a uniquely odd manner, which to many seems inexplicable
- it solves a problem that you didn't know you had
- it is fun, and
- it is borderline impractical
Fantastic.
For those who will inevitably seek to polish this into a fully fledged implementation:
- remember this is two loop antennas. eMI/EMC are real issues
- shielding will be your friend. I love the idea of mu metal being required for a volume control!
- magneto restrictive effects will become significant to achieve low distortion levels, as will the presence of ferrous metal in the vicinity. But maybe you could make a feature of this! The golden eared brigade could debAte the sound of various nuts and bolts!
Love the idea and execution. I hope you start a craze!
It ticks all the right boxes for "mad scientist" idea:
- it works
- it works in a uniquely odd manner, which to many seems inexplicable
- it solves a problem that you didn't know you had
- it is fun, and
- it is borderline impractical
Fantastic.
For those who will inevitably seek to polish this into a fully fledged implementation:
- remember this is two loop antennas. eMI/EMC are real issues
- shielding will be your friend. I love the idea of mu metal being required for a volume control!
- magneto restrictive effects will become significant to achieve low distortion levels, as will the presence of ferrous metal in the vicinity. But maybe you could make a feature of this! The golden eared brigade could debAte the sound of various nuts and bolts!
Love the idea and execution. I hope you start a craze!
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