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[Orion] Orion Audio Gain Control

To: orion@contesting.com
Subject: [Orion] Orion Audio Gain Control
From: "James C. Garland" <4cx250b@muohio.edu>
Date: Tue, 20 Jan 2004 19:00:08 -0500
List-post: <mailto:orion@contesting.com>
Hi Gang,
I notice that the Orion uses a linear taper on its volume encoders, rather than an audio taper, which is the convention used in virtually all other radios, audio systems, TVs, etc. As a reminder, an audio taper compensates for the logarithmic response of the human ear. It gives an extra boost to the volume when the control is first turned, and then a progressively smaller boost as it is rotated further. The effect is to make the actual perceived volume appear to coincide with the knob rotation. Thus, with an audio taper, turning the control, say 45 degrees, changes the _perceived_ audio volume by the same amount, no matter whether the starting volume is low or high..


By contrast, with a linear taper, the control seems to have very little effect when first turned, and then progressively greater effect at higher volumes. With the Orion, turning the control the first 90 degrees (1/4 revolution) from zero audio produces very little increase in volume. Although some may prefer this audio "bandspread" at low settings, for most users it is a nuisance, since it makes it difficult to quickly turn the volume up or down. The accepted convention is that a 300 degree turn of the volume contral spans the range of zero to maximum audio. (With encoder volume controls, which lack a mechanical stop, this is often increased to 360 degrees.) For the Orion, the span is 540 degrees ( 1.5 full revolutions), which I believe to be excessive. When this unusally large span is added to the linear taper, it makes the audio encoders seem very unresponsive.

It is a bit more difficult to implement an audio taper wihen a volume control is a rotary encoder instead of a potentiometer, since an encoder has inherently a linear output (a constant number of pulses per degree of rotation.). However, doing so is common practice. For example, the radio in my Infiniti FX-45 uses an encoder for the volume control. The first quarter turn (90 degrees) raises the volume to a comfortable listening level. The next quarter turn increases it to a loud volume, and the next quarter turn blasts your socks off. This audio taper is accomplished in the radio's firmware, which essentially duplicates the response of a conventional audio potentiometer.

I believe that implementing an audio taper in the Orion volume controls would make the radio seem more natural to use. It would also make it easier to turn the volume up or down quickly. Admittedly, this is not a big issue, but I think making the needed firmware change would be one step in addressing some of the "fit and finish" issues of the Orion, vis-a-vis its Japanese competitors.

73,
Jim Garland W8ZR


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