[TenTec] Orion Audio Gain Control

[James C. Garland]

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