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Front Panel Control
The Transimpedance knob provides sweepable loading from 300 Ohms down to 40
Ohms tied to a gain boost of 9db to 27db. The loading is not resistive; it is the native
input impedance of the transistors themselves. This knob has simultaneous control of
cartridge impedance loading and gain. As shown above, as you turn the knob
clockwise the loading value goes down and the gain goes up. The knob’s neutral
position is straight up, providing a 100 Ohms load for your cartridge. This is the most
common manufacturer-recommended load value for average moving coil cartridges,
and a good center point to start with. Use your ears to adjust the sound to your liking.
In case you wondered, the top blue edge of the Copla does get brighter and whiter as
the knob is turned clockwise. This is not just a visual effect. That white light is the power
being transferred to the amplifier circuitry through photo diodes.
This is a powerful tool that can adjust the response of your cartridge to different types of
music, recordings, masterings and pressings. We have found that well-mastered
recordings sound best with a gentle application of load/gain by setting the knob to about
200 ohms (9 o’clock dial position). With pressings sourced from normal digital sources,
(e.g. CD files or Pro Tools) a setting of 100-80 Ohms (12 - 2 o’clock on the dial) brings
out more richness and body, to offset the compressed dynamics often found in these
pressings. And finally, with pre-hifi era recordings or lo-fi garage recordings, an 80-40
Ohm load (2 –5 o’clock dial setting) will bring out even more body and midrange
resolution where the material is all about the musical performance and the technical
aspects of the recording leaves something to be desired. Of course, these are our
observations. Use the knob to find the sweet spots with your gear.
