Controlling volume with the Audiant and Eloquence series
We frequently have conversations with system owners, during which they link potentiometer position with amplifier output. This discussion is an attempt to explain the correlation between them and to contrast the Audiant and Eloquence volume control topologies.
It is important to take note of the following. Different sources (CD, streamer, server, record players) can output a variety of voltages. Different sources from the same category can also be at differing voltages. For example, 2 CD players can each play the same track and output a different voltage into the input of the amplifier.
CD’s can also be recorded at varying levels. Insert 2 different CDs into the same player and one plays soft and the other loud.
The term ‘pre amplifier’ was conceived during the time of vinyl recordings. The reality of the situation today is that when playing a CD through your amplifier, the ‘pre amplifier’ section will for the majority of its operation be acting as a ‘pre attenuator’, reducing signal input, until such a time as it reached 0.00dB, after which the input signal is boosted by the ‘pre amplifier’ stage.
The same input voltage can be applied to the amplifier, on different loudspeakers and one set can deliver a far greater SPL (Sound Pressure Level) than the other.
Amplifiers using a potentiometer to adjust volume
Setting the volume control knob of the Audiant 80i into the same position, it is possible with different sources to achieve very different SPL. When the volume control is in the 11.00 o’clock position, it is possible that the Audiant 80i amplifier can be over driven. On other sources, saturation may not occur until the knob is in the 5.00 o'clock position.
When playing music from a variety of sources, there is little correlation between knob position and amplifier output, other than to state the obvious, that a clockwise rotation should result in the amplifier reaching maximum output at some point.
Audiant series volume control
The Audiant series uses a motorised potentiometer which enables the user to interact directly with the device via the system remote control, alternately by manually turning the volume control. Minimum to maximum output is achieved in 1 complete rotation of the pot.
Eloquence series volume control
The Eloquence series utilises a different volume control topology to the Audiant series. Instead of a potentiometer, we use an encoder. The encoder transmits pulses into a dedicated volume control chipset which counts them and then adjusts the volume accordingly. Each pulse of the encoder corresponds to a 0.5dB change in volume. This fine resolution is one of the advantages of an encoder based volume control. The potential downside of that is it can take many rotations to achieve full output. We have cleverly managed to get around this by incorporating an accelerometer function which can detect the rate increase of pulses being received and automatically decrease resolution to match. By twisting the volume control quickly, volume increases very rapidly to match.
Additional features incorporated into the eloquence series.
In addition to volume control, we also utilise the knob as a navigation tool to get around and select menu items, appearing on the screen.
Trimmable input Volume
One of the most frequent causes of volume imbalance arises as a result of users selecting different sources which are at different input voltages. The eloquence series incorporates a volume trim function which allows the volume level of each input to be adjusted up or down, relative to the others, to equalise the volume across all sources. For example if a CD player and a radio tuner are connected, the CD player’s output volume may be louder than that of the tuner so this feature saves volume adjustment when switching between these sources.
Both systems work well. The eloqunce series offers an additional levels of sophistication with greater resolution and trimmable input volume levels as well as enabling multi use for the knob to control menu functions.