A volume control on a wireless receiver can cause problems:

For many years, manufacturers of wireless microphone systems have included a volume control (VR) feature on their receivers, usually on the front panel. This was to allow the user to adjust the wireless microphone (receiver) output level going to the mixer or amplifier. However, experience has shown that even with the benefit of a detailed explanation in the operation manual, many users set the VR incorrectly and do not fully understand the VR's place in the overall signal chain. If the VR is set incorrectly, it can cause either a poor S/N ratio due to insufficient sensitivity, or overload distortion due to too much level at the mixer/amplifier input. Either problem results in perceived poor performance from the sound system. When this occurs, users commonly complain or think ill of the wireless system, citing poor sound quality or insufficient dynamic range instead of the identifying the true cause of the problem: an incorrect VR setting.

Understanding the input characteristics of mixers and amplifiers:

A mixer or amplifier usually includes both "LINE IN" and "MIC IN" inputs. These inputs may use the same input connection with selectable settings or be separate. "Line In" inputs are used for inputs from "line level" sources, such as a radio tuner, cassette recorder, CD player, etc. "Mic In" inputs are used for microphones and are at lower signal levels than line level signals. In both cases, the inputs of the mixer/amplifier are roughly matched to the expected input signal level in terms of sensitivity and dynamic range. The mixer/amplifier usually includes a sensitivity trim adjustment for each input, allowing the user to exactly match any input signal to the performance specification of the mixer/amplifier. Therefore, as the output signal from a wireless receiver is optimized for that particular wireless system (and the output can be at microphone level or line level depending on the specification of the system), level adjustment and matching should take place at the mixer/amplifier, not at the wireless receiver output. The mixer/amplifier should process an optimized input signal, not a signal that has possibly been degraded by an incorrectly set VR on the wireless receiver.

Why Mipro prefer not to provide a user adjustable receiver volume control:

• MIPRO wireless receivers have an optimized output level that is factory QA aligned to exactly match the microphone capsules sensitivity. This means that the receiver can be connected directly to a mixer/amplifier with guaranteed optimum sensitivity and dynamic range levels. Therefore, users can operate MIPRO wireless microphone systems exactly as if they were working with a wired microphone, that is, without the need for any receiver adjustment.
• The absence of any user accessible VR means that premium results are guaranteed every time, without the fear that some well intentioned assistant may have changed any of the settings.
• Volume controls are traditionally a source of induced system noise, particularly as the system ages. Eliminating the VR simply means that premium results are guaranteed for longer.
• The absence of a volume control allows the designer to provide a cleaner and less cluttered front panel layout.