Hiss is a common problem with most of today's DSLR cameras. The front ends tend to be noisy which can lead to excessive hiss if the levels are not set right. The simple fact is that the higher the gain of the camera preamps, the higher the hiss. The solution obviously is to reduce the noisy gain in the camera and replace it with the very clean gain of our DXA-SLR or DXA-SLR PRO adapters. When no amplification is required as when using wireless mics, our low cost passive DXA-5Da can be used.
When using the DXA-SLR, adjust the level controls on the adapter so that the indicator LED's flash green. This tells you when you are in the proper recording level window to get the best signal to noise ratio and least amount of hiss. On the DXA-SLR PRO, you can use the built-in VU meters as a guide and set the levels so that the audio is peaking at no more than -12 dB. Use the AGC Disable feature on the adapter to reduce the noise created by the AGC in the camera.
If your camera allows you to disable the AGC from the camera menu, you can use manual mode to get even better audio. On the Canon 5D MK II or MK III set the camera gain to 25% of maximum. On Nikon cameras set it to LEVEL 1 on the older models, or 7 on the newer D4 and D800. In this case, you do not need to use the AGC Disable feature on the adapter - keep the switch to the left so that it is not activated.
It is critical that the levels be set right so that you are not starving the camera for audio as that will increase the internal camera gain which is something you want to avoid. Once the levels are set correctly, you should be able to capture clean, crisp audio.
The performance of all of adapters meets broadcast quality and far exceeds that of any camcorder of DSLR camera in terms of frequency response, noise and distortion. This means that your sound quality is determined solely by the quality of microphones and cameras that you have - and knowing how to use them properly.
Most professional audio devices are connected via balanced cables to minimize pickup of stray electrical noise. Consumer audio devices use unbalanced cables and are very prone to picking up noise, especially at low signal levels from devices such as microphones. Balanced circuits have an inherent ability to only pass audio signals and reject unwanted noise. Balanced refers to the fact that there are two symmetrical signal lines and one ground, while unbalanced uses just one signal line in reference to ground. Normally, XLR connectors are used in most balanced devices while unbalanced consumer gear normally use mini-plug connectors.
Passive simply means that no external power is required to operate the device. Our passive adapters use shielded transformers to convert the balanced input signals from XLR connected mics to an unbalanced output for connection to the camera. The beauty about passive circuitry is that it is completely noise free for pure, clean sound. However, it does not provide any amplification so it requires that the source signal be sufficiently strong enough to drive the recording device adequately. Active means there is powered circuitry to provide amplification or other processing to the source signal. This of course requires power to operate. The advantage of using active circuitry is the clean amplification it can provide to replace the noisy amplification in the camera for an improved signal to noise ratio.