Channel Blender

[Craig Maier]

Channel Blender



The Channel Blender provides the ability to reduce muddy bass from vinyl recordings, decrease the "ping-pong" effect from early stereophonic recordings, minimize multi-path distortion from FM stereophonic broadcast recordings and even remove vocals from stereo recordings. It can also be used as a spatial enhancer (spatializer) when one of the two channels is set for “Invert Phase”.

The Channel Blender

The Channel Blender serves (at least) 7 purposes:

1. 1. 1. 1. In the early days of stereo, channel separation was the rage. Sound engineers often literally segregated the recording artists into separate recording studios or booths in order to maximize the channel separation. This later became known as the “ping-pong” effect. In other words, with stereo separation, if a little was good, and more was better, then too much was thought to be just enough. The Channel Blender can be used to reduce the extreme stereo separation found on some of these early stereophonic recordings, restoring them to a more natural sound.

1. 1. 1. 1. Rumble on Vinyl recordings is dominated by the vertical displacement component of the master recording and playback stylus. Since bass is acoustically non-left or right below about a hundred Hertz, this rumble can be reduced by summing the low frequency signals (to mono) below a certain crossover frequency. This monophonic bass signal can then added back into the main stereophonic signal. The “Blend to Mono” feature performs this function when it and the “below” function are checked. This can add clarity and improved bass definition to vinyl recordings, which sound muddy due to excessive rumble. Keep in mind that rumble is not just a by-product of the turntable from which you are playing a record, but also involves the system which mastered it in the first place. Even though you may have a very expensive turntable, you will still encounter recordings that are laden with rumble. The recommended frequency for this feature is around 125 Hertz with the “below” box checked. Experiment to determine the best results for the material that you are dealing with.
         2. FM stereo multi-path distortion, when it occurs, is dominant in the top two octaves of the audio spectrum. By placing the channel blender in Blend to Mono above the corner frequency setting, you can reduce this distortion with a tradeoff of channel separation at the upper end of the audio spectrum. Try corner frequency settings starting at around 5 kHz with the “above” box checked.
         3. Lastly, ambience can be enhanced on a stereo recording by phase inverting one of the channels and summing by the L-R rather than the L+R information back into the main signal path. This is accomplished by phase inverting one of the two channels.
         4. The Channel Blender can reduce the “thump” that you hear when you play a cracked record by blending both channels to 100 via the Left & Right “Blend” controls.
         5. The Channel Blender can also be used as a Spatial Enhancer (Spatializer) or room acoustic dimension expander. This feature can be used to add more of a “live” feel to recordings that have most of the activity occurring in the middle of the sound-stage and where it would be desirable to extend some of those sounds more to the left and right side. This is accomplished by setting one of the channels for “Invert Phase” and the “Blend to Mono” checkbox being checked. You must also set the “Blend to Mono” feature for a crossover frequency less than around 200 to 500 Hz. Four factory presets are provided to help you get started using the spatializer functionality.

7. The Channel Blender can be used as a “Vocal Remover”
using several special presets that it contains. Vocal
removal (vocal attenuation) requires a Stereo recording
source wherein the lead vocalist is contained within both
channels.

There are 4 presets to choose from including:
Lead Vocal Attenuator 1
Lead Vocal Attenuator 2
Lead Vocal Attenuator 3
Lead Vocal Attenuator 4

The Channel Blender has the following unique controls:

• Left and Right Channel Blend Controls: These two controls take the summed or differenced signal and add it back into the respective left and / or right channels. When these controls are set to 0, there is no blending effect. At a setting of 100, the blending is maximized. An Invert Phase check box is located in the Left and Right blend control panels. This produces a 180-degree phase inversion of either of the channels before the summation takes place. Therefore, you can blend in L+R (with the phase inversion boxes not checked) or you can blend in the L-R signal (with ONE of the two Invert Phase boxes checked). The L-R signal contains the ambience information on most stereophonic recordings. If both Invert Phase boxes are checked, the signal reverts back to L+R, so if ambience enhancement is desired, only check one box.
• Blend to Mono Checkbox: This checkbox sums the signal to monophonic above or below the indicated frequency. You can select a crossover frequency (corner frequency) anywhere between 10 and 10,000 Hertz.
• Above: This blends to mono all frequencies above the corner frequency setting. This is used to reduce multi-path distortion from FM broadcasts.
• Below: This blends to mono all frequencies below the corner frequency setting. This is used to reduce rumble and muddy bass on vinyl stereophonic recordings.
• Invert Phase: This changes (shifts) the phase relationship of the chosen channel by 180 degrees with respect to the other channel. (If both boxes are checked, no net phase shift will occur.) This function is often associated with the spatializer effects (found in the presets area).
• Presets: Over 15 presets are provided for you to use as starting points.