For decades, we’ve been watching stereo audio levels using two VU meters:  one for the left channel, and another for the right.  Whether doing a live show on the air, producing a spot or PSA, or recording a live performance, we’ve used the same pair of meters, with our eyes constantly jumping back-and-forth between the left and right meter.  Which channel is louder?  Are the channels balanced?  Are the levels right?  Will it be OK in mono? With stereo, we also need to watch for phase and polarity errors.  So we use an “X-Y” vectorscope…and now our eyes are jumping between two meters AND the scope! 

There’s got to be a better way to visually monitor audio.  Now there is…. it’s called “SAM”.

SAM, the Stereo Audio Monitor, is a new stereo level and phase meter.  In ONE place, you can see BOTH channels of stereo audio.  And not just levels, but POLARITY, PHASE, and mono-compatibility. SAM shows you EVERTHING you need to know, in ONE place.  No more dual meters, scopes, or jumping eyeballs!

SAM uses two tri-color LED meters to show all this information in an intuitive, easy-to-understand display.  The large arc shows BOTH left and right levels, and the lower linear display shows the Sum and Difference (phase and polarity) components of the stereo signal. 
The spec sheet below describes SAM and how it operates.  But first, let’s hear from a few SAM users…

Don Elliot, a veteran Los Angeles area production engineer, has been using SAM for a few months. Here are his comments:

“It’s like going from a stick shift to an automatic. I don’t have to worry about the cumulative buildup of too much level in one channel especially when mono-compatibility is important to the final product.  It’s easier to get the levels right the first time, with less eye fatigue. It’s easier to correlate what I SEE with what I HEAR.  I get more useable information faster and cleaner, so I work more efficiently and save time.”

From Mike Callaghan, Chief Engineer if KIIS-FM, Los Angeles:

“A station aired a stereo infomercial that was recorded in a hotel. The two mics were out of polarity but nobody caught it.  The file was just copied to the server, then it went on the air. The host was inaudible because of the cancellation!  The mod monitors still showed normal modulation levels.  The station has a phase scope, but the non-technical weekend personnel don’t know how to read it.

It was SAM’s Phase display, lit up bright RED, that alerted an intern that the entire program was out of phase!

Product Description

The Stereo Audio Monitor (SAM) is a stereo level and phase meter that incorporates Single Stereo Display* technology. SAM provides a visual indication of the levels and phase relationships of a stereo audio signal. The unit indicates the usual Left and Right channel levels, and also displays the Sum and Difference components of the stereo signal. SAM’s dual tri-colored Single Stereo Displays show this information in an intuitive and easy-to-comprehend format. Both analog and AES/EBU digital signals can be monitored with SAM. Its compact size allows monitoring three stereo audio sources in only 1 RU of rack space. (*Patent pending)

SAM consists of two independent LED displays. The main Single Stereo Display arc of 17 tri-color LEDs provides an accurate indication of stereo audio levels over a range of -25 to +3 VU. The LEDs show the Left channel in green and the Right channel in red. When both channels are present, the LEDs will be yellow. By watching the Single Stereo Display, an observer can easily read the levels of both audio channels, see the balance between the channels, and instantly see if a channel is missing. In addition, a blue “Peak” LED indicates audio peaks that exceed 0 VU. Extensive field testing has determined that, after a short adaptation period, an observer can quickly see more useful information from SAMs Single Stereo Display than from watching a pair of traditional VU meters. The ballistics of the display conform to industry standard VU meters, and show the perceived loudness of most program material with reasonable accuracy.

Below the Level display is the tri-color Phase display, an array of 10 LEDs. These indicate the levels of the Sum (L+R) and Difference (L-R) components of the stereo signal. The Sum is shown in green, with the Difference shown in red. These colors will accurately indicate the relative levels of the Main (baseband) and Stereo Subcarrier components of an FM or TV broadcast signal. With typical stereo program material, the display will appear mostly green, with yellow or red indicating the amplitude of L-R content. Excessive red levels would indicate phase error or a polarity reversal in the audio system. In any case, the LED Phase display is easier to read and interpret than a lissajous pattern on a vectorscope, especially for non-technical personnel. The Phase display can operate in “VU” mode (showing average levels) or in “Peak” mode to provide better indication of high frequency L-R information.

The Stereo Audio Monitor accepts an analog stereo input or an AES/EBU input if ordered with the optional plug-in AES decoder. The AES/EBU source can be either balanced (XLR) or unbalanced (BNC). The Level and Phase displays can be independently calibrated over a wide range of operating levels. The Phase display can be calibrated to the same reference as the Level display, or it can be used to show “headroom before clipping” to ensure adequate headroom in the audio system. A headphone Monitor jack is provided for aural monitoring.

The Stereo Audio Monitor is powered with a built-in AC power supply. It is 1/3 rack width and can be rack-mounted with the optional rack-mount shelf, or wall or cabinet mounted using optional cabinet/wall mounting brackets.