Henry-engineering SAM User Manual download pdf

STEREO AUDIO MONITOR

DIGITAL AND ANALOG STEREO LEVEL AND PHASE METER

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. A large

arc of 17 LEDs indicates Left and Right channel levels; a horizontal row of 10 LEDs 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.

WARNING! For 230V operation, change mains voltage jumpers before connecting to AC power!

Remove jumpers between E6 & E9, and between E7 & E8. Install a jumper between E6 & E7 for 230V; replace

fuse with .125a fuse. See schematic on reverse side. Jumpers should be changed by a qualified technician only.

INSTALLATION

To monitor a stereo analog audio, connect to the left and right input. To monitor digital audio, connect to either of

the AES/EBU inputs. Wire the XLRs with Pin 2 HI, Pin 3 LO, and Pin 1 Ground. The XLR digital input is for AES3

signals (110 ohm termination); the BNC input is for AES3id signals (75 ohm termination). NOTE: SAM is shipped

from the factory with termination set to 110 ohms. If the BNC input is used, the termination should be changed to

75 ohms. Open the unit, and set JP1 to its alternate position. JP1 is located near the digital input XLR connector.

CALIBRATION

The Left, Right, Sum and Difference displays have independent calibration trimmers. SAM is set at the factory so

that an analog input of +4 dBu corresponds to “0-VU”, but it can be recalibrated over a wide range of input levels.

To calibrate the Level display, feed a tone at the desired 0-VU level into the Left input. Adjust the Left (L) trimmer

so the green 0-VU LED is lit. Then feed tone into the Right input, and set the Right (R) trimmer so the red 0-VU is

lit. Now feed tone into both channels; the LEDs will be yellow.

With tone feeding both the Left and Right inputs, adjust the Sum (S) trimmer for a green 0-VU reading on the Phase

display. To calibrate the Difference display, it is necessary to reverse the polarity of one input to SAM. With both

channels fed at the same level but opposite polarity, adjust the Difference (D) trimmer for a red 0-VU reading.

The calibration procedure is identical when using the digital input. (The factory setting is 0-VU = -20 dBfs.)

USER SETTINGS

On the back of the unit there are two pushbuttons, labeled IN and PH. The INput button selects either the Analog

(out) or the Digital (in) input. The Phase button selects the response time for the Phase display, either Slow (out) or

Fast (in). (The Phase display will more effectively show high-frequency phase information if it is set to Fast.)

NOTE: We goofed! The silkscreened labels for these two buttons were inadvertently reversed! The PH button is

actually on the LEFT, and the IN button is on the RIGHT.

OPERATION

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. High yellow levels would indicate excessive L-R

content or phase errors (which can exasorbate multipath and reduce loudness), and a redphase display would

indicate a polarity reversal in the audio system. In most cases, the LED Phase display is easier to read and

interpret than a lissajous pattern on a vectorscope, especially for non-technical personnel.

HENRY ENGINEERING

503 Key Vista Drive

Sierra Madre, CA 91024

Tel: 626.355.3656

Fax: 626.355.0077

www.henryeng.com

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STEREO AUDIO MONITOR 1

Summary of Contents

Page 1 - STEREO AUDIO MONITOR

STEREO AUDIO MONITOR DIGITAL AND ANALOG STEREO LEVEL AND PHASE METER DESCRIPTION The Stereo Audio Monitor (SAM) is a stereo level and phase met

Page 2

PAGE 2 PHONES JACK SAM includes a Headphone jack on the front panel. It may be used for aural monitoring. Use contemporary headphones with an imped

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