Model 750

Setup Direct Output

The setup direct output is a stereo line- level output that provides direct access to the voice and tone signals. Trim potenti- ometers allow adjustment of the output level from approximately –2 to +10dBu. The trim pots are located on the back panel, directly above the setup direct output’s ¼-inch phone jacks. At the fac- tory these outputs are loaded with 100k ohms, and then the trim pots are adjusted to give an output level of +4dBu.

If the setup direct output is to be used in an installation, it’s important that the left and right channel output levels be ad- justed to precisely match the requirements of the system. Even if you simply want to use the standard output level of +4dBu, it’s still important to confirm the factory calibration. Also note that while the output circuitry is capable of driving loads of 600 ohms or greater, the output level will drop slightly as the load impedance ap- proaches 600 ohms. A 0.5dB difference in output level can be expected as the load impedance changes from 20k ohms to 600 ohms.

In practice, calibrating the output level is quite simple:

1.Confirm that both the left and right channels of the setup direct output are terminated with their normal load impedance.

2.Ensure that the Model 750 is con- nected to mains power.

3.Activate the setup section’s single tone output by placing the single tone button to the on (in) position. The voice and multi-tone buttons should be in their off (out) position.

4.Using an appropriate adapter cable, connect an audio level meter directly across the left channel setup direct output. Ensure that your connection does not remove the normal load! The level meter must be a precision device that’s intended for audio use—a general-purpose voltmeter is not adequate!

5.Carefully observing the level meter, adjust the trim pot associated with the left channel to give the desired output level.

6.Repeat steps 4 and 5, this time for the right channel.

External Record/TB Audio Source

During installation, an external source of audio may have been connected to serve in lieu of the Model 750’s internal micro- phone. This audio source will be used for voice recording by the setup section, as well as by the talk back functions. The external audio source needs to have a nominal audio level of –20 to +4dBu. A trim potentiometer, located on the back panel directly above the record/TB exter- nal audio input jack, adjusts the input sensitivity of the circuitry. For correct operation it is crucial that this trim pot be adjusted so that the source audio level is “matched” with the requirements of the Model 750.

The procedure is a bit convoluted, but not difficult:

1.Ensure that mains power is connected to the Model 750.

Issue 3, May 1997

Model 750 User Guide

Page 18

Studio Technologies, Inc.

Page 14 Page 16
Page 15
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Fostex 750 manual Setup Direct Output, External Record/TB Audio Source
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750 specifications

The Fostex 750 is a premium closed-back headphone that has garnered attention for its combination of advanced technology, comfort, and sound fidelity. Designed primarily for studio applications, the Fostex 750 delivers an exceptional listening experience that caters to both professionals and audiophiles alike.

One of the main features of the Fostex 750 is its dynamic driver technology. The headphones are equipped with large 50mm titanium-coated drivers that provide a powerful and clear sound reproduction. This driver configuration is engineered to deliver a wide frequency response, ranging from deep bass to sparkling highs, ensuring that every detail of the audio is captured. With an impedance of 25 Ohms, the headphones are highly efficient and can be easily driven by a variety of devices, including portable music players and digital audio converters.

Comfort is another highlight of the Fostex 750. The headphones feature plush ear pads made from soft polyurethane, which provide excellent cushioning for extended listening sessions. The adjustable headband offers a customizable fit, allowing users to achieve an optimal acoustic seal that enhances sound isolation. This is particularly beneficial in studio environments, where external noise can interfere with critical listening.

In terms of build quality, the Fostex 750 boasts a robust yet lightweight design. The combination of high-quality plastics and metal components contributes to its durability, while the foldable structure makes it portable and convenient for travel. This practicality is further enhanced by the detachable cable, which allows for easy replacement in case of wear.

Another notable technology integrated into the Fostex 750 is the use of new acoustic engineering principles. These headphones feature a closed-back design that minimizes sound leakage and provides an immersive listening experience. This design is complemented by the innovative bass reflex system, which enhances low-end response without compromising clarity in other frequency ranges.

Overall, the Fostex 750 is an impressive headphone that combines advanced sound technology, comfort, and durability. Its dynamic drivers, ergonomic design, and acoustic engineering make it an ideal choice for both professional monitoring and casual listening. Whether you are mixing in a studio or enjoying music on the go, the Fostex 750 delivers an unmatched audio experience that is sure to satisfy even the most discerning listeners.
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