Tutorial
LE3000S
15
Using the Tone Generator and THD+N Features
Model 3000S is an all digital machine, capable of supplying and analyzing AES/EBU and SPDIF digital
audio data. While aimed at digital in/digital out applications, the use of external reference A/D and D/A
converters can expand usability to include analog domain measurements (accuracy will be limited to the
performance of such devices).
Example A: evaluating a single digital in/digital out unit.
1. Connect model 3000S output to unit under test. Select output sample rate on main screen. Connect
unit's output to Model 3000S input.
2. Set Model 3000S for appropriate output parameters: Highest tone accuracy is achieved when unit is
set to output 24 bits (Professional format).
3. Select test tone screen, set for desired tone frequency and amplitude, and press the “GO” button.
4. Select THD+N screen and press the "GO" button.
5. Read results (tone frequency, amplitude and THD+N).
You may now adjust "unit under test" parameters while viewing THD+N. You may go back and forth
between tone generation screen and THD+N screen for testing different amplitudes at the set
frequency. Selecting a new frequency requires you to press GO to re-tune the notch.
Example B: optimizing multiple unit interconnections.
Clearly, the microphone preamplifier resides at the front end, and the format converter at the back end.
Some units may be placed in various locations in the audio chain (which is better? digital equalizer
followed by sample rate converter? or vice versa). The old "trial and error" method may work well for two
units in series. The possibilities for connecting three units become cumbersome.
Evaluating each unit individually (see example A) and then connecting them in descending order of
performance yields the best results (i.e., best unit first, driving second best, with lowest performer last in
the chain).
Summary of Contents for 3000S
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