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35 Executive Solid Statesman FM Limiter Measured Performance

36 Any trademarks used in this manual are the property of their respective owners.

37 Executive Solid Statesman FM Limiter 1 Performance Measurements Measurements were made on the Executive Sold Statesman FM Limiter to confirm that performance of the unit met the published specifications. Performance is documented in this section for the following operating conditions (unless otherwise noted): Rack cabinet on the bench with the cover removed. AC input voltage = 117 V. Mode set to Limit. Recovery time set to Fast. Meter set to zero using the front panel control with zero audio input. Applied input = 10 dbm, 600 ohms, balanced, floating. Input level control set to the threshold of limiting as indicated on the front panel meter. Output load = 600 ohms, balanced, floating. Output level control set to provide +8 dbm at the output terminals. As documented in the following charts, some generalizations can be made with regard to overall performance: The unit is quite transparent within the audio range. Frequency response is flat up to at least 20 db of limiting. See Figures 1.1 through 1.8. Phase shift through the unit is reasonable and stable. See Figures 1.9 and The limiter circuit functions as expected, providing at least 20 db of gain reduction. See Figures 1.11 and The limiter has ample headroom, making more than +35 dbm output. See Figures 1.13 and Intermodulation distortion is quite low when the unit is operated below the limiting threshold, and remains low at 10 db and 20 db above the limiting threshold. See Figures 1.15 through Harmonic distortion is quite low from below the limiting threshold to 20 db of limiting. See Figures 1.19 through The noise performance is quite good, typically better than 70 db. See Figures 1.23 through The unit has a Limiter Clip Above mode that is intended to condition signals for application to an FM transmitter. There are six settings, each of which provides a different response roll-off. See Figures 1.27 through These charts are made with de-emphasis enabled in the Limiter Clip Above mode; this is the default setting for the unit. 3

38 Measured Performance d B r k 2k 5k 10k 20k Hz Figure 1.1 Frequency response over the audio spectrum. Input level set to just below the limiting threshold, and then the mode switched to Bypass. Output level set to produce +8 dbm d B r k 2k 5k 10k 20k 50k Figure 1.2 Frequency response over the audio spectrum to the 3 db points (approximately). Input level set to just below the limiting threshold, and then the mode switched to Bypass. Output level set to produce +8 dbm. Hz 4

39 Executive Solid Statesman FM Limiter d B r k 2k 5k 10k 20k Figure 1.3 Frequency response over the audio spectrum. Input level set to just below the limiting threshold. Output level set to produce +8 dbm. Hz d B r k 2k 5k 10k 20k 50k Hz Figure 1.4 Frequency response over the audio spectrum to the 3 db points (approximately). Input level set to just below the limiting threshold. Output level set to produce +8 dbm. 5

40 Measured Performance d B r k 2k 5k 10k 20k Figure 1.5 Frequency response over the audio spectrum. Input level set to 10 db above the limiting threshold. Output level set to produce +8 dbm. Hz d B r k 2k 5k 10k 20k 80k Figure 1.6 Frequency response over the audio spectrum to the 3 db points (approximately). Input level set to 10 db above the limiting threshold. Output level set to produce +8 dbm. (Note that 10 Hz is the lowest measurement point of the instrument.) Hz 6

41 Executive Solid Statesman FM Limiter d B r k 2k 5k 10k 20k Figure 1.7 Frequency response over the audio spectrum. Input level set to 20 db above the limiting threshold. Output level set to produce +8 dbm. Hz d B r k 2k 5k 10k 20k 80k Figure 1.8 Frequency response over the audio spectrum to the 1.5 db points (approximately). Input level set to 20 db above the limiting threshold. Output level set to produce +8 dbm. (Note that 10 Hz is the lowest measurement point of the instrument.) Hz 7

42 Measured Performance d e g k 2k 5k 10k 20k Figure 1.9 Phase shift through the unit as a function of frequency. Input level set to just below the limiting threshold, and then the mode switched to Bypass. Output level set to produce +8 dbm. Hz d e g k 2k 5k 10k 20k Figure 1.10 Phase shift through the unit as a function of frequency. Input level set to just below the limiting threshold. Output level set to produce +8 dbm. Hz 8

43 Executive Solid Statesman FM Limiter d B g Figure 1.11 Linearity of the unit as a function of input level. The value 10 dbm is just below the limiting threshold. Mode switched to Bypass. Output level set to produce +8 dbm. As shown, the unit begins to overload at about 2 dbm input. dbm d B g Figure 1.12 Linearity of the unit as a function of input level. The value 10 dbm is just below the limiting threshold. Output level set to produce +8 dbm. The influence of the gain-control system can clearly be seen beginning at an input level of 8 dbm. dbm 9

44 Measured Performance d B m k 2k 5k 10k 20k Hz Figure 1.13 Power bandwidth of the unit as a function of frequency. Mode switched to Bypass. Output level set to maximum. As shown, the limiter can provide more than +35 dbm output d B m k 2k 5k 10k 20k Figure 1.14 Power bandwidth of the unit as a function of frequency. Mode switched to Limit. Output level set to maximum. The action of the gain-control system is evident by comparing this chart with Figure Hz 10

45 Executive Solid Statesman FM Limiter % dbm Figure 1.15 SMPTE IMD as a function of input level. Mode switched to Bypass. For reference, 10 dbm is equal to the limiting threshold when the mode is set to Limit. Output level set to produce +8 dbm % dbm Figure 1.16 SMPTE IMD as a function of input level. For reference, 10 dbm is equal to the limiting threshold. Output level set to produce +8 dbm. 11

46 Measured Performance % Figure 1.17 SMPTE IMD as a function of input level. For reference, 0 dbm on this chart is equal to 10 db above the limiting threshold. Output level set to produce +8 dbm. The bump in distortion between 9 and 6 dbm is a function of limiter recovery timing. (See Figure 1.30.) dbm % Figure 1.18 SMPTE IMD as a function of input level. For reference, 10 dbm on this chart is equal to 20 db above the limiting threshold. Output level set to produce +8 dbm. dbm 12

47 Executive Solid Statesman FM Limiter % k 2k 5k 10k 20k Figure 1.19 THD+N as a function of frequency. Input level set to just below the limiting threshold, and then the mode switched to Bypass. Output level set to produce +8 dbm. Measurement bandwidth = 22 Hz to 80 khz. Hz % k 2k 5k 10k 20k Figure 1.20 THD+N as a function of frequency. Input level set to just below the limiting threshold. Output level set to produce +8 dbm. Measurement bandwidth = 22 Hz to 80 khz. Hz 13

48 Measured Performance % k 2k 5k 10k 20k Figure 1.21 THD+N as a function of frequency. Input level set to 10 db above the limiting threshold. Output level set to produce +8 dbm. The measurement bandwidth = 22 Hz to 80 khz. Hz % k 2k 5k 10k 20k Figure 1.22 THD+N as a function of frequency. Input level set to 20 db above the limiting threshold. Output level set to produce +8 dbm. The measurement bandwidth = 22 Hz to 80 khz. Hz 14

49 Executive Solid Statesman FM Limiter d B r k 2k 5k 10k 20k Figure 1.23 Noise spectrum relative to an input level of just below the limiting threshold, and then the mode switched to Bypass. Output level set to produce +8 dbm at the reference input. Measurement bandwidth = 22 Hz to 22 khz. No weighting filters. Input termination = 600 Ω. Hz d B r k 2k 5k 10k 20k Figure 1.24 Noise spectrum relative to an input level of just below the limiting threshold. Output level set to produce +8 dbm at the reference input. Measurement bandwidth = 22 Hz to 22 khz. No weighting filters. Input termination = 600Ω. Hz 15

50 Measured Performance d B r k 2k 5k 10k 20k Figure 1.25 Noise spectrum relative to an input level of 10 db above the limiting threshold. Output level set to produce +8 dbm at the reference input. Measurement bandwidth = 22 Hz to 22 khz. No weighting filters. Input termination = 600Ω. Hz d B r k 2k 5k 10k 20k Figure 1.26 Noise spectrum relative to an input level of 20 db above the limiting threshold. Output level set to produce +8 dbm at the reference input. Measurement bandwidth = 22 Hz to 22 khz. No weighting filters. Input termination = 600Ω. Hz 16

51 Executive Solid Statesman FM Limiter d B r k 2k 5k 10k 20k Figure 1.27 Frequency response in the Limiter Clip Above mode with settings of 400 Hz (top trace) to 10 khz (bottom trace) at an input level of just below the limiting threshold. Output level set to produce +8 dbm. Hz d B r k 2k 5k 10k 20k Figure 1.28 Frequency response in the Limiter Clip Above mode with settings of 400 Hz (top trace) to 10 khz (bottom trace) at an input level of 10 db above the limiting threshold. Output level set to produce +8 dbm. Hz 17

52 Measured Performance d B r k 2k 5k 10k 20k Figure 1.29 Frequency response in the Limiter Clip Above mode with settings of 400 Hz (top trace) to 10 khz (bottom trace) at an input level of 20 db above the limiting threshold. Output level set to produce +8 dbm. Hz % Figure 1.30 SMPTE IMD as a function of input level and recovery setting. 20 dbm on the chart is the threshold of limiting; 10 dbm is 10 db of limiting; 0 dbm is 20 db of limiting. The blue trace is for the Fast recovery setting, green is the Medium setting, red is the Slow setting. dbm 18