1. Switch on the module using the ON switch (16)
2. Begin with Output Gain (1) and Input Gain (15) at 0 dB, or set these controls corresponding to values matching your needs.
3. Turn the Attack Control (5) all to the left
4. Set the Steady-Release control (6) to the center position (0.3 sec)
5. Turn the LF-Release Ratio Control (7) all to the left
6. Turn the Peak-Release Ratio Control (10) all to the left
7. Turn the LF-Release Max Control (8) all to the right.
8. Turn the Peak-Release Min Control (12) all to the right.
9. Set the HUE Control (13) to the 0 dB position. The position of the Frequency Selector (14) is only important if the HUE control is not in the 0 dB position.
10. Switch on the Delay, using switch (3) .
11. Activate the limiter with the LIM-ON switch (2) und start with a Threshold (4) setting of 10 dB.
a) Use the Threshold Control (4), if necessary in combination with the Input Gain Control (15) to adjust 3 dB of Gain Reduction on the LED display. You can use the Input Gain Control (15) to shift the Threshold control (4) to a range with smaller steps (around 10 dB).
b) Adapt the output level with the Output-Gain Control (1) to your a/d converter.
c) Usually a gain reduction of 3 dB is not criticle and possible with almost all kinds of signals without audible side effects.
Increase the gain reduction using the Threshold Control (4) or the Input Gain Control (15) until the output signal is not free from negative side effects anymore.
d) Start with the fine trim of the Steady Release Control (6). Turn the pot to the right till you hear pumping. Find the point where the pumping dissappears by turning the control to the left.
e) In most cases low frequency signals will be distorted after trimming the Steady Release Control (6). The reason for the distortion is the short release time that causes regulation within the period time of the bass signals. Usually the setting of the Steady Release Control (6) is a compromize between audible pumping and distortion that eventually limits the maximum gain reduction. The additional circuits of the U795 allow to find a better compromise:
f) Turn the LF-Release Ratio Control (7) to the right and try to find a setting where the LF distortion disappears. Make sure that you don't overcompensate the distortion. If the control is more to the right than necessary for the compensation of the distortion, pumping right after heavy low frequency signals occurs. The LED displays the effect of this modulation.
(green - no regulation, yellow - regulation threshold, orange - medium regulation, red - massive regulation)
In most cases a setting between yellow and orange is sufficient.
g) After finding the best position of the LF-Release Control (7), check the mix for heavy bass signals, far above the average. This might be a drum break or something similar. Check for pumping right after the massive bass sounds. If this occurs, the LF-Release Max Control (8) should be used to limit the maximum modulation to a values that avoids pumping. Either loop around the break or use the ADJ switch (9) to accomplish this setting.
The ADJ switch (9) applies a test signal to the modulation circuit that is equal to a very high level bass signal. You can use this test signal to adjust the maximum release time instead of the mix.
Make sure that the ADJ switch (9) is released after the setting.
h) The LF-release modulation avoids low frequency distortion by increasing the release time while high level low frequency signals are present. If a short peak appears during such a bass signal, it can cause audible pumping due to the additional gain reduction caused by the peak, since the release time is still determined by the bass signal and above the pumping threshold. To avoid this effect, the peak modulation circuit can reduce the release time just for the short duration of the peak.
The Peak Release Ratio (10) allows adjusting the influence of peaks on the release time.
i) If peaks durings bass signals cause pumping, turn the Peak Release Ratio Control (10) to the right, until the pumping disappears. The LED displays this modulation.
(green - no regulation, yellow - regulation threshold, orange - medium regulation, red - heavy regulation)
The short duration of the peak makes it necessary to add a short hold time to the display. This hold time has no influence on the modulation itselft but it is necessary to see any effect. The original control signal is so fast and short that it would be not visible.
Make sure that the Peak Release Ratio Control (10) is set to the minimum possible position to compensate the pumping. If its to far to the right, the LF signal might be distorted for a short time right after the peak.
j) Like with the LF-Release circuit, an additional control lets you limit the influence of the peak regulation to a fixed value. The Peak Release Min Control (12) can limit the minimum possible release time. This might be necessary, if very heavy peaks cause a regulation that drives down the release time into the distortion range. If this occurs, use the control to limit the range of the modulation until the disortion disappears.
The ADJ (Adjust) Switch (11) applies a Test Signal to the circuit that is equal to the highest possible peak that the converter can handle. It might help you adjusting the minium time with the Peak Release Min Control (12).
Make sure that you release the ADJ Switch (12) after the setting.
k) The Hue-Filter lets you adapt the frequency response of the regulation to your taste or your needs. When the Hue Control (13) is in the center position (0 dB), the limiter has a neutral sound performance with and without regulation. There are no loss of high frequencies or any similar effects.
The Hue Filter can alter this neutral behaviour in both directions; more or less mid / high frequency signals. The Hue filter has a shelving characteristic; the frequency is controlled by the stepper switch (14) with 6 positions in the range from 1 kHz to 10 kHz. Turning the Hue Control (14) to the right boosts mid/hi signals in the side chain, which results in a reduction of this frequency band in the audio path and vice versa.
The control ranges for Threshold, Input and Output Gain and Hue can be determined by the customer as well as the frequencies of the Hue control.
Inputs and Output
The device is available with electronically balanced or transformer balanced inputs and outputs.
The colors of the faceplate, the control knobs, and switch caps can be determined by the customer.
Please, check for details here.
Why are the settings for LF-Ratio Release and Peak Ratio Release different from title to title?
Depending on the spectrum of the signal, the relation of low frequency signals and fast peaks to the total level, the control parameters of the modulation section are different. A mix with a high bass level will result in a control signal that is a lot higher than the control signal of an average mix. The situation of the peak control is quite similar. A soft mix with high reverb levels won't have that much peaks, while a transient-rich signal consists of almost only peaks. The necessary settings for the different controls depend not only on the signal itself but also on the audibility of negative side effects that cannot be calculated in any meaningful way. These effects result in different control signals from mix to mix and different necessary settings, appropriate to the actual signal. However, the control ranges of all controls are sufficient to cover all variants.
Why does the Hue control affect the Threshold?
The spectral density of the frequency range that is affected by the hue control determines if and how much the hue control affects the threshold setting. Since the hue filter is part of the side chain and changes the frequency response, it also changes the level in the specific frequency band at the input of the peak converter that causes the regulation. If peak levels are present in the frequency range that is affected by the actual setting of the hue controls, the altered level will determine the threshold. With common mixes, there is only a minor effect on the threshold; however, this must not be the case all the time. There is no way to avoid these effects without leaving out the hue filter. We consider the hue filter, primarily with settings that add a little more high frequencies at the upper end of the audio band to the regulation response, as a nice feature that is of advantage even if it makes necessary the little effort of readjusting the threshold one or two clicks every once in a while.
If you have any questions or comments, please let us know.