BillFitzmaurice.info

Brent is correct. What I think is important to remember is that the typical system arrangement where there is a limiter followed by the power amplifier is open loop. In other words, there is no feedback from the amplifier output to tell the limiter when to engage. This means that the output voltage of the amplifier is a function of the input signal level and the amplifier's gain:

output voltage = input voltage x gain
50v = 1.0v x 50

Using the recommended method for setting up a limiter, you first set the gain knobs to maximum which means no input attenuation and effectively the maximum gain. Then you adjust the limiter threshold to achieve the desired maximum voltage. This simply means that you are lowering the input signal with the limiter, so that at the maximum amplifier gain you have maximum desired voltage.

Now, after setting the limiter, if you then lower the gain knobs on the amp (which attenuates the input signal), the limiter will engage at the same point, but the output voltage of the amplifier will be lower because the gain is effectively lower.

output voltage = input voltage x gain x attenuation
35v = 1.0v x 50 x -6db

kkip wrote:Brent is correct. What I think is important to remember is that the typical system arrangement where there is a limiter followed by the power amplifier is open loop. In other words, there is no feedback from the amplifier output to tell the limiter when to engage. This means that the output voltage of the amplifier is a function of the input signal level and the amplifier's gain:

output voltage = input voltage x gain
50v = 1.0v x 50

Using the recommended method for setting up a limiter, you first set the gain knobs to maximum which means no input attenuation and effectively the maximum gain. Then you adjust the limiter threshold to achieve the desired maximum voltage. This simply means that you are lowering the input signal with the limiter, so that at the maximum amplifier gain you have maximum desired voltage.

Now, after setting the limiter, if you then lower the gain knobs on the amp (which attenuates the input signal), the limiter will engage at the same point, but the output voltage of the amplifier will be lower because the gain is effectively lower.

output voltage = input voltage x gain x attenuation
35v = 1.0v x 50 x -6db

Arr, I understand what you're saying, and am now wondering if I read what Brent wrote incorrectly.
I thought Brent was talking about in amp peak limiter for example...

Grant Bunter wrote:
Arr, I understand what you're saying, and am now wondering if I read what Brent wrote incorrectly.
I thought Brent was talking about in amp peak limiter for example...

In amp limiters may or may not work that way. You'd have to look at the schematic. Sometimes the limiter is after the input stage, sometimes not. On Crown XTI, it's post attenuator, and can be set by voltage (which is tres cool).