Author Topic: Amp settings  (Read 1007 times)

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Offline orion_jb2001

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Amp settings
« on: November 18, 2017, 04:29:30 PM »
Hey brain trust,

Now that I am tweaking mode for the Blue, a refresh on amp settings.  For instance, a setting of 8 x 1 will give you a total gain of 320, however a reversed setting of 1 x 8 will also give you a total gain of 320. Now I imagine these amp figures are the same for red and blue, but what does the first figure represent or connected or controls what and what is the second figure represent or connected or controls what?? But to add further intrigue to the question, you can reach the same "320" gain result with 4 x 2 or 2 x 4.  So which one would you use, the 8 x 1 or the 4 x 2??? 
« Last Edit: November 18, 2017, 06:23:31 PM by orion_jb2001 »

Offline miraculon

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Re: Amp settings
« Reply #1 on: November 19, 2017, 08:42:38 AM »
There are two Programmable Gain Amplifiers (PGA) that these values set the gain on. There are two per channel and they are in series with each other. The first number adjusts the gain of the first PGA, and the 2nd one the 2nd one. How logical...

Although the product of these gains can give the same result as you point out, my preference would be more towards the "4x2" setting as opposed to the others. Having the higher gain in the 2nd amplifier amplifies not only the signal, but the noise inherent in the first amplifier stage. So, 1x8 is the least desirable setting.

In "olden times" gain was adjusted by resistor values in the feedback path of an Operational Amplifier (OpAmp). There are other amplifiers in the "signal chain" that work this way and are not adjustable by software control.

Greg H.

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