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TOPIC: Please help me understand 88A Voltage output

Please help me understand 88A Voltage output 1 year 1 month ago #21533

  • AustinJerry
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I have attached below a recent measurement of the output voltages in my setup. All connections are balanced, and the 88A settings are 8V input and 8V output. Kindly help me understand why the 88A output is only .4V when driven by a 2.2V input. Is this normal, or an indication of a problem?

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Please help me understand 88A Voltage output 1 year 1 month ago #21535

  • john.reekie
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Hi Jerry, I don't understand why you would think it to be a problem. Are your measured acoustic output levels OK?
I am not miniDSP support.

"You must ask the right questions." - Dr. Alfred Lanning's hologram.
-> Have you read the User Manual??
-> Have you drawn and posted a diagram?
-> Have you posted a screenshot?
-> Have you posted your config file?
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Please help me understand 88A Voltage output 1 year 1 month ago #21538

  • AustinJerry
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I don't perceive any issues with output levels, John. The question is more so that I can understand the behavior of the 88A more fully. My first question would be, is this a typical result? For someone who asks about 88A output voltages, can I simply tell them "Measure the input voltage, multiply it by 20%, and that will be your output voltage"?

If this behavior is not typical, or if the output is not always 20% of the input, then I would like to know what factors influence the output voltage levels. Make sense?
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Please help me understand 88A Voltage output 1 year 1 month ago #21541

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AustinJerry wrote:
For someone who asks about 88A output voltages, can I simply tell them "Measure the input voltage, multiply it by 20%, and that will be your output voltage"?

Hi Jerry, I believe that would be a "no" :) Would you be interesting in trying an experiment? - change the gain on your subwoofer amps by say 6 dB, and then recalibrate. Your measured output voltage will (should) change by a factor of two.

(I say "should" because the experiment assumes the same acoustic response in the room for both calibrations.)

You could change the gain in the miniDSP instead if changing it on the sub amps is tricky.

J
I am not miniDSP support.

"You must ask the right questions." - Dr. Alfred Lanning's hologram.
-> Have you read the User Manual??
-> Have you drawn and posted a diagram?
-> Have you posted a screenshot?
-> Have you posted your config file?
Last Edit: 1 year 1 month ago by john.reekie. Reason: Grammar bad.
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Please help me understand 88A Voltage output 1 year 1 month ago #21545

  • AustinJerry
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Unfortunately, this is not an experiment I am willing to make. The gain setting on my amps have been carefully set so that the combined sub output level matches the output level of the main speakers as measured by the level-setting test tones in DLCT. Raising or lowering the sub gains would have an undesirable effect on the Dirac Live calibration. While I suppose I could do it as a proof-of-concept exercise, I am reluctant to disturb the settings that have resulted in the excellent results I am now enjoying.

So I believe what you are saying is that the output voltage is determined by the Dirac calibration, and is set to achieve the appropriate output levels. That makes sense. And, of course, this voltage level would vary from one setup to another, depending on a number of factors such as the input sensitivity of the subs. If I am understanding you correctly, I think my original question has been answered.
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Please help me understand 88A Voltage output 1 year 1 month ago #21599

  • devteam
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Jerry,

Your final paragraph is indeed right on the mark. Dirac Live will calibrate for "acoustic level" rather than electrical level. It will look at the entire system of anything downstream the DDRC-88A and will adjust accordingly its gain structure. So the reasoning for these levels is basically based on the unique setup of amplifier gain + speaker sensitivity (+ 2x4 gains on the path) that the Dirac Live algorithm measures. No magic formula I'm afraid. :-)

Does this make sense?

DevTeam
MiniDSP, building a DIY DSP community one board at a time.
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Please help me understand 88A Voltage output 1 year 1 month ago #21607

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Yes, your answer makes total sense. Thank you for confirming.

Jerry
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