Do I need to change gain if merging from stereo to mono?
I have a patcher that takes two separate inputs, by default goes through 1.0 gain (allowing me to adjust gain if I want) and then goes to two outputs of a dac. Here’s the section of the patcher in question
-- Pasted Max Patch, click to expand. --Copy all of the following text. Then, in Max, select New From Clipboard.----------begin_max5_patcher---------- 702.3oc4W18aSCCD.+4z+JrBug5prcbyG7FBg3EPHg3sooI2D2VCINQItaEl V+aG+QRaJpKMsaKiIdIeb9r8c+7Yemuaji6r70rJWv6.WBbbtajiiQjVfS8+ NtYz0wozJiZtB1s4y9g6XaSR1ZoQbxLYNcSiXwpr7UxTlzzGTszBpLdIWr35 RVrzNmS8gSfiAXh4EIz7i5avU08gmXFd0TdAInY3mmKjBZFyzz6K4zzlVryp 7WEL636VwWHTMuc7zcsh+aSyHrZ51ZvbwV6UK69QizOF+3vRJWv1.fSNLXvG GLHj90TXmfw+7AyXf6LpXwoAH7SGfTdLieCC7oz7YzzOtVxJUl0WWIKVI+dI O6binPgFvghPcQNL5LH2owJ3SGqd6F.ZxoCjHOCBBMat776hGHz.sEC+hSER +oB40GTJnw+7jYBIJv.CTvwYBF9ruy4bvQFSc.x1zP2RKyhySyKsyObR3TXT 331enOinkG1aV4O0F3XLd.xGaSi0ZnJJYULgjJ44h1CVKHF9fjZdZNUtCWbg xstQGOoFGXCslsXOmi.8hv3wG7q19npSI60QnVSkCEhIG.IRVAee880ZEfiH H7Azuse2FXjZEUYyBsGMuO2eb4eGtEdOyRsGwleAZKYAcZK7Q+Gsv6MAE5S7 vOiK9OTMozXUtA.9vGDBOZxAOeyQfAcV7EpGEe8xTS0FvaPW+E9ZV4GVREBV cUUeiuXo7jyMDDZ2+RH138NqTG+5qP8tY1mYykmaIFHuHKx5NL5E.YlNZthx ecCPiynkuOGqxWUF2L4M2HCrycRXURtX64dWtqlR0tvFkVxSRXh1a.y3IE4p C5pMBvUGbU8I0lHCpIoukwwMI+8T5YGS98wlBFTaB0yUtAzh5iIoy.LjQS8c O2vgI8kA5GlFv.7WmlTz+dw2gOBSR8y8i9COMTKc -----------end_max5_patcher-----------
Now suppose I need to merge those two inputs (left and right) so as to go out through a single channel rather than two channels. Do I have to reduce the initial gain from each input before I connect them to a single input port on a dac?
If both signals are scaled to 1.0, then there is a strong likelihood that the combined signals will produce an output above 1.0 when their peaks line up. Most DAWs that allow you to combine a stereo signal into mono give you the option of reducing the signal by 3dB in the process to prevent clipping. I’ve always made it a practice to do the same thing in Max by using [*~ 0.5] on either the two channels before summing, or on the summed signal before it gets to the [dac~].
Just a note: [*~ 0.5] would be -6 dB. For -3 dB (which is the typical adjustment) you need [*~ 0.71]. Ask a pocket calculator for the exact value of sqrt(2) if you want more precision (don’t forget, about 6 digits is as good as it gets for Max).
The -3 dB guideline may depend a little bit on your material, but it’s a standard rule-of-thumb.
Oh, I always thought the DAW was doing a -3dBm conversion, which would be [*~ 0.5]. Is that not the case? Is it dB SPL?
Thanks for the responses — the goal is that I am sending a stereo pair to channels 1/2 at FoH such that the two faders are at 0db (say) and then I temporarily sum my stereo pair to a single channel that I now send out on channel 1, the FoH engineer should not have to adjust the channel 1 fader at all.
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