# Please explain sigma-delta modulator in my signal path

**URL:** <https://community.roonlabs.com/t/please-explain-sigma-delta-modulator-in-my-signal-path/79277>\
**Category:** Roon Software Discussion\
**Created:** [September 28, 2019, 5:20pm UTC](https://community.roonlabs.com/t/please-explain-sigma-delta-modulator-in-my-signal-path/79277 "2019-09-28T17:20:27Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![Jim\_Austin](https://community.roonlabs.com/letter_avatar/jim_austin/32/5_5575768a8748004e209b776fc1b2916d.png) [@Jim\_Austin](https://community.roonlabs.com/u/Jim_Austin)\
**Post date:** [September 28, 2019, 5:20pm UTC](https://community.roonlabs.com/t/please-explain-sigma-delta-modulator-in-my-signal-path/79277/1 "2019-09-28T17:20:27Z")

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![15%20PM](https://roon-community-uploads.s3.amazonaws.com/original/3X/4/9/499029f0cd2d1bffd76e45f0a0fd9e7bad76b4ed.png)

I understand why this 2xDSD file is being down-converted: The Devialet Expert Pro is specified as handling only DSD64. But what’s with the sigma-delta modulator?

Thanks,  
Jim

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**Author:** ![ged\_hickman1](https://community.roonlabs.com/user_avatar/community.roonlabs.com/ged_hickman1/32/259791_2.png) [@ged\_hickman1](https://community.roonlabs.com/u/ged_hickman1)\
**Post date:** [September 28, 2019, 5:53pm UTC](https://community.roonlabs.com/t/please-explain-sigma-delta-modulator-in-my-signal-path/79277/2 "2019-09-28T17:53:00Z")

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What’s under the sigma box? Any DSP? Or volume control on the devialet? If so this may apply

> [@Native DSD processing](https://community.roonlabs.com/t/native-dsd-processing/24286/2):
>
> Unlike with PCM, processing 1-bit DSD signals in their original form is not practical because 1-bit signals do not have enough dynamic range to perform common operations like volume adjustment, eq, mixing, or convolution directly on the 1-bit representation. So when DSD IS processed, the input to the processing chain is a 1-bit DSD signal, but the output must have more dynamic range. In Roon’s case, we perform processing with 64-bits of precision, so whenever you process DSD, you end up with so…

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**Author:** ![Jim\_Austin](https://community.roonlabs.com/letter_avatar/jim_austin/32/5_5575768a8748004e209b776fc1b2916d.png) [@Jim\_Austin](https://community.roonlabs.com/u/Jim_Austin)\
**Post date:** [September 28, 2019, 6:22pm UTC](https://community.roonlabs.com/t/please-explain-sigma-delta-modulator-in-my-signal-path/79277/3 "2019-09-28T18:22:36Z")

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Here’s the image without the Sigma-Delta box. Yes, there’s a volume control in the Devialet, but it should be able to accept DSD64 input. That conversion appears to be happening before the Devialet, if I’m thinking about it right.

 ![30%20PM](https://roon-community-uploads.s3.amazonaws.com/original/3X/3/5/35f32e5c00d51362810f49c87f884b7055919b9e.png)

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**Author:** ![brian](https://community.roonlabs.com/user_avatar/community.roonlabs.com/brian/32/48353_2.png) [@brian](https://community.roonlabs.com/u/brian)\
**Post date:** [September 28, 2019, 8:29pm UTC](https://community.roonlabs.com/t/please-explain-sigma-delta-modulator-in-my-signal-path/79277/4 "2019-09-28T20:29:12Z")

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The output of the sample rate conversion is multi-bit audio, but at the sampling rate of the DSD that is to be generated–in this case 2.8224MHz.

The sigma delta modulator transforms that multi-bit stream back to a 1-bit DSD stream that the Devialet can understand.

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**Author:** ![Jim\_Austin](https://community.roonlabs.com/letter_avatar/jim_austin/32/5_5575768a8748004e209b776fc1b2916d.png) [@Jim\_Austin](https://community.roonlabs.com/u/Jim_Austin)\
**Post date:** [September 28, 2019, 8:47pm UTC](https://community.roonlabs.com/t/please-explain-sigma-delta-modulator-in-my-signal-path/79277/5 "2019-09-28T20:47:16Z")

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Got it–thanks Brian.