In this application note, we will show you how to record an analog signal to your computer using a suitable miniDSP processor. This is useful for digitizing analog tapes and vinyl records, for example. This app note is applicable to miniDSP processors that provide their processed outputs over USB, specifically:
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2x4 HD (miniDSP-2x4-HD plugin)
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DDRC-24 (DDRC-24 plugin)
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miniDSP Flex (with either miniDSP-2x4-HD or DDRC-24 plugin)
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SHD Series (SHD plugin)
Contents
- 1. Overview
- 2. Get connected
- 3. Set up the plugin
- 4. Set up ocenaudio
- 5. Make the recording
- Wrapping up
1. Overview[Top]
While we live in a "digital age" as far as music playback goes, many of us still want to digitize analog signals. This may be to save wear-and-tear on our analog media (vinyl records, tape, or even cassette tapes). It may be for greater convenience – once we have our music in digital form, we can stream it to a miniDSP SHD processor elsewhere on our home network using Roon, for example. Finally, we may have rare recordings or releases that we want to ensure remain preserved.
The name used for a digitized version of an analog recording is a "needle drop." (See https://en.wikipedia.org/wiki/Needle_drop_(audio).) To make your own, you will need:
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One of the miniDSP processors listed above. We will assume that you have the miniDSP software installed and working already (if not, see the correct User Manual).The miniDSP processor is being used as the ADC (analog-digital convertor) that you will read about if you search for articles about digitizing vinyl or tape.
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Audio recording software. There are a lot of options. Some examples of free software that runs on both Windows and Mac are ocenaudio, Audacity, and Ardour. If you are digitizing vinyl or tape, you will likely need to perform various processing steps on the recorded audio. For examples of the types of processing, see Audacity's Sample workflow for LP digitization. You could also try out software designed specifically for the purpose, such as VinylStudio.
In this app note, we will demonstrate the use of ocenaudio for recording, as it's very easy to use.
2. Get connected[Top]
This diagram illustrates a typical connection for analog recording:
Note that, if recording vinyl records, you will either need a phono preamp as shown in the diagram, or a turntable that outputs a line level signal. That is, you can not connect a phono cartridge directly to the input of a miniDSP processor.
As suggested by the diagram, the miniDSP processor should not be connected to a power amplifier or subwoofers while doing analog recording. This is because the master volume on the miniDSP will be set to 0 dB, which will be very loud if power amplification is connected and turned on. As a safety precaution, we therefore suggest that you disconnect power amplification when setting up for analog recording.
3. Set up the plugin[Top]
Start your plugin and click the Connect button.
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Choose a specific preset to use. This will need to pass the signal directly through without any filters applied. The diagram above indicates Preset 4 – this is a good choice to "reserve" as a straight-through configuration for analog recording.
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Reset the selected preset to defaults using the Restore menu:
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If using a Dirac-Live capable processor, confirm that the input delay and level settings are zero:
If they are not, it is because you have previously loaded a Dirac Live filter set into this preset. See if you have another preset slot with zero values. Otherwise, one option is to clear all the Dirac Live settings by re-installing the firmware on your unit. However this will mean reloading all filters and configurations into the other presets. A quicker option is to set the gain and delay in the output channels:
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Set output channel 1 to have the gain and delay of Dirac Live channel 2.
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Set output channel 2 to have the gain and delay of Dirac Live channel 1.
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Double-check that the crossovers are bypassed on output channels 1 and 2:
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Set the master volume to 0 dB:
This is so that a full-scale analog input will produce a full-scale digital output.
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Select the analog input:
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Play some audio on your source and confirm that you have signal on the input meters:
And on the output meters:
3. Set up ocenaudio[Top]
Note the sample rate that you will need to use in the following step. This sample rate is the internal sample rate of your plugin, as listed in this table (if using a Flex, choose 2x4 HD or DDRC-24 according to the plugin that you use to access it):
| Plugin | Sample rate |
|---|---|
| MiniDSP-2x4-HD | 96 kHz |
| DDRC-24 | 48 kHz |
| SHD | 96 kHz |
Open the ocenaudio settings, go to Sound, then select the miniDSP processor as input and your computer speakers as output. Set the sample rate to the value noted above. Here is a typical setting for Windows:
Here is a typical setting for macOS:
Check that your operating system is using the same sample rate for the miniDSP processor. You may need to change the sample rate in Windows to match. If you don't know how to do this, see the section "Set Sample Rate" in the app note UMIK-1/2 setup with REW.
5. Make the recording[Top]
Drop down the File menu and select New. In the dialog that appears, set the sample rate to the correct rate for your plugin:
Press the Record button, then start audio playing on your source. You will see the waveform update in real time:
You can press the headphone button (next to the Record button) to monitor the sound while recording. When you're done recording, press the Record button again to stop recording. Then save your recording to a file.
Note: if your audio signal has clipping, you will need to reduce the gain in your source, or insert attenuation before the miniDSP processor. The maximum input level of the processors listed at the start of this app note is 2.0 Vrms on RCA inputs, and 4.0 Vrms on XLR and TRS inputs.
ocenaudio has a lot of tools that you can use for processing your recorded audio, but we will leave exploring those to you!
Wrapping up[Top]
That's it! Have fun, and let us know how you go making your own needle drops in our forum.
