Ascend VPU: Noise Reduction

Noise is my number one enemy. Always. I’ve frequently been asked why I don’t offer a built-in mixer for the Nu pickups, so they can use the Nu as a direct replacement to monophonic pickups while still being able to have multichannel guitar audio. Best of both worlds, right? Well… the reason has a lot to do with noise. While the Nu Capsule has a very low noise floor (measured at -124 dBV for broadband noise and -113 dBV for hum and its harmonics), this noise will be multiplied by NxG, where G is your system gain, and N is the number of channels (the number of Nu capsules used). The noise adds up for each channel used.

Note: This entry should have been part 5 of the Virtual Pickups article series. I decided to have this fall under Ascend, which involves a specific virtual pickup implementation: Ascend-VPU.

Hum is not an issue with the Nu pickups. Low impedance coils are a lot less susceptible to electrostatic noise. The more pressing issue is hiss (broadband noise) introduced by the active electronics (the preamplifier). Unlike other input sources such as microphones, guitar pickups sit in a precarious place in the signal path before high gain stages (compressors, distortions, overdrives, preamps, etc.), which can potentially push the gain to extreme levels. For use-cases that require direct connection to standard monophonic high-gain external gear, my recommendation is to pair a monophonic pickup with the Nu-Multi, and use the mono pickup for that specific purpose.

Ascend-VPU Downward Expander

Now, if you go down the DAW path, you have better options. The Ascend-VPU plugin is a must when using the Nu-Pickup (or any divided pickup for that matter). It has a built-in downward expander. It works like a soft gate. Dial in the noise floor with the threshold control and a suitable expansion ratio, and you can eliminate most of the annoying noise. Downward expansion happens before any high-gain stages and before mixing, so you do not have the compounding channel mixing noise issue mentioned above.

In addition to the downward expander, the Ascend VPU incorporates a dynamic noise reduction filter that takes effect on lower level signals for minimizing broadband noise (hiss). A moving average filter, best suitable for reducing random white noise, is inserted at the input. When the signal goes below +12dB the expander threshold, the moving average filter output is cross-faded with the raw input. This noise reduction scheme works well for guitar signals due to the natural decay of high frequencies as the string decays. The filter is very transparent. You will not ever notice that it is there.

Furthermore, a nice little secret with virtual pickups is that each virtual coil reduces random noise due to its inherent averaging effect. Comb filters have that very welcome effect! The more virtual coils you use, the better the noise reduction.

To demonstrate, with the downward expander off, here’s the actual spectrum graph of the Nu Capsule’s noise floor plus any other system noise, amplified by a gain of 48 to emphasize the noise level in the graph (hence, the actual noise floor is 33dB below this):

Noise Floor

Now, when you enable the virtual pickups, you’ll be amazed. You can get at least 30dB additional noise reduction! The graph below shows the noise reduction effect of a typical Ascend-VPU preset. Interestingly, a happy coincidence is that virtual “humbuckers” provide better noise reduction due to the double coils! The more virtual coils used, the better the noise reduction. Keep in mind that the actual noise floor is 33dB below this, so your noise floor is now somewhere in the -130dB territory):

Virtual Pickups Noise Reduction

Noise is a real enemy. We want to have the least amount of noise as possible. With the Ascend-VPU plugin, you get to have your cake and eat it too. You are free to use the multichannel pickups with high gain stages (monophonic or polyphonic) without fear of noise corrupting your well crafted performance.

Downward expander + VPU = Total noise free bliss!



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