Fast and Efficient Pitch Detection: Synth Tracking

      DSP, Pitch Detection, Q, Software

A couple of posts back, I wrote about Bitstream Autocorrelation (Here and Here). It was an evolutionary path from even older posts on the subject (Here and Here). Now it has matured quite a bit from its inception a few months back.

I’ll discuss what’s new later in another post, but before that, to give you an idea how well this continuous pitch detector tracks, I’ll present some demo sound clips. The left channel contains the original raw guitar signal (normalized), while the right channel contains a simple synthesized pulse wave, modulated by its own envelope, tracking the source. We’ll start with single notes and proceed later with a few single-string phrases demonstrating various guitar playing techniques such as legato, hammer-on, pull-off, etc.

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Modula Pre-Production Prototype

      Modula, Modula Series, Pickups

Cycfi’s new baby is coming very soon: A full-range, semi-modular pickup: Modula. If you haven’t heard about this yet, go check out the New Breed of Pickups post. These aesthetically pleasing, sleek Lo-Z multi-coil pickups were designed from the ground up based on our experience with the Nu and XR pickups. This baby sports dual-coil humbucking with dual rails design for each module and powered by a fully balanced, high headroom rail-to-rail output (5v to 18v), low-noise preamplifier.

Nu v2 Capsules

      Nu Capsule, Nu Series, Pickups, V2

The Nu version-2 capsule is ready to go!

  1. Thicker permalloy ring for improved electromagnetic isolation, better string focus and crosstalk reduction.
  2. Bobbin-less coil to make room for the improved permalloy ring.
  3. Lower magnetic pull.
  4. Epoxy impregnated injection molded capsule.
  5. Improved preamplifier.
    1. Low noise discrete/Op Amp hybrid differential preamplifier for improved immunity to electrostatic noise.
    2. Less stringent requirements on power supply regulation and noise (although I still highly recommend using a very low noise power supply suitable for low noise audio).
    3. Expanded power supply range. You can now power the capsules from 5v up to 18v. A higher supply voltage will give you a significantly higher dynamic range. Nu v1 maxed out at 5v.
    4. Instrument-level, like before, but not as hot as Nu v1. Roland synth users say the output of Nu v1 is too hot.
    5. Better output drive. Nu v1 has a 10k output impedance. Nu v2 has a very low output impedance with a 17 mA current drive capability.
    6. Rail-to-Rail Output. Which also translates to optimal dynamic range.
The preamplifier design changes follow developments in our preamp research for the Modula line of pickups. See Modula Update: Preamp Performance Tweaks.
Technically, this is v3 now, if you count the Neo as v1. I almost forgot the Neo and the Six-pack project, where it all started.

 

 

Fast and Efficient Pitch Detection: Notification…

      Uncategorized

Hah, so I accidentally clicked on the Publish button before I finished writing the article Fast and Efficient Pitch Detection: Bliss! And so a notification was immediately sent to all of you subscribed to my blog. Then, after I reset the status to Draft, clicking on the link in that notification gives you that “This is somewhat embarrassing” message. Ooops! Pardon me. Anyway, I decided to add this post in order to generate another notification that the article is now available for viewing.

Fast and Efficient Pitch Detection: Bliss!

      DSP, Electronics, Pitch Detection, Software

In my previous post, I introduced my invention, Bitstream Autocorrelation: an accurate, extremely fast and efficient, time-domain pitch detection scheme. I argued that it can be as accurate as standard Autocorrelation based pitch detection schemes, especially, or at least, for very specific source inputs, such as the guitar.

As far as I can tell, this is a new invention and has not been done like this before. And so, the past few weeks, I investigated deeper and studied its performance and characteristics on real world guitar samples. For analysis, I recorded single-note samples for all strings (6 strings for now) at various fret positions. Additionally, I also recorded various guitar audio samples incorporating techniques such as hammer-ons and pull-offs and fast right hand arpeggios. I am impressed!

Here are my findings and some direction changes and updates along the way…

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Fast and Efficient Pitch Detection: Bitstream Autocorrelation

      DSP, Electronics, Pitch Detection, Software

So, since last year, I’ve been mulling over a unique, and extremely fast(!) Autocorrelation scheme for monophonic pitch detection. Last weekend, I finally got myself to write the proof of concept. It’s not like any autocorrelation scheme I’ve seen before. I am still wondering why no one has thought about doing it this way. As far as I can tell, this is my invention, but please tell me if there’s something I am missing and if I’m not the first to actually do it this way. I dubbed the technique Bitstream Autocorrelation.

Unlike standard Autocorrelation, my scheme works on single bit binary data streams instead of floating point (or fixed point) real numbers. Compared to standard Autocorrelation, Bitstream Autocorrelation is wicked fast. As I’ve been working on multiple channels of audio on small Microcontrollers, I’ve consistently shied away from Autocorrelation schemes for pitch detection (see my original article: Fast and Efficient Pitch Detection). Popular time-domain Autocorrelation (ACF)  based pitch detection, including variants such as AMDF (Average Magnitude Difference Function), ASDF (Average Squared Difference Function),  YIN, and MPM,  are quite expensive in terms of CPU cycles required (ACF is basically an N² operation for N samples).

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The Last of the XRs

      Evolution, Pickups, Uncategorized, XR Series, XR Update

Almost immediately after I announced our Roadmap for 2018, the XRs and the current Nu modules went out of stock as people hurriedly grabbed what’s remaining in our inventory. I am very sorry that I had to turn down orders after the stocks were depleted.

Dan Rhodes sent me these nice pictures of his electric with Cycfi XR dual pickups, Cycfi Resonant Filter, Warmoth body and neck with a Decoboom pick guard, Fender locking tuners, roller bearing nut and Wilkinson tremolo.

“Looks and sounds amazing Joel! I spent some time with it last night and the tonal range of these pickups is amazing. The openness with the tone and Q maxed out is a sound I’ve never had before.”

Thank you very much for such nice appreciation. I am missing the XRs already!

But watch out. We are still actively pursuing the Modula, a new breed of pickups and the next evolutionary step for the XR. It didn’t die, it simply evolved! 🙂

Roadmap

      Evolution

Simplify! I think that will be my mantra for 2018.

Looking back, the current product line that we have including the XR Pickups and all its support electronics, the Nu pickups and all its support electronics including the Nexus, and in addition to all projects, planned and in the pipeline, including Infinity −hardware and software, is just too ambitious and unmanageable given the resources we have. I want to achieve so much, but there is simply no time to do it all in a reasonable amount of time. Those of you who know me know that I am also a full-time C++ consultant and Cycfi Research is a much loved baby that blossomed out of pure passion (or is that obsession?) and love for the guitar, electronics, and music in general, that goes back decades since the 80s.

When we started, it was just the Neo pickups, nothing more. It started to get crazy when we developed and eventually released the XR pickups. When the XR happened, we started losing focus and precious time for doing research and development was slowly consumed by manufacturing and support. We’re getting ahead of ourselves. We have to walk before we can run.

Restart

So, in 2018, something has to give way. We will have to focus on only one product: The Nu Capsule. Less is more. Focus on one item, do it really well. I know there’s an untapped market for the Nu capsules, a general purpose, miniature magnetic pickup. And it goes beyond the guitar. A number of Nu users are actually non-guitar players.

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