Category Archives: Electronics

Nexus Update: Programming MCU Module

      How To, Nexus, Support Electronics

The MIDI module includes a small, general purpose 16-bit MCU (Texas Instruments’ MSP430) that converts control voltages (CV) to MIDI. It is designed to be hackable. If you are adventurous enough, you can reprogram the code for your own purposes. The software is Open Source and can be cloned via Github (see Nexus repository). The code is based on the ubiquitous Arduino platform to make it easy to hack into.

You need a programming device to update the MCU Module firmware. There’s a lot of MSP430 programmers available out there, but the question is. “What is the cheapest we can get?”. Answer: the MSP430 launchpad dev board from Texas Instruments. Dev boards from chip manufacturers are often heavily subsidized, making them very inexpensive. The table below shows the price comparison for a few MSP430 programming devices including the MSP430G2 Launchpad Development Board.

Device Price
TI-MSP-EXP430G2 $9.99
Olimex MSP430 – BSL $11.24
Olimex MSP430 JTAG-Tiny-V2 $58.96
FlashPro-430-LB $159.00

What we need:

  1. Nexus MCU Module

  2. MSP430G2 Launchpad dev board
  3. Female-to-female jumper wires
  4. USB Type-B mini cable

Step 1. Remove all header shunts

Carefully remove the shunts highlighted on the dev board. RX/TX pins should also be removed to avoid data collision when programming an external MCU.



Step 2. Connect the jumper wires to the Launchpad

Follow proper jumper wire color coding indicated in the pictures below.

Step 3. Connect the jumper wires to the MCU Module

Step 4. Connect the USB Cable

Step 5. Install Energia IDE

Follow this link for Mac, Windows and Linux installation guides.

Step 6. Download and clone the firmware

Follow this link. You can download or clone the repository to your local drive.

Step 7. Flash the Firmware

  1. Open the source file using the Energia IDE.
  2. Click upload.
  3. Wait until the app indicate finish upload without errors.

Op Amp Shootout Updated

      Electronics, Op Amp

Time flies! It’s been almost 4 years since I last updated our Op Amp Shootout page. Now It’s 2017, and this page is still our top hitter. I guess that only means that people find this page helpful. And I am always happy to share information. I’ve updated the page to reflect recent developments. I always have a keen eye for new Op Amps and the new additions (shown in light purple) were taken straight from my notebook.

There are some interesting additions such as the OPA188 with a wide supply range of 2V to 18V, and very low 500μA current consumption. I also added a bunch of very Op Amps from Japan with rather respectable specs. Check out the NJ series Op Amps from JRC New Japan Radio Co., LTD. I found out about these cool Op Amps from studying Roland schematics. Have a look at the NJU77806, for example, with a noise figure of 5.5 nV/√Hz at 1kHz while consuming only 500μA.

There are also retirees. For example, the ultra-low noise LME49990 has reached its end of life. But there is certainly a new audio Op Amp king of the hill: the LMH6629 with a super impressive 0.69 nV/√Hz at 1kHz noise figure! The LMH6624 takes second place with very respectable 0.92 nV/√Hz at 1kHz noise figure.

Interesting tidbit: In that page, Mark Norton commented: “I feel sorry for all of you using op amps. Sterile squinching of sound imho.” He’s obviously not a fan, but then I had to reply: “I feel sorry for you believing such myths :-)”. Op Amps: Myths & Facts. The funny thing is, all forms of modern recorded music would have gone through dozens if not hundreds of Op Amps in the signal chain, through the recording process (EQs, compressor, limiters, etc.). If “sterility” means not degrading the purity of the sound (e.g. preamps), then I suppose that is good. But “transparency” is a better term.

Now go and check out the updated Op Amp Shootout page.

Nexus Update: In-Guitar Control and Connectivity

      Electronics, Nexus, Support Electronics

This is the fourth part of the Nexus documentation series. The first part documents the Basic Kit, the second part details the Mixer Module and the third part, the MIDI Module. This time, we explore In-Guitar Control and Connectivity —stuff that you install in your Nu-equipped guitar. Eventually, all of this will end up in a single document.

With up to 12 channels of Audio, the Nexus offers a lot of versatility. There are many ways to set up your guitar with a Nu multichannel pickup alongside other standard monophonic pickups such as the Cycfi XR active pickups.

But how do you control an N-channel system? Take the master volume for example. Adding a master volume to a traditional monophonic guitar is easy. A simple potentiometer will do. For an N-channel instrument, good luck if you can find an N-ganged potentiometer. Or how about switching? How do you switch N-channels? The traditional Strat-style 5-way switch and 3-way Les Paul toggle switch will no longer be adequate. The most versatile solution of course is MIDI. Use your external gear (or DAW) control master volume or patch settings or just about any parameter you wish.

Control voltages may be sent along with audio through any of the 15 channels via a LEMO compatible connector. Control voltages come from specialized potentiometers and switches. This will be converted to MIDI messages in the Nexus.

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Nexus Update: MIDI Module

      Documentation, Electronics, Nexus, Support Electronics

This is the third part of the Nexus documentation series. The first part documents the Basic Kit, the second part details the Mixer Module. This time, we explore the MIDI Module. Eventually, all of this will end up in a single document.

The MIDI Module converts control voltages (CV) from the guitar to MIDI. The basic firmware supports up to 6 analog and 7 digital inputs. The Multichannel Guitar Input (see Basic Kit) can carry up to seven control voltages or switches. Some of the back panel 1/4″ jacks may also be repurposed to carry additional control voltages or switches. The MIDI output is sent through a standard 5-pin DIN connector at the back panel.

Note: Please do not be confused with MIDI control and MIDI conversion. The MIDI module does not do any pitch tracking and MIDI conversion of the notes.

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Nexus Update: Mixer Module

      Documentation, Nexus, Support Electronics

This is the second part of the Nexus documentation series. The first part documents the Basic Kit. This time, we investigate the Mixer Module. Eventually, all of this will end up in a single document.

The (optional) Mixer module is a daughter board that sits atop the Main Board (see Basic Kit). This module provides a simple, yet extensible and hackable mechanism for mixing (up to) 12 audio channels down to stereo. Each channel can be mixed to either left or right using the L/R selector configuration headers.

The diagram at the right shows the routing for each channel. The center pins connect to the buffered outputs of channels 1 through 12 via 10K summing resistors. The left and right pins connect to the summing junctions of a dual OpAmp (OPA2209 low noise precision operational amplifier). The mixer gain is -1.

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Nexus Update: Basic Kit

      Documentation, Nexus, Support Electronics

I’ll be providing the Nexus documentation in tranches. This is the first part of the series. Eventually, all of this will end up in a single document. Let’s start with the Basic Kit.

nexus-block-diagramThe Basic Kit includes the 1) Main Board where all signals from the multichannel input as well as control voltages pass through, plus where power regulation and conditioning are handled, 2) I/O Module: 12 channels where each channel can be configured as an input or output. Typically, these are used to send multichannel audio to your effects, amp, mixer or multichannel audio interface. But, if you do not need all 12 channels, they can also be configured as inputs (e.g. Foot switches and Expression pedals). The Basic Kit includes the blue boxes in the Nexus block diagram at the right.

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Announcing the Nexus

      Electronics, Hardware, Nexus, Nu Series, Release, Support Electronics, XR Series


After more than a year of continuous refinement, I’m proud to finally release the Nexus. This small, hacker friendly breakout box connects your multichannel guitar to the outside world using a specialized (LEMO compatible) multi-pin connector for up to 12 channels of audio and 7 channels of analog control voltages for by-wire (remote) control of volume, tone, patch or effects. Audio may come from standard mono-pickups or from the Nu multichannel pickup. Analog control voltages are converted to MIDI control messages.

The Nexus and related support electronics are currently only available on pre-order basis, with a 3 week lead time for the first batch. Please send us a message for inquiries and orders.

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Nu Mixing

      Nu Series, Pickups, Support Electronics

solid_state_logicAn often asked question about the Nu modular pickups is about mixing to mono, or even stereo. The typical assumption is that, just like any other active pickup, you simply tie the outputs together to have a summed output. But not so fast! With 2 or 3 pickups (typical guitar setup), you might be able to get away with passive mixing. But mixing anything more than three channels is not a simple task and cannot be overlooked.

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