Look what we have here! Concentric pots, anyone? We’re developing the next generation Resonant Filter and this might just be the key. Before, we had to use two separate pots to control frequency and resonance, which required more space! With the Modula project, we’ll be using concentric pots, along with a redesigned State Variable Filter E.Q., thanks to recent developments in low-power, low noise, Op Amp technology. A full-frequency response pickup (Nu, XR, Modula) plus a resonant state variable filter can simulate all types of pickups by mimicking their electrical characteristics (Resonant frequency and Q). See Helmuth Lemme’s table: Resonant frequencies of some well-know pickups for various parallel capacitors. With a state variable filter, we can even go beyond the sound of the traditional pickups, for example using very high Q settings. Synthesists know this very well!
Can it get better than this? Oh, I’m sure it will! I’m pretty sure we’ll see continuous improvements in Op Amp performance over the years. It is 2017 and we’ve come a long way since the early days of the Fairchild µA702 op amp, created in 1964 by Dave Talbert and designer Robert Widlar, and then a few years later: the μA741, also from Fairchild —the most popular op-amp of all time. I fondly recall the smell of solder (oh my… lead!) and a drawer full of LM741 DIP ICs as I was learning about these magnificent Op Amps with the Art of Electronics book at my side.
Check out our Op Amp Shootout page for more Op Amps. If you need some background information, I invite you to read the series of articles by Douglas Self (EE Times) Op amps in small-signal audio design (part1, part2, part3, part4).
So… I’m always on the lookout for low-power, low-noise Op Amps. Last time, we had a look at OPA1692. With a 4.2-nV/√Hz noise density and only 650 µA of supply current per channel, it is hard to beat. Alas, it is not available in singles (only duals and quads), which makes it a non-contender for the Modula pickups.
So, the search continues and as I moved outside my typical search area, I discovered a splendid Op Amp from Analog Devices —the ADA4084:
- Rail-to-rail input/output
- Low power: 0.625 mA typical per amplifier at ±15 V
- Gain bandwidth product: 15.9 MHz at AV = 100 typical
- Unity-gain crossover: 9.9 MHz typical
- −3 dB closed-loop bandwidth: 13.9 MHz typical at ±15 V
- Low offset voltage: 100 µV maximum (SOIC)
- Unity-gain stable
- High slew rate: 4.6 V/µs typical
- Low noise: 3.9 nV/√Hz typical at 1 kHz
- Long-term offset voltage drift (10,000 hours): 3 µV typical
- Temperature hysteresis: 4 µV typical
The ADA4084-1 (single), ADA4084-2 (dual), and ADA4084-4 (quad) are single-supply, 10 MHz bandwidth amplifiers featuring rail-to-rail inputs and outputs. They are guaranteed to operate from +3 V to +30 V (or ±1.5 V to ±15 V).
These amplifiers are well suited for single-supply applications requiring both ac and precision dc performance. The combination of wide bandwidth, low noise, and precision makes the ADA4084-1/ADA4084-2/ADA4084-4 useful in a wide variety of applications, including filters and instrumentation.
Wow! 625μA and 3.9 nV/√Hz!!! Is this it? We’ll see… I have a few samples coming and I’ll share our test results.
Aside: At 1mA, you get the ADA4807 3.3-nV/√Hz noise density with vanishingly low distortion (−141 dBc/−144 dBc at 1 kHz). A fair tradeoff, I would say.
This LTD SC-208 began life as an entry level 8-string for those interested in dipping their toe in the “deep end”. The stock setup included passive humbuckers, a 3-way selector, master volume and tone control. By converting to a Flex Set the switching options expanded from 3 to 5, the frequency response was greatly extended, and the guitar shed some weight along the way.
What do you get when you cross the Nu and the XR? The Modula. Our new baby: A full-range, semi-modular pickup that can be used for just about any guitar or bass. Yeah, finally the bass! So far, the results of our tests have been very positive. We applied what we learned over the years from the development of the Nu and the XR and the result is no less than outstanding!
Presenting the Modula
- Modular. Three module types can accommodate all guitars and basses.
- Aesthetically pleasing, sleek, modern design.
- Allows arbitrary placement, either straight or angled.
- Traditional mono or (custom) stereo split configuration.
- Lo-Z full frequency response. The blank canvas.
- Tweakable passive tone-blocks emulates all known pickups.
- Fully balanced, low-noise preamplifier. High headroom Rail-to-Rail output (5v to 18v).
- Dual-coil humbucking, dual rails design for each module. Quad coils for a single coil (Strat-style) pickup. Octa (8) coils for a full-width (PAF-style) pickup.
I’ll post more information as this project evolves. I value feedback. The Nu and the XR projects started from online forums, fueled by feedback from people all over the world. I invite you to come and join our facebook forum. Be involved in the discussions that will shape Modula’s future design and implementation.
Here are two pictures of an early prototype for a six string guitar. There are two modules for each 3-string group, reminiscent of the Fender precision bass pickup. Click to zoom in.
Our Op Amp Shootout page has always been the site’s top post. I’m always on the lookout for new and better Op Amps I can use in our products and I am continually updating the page as new products come along.
I’m never satisfied with the current offerings. Typically, you either have ultra-low noise OR very low power, but not both. Somehow, these are conflicting requirements. See the Shootout link to understand what I am talking about. For benchmark, in terms of low-noise performance, anything close to the 5532 (and its sibling, the 5534), with 5nV/√Hz noise figure (3.5nV/√Hz for the 5534) is wonderful. But the 4mA quiescent current consumption of these audio Op Amps is unacceptable for low power operation, especially when using batteries.
For applications requiring batteries, like that ubiquitous 9v battery found in typical active guitar electronics, I’m always searching for Op Amps in the 500μA range. My current favorites are 1) NJU77806, from JRC New Japan Radio Co., LTD, with a noise figure of 5.5 nV/√Hz at 1kHz while consuming only 500μA. But the NJU77806 can only go up to 5.5v supply, making it a nonstarter for 9v operation. So, for low power, my other favorite is 2) OPA180 from Texas Instruments, with a quiescent current: of 525 μA (max), but with a noise figure of 10 nV/√Hz at 1kHz. Looking at that spec, it’s not quite at par with the 5532 (or the NJU77806), but in reality, with very low 1/f noise, the 180 performed quite admirably in our noise tests. The 180 can operate from 4.0v to 36v. I’ve always wanted to release a very high headroom preamplifier for our pickups.
Now, there’s this new kid in town: The OPA1692 – SoundPlus Low-Power, Low-Noise, High-Performance Op Amp from Texas Instruments. Hey, Low-Power AND Low-Noise! Have your cake and eat it too?
- Low Noise: 4.2 nV/√Hz at 1 kHz
- Low Distortion: 0.000045% at 1 kHz
- Very Low Quiescent Current: 650 µA per Channel
- Slew Rate: 21 V/μs
- Wide Gain Bandwidth: 5.7 MHz
- Unity-Gain Stable
- Rail-to-Rail Output
- Wide Supply Range: ±1.75 V to ±18 V, or 3.5 V to 36 V
- Dual and Quad Versions Available
- Small Package Sizes: Dual: SOIC-8, VSSOP-8, SON-8 Quad: SOIC-14 and TSSOP-14
The OPA169x operational amplifiers achieve a new level of performance for low-power amplifiers with a low 4.2-nV/√Hz noise density and distortion of 0.000045% at 1 kHz. These op amps offer rail-to-rail output swing to within 150 mV of the power supplies with a 2-kΩ load, which increases headroom and maximizes dynamic range. These devices also have a high output drive capability of ±50 mA. The OPA169x operational amplifiers operate over a very wide supply range of ±1.75 V to ±18 V, or 3.5 V to 36 V (on only 650 µA of supply current per channel), are unity-gain stable, and provide excellent dynamic behavior over a wide range of load conditions.
The OPA169x family of amplifiers uses a propriety technology to reduce signal distortion that does not increase the power-supply current. The distortion cancellation technique reduces odd-order harmonic distortion, which is produced by the input transistor pair of the amplifier.
I’m getting some samples for testing as soon as they are available!
Beginning Father’s Day, Cycfi Research is pleased to offer a 25% discount on complete systems featuring our XR Flex Series extended-range pickups. The discount applies to the purchase of our pre-configured XR Flex systems including S-S-S (3 XR Dual pickups) or H-H (2 XR Quad Pickups) for 6, 7, and 8 string instruments. In addition to the pickups, systems include a 5-way switch, Active Volume, Blend or Tone Control, Output Jack, 9V battery clip and all necessary cables and hardware. Complete systems with the Resonant Filter are also available.
The new discounted XR Series pickup-system pricing kicks off Sunday June 18, and will continue until new pricing is announced. Come and visit our store.
You’ve been asking for this for a long time now. A gift to the Roland aficionado. Finally, a Roland 13 Pin Adaptor for the Nu Series Modular Active Pickups.
- CH1-4 – Nu Multi Channel 1 to Channel 4 In
- CH5-6 – Nu Multi Channel 5 to Channel 6 In
- 1 & 2 – 13P FPC Receptacle
- S1 – Switch 1 Input
- S2 – Switch 2 Input
- GND – Ground Pin
- MONO – Guitar Mono In
- GK-VOL – Volume Control
- GND – Ground Pin
2×4 Male Power Pins
- GND – Ground Pins
- 5V – 5V Regulated Power Pins
- -VE – (-)7V Power Pins
- +VE – (+)7V Power Pins
Gone are the days of DIP (Dual in-line) ICs. Most modern ICs are no longer offered in easy to use 2.54 mm (0.1 inch) pitch packages. The descendants of DIPs, the SOIC (Small Outline IC) and its friends (e.g. the TSOP (Thin Small Outline Package)) are shrunk down to 1.27 mm (0.05″) and even as low as 0.5mm (0.019″).
So how do we prototype using such tiny critters? We do it using the Dead Bug approach: A free-form construction, point-to-point soldering, often with the ICs flipped upside-down with their pins sticking up into the air like dead insects. The components are constructed, ad-hoc, using a bare copper-clad board serving as common ground. This construction technique drastically reduces electrostatic noise compared to other prototyping techniques using perf-boards or bread-boards.
Dead-bug constructions are typically ugly beasts! We use a variation of the technique called the Manhattan Dead-bug Style, using small pads punched out of copper-clad board and glued into the main copper base. The pads serve as islands for soldering circuit nodes.
I like modular, reusable building blocks. And so we build small modules and connect them together, all on top of another bigger copper clad board. This construction is very favorable to noise sensitive electronics. The module you see here is a high efficiency Class-D amplifier.
Time to revisit the Alpha and replace Alpha’s pickups with what else but Nus and XRs! Dimarzios out, Nu and XRs in… Ehmm, OK I suppose I’d refret the guitar as well.
In case you have no idea what Alpha is, check out this link. Alpha is a thru-Neck Carbon Fiber over Bamboo with a Carbon Fiber Body I designed and built a few years ago. I’ll have more of Alpha in the coming days. Stay tuned. I am highly considering building a few of these sexy Carbon Fiber guitars with even crazier ideas brewing in my mind over the years, perhaps in collaboration with a fine luthier in the U.S. or in Europe (To my luthier friends: send me an email if you are interested and let us talk). You want the bleeding edge, this is it! It will be a complete multichannel system with the Nu, Nexus and Infinity all standard features, just as I envisioned it when this all started a few years ago. Yes, Infinity! My holy grail is now within reach with recent breakthroughs!