You Can DIY: A New Op-Amp for Phono Preamps - Part 2 - Development and Measurements

Brian Lowe (Belleson) developed a unique custom-designed transconductance amplifier (Bel Amp) with fully differential (balanced) low-noise JFET inputs and current output. it offers 50dB of current gain prior to any voltage excursion, virtually eliminating distortion caused by voltage-dependent node capacitance exhibited by more conventional approaches. This is the second article detailing the op-amp design, containing simulations and measurements.

Brian Lowe (Belleson) developed a unique custom designed transconductance amplifier (Bel Amp) with fully differential (balanced) low noise JFET inputs and current output for phono preamps. This article details the requirements and parameter values, while exploring design options. A second article explains the discrete op-amp design, complete with simulations and measurements.

audioXpress March 2025, focused on Test and Measurement and audio electronics, explains how to test Power Amplifiers, and how to measure HDMI Audio. Explore the possibilities of George Ntanavaras' SL-100 Sound Level Adjuster and Tom Perazella's Reinforced Speaker Protection solution. Read the interview with Mike Engelhardt, explaining everything about audio THD with QPSICE circuit simulation. Brian Lowe concludes its article on Op-Amp for Phono Preamps, and much more.

Read the Market Update on MEMS microphones, Shure’s valuable perspective about Wireless Multichannel Audio Systems (WMAS) technology, and a review of the extraordinary Eigenmike em64 Ambisonics microphone. Brent Butterworth reviews the new Sony MDR-M1 headphones, and Alex Bonnet and Eric Benhaim (Orosound) explain how to leverage ANC in open-ear designs. Brian Lowe (Belleson) shares his Top Amp design for phono preamps, Douglas Self reveals more op-amp distortion tests, and Richard Honeycutt revisits the legendary Dynaco ST-70 and ST-70 II tube power amps.

Belleson announced it will present the new Radiance phono preamplifier at Capital Audiofest 2024. According to the high-performance audio equipment manufacturer from South Carolina, the Radiance preamp is based on Brian Lowe's custom designed Top Amp circuit, in a single stereo phono input configuration, with exceptional low noise, and low distortion, allowing users the convenience of fine-tuning cartridge loading while listening to music, all remotely controlled via Wi-Fi.

In this second article, Brian Lowe (Belleson LLC) continues his search for the Unicorn of "Measuring Voltage Regulator Ripple Rejection," this time focusing on the test fixtures. Testing a voltage regulator with exceptionally good performance requires an even more exceptional signal source and measurement setup to measure sub-microVolt ripple across a wide frequency range. Complementing the final article, Jan Didden, offers an informative sidebar about super regulators. This article was originally published in audioXpress, June 2019.

In this article Brian Lowe shares a fascinating journey in his search for a "Unicorn" that is measuring voltage regulator ripple rejection - or power supply rejection ratio (PSRR). Lowe is the founder and principle engineer at Belleson, LLC, and he has devoted a lot of time to this fascinating "quest." This article was originally published in audioXpress, May 2019.

For audioXpress May 2019 -Glass Audio Special - we’ve put together a very strong edition, with some of best tube experts sharing a series of DIY projects for all skill levels, from restoration projects to new amplifiers, preamps, and headphone amps. We review the Nu:Tekt HA-K1 headphone amplifier using the novel Korg Nutube 6P1 device, and interview the founder of Parks Audio. We go deep on measuring voltage regulator ripple rejection and we even look at square-wave testing. All inside audioXpress May 2019!