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.

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.

Asahi Kasei Microdevices (AKM) has developed the AK5705, a low power consumption 4-channel 32-bit A/D converter (ADC) with a built-in transimpedance amplifier in addition to a low-noise microphone amplifier. The new AKM the AK5705 ADC is connectable to current output sensors, supports a sampling frequency of 384kHz, and achieves a dynamic range of 109dB, while consuming 43% less power than existing AKM products. The built-in AC coupling capacitor significantly reduces the mounting area including external components.