Your basket is currently empty!
Author: bonsai
Hifisonix Discrete JFET Input Line Stage
This discrete JFET input line stage can drive a 2k ohm load to 6V RMS in class A at less than 30 ppm distortion and at 3V RMS into 2k ohms, the distortion is around 7ppm at 1 kHz. The output stage runs at 20mA standing current. A jumper allows the user to select either…
Hifisonix Micro Ripple Eater
Click here to buy a Micro Ripple Eater PCB in the Shop This simple ripple eater (aka MRE) can deliver up to 10A per supply rail (provided it is suitably heatsinked!) and will reduce mains related ripple on amplifier supply rails by up to 40 dB and as much as 50 dB at HF. The…
Hifisonix Speaker Protection Board
This simple, low cost speaker protection board measuring just 82mm x 50mm uses the ubiquitous UPC1237 from Unisonic, a Taiwan based semiconductor manufacturer. The circuit will work from 25V through to 75V and uses mosfets to switch the speaker load rather than relays which are problematic and unreliable. A current overload input is also provided,…
Hifisonix Standard PSU
Click here to buy a PCB for the Standard PSU Click here for the build documentation Click here for the BOM The Hifisonix Standard PSU features low noise, up to 400mA per rail output current, a MUTE relay driver to ensure when the load powers up or down there are no clicks or thumps, a…
Hifisonix HPA-1 Class A Headphone Amplifier
The circuit combines a dual ultra-low distortion opamp, the LM4562 or OPA1642, with a class A discrete power output stage to deliver outstanding performance both measured, and sonically. The complete amplifier, including the opamps, runs in class A. Into 60 Ohm headphones and above, the HPA-1 remains fully in class A up to the rated…
Hifisonix Accurate Inverse RIAA Network
The diagram above summarizes the interaction of the cutting head response (purple) and the playback EQ (red) which produces the final flat response (green). Note that the cutting head and the phono pickup (cartridge) are velocity transducers and therefore the cartridge output rises at 20 dB/decade if the record groove is cut at constant amplitude.…
Using the QuantAsylum QA401 for accurate Audio Measurements
The QA 401 from QuantAsylum (superseded by the QA403) has emerged as a popular, comprehensive audio test instrument in the DIY audio fraternity and the go to instrument in many cases for commercial production testing. It combines a first rate DAC and ADC with a simple user friendly PC interface to realize a fully integrated…
Building Quiet Audio Power Amplifiers Requires Best Wiring and Layout Practices
There is a misconception that noise pickup is reduced by placing the input RCA connectors (and similarly XLR input connectors in a fully balanced system) on opposite sides of the amplifier rear panel and then running short wires to the amplifier modules. This arrangement is the worst of all worlds. The internal loop areas available…
So Just How Quiet is Your Phono Stage?
You may be in for a surprise: actually not that quiet! The reason of course is that the cartridge inductance and resistance dominate the noise in any decent phono amp. To get the best in terms of noise performance, you really need to keep the input referred noise voltage and noise current to a minimum.…
Fast Recovery Transimpedance aka Voltage Amplifier Stages for Audio Power Amplifiers
Here is a quick look at some of the problems that can occur when the VAS (aka TIS) in an audio amplifier is driven into saturation without considering the effects of base charge storage – a phenomenon all bipolar transistors suffer from.