A State of the Art Phono Stage (MC/MM to Line Level with RIAA Equalisation)
History in Analogue
In recent years Audio Synthesis has become known for its expertise in the digital audio field, especially with the DAX and TRANSCEND range of digital front-ends. But, as some of our older customers may remember, our most successful initial product was the ADEQ phono stage, many of which are treasured items and still remain in everyday use. Ten years later and we continue to receive regular requests for the ADEQ, but instead of bringing it back into production we decided to use it as our new starting point and set out to improve the design. So began the evolution which resulted in the PASSION Phono…
Experience dictates that an L-pad attenuator, when interfaced correctly, forms the most accurate and transparent volume control. By avoiding active gain stages and any switching complexity, this passive L-pad can be used to create a benchmark ‘preamplifier’ able to give the ultimate in audio quality. This has been the direction taken from ADEQ – identifying the elements necessary for outstanding audio performance, fine-tuning them before eliminating any non-essential circuits or connections responsible for damage to the delicate audio waveform. Once an elegant assembly of the minimum number of building blocks had been identified, we set about designing, with an unlimited budget, the most perfectly tailored circuit topologies dedicated to each function.
High Gain Direct Coupled Input Stage
An ultra-low noise, low impedance input gain stage, utilising extremely wideband, discrete active devices able to handle the fastest music or vinyl generated transients without incurring slew-induced distortion. We created a unique and paralleled power matched configuration, to achieve a noise floor well below the background vinyl floor, even when partnered with the lowest output moving-coil cartridges ever made…
The RIAA Stage - An Equaliser without Equal
The heart of the PASSION Phono and a stage created exclusively out of Vishay Bulk Foil resistors and hand-trimmed precision polypropylene capacitors - designed to guarantee the most accurate RIAA decoding imaginable and a sound quality to die for.
Rapid Class A Line Driver
A high current and fully discrete output interface driver of proven performance. The Line Driver minimises the complexity of the audio path without compromise to the circuit’s technical requirements or its ability to effortlessly convey music’s complex dynamic contrasts.
Construction without Compromise
PASSION Phono preamps are lovingly hand constructed using selected precision components.
These include ground planed and intelligently designed circuit boards; carefully chosen discrete semiconductors; high purity solid silver conductors and WBT machined phono connectors. The majority of resistors specified in both the gain and equalisation stages are Vishay Bulk Foils. These expensive components are chosen for their tight resistance tolerance, ultra-low noise, outstanding temperature stability and negligible parasitic inductance and capacitance - allowing extremely high speed without distortion. But most importantly Vishays are chosen for their acknowledged supremacy in the field of sound reproduction.
On completion, each PASSION Phono undergoes a three day cyclic soak-test, is individually calibrated by hand then measured for noise performance; RIAA equaliser accuracy; channel balance and overall gain. Graphs of THD and FFT spectra are plotted for comparison to our in-house benchmark module and recorded by serial number for reference purposes. All measurements are performed with our calibrated industry standard Audio Precision System.
© 2010 Audio Synthesis