Star performance from Stella

How PS Audio got its start back in 1973 is a great story – if you have the chance, click on the ‘About’ link on their website. However it has been the last few years which have seen this extremely innovative company come to the forefront. Products like the unique DirectStream Memory Player covered in our last publication showcase a lot of technology, and have captured the interest of the audio loving consumer.

Not a company to stand still, PS Audio have just released a new range of amplifiers – Stella. We are currently carrying two products from this range, the Stella Gain Cell DAC, and the Stella S300 Stereo Power Amplifier.

Stella Gain Cell DAC

We also made mention of the NuWave DSD DAC in our last newsletter – this is one of the best value for money DACs on the market. At $2,595 the new Stella Gain Cell DAC (below) is an improved version of the DSD DAC, built into an analogue preamplifier. At the heart of the preamplifier stage is the Gain Cell. Invented in the early 2000s by PS Audio founder Paul McGowan, this unique approach to variable gain amplification eliminates a classic problem for preamplifier designers – the volume control.

All preamplifiers must provide a means for the level to be turned up or down. There are numerous methods of accomplishing this seemingly simple task: potentiometers, stepped attenuators, light-dependent resistors, transformers, electronic switches, etc. All have something in common – they are inserted in the signal path and degrade the musical signal to varying degrees. If you have ever owned a product with both variable and fixed outputs and compared the two, you will understand what we mean.

Instead of inserting an additional level control in the signal path, the PS Audio Gain Cell relies on a different technology known as a variable gain amplifier (Gilbert Cell). This topology was invented in the 1960s by Howard Jones and Barry Gilbert, and became widely adopted by recording and mastering studios in their analogue heyday — then later abandoned when these same studios went digital.

The idea behind the variable gain cell is simple. Instead of adding additional circuitry to the signal path to vary loudness, the preamplifier’s actual amplifier stage varies its gain in response to the user’s front panel volume control. This method requires zero additional circuitry in the signal path, offers more than 80dB of attenuation and, if designed properly, performs to the equal of most high-end preamplifiers.

Stella S300 Power Amplifier

The S300 stereo power amplifier (pictured above) is rated at 140 watts into 8 ohms and doubles its power into 4 ohms. Once again this product utilises PS Audio’s ‘cell’ technology – this time the ‘Analogue Cell’. This is a zero feedback, balanced, Class A, MOSFET input stage, mirroring the sonic qualities of valve components.

The output stage is a high current Class ‘D’ design. There is a common school of thought that Class ‘D’ amplifiers are digital – which is incorrect. A Class D amplification stage is an analogue process, known as Pulse Width Modulation (PWM). Class D amplifiers do switch in on/off fashion, possibly why they wrongly acquired the “digital” moniker – or it may be simply the ‘D’ in the description.

The Stellar S300 is a dual mono design, with each of the two channels having complete and independent power supplies and power amplification stages.

Interestingly PS Audio has stated that their goal with the development of this amplifier was to design “one of the most extraordinary under $5,000 stereo power amplifiers ever crafted”. We cannot say that they have achieved this goal – but given that the Stella 300 sells for $2,295 we would suggest that they have come up with an outstanding bargain.