SparkoS Labs have been manufacturing discrete op amp and discrete voltage regulator products for high end audio use for around 4 years. Now they’ve decided to start making high end audio equipment themselves using those discrete devices.

For months now, they have been developing a phono amplifier product that aims to compete with the best on the market. It is currently midway through development. An initial proof of concept prototype was released back in January, and since then they’ve developed all of the microcontroller software for the touch screen display, and laid out and built a 6 layer board with all of the functionality included.

They hope to have this product in production and available to the market by late this year or early next. The price has not been determined yet as the enclosure has not been designed, but one can expect somewhere in the $5K – $10K retail price range.

This product will make use of the SparkoS Labs discrete op amps in all of the audio stages, and will have the SparkoS Labs discrete voltage regulators used throughout the power supply. It will have two RCA inputs and a set of both RCA and XLR outputs. There are no capacitors in the signal path, and everything is DC servoed.

The SS Phono Amplifier will have a touch screen display that will allow the user to control several functions. The two sets of RCA inputs will allow two turntables that can be switched between. Each input can have a unique gain and cartridge loading setting that will automatically get recalled when the input is switched from one to the other.

The user will have complete control of the touch screen background and foreground colours. At 16 bits each, there are 2^32, or 4.29 billion possible colour combinations. There will be 4 gain settings of 33dB, 43dB, 53dB and 63dB to allow use with both Moving Magnet (MM) and Moving Coil (MC) cartridges. The cartridge resistance and capacitance loading can also be controlled via the touch screen, and are switched by latching relays to avoid magnetic fields near the audio paths.

Both the resistance loading and capacitance loading have 8 settings each ranging from 10 ohms to 47K ohm, and

0pF to 720pF. There is a 24dB/octave low pass rumble filter (implemented by DC servos) that can be set to 1Hz, 10Hz, or 17Hz. Additionally, there is a left / right trim feature that allows 3 attenuation steps of -0.5dB each (-1.5dB total) that can be applied to either the right or left channel to account for cartridge L/R balance errors.

Initial noise measurements indicate around 0.35nV √Hz noise even before RIAA equalization is applied. The RIAA stages employ active equalization using inverting mode discrete op amps, 1% tolerance polypropylene film capacitors, and 0.1% tolerance thin film resistors to achieve an RIAA accuracy of around 0.1dB.

Architecturally, the first stage is a flat gain V to I / I to V single ended current feedback design. The V to I section is comprised of numerous parallel current source biased JFETs, and the I to V is accomplished by a SparkoS Labs SS3601 discrete op amp. A discrete high current class A diamond buffer is also included in this stage to drive the low impedance feedback network, and drive the low input impedance of the 2nd stage. The 2nd and 3rd stage are both inverting mode discrete op amps that provide the variable gain control as well as the RIAA equalization. The XLR outputs are likewise implemented with the SS3602 discrete op amp, and is a true single ended to differential converter.The propagation delay and phase shifts are perfectly aligned.


There will be more updates about the SS Phono Amplifier as time progresses.





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