Stateline Amp 2

• Inputs: 5x line-in RCA, SPDIF-RCA, USB-A
• American walnut feet
• Treated with additional OsCon caps, E-Pads and Maestro lacquer
• Minimalist, stylish design
• Stainless steel housing and glass front panel

Hi-fi high-end amplifier. The Stateline Amp 2 is the result of years of research in which we optimised every detail of the circuit topology, as well as the choice of the components that, in our understanding of music, work best in each position. In an integrated amplifier with DAC, line stage and power amplifier, this is quite complex, as there are many interactions to consider. The advantage on the other hand is that we can create an integrated unit with very coherent characteristics.

Line stage

For the line stage, following Einstein's statement "Everything should be made as simple as possible, but not simpler", we started with a one-transistor circuit without negative feedback. With a careful selection of active components it sounded beautiful and worked as intended. Distortion was mainly second order, in the range of 0.2%, which we personally prefer to a lower percentage of third- or fifth-order distortion. Still, lower distortion means more real information, as long as it does not come with higher transient intermodulation from negative feedback. So we arrived at a circuit with two transistors, where the second transistor works as an error correction amplifier outside the actual signal path. There is no feedback from the output of the line stage to the input with all its negative aspects, yet we were able to lower the distortion of this stage to 0.001%, keeping it mostly second order.
Listening comparisons showed that this concept carried much more musical information, being two orders of magnitude further away from the distortion level.

Power amplifier

Although we usually favour discrete transistor circuits, in this case we chose the advantage of the shortest possible signal path of an integrated solution.
The output stage runs in bridge mode, which means there are two amplifiers per channel, and the plus and minus terminals of the loudspeaker are connected between these two amplifiers.
So there is no current flow on the ground plane, which is very positive for low-level resolution, since ground is the reference point for all signals.
Another aspect is improved control of the loudspeaker, which is driven and held by two amplifiers.

Volume control

A remote-controlled, custom-made Alps potentiometer with linear characteristic, which offers much better channel matching than any logarithmic potentiometer. It has special taps where, by adding a resistor of a specific value, we can match the characteristic perfectly to the human ear, without the poor channel matching that is inherent to a logarithmic potentiometer.

Power supply

The power supply is another fundamental part with a significant influence on the overall sound. After trying various topologies, it turned out that a professionally developed switch-mode power supply was the right match and clearly outperformed several transformer-based solutions as well as other switch-mode supplies we tried.
All stages are decoupled by 5 different voltage regulators, with low-noise discrete circuits for the line stage and the DAC. The total supply capacitance besides the base SMPS is more than 36,000 μF, combining different types of capacitors chosen for their sonic performance in each position.

DAC

The DAC is a non-oversampling design that offers bit-perfect performance and can be fed via SPDIF or USB. The Stateline Amp 2 accepts sample rates up to 96 kHz.

In short, despite its compact size, the Stateline Amp 2 is a true hi-fi high-end amplifier.

Review