This MSB DAC III is the one of the latest built and has the latest firmware. The DAC III uses the same technology DAC modules as the current series IV. The inputs have MSB's own clock that is less than 2 ps for all inputs including Toslink. If you are using single ended or balanced it is optimized with two DAC s per channel. For balanced mode it is true balanced using both DAC modules for true balanced push-pull with very high common mode noise rejection. For single ended there is a switch on the back panel to piggy back the two modules per channel raising the DAC module precision and lowering the noise floor by one half. The knob on the front switches the inputs. This DAC also has the MSB Network input to use with MSB sources. This DAC sounds amazing with MSB's Data CD IV or Universal Media Transport either one unleashing what this DAC can really do. Compare it at any price. The condition appears to be perfect upon close inspection. Please contact me with any questions. Thanks for looking.