I have up for sale my Singxer SA-1 balanced headphone amp. I am the original owner and I have installed an aftermarket volume knob on it. Otherwise it is in stock configuration. The original volume knob will be included in the original box which also includes manual and power cord. I am only shipping to continental USA, and I will pay for free ground shipping. Please note that there appears to be a tiny scratch on the top of the unit, but is otherwise in very good condition. Please PM if interested.