It can be confusing to understand the numbering associated with the Holo Spring, apologies if I am telling you things you already know.
The Spring has been released in two models. The current model II improved on model I by adding:
- a remote control;
- a 48kHz family DSD oscillator (means you can run closed form and other integer filters in HQP on all source material);
- a better USB input.
Each model has been marketed by Katsune and other distributors with three levels of tinkering:
- level 1 - stock;
- level 2 - Jensen capacitors in power supply;
- level 3 - silver internal wiring and transformer winding.
I have a model I level 2 and have been very pleased with it. I exclusively use the NOS (non-oversampling) setting which bypasses all the internal filtering, leaving that role exclusively to HQP. The Spring has 4 resistor ladder boards (R/2R), one each for PCM and DSD with a twin to control linearity. The native DSD board means that a DSD signal from HQP is never converted back to PCM.