Hi All -
We get a lot of questions about using the VMS with variable-gain interfaces and line amp stages, so I've tried to explain some of the basics below.
When using the VMS-1, ideally your interface's line input would be set to "Unity Gain." This refers to the state of neither adding nor subtracting gain. Many interfaces will explain how to do this in their manuals. Often the "line in" is routed through the "mic in" circuit after a pad, or goes through part of the mic amp circuit after the first gain stage. This is not always bad and sometimes handy, but for our purposes here we want unity gain at a "+4" reference level. Some interfaces will have a few variable gain circuits and a few fixed gain circuits. The fixed gain circuits, at +4 reference level, will be best for the VMS.
Unity gain is an important concept in audio. The best signal structure is one where gain is at unity all the way through the chain, until the channel fader to the mix bus. So, the mic pre steps up the gain, and all other line amps and signal processors neither add nor subtract, until the fader. This allows you to bypass any processor and really hear what it is doing, and provides the greatest headroom to noise ratio. This is also the genesis of the term "make-up gain" on compressors. When the circuit is cutting gain by compressing, you add gain back so that the overall effect is unity gain, but with compression. EQs add and subtract gain but do not always have adjustable make-up gain, so keep this in mind. Of course, in the real world, concessions are made to achieve various ends, but the concept will guide you to excellent signal chains.
It is not recommended to add any processing between the VMS-1 and the VMR plugin rack, as this will negatively affect the modeling. This includes modeling and processing that may happen in your interface's software mixer. If you are having trouble with peaks that are not controllable with the gain range of the preamp, consider a different mic placement and be sure to use a strong pop filter when using the mic on-axis at close range. You can also read this article about levels - I feel like the level is too low in my DAW.
We're often asked "What is the ideal setting on the VMS-1 preamp?" The answer is simple - none! On a preamp, there can be no ideal gain setting as the gain is there to adjust for the input source. The ideal setting is simply one that provides adequate signal (to avoid noise) and adequate headroom (to avoid clipping) for the given input source. Once extra gain blocks are removed (see above) this will become clear.