## Choosing a USB Audio Adapter

The qualitty of the audio adapter dramatically affects the quality of the guitar effects. Amp models are particularly sensitive to poor signal-to-noise ratios, because overdrive effects boost the level of noise more than the level of the actual signal. For best results, you should choose a 24-bit audio adapter that provides at least 105db (A-weighted) signal-to-noise ratio. I personally use and recommend the Motu M2 USB audio adapter, although there are plenty of other pro-quality audio adapters that will work as well. I would urge you to avoid cheaper USB audio adapters that sell for less than US$70, which will almost certainly not provide input signals of sufficient quality.

Ideally, you want a USB adatper that provides an input volume knob. For best results, you want the input signal to be as high as possible without clipping. (Clipped input signals sound horrible). USB audio adapters without volume knobs usually do provide internal input volume controls, which have to be set using custom software. PiPedal does not currently allow you to set the internal trim levels of USB audio adapters. By default, these adapters will expect line level-signals. But instrument levels are about 40db quieter than line-level signals; so you will not get good results if you don't adjust the input signal trim levels of your audio adapter. 

Pay close attention to the input VU meter of the first effect in your guitar effect chain. That will indicate the signal level coming into the USB adapter. Ideally, you want the value peaking solidly in the yellow range of the VU meter, and NEVER going red.

Again, the MOTU M2 excels in this regard. It provides large, volume knobs for input and output, along with very readable VU meters which indicate both input and output signal levels. 


