21. Silencing open inputs

The first time I read about RCA caps was in the instruction manual of the Restek V1 preamplifier. In this it is explained that all unused RCA input circuits must be shortened to suppress noise potential coming from high frequency radiation. It is stated that the unit could not otherwise fulfil its specifications in terms of total harmonic distortion and signal to noise ratio. Not knowing what to make of this information, I was relieved to find that they come in packs of a dozen and are relatively inexpensive to purchase new.

Despite the Restek V1’s gold plated inputs, I decided to purchase the caps from a Chinese importer called Audiocrast. The base material is brass which has then been rhodium coated. These plugs were much better rated than their golden equivalents, otherwise I would have attempted to lessen the effect of material transitions by using the same contact material as the inputs.

On the Restek, the plugs have the effect of making the noise floor dead silent on all sources. This is less pronounced on the phono stage where the input signal is much lower than that coming from the DAC. Listening to Diana Krall’s ‘Turn up the Quiet’, the fading out of the studio’s ambient noise is much more apparent with the plugs than it was before. This means the system’s noise floor is far lower than that of the recording studio. I also can appreciate listening at higher volumes much more than I did before, simply because the music stands out more prominently from the background. I especially enjoy the effect the plugs have on stage depth, which has just become a little more realistic. Restek was not wrong in suggesting the use of the plugs. If your system is capable of great sound, this little add-on can well be considered an audio essential.