Stereo Lab Listening Room

Click and Pops processing and getting the EQ curves right

One of the advantages of digitising an LP record collection is the ability to repair the results of surface damage once the recording is in the digital domain.

A de-clicker for audiophiles

Stereo Lab incorporates an audiophile de-clicker which is optimised for fans of the vinyl disc whose LPs are good condition and for the most part need little or no correction. Importantly, the Stereo Lab algorithm doesn't interpolate or predict the audio. Instead, a robust click-detection algorithm is coupled to an adaptive attenuator which lowers the intensity of clicks rather than attempting to remove them altogether. In this way, audio is never lost or synthesised.

The importance of a robust detection is to ensure there are no false positives and correction is not wrongly applied to musical transients rather than clicks. The Stereo Lab detection algorithm is virtually foolproof. It is biased against detection so, in the event of an ambiguous detection it will rather let a click go through than replace good audio.

Click and noise removal works much better if it is applied before RIAA equalisation because the massive bass-boost of the RIAA equalisation process transforms a very brief dust particle "snick" into a very noticeable "thwack" . So the Stereo Lab de-clicker is incorporated in the phonograph dialogue. When the check box for de-clicking is checked, the process will be automatically invoked as the appropriate disc replay-correction is applied.

De-clicker and Historic Equalisation demonstration

This recording was made in the 1950s on DECCA's then state-of-the-art recording system known as FFRR for Full Frequency Range Recording but before the switchover to RIAA equalisation.

Early Decca LPs of this period used the Decca 33⅓ characteristic (500C-11.5) which is characterised by the time-constants of 1590/318/60µS. If RIAA equalisation is used to reproduce these discs, the bass is over-boosted because of the 100Hz bass-shelf in the 500C-11.5 characteristic. Pspatial Audio's EQ-A2 is a modified version of Quad setting A which is optimised for Decca records and that is the equalisation on demonstration here. The de-clicker is also demonstrated.

The examples below are in two parts. The first part is a recording of an all analogue needle-drop recorded via a very high-quality RIAA pre-amplifier. The second section is the same short musical segment recorded with Groove Sleuth preamplifier and processed via Stereo Lab. In this case, the software was responsible for the DECCA EQ correction and the click removal.

Demo 1 - from the Adagio introduction to movement 1 of Dvorak's Symphony no. 9 in E minor (From the New World)

Things to listen out for:

Demo 2 - from the famous Largo

Demo 3 - Noise levels

A demo for the technically minded this.... The track contains a recording of the residual noise of the LP capture system, before the needle is placed on the record and then after. Once again, the first is with a high-quality analogue set-up: the second via the Groove Sleuth, the PHLUX active cartridge and Stereo Lab. The track is boosted in level by 30dB above normal so as to make the differences easier to hear. Note that:

All of which means, when you process needle-drops with Stereo Lab, you're listening to the music, pure and separated from the noise mechanisms which surround replay from records.


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