What causes pre-echo / groove-echo?

What causes pre-echo / groove-echo?

Pre-echo on a record is somewhat of a phenomenon, it is not commonly known what causes a faint audio signal on a record slightly before the main recording.

It is often the result of excessive groove swing and depth changes on the lacquer from stereo width in the bass frequencies.  This is one of the reasons as to why bass frequencies are mono’d on a vinyl record.

ElectronMicroscopeImageOfDirtyVinylRecordGroove
So what actually is pre-echo or ‘groove-echo’? It is a result of the transmission of sound from one record groove to the next.  It is caused during cutting, but can also be made a lot worse during the processing of the lacquers.  A decent lathe will cut a groove that just touches the previous rotation, whereas some of the later lathes actually nestled part of the groove into the previous one.  The cutting engineer would have to use the ‘add land’ button to create more space between the groove artificially.

The acetate or lacquer is pretty much a living thing, and how it electroplates is a result of how well cured it is.  This is determined by the amount of oils used, how long it was cured, and how long it was given to acclimatise at the cutting room.

Once the lacquers are used on a lathe then the pre-echo starts to build up, the first 24-hours are crucial so it’s important to get the lacquers into the electroplating bath as quickly as possible.

It is often thought that the cutting engineer could only be responsible for groove-echo, though galvanic process does have a big part to play, and it’s often this procedure that causes the biggest problem.  To reduce the possibility of this, the plating process needs to be very slow and cold to reduce any effects that could be evident on the lacquer.  Rushing the plating process during busy periods at a pressing or having the bath too hot can result in greatly exaggerating problems evident on the lacquers.

As a vinyl producer trying to get the best possible product out the door the best thing you can do is have the Cutting Engineer post out your lacquers immediately, and make whichever plant you are using aware that they are on the way and you have your order actually in place.

 

 

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