Browsed by
Category: DMM

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.

 

 

DMM (Direct Metal Mastering) vs Lacquer. Which should you choose?

DMM (Direct Metal Mastering) vs Lacquer. Which should you choose?

DMM (Direct Metal Mastering) vs LacquerDMM (Direct Metal Mastering) became popular during the 80’s but was soon less favourable as more cutting engineers went back to lacquer.

 

DMM (Direct Metal Mastering) was co-developed by Neumann and Teldec, and in stead of engraving the groove into a soft metal lacquer-coated aluminum disc, a DMM lathe engraves the audio signal directly onto a hard metal copper-plated master disc.

The difference between a DMM cut and a lacquer cut is that the DMM is more precise, with sharper transients and better image “edge definition,” while the lacquer cut is smoother, warmer and more pleasing on the ears.

DMM (Direct Metal Mastering) cuts always appeared to have a brighter and more defined top-end. Upon early inspection of DMM discs, this appeared to be due to a higher frequency modulation in the groove, caused by an ultra-sonic carrier tone. However there is no carrier tone on DMM cuts and the modulation is simply caused by the vibration of the cutter head.

Many critics often describe a DMM cut as too bright or too ‘edgy’. Often the reason for playing a vinyl record is to have the warm and analogue sound that is often not present in a DMM cut.

DMM did though eliminate the problem of pre-echo sometimes audible on a lacquer. Pre-echo is caused by the cutting stylus unintentionally transferring some of audio signal into the previous groove wall, causing a faint audio signal, a pre-echo.

Another argument for the use of DMM is that it removes the need for one stage of the galvanic process. Since the DMM (Direct Metal Mastering) is cut onto copper the first stage of electroplating is bypassed, resulting in cleaner processing with less surface noise and less chance of error during processing.

Although the warmer sound of lacquer could arguably be put down to the cuts not sounding as bright as DMM, the fuller sound of lacquer could be credited to the depth of the grooves on a lacquer. Lacquers can be cut much much deeper than DMM which is essential for music with a prominent low-end signal. As well as giving the fuller sound, a deeper groove is needed to avoid jumps and skips on a turntable. And even though DMM has much brighter more defined frequency response in the top end, this certainly isn’t the case with the bass frequencies, evident in most of today’s electronic music.