"Ghost" notes on LP playback?

[Richard]

gosh, isn't the web wonderful, just entered "pre-echo" and got this, no idea if it's true though or one of Wiki's tall tales , I too thought it was just magnetic print through.....

Pre-echo

From Wikipedia, the free encyclopedia


Jump to: navigation, search
Pre-echo is a psychoacoustic phenomenon where an unusually noticeable artifact is heard in a sound recording from the energy of time domain transients smeared backwards in time after processing in the frequency domain due to the Gibbs phenomenon. Because forward temporal masking is so much stronger than backwards temporal masking, the Gibbs phenomenon can give rise to this audible distortion which sounds like an echo which comes before the actual sound.
In an effort to avoid pre-echo artifacts, many sound processing systems use filters where all of the response occurs after the main impulse, rather than linear phase filters. Such filters necessarily introduce phase distortion and temporal smearing, but this additional distortion is less audible because of strong forward masking.
Avoiding pre-echo is a substantial design difficulty in transform domain lossy audio codecs such as MP3, MPEG-4 AAC, and Vorbis.

[colin.hepburn]

Hi All
My view on this it’s more than likely its break thought from the master tapes as these tapes were bulk erased over and over too save money or when a band had to do lots of retakes the erase heads on these master tape machines were not always as good as one may think

[pre65]

Hi-well,all the "ghost" notes i remember hearing were always the same as the start of the track that was about to play.

Tapes not wiped properly would not make that happen (would it ?)

On recordings i play i am often aware of the next track before it starts,but that must be memory because i dont remember it happening with CD s when on "Random" play setting.


Philip

[Richard]

It always seems to preceed the track and be of the actual track about to start. I remember it being put down to print-through from the piece of tape wound next to it on the reel.

Ah, enter Wiki again for "print-through". Corrr, a bit easier than the Gibbs phenomenon , also mentions pre-echo, and explains why it doesn't happen in digital, so was the last bit a mickey take

Print-through

From Wikipedia, the free encyclopedia


Jump to: navigation, search
Print-through (sometimes referred to as bleed-through) is a generally undesirable effect that arises in the use of magnetic tape for storing analogue information, in particular music.
The proximity of layers of tape on the spools of a cassette or reel to reel tape causes a weak imprint of magnetic information to be transferred to adjacent layers, effectively shifting a copy of the signal backwards and forwards along the tape. This can sometimes be heard as pre- or post-echo. Thinner tapes (designed for longer running times, since more tape can be held on the same spool) are more prone to the effect than thicker tapes, and tapes held in storage for a long period or exposed to a weak magnetic field can show pronounced print-through. Digital tapes are not affected in the same manner as the imprint is generally too weak to change the state of bits recorded on adjacent layers of the tape.
The classic example of print-through occurs during the quiet portions of Led Zeppelin's Whole Lotta Love. The pre-echo of "way down inside, woman" is heard during this passage (4:00 to 4:16).[citation needed]
Print-through on a silent section of analogue tape can sometimes be corrected digitally by replacing it with a 'clone' of a silent passage without print-through. It is usually necessary to take the cloned section from the same tape in order to preserve the original ambience.
Print-through is actually used deliberately to mass-record prerecorded audio cassettes. In the duplicator, an endless loop of the source tape is forced into close contact with blank tape and run across a "print-through head" in which a weak AC high frequency sinewave is used to transfer the information to the blank tape without erasing the source tape. This permits the tapes to be run at very high speed, speeding up production. However, audio quality using this method is not as good as when the signal is directly recorded onto the tape.

[Richard]

That echo on Led Zep is still there on cd, strange, I always thought of that as a deliberate effect, listening now though maybe not, whatever, it wouldn't be the same without it, a bit of analogue ambience....

[david counter]

very interesting,it might explain why you almost know the next track just before it starts,
I must admit in 40 years of hifi I've never heard of it before

does it also explain why you are supposed to be able to hear the Beatles on the run out track of Dark Side of the Moon,

Its caused by magnetic transfer, the Muddy Waters LP I played at the weekend is a new pressing from the 40 year old master tapes and the transfer is on every track.

[Ianm2]

I heard it last on rush, spirit of radio, it is as philip says almost a precis of what's to come, the same notes, so not really a sort of fade in

[Baggy Trousers]

Originally Posted by John T

This is can be quite common on highly modulated discs and also on those where the maximum recording time has been "sqeezed" onto the surface. One grove "effects" the adjacent "groove" which results in a similar result to print-through on tape. It may, of course also be the result of print-through on the master tape...

This condition has been around for years - at least since the advent of the LP. 78's had a substantial "wall" separating the grooves and the high polar moments of inertia (compared with later equipment) of the pick-up/needle mitigated against this type "bleed-through".

The compression of recorded information onto the long-playing format required the "wall thickness" to be much reduced with concomitant mechanical corruption of the adjacent tracks; particularly noticeable with higher energy as has been noted. The Philips Minigroove was an early casualty here but by the mid '50s the boffins had produced a cutting machine in which the radial spacing of the grooves could be varied as a function of the recorded dynamics. This afforded a big improvement in the "ghosting" problem.

Simultaneously, with the requirement for an LP side to be 30 minutes or so, recording tape became thinner to allow reels of manageable size to be used at 7,5/15ips. Increased levels of magnetic "print through" became an inevitable corollary of this.

In my judgment, the quality of audio reproduction equipment has improved only marginally, if at all, in the last 50 years. Sadly the standards adopted by the recording industry have fallen from those established so many years ago.

[Stratmangler]

I've always thought that the pre echo thing was down to delay problems between the playback and record heads on the recorders in the studio. I've only noticed it on analogue recordings which are known to be multitracked.

Chris