Eliminating distortion from warped LP record -Sound Forge - PC

Subject:Eliminating distortion from warped LP record Posted by: keether Date:8/15/2003 10:55:01 AM I agreed to make CDs of my mother's favorite old production of Handel's Messiah, which she has on LPs (a highly technical term referring to "records"). I recorded the music on high-quality Fuji tapes and thought I had it made. But on digitalizing the music using Sound Forge, I discovered that one entire disk must have been slightly warped, causing a gentle up-and-down flutter in the music 33 times per minute. It is more than a minor distraction. Is there some feature in SF, like "steady-shot" in camcorders, that can (help me) eliminate this distortion?
Subject:RE: Eliminating distortion from warped LP record Reply by: Chienworks Date:8/15/2003 2:51:48 PM Try Effects / Pitch Bend. You can "keyframe" it, so to speak, having it get slower and faster at various points throughout the recording. You can't set many points though, so you may have to split it up into, say, 15 second sections and process each individually, then paste them back together.
Subject:RE: Eliminating distortion from warped LP record Reply by: kilroy Date:8/16/2003 10:15:50 PM My guess is that the turntable you used for the transfer was a belt drive, and of not very astounding quality to begin with. If you can get access to a quality machine with a good hi-torque direct drive motor you will get a much better transfer...that is unless the record is really bent badly. We use quartz synthesizer turntables, with very hi-torque multi phase motors and heavy magnetically damped platters for vinyl transfer archiving jobs. The timing is far, far superior, and they have the power to "pull" the needle up and down warped record slopes without slowing down going up the hills or accelerating down the other side, which is what causes the pitch fluctuations. The other concern you will be having is that the warped record surface causes the needle to "dig" a little going up the slopes, especially at the apex of the bend, and "float" a little coming over the top. In other words, the stylus pressure in being "modulated" so to speak, as it rides these waves. The result is a periodic amplitude modulation of the source, something that is pretty much impossible to to overcome in an elegant fashion. Adjusting the stylus pressure does nothing to alleviate this problem, unless more pressure is required just to keep the stylus in contact with the record as it comes off the top of a serious bend. What you could try is "baking" the record between two pieces of glass, sometimes refered to affectionately as a vinyl sandwich. The exact protocol to observe regarding this procedure is the subject of some debate among those that tout it. Here is what we do if, and only if, the record in question is not a rare collectible, and if we are given permission to try the procedure by the record owner, after having clearly explained the process and plainly stated potential risks involved. Pre heat your oven to no more than 150 degrees F. Check the temperature with a good thermometer, do not just go by the setting on the oven, it will usually always be wrong. Thoroughly clean and dry the record (very important) and place it between two pieces of tempered glass. The glass should be slightly larger than the record, 14-16 inches is good. 3\8ths inch tempered is preferred, it's got some weight and it won't break if you totally screw up on your heat settings. Do not add any more weight on top of the glass...ever. Read the last sentence again. Read it one more time. Position one of the oven racks in the middle position and place the glass and vinyl sandwich on this. Set a timer for about 10-15 minutes. This can vary somewhat but go with the low number first and see how it goes. When the time's up take it out and set it on a cooling rack, not a flat surface, you want both surfaces to cool at the same rate. Leave it for at least half and hour, there's no hurry to remove the glass. We have heard of a variation of this procedure using solar energy, i.e. exposing it to the sun on a warm day. I would do a search on the web for more details on the exact procedure, as we have no experience using this approach. And finally, the risks as we see them. The record should be surgically clean. Try this with a filthy record and you may as well chuck it out. Any grit will be baked into the grooves. You might get away with it if your temperature is no more than that stated, but I wouldn't count on it. Too much heat and the grooves could "flat top". Do not apply any more weight on top of the glass thinking you are helping things out. The whole procedure may be totally unsuccessful and your record maybe still playable...but still warped. Burning yourself and/or cutting yourself on unfinished cut glass edges. In closing, you might try a record clamp first. This brings the record in close contact with the platter and can sort of straighten out mild bends but with seriously warped records it can sometimes actually compound the problem.

My guess is that the turntable you used for the transfer was a belt drive, and of not very astounding quality to begin with.

If you can get access to a quality machine with a *good* hi-torque direct drive motor you will get a much better transfer...that is unless the record is *really* bent badly.

We use quartz synthesizer turntables, with very hi-torque multi phase motors and heavy magnetically damped platters for vinyl transfer archiving jobs. The timing is far, far superior, and they have the power to "pull" the needle up and down warped record slopes without slowing down going up the hills or accelerating down the other side, which is what causes the pitch fluctuations.

The other concern you will be having is that the warped record surface causes the needle to "dig" a little going up the slopes, especially at the apex of the bend, and "float" a little coming over the top. In other words, the stylus pressure in being "modulated" so to speak, as it rides these waves. The result is a periodic amplitude modulation of the source, something that is pretty much impossible to to overcome in an elegant fashion. Adjusting the stylus pressure does nothing to alleviate this problem, unless more pressure is required just to keep the stylus in contact with the record as it comes off the top of a serious bend.

What you could try is "baking" the record between two pieces of glass, sometimes refered to affectionately as a vinyl sandwich. The exact protocol to observe regarding this procedure is the subject of some debate among those that tout it. Here is what we do if, and only if, the record in question is *not* a rare collectible, and if we are given permission to try the procedure by the record owner, after having clearly explained the process *and* plainly stated potential risks involved.

Pre heat your oven to no more than 150 degrees F. Check the temperature with a good thermometer, do *not* just go by the setting on the oven, it will usually always be wrong. *Thoroughly* clean and dry the record (very important) and place it between two pieces of tempered glass. The glass should be slightly larger than the record, 14-16 inches is good. 3\8ths inch tempered is preferred, it's got some weight and it won't break if you totally screw up on your heat settings. *Do not* add any more weight on top of the glass...ever. Read the last sentence again. Read it one more time.

Position one of the oven racks in the middle position and place the glass and vinyl sandwich on this. Set a timer for about 10-15 minutes. This can vary somewhat but go with the low number first and see how it goes. When the time's up take it out and set it on a cooling rack, *not* a flat surface, you want both surfaces to cool at the same rate. Leave it for at least half and hour, there's no hurry to remove the glass.

We have heard of a variation of this procedure using solar energy, i.e. exposing it to the sun on a warm day. I would do a search on the web for more details on the exact procedure, as we have no experience using this approach.

And finally, the risks as we see them.

The record should be surgically clean. Try this with a filthy record and you may as well chuck it out. Any grit will be baked into the grooves. You might get away with it if your temperature is no more than that stated, but I wouldn't count on it.

Too much heat and the grooves could "flat top". Do not apply any more weight on top of the glass thinking you are helping things out.

The whole procedure may be totally unsuccessful and your record maybe still playable...but still warped.

Burning yourself and/or cutting yourself on unfinished cut glass edges.

In closing, you might try a record clamp first. This brings the record in close contact with the platter and can sort of straighten out mild bends but with seriously warped records it can sometimes actually compound the problem.