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Converting 33 recording to 78 how

New Here ,
Oct 22, 2017

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How do I record at 33 rpm and convert to 78 rpm? I know about different grooves and stylii.

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Converting 33 recording to 78 how

New Here ,
Oct 22, 2017

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How do I record at 33 rpm and convert to 78 rpm? I know about different grooves and stylii.

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Adobe Employee ,
Oct 22, 2017

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I'm glad you know about different grooves and stylii. You're ahead of the crowd. Just to check, however, are you familiar with the different reproduction curves used in the preamps for 78 vs 33&1/3rd or are you transferring flat?

The way I've done it is to calculate the ratio between 78 and 33&1/3rd.

78/3 * 100 = 2.34.  So, you'll simply want to use that ratio when using the Edit > Interpret Sample Rate function. So if you recorded at a hardware sample rate of 44100 Hz, and the turntable was at 33.3 RPM then I'd enter in a sample rate of 44100 * 2.34 = 103194 Hz.  This will effectively speed up the recording, and we'll automatically resample to your playback sample rate (likely still at 44100 Hz).  However, it would be a good idea to resample to a common sample rate when you save the file. So you may want to perform Edit > Convert Sample Type and try whatever settings you wish and listen to it ​before ​saving to the new sample rate.

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Adobe Community Professional ,
Oct 23, 2017

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You may also wish to consider the final pitch of your recording as being a better arbiter of the sample rate conversion numbers. The reason for this is that virtually NO 78's were ever cut at exactly 78 rpm! It was all mechanical back then, and speed regulation was appallingly poor.

You might want to read this article, and be prepared to be a little surprised by the potential extent of the variations...

Speeds and pitching of 78rpm gramophone records

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Community Beginner ,
Jul 31, 2020

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I'm actually having the same problem, except I'm recording from 45 and converting to 78rpm.  (In hindsight, I guess I could have re-done it at 33rpm, but I'd already recorded them at 45 and didn't want to repeat a step.)

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Adobe Community Professional ,
Jul 31, 2020

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Okay - speed ratio between 45 and 78 is that you have to speed up the playback by 78/45 = 1.7333 times. (Charles's formula seems to have gone wrong, although the answer is correct for 33 1/3). So you then use Edit > Interpret Sample Rate and multiply the original sample rate by 1.7333 - which for 44100 gives 76438. If you do this, then it will play at the correct speed - although see my comment above. And then the last thing you do is go to Edit > Convert Sample Type and convert back to your original sample rate - only this time it will play at the correct speed. Then you save the results.

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