45 to 78 rpm speed conversion with Audacity

I have a record player that will play 45 rpm but not 78. Will Audacity allow me to speed up a 45 rpm track I have recorded to 78? Is this in any way automated, or is there any way to guarantee I have gotten it sped up to the correct speed, other than doing it by ear?



Yes you can, but it won’t sound right. I blame the non-standardization of early vinyl record manufacture.

Once you’ve recorded you can use Effects → Change speed and go from 45 → 78. But the EQ will be wrong.

The problem is that 45’s were EQ’d with RIAA EQ before the discs were cut. Your turntable amp is designed to undo the RIAA EQ to make the audio sound correct. Read this:

In order to get the record to sound correct you’ll have to do three things once you get it into Audacity

  1. Speed it up (as I mentioned before).
  2. Apply the opposite of the RIAA curve (to undo what your turntable has done).
  3. Apply the proper 78 EQ curve.

The problems you’ll run into are in steps 2 and 3. Audacity comes with an Equalizer that already has an RIAA curve, but it doesn’t have the opposite curve. So you’ll need to draw one yourself, this will be difficult. Once that’s done, you need to use the correct 78 curve. Audacity has a few of them pre-loaded, but as that article mentioned there were over 100 of them in use during the end of the 78 era. So try them all to see which sounds nicest (hurray for unlimited undo).

I’m sure that the next stable version of Audacity will fix the EQ-curve save feature (it’s broken now and sometimes erases your curves), so hopefully the Audacity team will be able to supply a negative RIAA curve for this purpose.

Hey, great info. Since I am using a separate preamp with phono section, I can not apply the inverse RIAA eq by using a line input rather than the phono input. Then I can apply a 78 curve without having to “undo” the RIAA eq. Does this sound right? Does the “stable” version of Audacity have the ability to do the things you mention, or do you need the beta version?

Thanks for your help!


Unfortunately, the Line In on your pre-amp expects an input signal that peaks at about 1 volt. Most Moving Magnet styluses will only put out about .01 volts, and Moving Coils about .005 volts. In other words, the Line Input isn’t going to work very well with your turntable.

By all means, try it and see, you’ll have to crank the pre-amp and completely, but it’s possible you’ll get a useable signal out of it. You do run the same risk that all low (or weak) signals run though, the noise floor might be much higher than it should. So while the processing will be easier, you’ll get a much noisier recording.

To answer your other question, yes Audacity 1.2.6 has some built in EQ curves that will be useful. I actually can’t recommend using the beta version for doing EQ work, it’s buggy when it comes to saving and loading pre-defined curves (this only applies to the built-in equalization effect, other plugins are fine).

Great points, and you are right the output is not enough from the line outs. Is there no way to invert the RIAA eq that is present in Audacity and apply that to the sound clip, thus “undoing” the RIAA? Actually, if you think about it it would make a lot of sense to have this as one of the eq options in this program. My issue shows that one of the three necessary steps in my project cannot be done by this program.

So can anyone help out with this?

Thanks, Steve

Well, it can be done, you just have to draw the curve yourself. You’re right though, this is something that should be fixed. Please post a summary of your problem in the “Adding Features to Audacity” forum.

Okay, sounds good. There would be three ways to do this that I can think of. One would be to have inverse eqs as direct choices in the eq menu. Another would be to highlight the particular eq and invert it with a choice by something like a right click selection. The one I like the best, due to most universal application, would be to have a dedicated button on a toolbar that would do this once an eq has been highlighted.

Let’s see what the gang that is refining this great software thinks. I will post the issue as you recommend, and again, thanks for all your assistance.