When is Inverse RIAA appropriate?

I read in the instructions for recording 78 rpm records (when recording at 33-1/3 or 45 then adjusting) that one should apply the Inverse RIAA EQ, then reapply the appropriate EQ. Beyond the fact that I don’t know what the “appropriate EQ” is for 78 rpm’s (and anyone enlighten me, please), I am wondering about the application of the Inverse RIAA EQ when recording 33-1/3 or 45 rpm records themselves. Is it still appropriate to apply the inverse, then re-EQ or not?

Thank you.


I don’t necessarily know what “Inverse RIAA” is, but music will not fit in a photograph record groove, so a standard method of suppressing bass notes and boosting high notes was devised. By the RIAA.


This compensation is applied at the recording making step and you have to take the effect out before you can listen to the music.

If you have an amplifier, preamp, or other device with Phono-In connections, you should use that to connect to your older turntable. Those connections are intended to perfectly electrically match the turntable and carefully take out the RIAA effect. All automatically.

You should also be using a “78 Needle” to play 78s because it’s different from 33 and 45. If you cross them, the playback will be noisier and more distorted than it should be. And it’s a given that the turntable needs to be turning at 78.

If you decide to violate all those rules, then yes, you can force a 78 to play at the wrong speed on a newer turntable and with the wrong stylus, but then you have to play all sorts of games with the music and you will never recover “normal” music. You have to take out the RIAA that your 33 turntable put in, change the speed of the music, and then put the compensation back in. All without overloading the sound channels.

We wrote about it here…


… and here …



kozikowski, For one specific project, I will probably record 78’s at 45 rpm because my turntable does not support 78 rpm and I am not impressed with the low-cost USB turntables that do. My TT is a Technics SL-1700mk2, so it’s a decent quality table from back in the day. Also, it does not employ automatic return on the arm and that is essential for the project I have for my mom. My dad had been in a Southern Gospel quartet and they recorded some discs in which the groove runs from the inside out and my TT should handle that fine whereas the low-cost USB TT’s won’t and I am not in a position to spend another $200-300 for a USB TT that has the same quality as what I already have.

I have read about using a stylus designed for 78’s and that is on my check-list of things to get. But as much as I hate the idea, I’m gonna have to record at 45 rpm then use the conversion in Audacity to correct for the improper playback.

I’ve read in the forums about “DC offset” being required when coming in through the standard audio in on a computer from a pre-amp but I don’t know what that is. I’ve also read that using a USB interface avoids that problem but then it would seem we are back to the Point A of this question, that being that if I come in from the TT through a USB interface am I back to having to manually apply the Inverse RIAA EQ in order to flatten the signal, then reapply the appropriate EQ? Does something like the Behringer UCA202 compensate for the RIAA compression or not?

Thank you.

The 78 rpm record was recorded with some form of equalization, but not the standard RIAA curve. All current pre-amps (including the UFO-202) apply the RIAA EQ curve.

You definitely need a 78 rpm stylus (3 mil, versus 0.7 mil for an LP stylus).


  1. Transcribe the record
  2. Apply the inverse RIAA curve
  3. Correct the speed.
  4. Apply the correct EQ curve.

You don’t need a UFO-202 if you have a standard phono pre-amp and a line input on your computer. DC offset can be corrected in Audacity if needed.

– Bill

Okay, good to know. But I am curious about what DC offset is…

When 78rpm reaords were made, each company used its own equalisation curve, until they were standardised by the RIAA in the 1950s.
There is a list of these curves on the Audacity wiki at http://wiki.audacityteam.org/wiki/78rpm_playback_curves.

Each curve is defined by two parameters, a Bass Turnover frequency which defines the bass boost part of the curve, and a 10 kHz Gain Rolloff value (in dB) which defines the treble cut part. I have written a plug-in for Audacity which will take these parameters as inputs, and create an xml file which can be imported into Audacity’s Equalization effect.
The latest version of the plug-in is here: https://forum.audacityteam.org/t/automatic-recording-at-start-up/241/1

When you download it, and put it in the Audacity plug-ins folder, it will appear in the “Generate” menu.
It requires Audacity version 1.3.13 or later.

There are help screens in the plug-in which should explain things but, if you have any questions, I’ll try to answer them.


Well, it sounds like I’m just gonna have to shoot in the dark and hope I get close on this one. It’s been awhile since I’ve looked at the 78’s that are the special project for my mom so I don’t know anything about them at the moment. Since they are custom recordings trying to determine what curve was used may be an impossible goal unless it happens that there is some indication on the labels or the name on the company and equipment which was used is on the label and provides a clue. But I’m gonna guess that is a long shot.

Still curious about DC offset: What it is, how it works, why it is and so on…

Thanks for the info. I’ll keep it on hand for the project (which should hopeful be started soon).

I agree that it is sensible to use you Technics deck rather tahn a cheapo USB deck. I started out my LP conversions with an ION iTT-USB but soon junked it as it gave far too much wow and flutter, the electronics were good thogh but the cartridge was average. I resurrected my old Technics TT feom that attic, gave it a home service and treated it to a new cartridge - and bought a small ART phono pre-amp - MUCH better.

You definitely nedd a stylus designed for 78s. The grooves are wider on 78 so your vinyl stylus will wallow around on the bottom of thhe groove and pick up lots of crud and noise and little signal. This could weel damage a stylus designed for vinyl so don’t be tempted to deplot it on 78s.

If possible (if your TT arm has a removable headshell and you either have or can source a spare) then it may be better to get a separate cartridge for the 78s and swap headshells - less risky than swpping the stylus.

Purists in this game will often use several different styli or headsheels as the width of the groove varies on 78s.

Sometimes you can be very lucky and find that the stylus size you deploy will fit a part of the track wall that has never or seldom been played (the previous stli used may have been larger or smaller) in which case you can get excellent sount - but don’t expect tat, it’s just a bonus if it happens.

Some pre-amps allow you to swich off the RIAA Eq - and for 78’s this is a better approach. If yours can do this then you can omit the step for inverting the RIAA Eq in the 78s tutorial.

Be aware that unlike vinyl there is no real standard for Equalization curves - each manuafucture used their own - some manufacturers even used more than one. Earlier versions of Audacity had several Eq curves built in for 78s - I don’t know if they are still there (mine get carried forward from my earlier installations of Audacity).

Also be aware that unlike LPs that run at a standard 33 1/3 rpm - 78s often didn’t actually get recorded at 78 but a a speed closish to 78 rpm.

Update: I note that Irish and you have both written while I have been writing this.


If there is no indication on the recording, then all you can do is play around with the most common settings, (Bass turnover at 250, 350 and 500Hz, 10kHz Rolloff at 0, -5 and -10dB, for example) and adjust until it sounds right.

A sound signal should be pure AC, oscillating equally positive and negative around zero volts. If there is a fault in the equipment somewhere, a DC voltage can be added to the signal, with the result that it oscillates around a value which is not zero. This can cause nasty clicks, especially if you join audio clips with DC offset to those without it.

To get rid of DC offset, you can use Audacity’s Normalize effect, with “Remove DC Offset” checked and “Normalize maximum amplitude” unchecked.


DC offset (if you have it) is a result of a faulty or poor soundcard, a small (sometimes large DC current) is appled to the signal, sometimes just one of the channels. It shows up visually as a waveform that is not centred on the zero centre line.

As Irish says Normalize will remove this - see: http://manual.audacityteam.org/man/Normalize


Is there a way to test for the presence of the DC offset? I presume that be testing one can determine the exact amount and improve the adjustment setting?

Thank you.

The “Remove DC Offset” option in the Normalize effect calculates the required correction.

If you want to see if you have DC offset, record with no signal (but your equipment connected), then zoom vertically to maximum. If the signal is not centred on the zero line then you have DC offset.


– Bill

Got it. Thanks.