Tracking 78 rpm records

**mberry593** · 06-22-2012, 08:28 AM

This is 'home project.'

I inherited a collection of 78 rpm records and I want to digitize them and add them to my iTunes library. I have an excellent turntable and a Shure cartridge with a N78s stylus that does a great job. Unfortunately many of the records are warped and the stylus jumps grooves even at fairly high tracking forces. I have experimented with trying to flatten them by putting weights on them and leaving them to bake in a warm place. I got some improvement with this technique, but there are still several that I can't play.

I can, however, play them with no problem at 45rpm. I have experimented with Autotune to restore the correct pitch and that does seem to work ok. The remaining problem is an equalization error. When playing the records at 45, they hit the RIAA equalization in the preamp at the wrong frequencies. I can correct that by ear but that seems to be a little uncivilized to me.

It seems to me that it should be possible to calculate a correction curve to crank in to make everything come out properly. I guess I could do that but before I tax my poor, old brain to that extent I thought I would ask if anyone here has been through this exercise before and might share their experiences.

Alternatively, does anyone know of a 78rpm test record that I could use to measure the error? I have both the CBS & NAB test records but they
are at 33 1/3 & won't help with this error.

Thanks.

**Boswell** · 06-25-2012, 07:20 AM

You have lots of options here, many of which depend on whether you are prepared to spend real money on a proper commercial 78rpm external equaliser. This does not have the same characteristics as an RIAA equaliser as used for vinyl (33rpm) disks.

There are 78rpm equaliser DAW plugins you could try after you have rate-corrected the recorded file by 1.73 (from 45rpm to 78 rpm). Note that rate correction is different from pitch correction, as you need to scale the time as well as the frequency.

Alternatively, you could use a standard external analogue equaliser after the rate correction as though it were an external effect unit. My preference, though, would be to make your own equaliser with capacitor values 1.73 times greater than those in the 78 rpm published circuits and record through that. The rate correction would then be purely to correct the tuntable speed.

There is lots of advice (both good and bad) available on various web sites about 78 and 33 rpm disk transfers. The Danish company Vadlyd is a good starting point.

**bigtree** · 06-25-2012, 07:51 AM

Originally Posted by Boswell

You have lots of options here, many of which depend on whether you are prepared to spend real money on a proper commercial 78rpm external equaliser. This does not have the same characteristics as an RIAA equaliser as used for vinyl (33rpm) disks.

There are 78rpm equaliser DAW plugins you could try after you have rate-corrected the recorded file by 1.73 (from 45rpm to 78 rpm). Note that rate correction is different from pitch correction, as you need to scale the time as well as the frequency.

Alternatively, you could use a standard external analogue equaliser after the rate correction as though it were an external effect unit. My preference, though, would be to make your own equaliser with capacitor values 1.73 times greater than those in the 78 rpm published circuits and record through that. The rate correction would then be purely to correct the tuntable speed.

There is lots of advice (both good and bad) available on various web sites about 78 and 33 rpm disk transfers. The Danish company Vadlyd is a good starting point.

Bos, you rock!
http://www.vadlyd.dk/English/RIAA_an...PM_preamp.html

Am I just understanding all this after years gone by. Are 78's etc cut with a eq setting that was made to go along with a playback amp to match this era? So if you play a 78 on a regular turntable it isn't really flat, we are missing freq and why they always sound so thin? So this clever preamp solves this and allows us to run a modern turntable into our DAW's to process them for CD etc?

Interesting thread.

**Boswell** · 06-25-2012, 08:28 AM

It's more a matter that every recording company of the day used its own pre-emphasis network for their 78 rpm disk cutting machines. That means that for replay there is no single network that deals correctly with all makes of disk, and it's why specialist pre-amps like the Vadlyd have many equalisation settings.

I had a colleague once who was very much into 78 disks, and I built him a multi-eq circuit. I had a good listen to the unit on several makes of disk, and, to be honest, I could not reliably tell which was the "correct" setting, but I could distinguish a difference between most of them.

**mberry593** · 06-25-2012, 08:50 AM

Thank you for the link. That is very interesting information. It looks like even the ones that I have played back 'on speed' at 78 are wrong. I guess that I need to get that correct before I fool with playing records at alternate speeds.

I do have the rate & pitch covered ok but I am considering constructing my own preamp. The Vadlyd looks very nice but it doesn't solve my complete problem. I did build a RIAA preamp back in the 1970s & it is still somewhere in the depths of my basement so the metalwork & bi-polar power supply are already done.