TDL® Technology, Inc. – Case Study Number 3
Restoration of a 78 RPM Album, Cugat’s Favorite Rhumbas,
Columbia Records Set C-110 (ca. 1946)
Written: 29 May 2008
I found this four record set in its original album in a thrift store for two dollars. The records were very dirty (dusty) but looked in fair condition otherwise. After a through washing I played all eight sides just to judge the overall sound quality. I heard lots of pops and clicks but only two sides had any major scratches which affected 10 to 15 seconds of the music. I used a Stanton model STR8-80 direct drive turntable with a straight tone arm and a Stanton 520 cartridge equipped with a Stanton D5127 2.8 mil stylus (which is recommended for 78 RPM records).
I have been unable to accurately date this album but taking into consideration when Mr. Cugat was appearing at the Waldorf-Astoria, 1946 may be a good guess although it could have been a couple of years earlier. Columbia Records released these same eight titles on a mono-LP in 1954 as CL-579.
This restoration gave me the opportunity to use our new model 4010, The Restoration Preamp TM, which I setup as follows:
Mode to L+R (because this sounded best)
Turnover: 300 Hz
Rolloff: -16 dB
Rumble Filter: 40 Hz
HF Filter: 10 kHz
The Turnover and Rolloff settings came from the model 4010 User Guide for a Columbia 78 recorded in the 1940s. I experimented some with these settings but the table entries sounded best.
The transfers to the computer hard drive were done with a Waveterminal 192X  sound card which can record at up to 192/24. That is, a sample rate of 192 kHz and a bit depth of 24. My friend, Don Walizer, has discovered that the filters in the Diamond Cut  restoration software work best with a high-resolution file so I recorded at 96/24. I have found this to be true as I could use more aggressive filtering without introducing “artifacts” than with transfers made at the CD standard of 44.1/16. (The Diamond Cut program has a menu selection to convert the high-resolution file to the CD standard.)
Setting up the filtering does require some trial, previewing, adjusting and more previewing. But experience helps and each restoration you do adds to your experience. I prefer to listen using headphones because they help block out external noise and I can hear details that I miss when using monitor speakers. I used a TDL® model 444A Headphone Amp and Sennheiser model HD-280 headphones.
I first normalized the amplitude (volume) all eight sides (tracks) to -2 dB because this helps to maximize the signal-to-noise ratio before doing the filtering. I setup a Multi-filter in DC6 with two EZImpulse filters both set to the “Very Aggressive 2" preset followed by a Continuous Noise Filter using the “Flat Line Noise” preset. In several cases I have found this preset to work better than taking a noise sample from the recording.
Sides 6 and 7 both had a scratch at about mid-way which the EZImpulse filters greatly attenuated but did not completely remove. So I had to remove the residuals manually by listening and then zooming in on the click. You have to be careful with the next step or you may do more harm than good. You have to highlight and then delete part of the music. If you take too much, you leave a “hole” which you can hear. And, you need to avoid leaving a discontinuity which can also be heard. I like to work from one zero-crossing to another zero-crossing so the resulting waveform, after the deletion, is smooth. Then zoom out and listen to what you just did. If it sounds OK, save the file and go to the next click. It takes some practice but the end result can be very satisfying.
When you are satisfied with your restored music, you can just listen from your hard drive (remember to make a backup of all your hard work!) or you can “burn” a CD. Another advantage of having done the restoration on a high-resolution file is being able to listen to the high-resolution music. You can also “burn” it to a DVD-Audio using, for example, Disc Welder software.
1. Unfortunately, this sound card has been discontinued. See the Tracertek web site for some alternatives. www.tracertek.com
2. Diamond Cut Productions software is available from Tracertek. DC6 and the newer DC7 are both available. DC6 runs under Windows 98SE, ME, 2000 and XP while DC7 requires XP or VISTA (and has many new and improved features). (All versions of Windows are trademarks of Microsoft Inc.)
3. Get the best headphones you can afford because it will make your restoration work more enjoyable.
4. Disc Welder Bronze is also available from Tracertek. (And, no, I’m not affiliated with them in any way!)
TDL® Technology, Inc.
Las Cruces, New Mexico USA