So, after many years of putting up with compromises I have decided to get a properly-sorted-out 78rpm front end together. I have a large, and growing, collection of 78rpm shellac records which need something decent.
I believe that there are three issues to consider:
1) I need to put together a turntable with a speed variable around a nominal 78rpm, say from around 60rpm to perhaps 90rpm as the recorded speed varies between different records.
2) I need a cartridge fitted with a correct 78rpm stylus to properly fit the large grooves of 78rpm shellacs.
3) I need to make a pre-amplifier with variable equalisation and filtering as this varies between shellacs, with RIAA only being used at the very end of the 78rpm era.
For (1), given my familiarity with Thorens belt-drive turntables I am thinking that some kind of variable motor speed control circuit applied to either a TD150 or TD160 should do a great job. I am thinking possibly something along the lines of a Linn 'Valhallah' or Thorens TD125 motor control board, but with a more variable frequency range. If anyone has already done such a project I would, of course, but very interested.
Addressing (2) I am thinking of buying the 78rpm stylus for either my Ortofon OM-pro or Ortofon 2M. Alternatively, I could see what Audio Technica have to offer.
Point (3) has, I believe, already been successfully addressed by 'monty78pig' in his '78rpm heaven - a discrete multicurve phono preamp for your shellac' thread.
I would love to discuss this with any other enthusiasts of the old 78rpm records and am particular eager to see what alternative people might think of.
For the record (pun intended) my current systems are fronted by a Thorens TD125 in one room, and Thorens TD150 plus TD160 in another room. All three turntables have been 'tweeked' in the same way as Linn recommend fettling their LP12 Sondek and perform rather well.
Whichever cartridge is used with either the TD150 or TD160 will be fitted to one of four pickup arms: Rega RB300, Mission 774, Linn LVX or ADC ALT-1.
Amplification will be taken care of by a Linn 'Aktiv' system of a pre-amp, active cross-over and three stereo power amps with the sound emerging from Linn Kaber speakers.
Comments are welcome, even more so if they are constructive !
Best to all,
Kepla.
I believe that there are three issues to consider:
1) I need to put together a turntable with a speed variable around a nominal 78rpm, say from around 60rpm to perhaps 90rpm as the recorded speed varies between different records.
2) I need a cartridge fitted with a correct 78rpm stylus to properly fit the large grooves of 78rpm shellacs.
3) I need to make a pre-amplifier with variable equalisation and filtering as this varies between shellacs, with RIAA only being used at the very end of the 78rpm era.
For (1), given my familiarity with Thorens belt-drive turntables I am thinking that some kind of variable motor speed control circuit applied to either a TD150 or TD160 should do a great job. I am thinking possibly something along the lines of a Linn 'Valhallah' or Thorens TD125 motor control board, but with a more variable frequency range. If anyone has already done such a project I would, of course, but very interested.
Addressing (2) I am thinking of buying the 78rpm stylus for either my Ortofon OM-pro or Ortofon 2M. Alternatively, I could see what Audio Technica have to offer.
Point (3) has, I believe, already been successfully addressed by 'monty78pig' in his '78rpm heaven - a discrete multicurve phono preamp for your shellac' thread.
I would love to discuss this with any other enthusiasts of the old 78rpm records and am particular eager to see what alternative people might think of.
For the record (pun intended) my current systems are fronted by a Thorens TD125 in one room, and Thorens TD150 plus TD160 in another room. All three turntables have been 'tweeked' in the same way as Linn recommend fettling their LP12 Sondek and perform rather well.
Whichever cartridge is used with either the TD150 or TD160 will be fitted to one of four pickup arms: Rega RB300, Mission 774, Linn LVX or ADC ALT-1.
Amplification will be taken care of by a Linn 'Aktiv' system of a pre-amp, active cross-over and three stereo power amps with the sound emerging from Linn Kaber speakers.
Comments are welcome, even more so if they are constructive !
Best to all,
Kepla.
Check out this thread by monty78pig. Front end for 78rpm shellac records. - diyAudio
He designed a circuit with switchable roll-offs for different eras and brands of 78 records. He also provides guidance for which setting to use for which brands etc.
Pity search engines can't find this stuff. Google was pretty good when they put altavista out of business, but now they are just a online version of the yellow pages. No pay, no listing.
He designed a circuit with switchable roll-offs for different eras and brands of 78 records. He also provides guidance for which setting to use for which brands etc.
Pity search engines can't find this stuff. Google was pretty good when they put altavista out of business, but now they are just a online version of the yellow pages. No pay, no listing.
Um, your link to Monty's thread comes right back here. 
EDIT: Here is the link. 78RPM Heaven - a discrete multicurve phono preamp for your shellac!
I've read a number of 78 enthusiasts how say that using a stereo cart is not a good idea. Does that have any merit?
EDIT: Here is the link. 78RPM Heaven - a discrete multicurve phono preamp for your shellac!
I've read a number of 78 enthusiasts how say that using a stereo cart is not a good idea. Does that have any merit?
Getting an AC synch motor that was designed to run at 600 RPM to operate at 1404 RPM is a tall order. The back EMF generated at that speed will most likely exceed the normal drive voltage so the motor would not run. Even with increased drive voltage, it's doubtful the motor would either operate at that speed or have enough torque to do the job. If it stalls at higher voltage, the power consumption will spike and damage the motor.
Unless you have a pulley made to run the platter at 78 RPM when the motor is turning at 600 RPM, your best bet will be a DC motor or a BLDC motor. A DC motor will need more than a voltage regulator to hold speed under load and the BLDC motor will also need sophisticated electronics to ramp up to speed or to accurately hold speed.
SOTA will be releasing a BLDC motor/controller combination that will do 33/45/78 RPM with one pulley, has plenty of torque and will work with the RR tach closed loop feedback.
Unless you have a pulley made to run the platter at 78 RPM when the motor is turning at 600 RPM, your best bet will be a DC motor or a BLDC motor. A DC motor will need more than a voltage regulator to hold speed under load and the BLDC motor will also need sophisticated electronics to ramp up to speed or to accurately hold speed.
SOTA will be releasing a BLDC motor/controller combination that will do 33/45/78 RPM with one pulley, has plenty of torque and will work with the RR tach closed loop feedback.
... "I've read a number of 78 enthusiasts how say that using a stereo cart is not a good idea. Does that have any merit?"
A mono cartridge does not pick-up vertical movements so the playback noise due to record surface imperfections can be reduced.
A mono cartridge does not pick-up vertical movements so the playback noise due to record surface imperfections can be reduced.
Welcome to the club, Kepla. There's joy to be found in those old shellacs. A few comments follow.
1. Heed what Pyramid said above re pushing low-rpm ac motors to a much higher speed. I did the electronics board mod to my TD-125 (Mk I) to convert its 16-rpm speed to 78. It works, and the table does turn at 78 (after a starting push). But the motor generates an acoustical whining noise suggesting that it's not happy.
2. Using a stereo cartridge to play mono 78s has advantages compared to a dedicated mono cartridge. But ensure your preamp has a MONO switch to sum the two stereo channels. This cancels out a lot of shellac surface noise as well as low-frequency rumble that was prevalent in the cutting lathes of yore. Alternatively, you can sum at the cartridge by combining the two stereo channels. OBTW, the Library of Congress prefers stereo cartridges for archiving their historic mono records. Even for cylinder recordings!
3. You're probably aware that some early 78s had vertically modulated grooves. Pathe and Edison discs among them. If you're interested in those, you'll have to rewire your stereo cartridge to sum the two channels out-of-phase to cancel lateral groove motion. (Unless your preamp can do this electrically.)
4. Often cleaner playback of a very worn mono record results from using EITHER the right OR the left channel of a stereo cartridge. So hopefully your preamp has this option.
5. Just as turntable speed and equalization curves were not standardized in the earliest days, neither was groove geometry. The usual 3-mil "wide-groove 78" stylus will play most of the old records. However, improved results can sometimes be had by other stylus sizes. The Library of Congress has dozens of slightly-different sized-tipped styli for their Shure and Stanton cartridges for this reason. These styli are still available for enthusiasts, but I've not seen similar options for A-T or Ortofon cartridges.
1. Heed what Pyramid said above re pushing low-rpm ac motors to a much higher speed. I did the electronics board mod to my TD-125 (Mk I) to convert its 16-rpm speed to 78. It works, and the table does turn at 78 (after a starting push). But the motor generates an acoustical whining noise suggesting that it's not happy.
2. Using a stereo cartridge to play mono 78s has advantages compared to a dedicated mono cartridge. But ensure your preamp has a MONO switch to sum the two stereo channels. This cancels out a lot of shellac surface noise as well as low-frequency rumble that was prevalent in the cutting lathes of yore. Alternatively, you can sum at the cartridge by combining the two stereo channels. OBTW, the Library of Congress prefers stereo cartridges for archiving their historic mono records. Even for cylinder recordings!
3. You're probably aware that some early 78s had vertically modulated grooves. Pathe and Edison discs among them. If you're interested in those, you'll have to rewire your stereo cartridge to sum the two channels out-of-phase to cancel lateral groove motion. (Unless your preamp can do this electrically.)
4. Often cleaner playback of a very worn mono record results from using EITHER the right OR the left channel of a stereo cartridge. So hopefully your preamp has this option.
5. Just as turntable speed and equalization curves were not standardized in the earliest days, neither was groove geometry. The usual 3-mil "wide-groove 78" stylus will play most of the old records. However, improved results can sometimes be had by other stylus sizes. The Library of Congress has dozens of slightly-different sized-tipped styli for their Shure and Stanton cartridges for this reason. These styli are still available for enthusiasts, but I've not seen similar options for A-T or Ortofon cartridges.
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