Hi All,
My friend and I recently got a Radiotone Hollywood Lathe cutter/radio that looks like it was from the 1930s or 1940s. It is currently not working but I believe it would be a good candidate for a summer project. The mechanicals for the cutter (with the exception of the roller wheels) seem like they are in decent shape, but the electrical (radio and amp) is a big mess of old capacitors and, with no wiring diagram, I don't think it is worth figuring out and restoring. For our project we would like to use the mechanicals and cutting head, add an appropriate modern power amplifier to drive the cutting head, and maybe build a new box to house everything. Our sound output would be from a PC to the amplifier with all filtering (RIAA, power amp and cutter head compensation) done in software. Since we got the cutter I have been going through the old threads learning as much as I can about lathe cutting. I am sure I will be starting or adding on to threads in the future, in the meantime I have a couple of questions before we dig into this project.
The cutting head doesn't have any markings on it, but appears similar to the RCA MI-4887. Does anyone know if it is an RCA head or have any info on Radiotone heads?
Based on what I have read here, it looks like the first thing I should do to check it is measure the resistance to see if it is OK.
What size power amplifier should we use? Some threads I have read mention 500W is a good size.
Can the wheels be pruchased off the shelf or should I try to have them rebuilt/repaired?
Anyone have any info on this unit? I could not find too much with a quick search on google or this forum for this exact unit, but I think other people have Radiotones out there.
We also have the electricals for a Rek-O-Kut Imperial if anyone is interested. We would like to sell it to someone who could use it (Detroit area if possible) to help fund this project.
Radiotone Hollywood Project Lathe
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RadiotoneH
- Posts: 2
- Joined: Fri Jul 08, 2022 7:57 pm
Radiotone Hollywood Project Lathe
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Re: Radiotone Hollywood Project Lathe
Hi,
Sounds like you have the right approach.
Measure the DC resistance of the head and if its in the 2-16 ohm range, you should have no trouble driving with a modern amp. Given the its natural limit, I would think 10-50 watts would be plenty. I doubt the original amp output more than few watts. Having extra power might allow you to extend the bandwidth and/or the loudness of the cuts, but past certain point, no increase in power will produce any effect (just heat and distortion). The head might need some rebuilding given its age if you want to get the best performance. It looks easy to work on. I would suggest you go for embossing rather than cutting since its less demanding lower in operating cost. You can test the head qualitatively by connecting to an amp with a stylus or a 1/16" drill or something similar place of a stylus and couple it to a plastic cup (to act as a speaker cone) while feeding some program material at a drive level of a watt or so. If you can hear nice clean and reasonable loud sound, the head is in decent shape. It still might benefit from an overhaul.
Getting the mechanicals in order will require some effort. You may end up wanting to drive the platter and feed screw with separate motors to allow speeds other than 78 and variable pitches.
Good luck and let us know how you make out with the project.
Mark
Sounds like you have the right approach.
Measure the DC resistance of the head and if its in the 2-16 ohm range, you should have no trouble driving with a modern amp. Given the its natural limit, I would think 10-50 watts would be plenty. I doubt the original amp output more than few watts. Having extra power might allow you to extend the bandwidth and/or the loudness of the cuts, but past certain point, no increase in power will produce any effect (just heat and distortion). The head might need some rebuilding given its age if you want to get the best performance. It looks easy to work on. I would suggest you go for embossing rather than cutting since its less demanding lower in operating cost. You can test the head qualitatively by connecting to an amp with a stylus or a 1/16" drill or something similar place of a stylus and couple it to a plastic cup (to act as a speaker cone) while feeding some program material at a drive level of a watt or so. If you can hear nice clean and reasonable loud sound, the head is in decent shape. It still might benefit from an overhaul.
Getting the mechanicals in order will require some effort. You may end up wanting to drive the platter and feed screw with separate motors to allow speeds other than 78 and variable pitches.
Good luck and let us know how you make out with the project.
Mark
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RadiotoneH
- Posts: 2
- Joined: Fri Jul 08, 2022 7:57 pm
Re: Radiotone Hollywood Project Lathe
Thanks for the response. A 50W amp is a lot less power than I expected. Will update as the project progresses. Thanks!
Re: Radiotone Hollywood Project Lathe
Hi,
You are thinking of professional moving coil heads. The moving iron type heads require much less power than the other type. Its not really a problem to use a more powerful amp, but you will not need the reserve. If you ever get a Grampian, which is a higher end moving iron design, having 150 watts is needed to get response out to 15-20Khz at a reasonable level. The head you have will top out in the 5-8Khz range. You might be able to push it to 10Khz, but it will be a stretch. A trick to get better performance out of these heads would be to use half speed mastering.
Mark
You are thinking of professional moving coil heads. The moving iron type heads require much less power than the other type. Its not really a problem to use a more powerful amp, but you will not need the reserve. If you ever get a Grampian, which is a higher end moving iron design, having 150 watts is needed to get response out to 15-20Khz at a reasonable level. The head you have will top out in the 5-8Khz range. You might be able to push it to 10Khz, but it will be a stretch. A trick to get better performance out of these heads would be to use half speed mastering.
Mark