My DIY stereo lathe diary - design and build

[zdenda.jircik]

Hello, my name is Zdenda and I decided to make a lathe. Inspired by many at this forum I'm going to start. I have already a lot of ideas and many more questions.. But let's start somehow. I will be posting my progress.

This is idea for first version of cutting head:

Snímek obrazovky 2025-12-21 205636.png

Snímek obrazovky 2025-12-21 205057.png

This will be 3D printer for first experimenting.


Please let me know your hints if you can..

Question: I want to use 320 diamond stylus from MyShank. I don't like solution with drilled hole in the torque tube. If someone can hint any clamping solution, it would be nice.

I'm not decided what material for torque tube use. Maybe alu, but also considering carbon fiber (tube or square profile).

[zdenda.jircik]

Hi trolls,
the story contiues..

Frame construction:

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Frame will fit directly for this piece.

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[zdenda.jircik]

Hi trolls,
I was assembling the frame today. You can see that I forgot to order alu profile for bridge part. So, I made a alternative one.

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And finally let's check it together. Seems not bad.. Just few improvents needed..

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[Semar]

Force à toi, bienvenue , bonne fabrication et bon voyage camarade

[zdenda.jircik]

Hi Trolls, I appreciate any hint or help If you want to share. Anyway, story continues..
Semar: Thank you bro..

I'm waiting for delivery of some parts for transmision and decoupling of linear actuator. In between I've done some arduino job for controling the system. Waiting for MIDI component to try controlling by MIDI directly from DAW.
Thinking about how to continue..

Lifting mechanism:
I'm going to make a lifting mechanism with solenoid and variable force system. Neumann suspension dropping system solution seems to be too much complicated. I've seen Opcode66 lathe and he did really good copy, I like it. Farmer has also nice looking system based on Neumann I think so. I was thinking about to measure pressing force continually, but have not found proper sensor so far. Maybe I'm overthinking this task.

Survey:
Do you use any active force correction system for cutterhead? Do you have troubles with deepness when silent part is cutting?

Idea:
Could active correction system help to cut warped discs when no vaccum plate is used? I know, that you do not want to cut any warped disc.. But let"s talk..

[Semar]

Ta question est trop technique pour moi mais je suis tenté de te répondre de t inspirer de tout ce qui a été fait plutôt que de "réinventer l eau chaude " , à mon humble avis et pour ce qu il vaut....

[farmersplow]

Nice work. Everything looks great!
If you ask for help, you should get it. I'll do my best:

Lifting mechanism: I'm not entirely sure what you mean by this, because on the one hand you mention the lifting system, i.e. raising the cutting head. But you also mention pressing force and sensors. So I'll split the question up:
Lifting system for raising the cutting head (when it is not cutting): Usually, a cam that presses on a part is sufficient to raise the head and, when released, provides enough space so that the head does not touch the part during cutting.

Pressure (contact pressure): Three things are important here:

One: “BALANCE”: Bring the head into a balanced position, like on a scale. This means that if you use a counterweight, adjust it so that it balances the head in a floating position. If you use a spring, tension it so that it holds the head in a floating position in the cutting position.

Two: “DAMPING”: If you use a counterweight, you must install a dashpot or spring for damping. This is a process of experimentation. The damping must be different depending on the weight of the head and the length of the suspension (from the pivot point).
If you use a spring from the outset, it can be used as a damper.

Three: “CONTACT FORCE”: If you use a counterweight, you must use it to adjust the contact force. If you use a spring, you can also use it to adjust the contact force or insert a coil with a magnetic ring. You can imagine this as the counterweight arm at the back, except that you use a coil instead of the counterweight. The magnet is mounted on the housing. When the coil is energized, it pulls toward the magnet and thus lowers the head (at the front). This increases the contact pressure.

Continuous measurement of pressing force: Possible with strain gauges. Used in household scales, for example. However, this is complicated because the calibration process has to be repeated each time (as with household scales).

Do you use an active force correction system? I use it, but as I said, it is very complicated. I think that 99% of people do not use such a system. You can achieve very good results without this system.

Could an active correction system help to cut warped discs? Theoretically YES, practically NO. The effort involved would be immense and such a development would probably cost more time and money than the entire system. No record player manufacturer has developed a system for this, and they have done almost everything else. I own a Victor QL-Y55f. It has a system with a sophisticated electro-servo-controlled tone arm. This allows it to dynamically adjust the tracking force. Of course, only when a problem arises – i.e., when a wave occurs due to unevenness in the record. The system can reduce the problem (active correction system) to a large extent, which is already very good. I tried to imitate it. For 100% accuracy, you would have to measure the unevenness in front of the torsion tube optically (laser) as the distance to the record surface. This measurement accuracy is difficult to achieve because it has to happen “permanently.” When the distance is reduced, an electro-servo-controlled unit would have to raise the head by the corresponding values (e.g., 60µm). And then the system would also have to take into account the values of the transmitted music (because the entire “stereo” head pushes away from the record in the µm range). And if there is a speck of dust on the surface, this must also be detected and the measured value negated. Etc., etc., etc.
Conclusion: No

Summary:
Lifting mechanism: Yes, you're worrying too much. Tackle it when your device is finished and you're looking to make improvements.
Measuring pressing force: Leave it for now. There will still be time for that once you've achieved a reasonably good cut.
Force correction system: Leave it. There are about 5000 things that have more influence. Once you've worked through all of those, then there's time for that. It's much more important to improve the three points (“BALANCE,” “DAMPING,” and “CONTACT FORCE”) through experimentation so that you don't need it.

Nevertheless, I understand you well and think it's great that you're thinking about these things. Let yourself be inspired (as Semar suggested), but feel free to question things. Much of this is based on experience, but much has not yet been experienced.

I hope this was understandable and helpful. (For me, it was always the case that when one question was answered, three new questions arose.).

Oh yes, I almost forgot. In the early days of record cutting, the problem was even greater. So in 1948, Russell O. Hanson and William F. Saars invented the lead-in ball for the cutting head. (See patent US 2528826A).
You may lose some sound quality, but you don't have to worry about tracking force, warped records, correction systems, etc. Once set, the distance between the cutting head and the record surface remains the same. The system was also used in the Westrex 3DII at Scully in 1976. So if it's done well, you lose less sound quality than you gain in advantages!

Thomas

[zdenda.jircik]

Hello Semar and Thomas,
firstly thank you for you reactions. I really appreciate it.

I mixed up lifting mechanism and pressure correction together. I thought that Neumann has solved both functions by one mechanism (magnet+solenoid). I think you explained problematic really well. I will keep trying simple, but functional lifting mechanism for first version. Lathe will need changes and modifications anyway.


This was my idea about merged lifting and contact force correction system:

Use a hydraulic damper with spring inside as a counterweight. So, Cutterhead would be raised by spring in damper, when no voltage applied to a coil.
Then the magnet and coil would be pulling the cutterhead to cutting position. Solenoid and magnet would act in opposite direction to the spring. In case of contact force correction I'd use probably second winding to handle small corrections. But for the corrections I need to measure contact force. So, strain gauge would measure force and feedback amp is making corrections at second coil winding immediatelly (in best case). When the voltage from main winding diappears the cutterd is raising up..

This is just theory of my idea. But it would probably spend a lot of time and experimenting. So, I will keep this idea for the next time maybe..

PS.: Lead-in ball is great idea. I've seen woodworkers use copy bearing similar way to guide the router for routing nice facets.

Example of damper with spring:

Screenshot 2026-01-09 094332.png

Have a nice weekend and keep cutting..

Zdenda

[Fela Borbone]

Hello Zdenda,
​A mechanism for servo-controlling stylus pressure may consume significant time and resources, so you might want to focus on making it work smoothly, quietly, and accurately first. But as we are talking about measuring and controlling pressure,I have to say it is doable; I tried using a load cell at the base of the spring with an HX711 connected to a microcontroller. I use Microchip PIC, but there must be libraries available for the Arduinos that everyone uses here. Since the readings aren't directly in grams, you’ll need a software lookup table, and keep in mind it changes depending on the settings.
​Another method is using a capacitive bar sensor from a digital caliper to measure the expansion of the spring (even cheap digital calipers have a 'secret' serial output). It’s an interesting idea, but a bit too bulky.
​Finally, I’m experimenting with a tiny linear actuator to control the spring. It doubles as both a head lift and pressure control. A Hall sensor and a magnet detect when the head has landed, and I use a software self-calibration process to achieve this. Once the head has landed, the actuator expands a specific distance to provide a set pressure. This can be adjusted on the fly using a knob on the control board.
This is work in (slow) progress, I wish I have time to work on it and open my own thread to document properly...

[Semar]

farmersplow , Fela Borbone, you're insane, thanks for the community !!!

Zdenda, please begin simple, reach simple good results as wright up , silent and regular groove, and make it hard later ... the less is the much.....

[Semar]

Have a good travel in your way bro

[zdenda.jircik]

Hi Trolls,
thank your for your valuable advices.

@Semar:
I will begin simple way for first version. But I'm looking forward for further experimenting. I undertand that I should have some positive results before making things more complicated.

@Fela Borbone:
It seems that you are already on this way for some time. I know that it is a lot of experimenting and making your own know-how. I'm glad that somebody is developing own solution. I definitelly want to try similar cotrol of lifting system. Firstly I will be focused on properly working cutting system and hopefully afterwards I will try something like you.

Thank you for sharing your experience guys. It is motivating..
I had to do some other jobs in few past days. Hopefully, update will come sooon.. I ordered diamont stylies from MyShank and some other stuff..

Zdenda

[farmersplow]

Hello Zdenda,
​A mechanism for servo-controlling stylus pressure ...

​Finally, I’m experimenting with a tiny linear actuator to control the spring. It doubles as both a head lift and pressure control. A Hall sensor and a magnet detect when the head has landed, and I use a software self-calibration process to achieve this. Once the head has landed, the actuator expands a specific distance to provide a set pressure. This can be adjusted on the fly using a knob on the control board...

Excellent! A great development!

[Semar]

Someone who is pushing high the technology

https://www.facebook.com/share/v/1Wxjogmmim/

[zdenda.jircik]

Hi Semar,
the link is not working for me.. Maybe because I'm not member of the group?? I'm also not so much familier with FB

[Semar]

Hi Semar,
the link is not working for me.. Maybe because I'm not member of the group?? I'm also not so much familier with FB

[zdenda.jircik]

Ohh, cool system. Thank you for sharing it. Seems to be precise enough. This is the path..

I have been struggling with Arduino for couple of days. I'm trying to control a stepper via MIDI from DAW. It is almost finished, but for some reason I'm loosing some bits. I'm waiting for better midi cable, the old one was not so much convincing.

[zdenda.jircik]

Hi all,
I was struggling with MIDI receive by arduino. It was working, but some bytes were missing some bites. Or bites were distorted somehow. After chain of investigation I found a trouble in MIDI shield. Unfortunately I bought the cheapest one available.
This one:

Screenshot 2026-01-30 100911.png

The shield has fine optocoupler (6N138), but circuit is little bit cropped. I was checking signal by oscilloscope and the egdes were horrible. There is missing connection from pin 7 to GND and pull-up resistor value at output is also not the best. I added 4k7 resistor between pin 7 and GND. MIDI shield works reliable now. Lessons learned. Next time I will check the circuit diagram, before I buy it. And I was too lazy to make my own layout..

Let's watch stepper control from DAW:

Now I can finally continue with hardware stuff like redraw of cutterhead and make a mounting system on the frame.

Have a nice weekend

[farmersplow]

Well done!

[Semar]

Nice