The farmer and his plow - When I set out to build a record cutter

[farmersplow]

Absolutely fantastic.

Thank you, faithful companion

[farmersplow]

Suspension box FP-9
11/2023

Because the new cutting head is now not only smaller but also lighter than the old one, both the counterweight in the form of a spring and the oil damping have to be adapted. To do this, I machined the piston and added additional flow-through holes.
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For this and other work, I have to remove the suspension box, dismantle it and completely rework it.
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Greetings from Austria
Thomas

[farmersplow]

Suspension box FP-9
11/2023

Next up is an even bigger challenge when building the suspension box. I have to rework the eccentric for the lever mechanism. Instead of just a manual lever movement as before, the new body will also have an electrical and a mechanical release. An unlocking mechanism that moves the cutterhead back up. Either because the cut at the end of the outlet groove should be equipped with an automatic lifting of the cutterhead, or simply to prevent incorrect operation. Nevertheless, it should also be possible to control the mechanism manually.

To do this, I have to go back to the lathe.
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I have to turn an unusual eccentric, which should also be pre-tensioned via a Bowden cable and tension spring. The lever for lowering and raising the cutterhead is then mounted on this eccentric.
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I also managed to do this (on the third attempt).

Greetings from Austria
Thomas

[Thelatheofus]

Amazing stuff as usual ! Can't wait to see (and hear) the tests of the new head.
I noticed that you put some plastic/rubbery tubes around the pushrods and torque tube, I guess it is to dampen the high frequency resonnances of those elements ? From what I understood that's what the rubber on the piano wire of the V-Spring is supposed to do on other cutting heads. I think Souri does it aswell, I wonder if it's for the same reason

[farmersplow]

Amazing stuff as usual ! Can't wait to see (and hear) the tests of the new head.
I noticed that you put some plastic/rubbery tubes around the pushrods and torque tube, I guess it is to dampen the high frequency resonnances of those elements ? From what I understood that's what the rubber on the piano wire of the V-Spring is supposed to do on other cutting heads. I think Souri does it aswell, I wonder if it's for the same reason

Plastic tubes: You have a very keen eye! I thought I had mentioned it, but I guess not. The reason is, as you suspected, the damping of resonances. I have already tested this with the "old" large cutting head and after I used these tubes, the resonances in the high-frequency range were somewhat lower. These are very thin (and therefore light) shrink tubes (as are also used for wire insulation). They are simply pulled over the pipe in the right size and warmed up - voilà, done.
Cutting head: I can hardly wait either!

[farmersplow]

Suspension box FP-9
11/2023

I also had to go back to the lathe for the mechanical release. I made this screw-on operating knob from brass parts. I knurled the screw part to tighten it and then polished the parts to a mirror finish.
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Add the matching spring and the push button is finished. The polishing is not necessary for the function, but for my eye. Things that look good also have a good chance of being good.
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I re-milled the front plate of the suspension box to be able to integrate the button.
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Everything fits as planned. I am delighted.

The short video shows how the release works:

VIDEO:
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Greetings from Austria
Thomas

[farmersplow]

GROOVE DEPTH CONTROL (GROOVE DEPTH CONTROL)
Suspension box FP-9
11/2023

As I am currently working on the suspension box, I would like to add another element at the same time.

My plan from the outset was to install a groove depth control in the suspension box. I planned to do this without knowing exactly how it works and what advantages such a control system has. I only knew that it had advantages and was a good thing. A few years ago, however, I didn't realize what conditions had to be created for such a control system to make any sense at all. But my thirst for research was too great to miss out on this experience. That's why I learned about the various challenges that such a control system entails.

First of all, I had to learn how to build such a depth control system in the first place. Since there is very (very very) little information about it, this was difficult and I had to get my inspiration from the few pictures available.
In principle, the contact pressure of the cutting stylus should be increased or decreased. This can be done using a lever arm, which in principle engages where the counterweight for the cutting head is usually located.
I have produced a couple of pictures to explain this principle.

Figure 1: Cutterhead - raised state
Here the cutterhead is raised and the picture shows the axis of rotation around which the cutterhead can be lowered (red)
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Figure 2: Cutterhead - lowered state
Here the cutterhead is lowered onto the surface of the blank and has a adjusted (low) contact force.
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Figure 3: Device with rod for support weight control
Here a rod is mounted on the suspension unit, similar to a counterweight. If the rear end of the rod were lifted, the contact force of the cutting stylus would increase.
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Figure 4: Pull magnet on the rod
A coil is now mounted at the rear end of the rod and the matching pull magnet is mounted on the housing of the suspension box (the magnet is shown in GREEN). The two elements correspond to the principle of a loudspeaker.
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Figure 5: Active coil for support weight control
If a DC voltage is now applied to the coil (e.g.: 1 volt =), the coil is pulled upwards into the magnetic field. (If the polarity were reversed, the coil would be pushed out of the magnetic field and move downwards). The upward movement of the coil (and the rod) in turn pushes the cutting head downwards and the contact force increases.
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THE PRACTICE:

As an experiment, I will build such a device from a China 25W 4Ohm resonance loudspeaker. As you can see in picture 5, the coil does not move linearly up and down, but changes the angle (because of the axis of rotation). This requires much more space, both outside and inside the coil.
This means I have to go back to the lathe and unscrew the speaker housing (after removing the glued magnets).
Picture and video of the turning work:
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VIDEO:
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I then turn another coil holder and assemble the parts. I insert a strong neodymium magnet into the newly turned speaker housing.
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Finally, the coil is glued to the coil holder.
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So step one is done. Now the package still has to be installed in the suspension box and then the first tests can begin. I'm already curious to see if the design works and if anything moves. And if something does move, how much tension do I need on the coil to generate what weight? How fast does the construct move and how quickly does the magnetic field dissipate?
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FUNCTIONAL PRINCIPLE:

Even if the control system works, the question remains: why is it necessary?

"dmills" once explained this well in an article. Basics: According to this, the cutting depth must be seen in connection with the cutting width.
If you have a constant feed rate and a constant cutting depth, you can make a good cut. However, you have to bear in mind that a piece of music sometimes contains loud or low frequencies and requires much more space for the groove at these points. To ensure that such a groove does not collide with the preceding (or following) groove, the groove spacing must be chosen accordingly large. Large groove spacing (constant groove spacing of e.g.: 400µm [~64 lines/inch]) would mean that the 12" record only has a recording time of 5½ minutes. This is despite the fact that there are usually quiet signals on it that require much less space. What a waste. Alternatively, you could also record more quietly and choose only 200µm [~127 lines/inch] constant groove spacing. In addition, cut off bass below 80Hz. You would get more recording time, but with much lower quality. (I hope I have interpreted "dmills" correctly).

Action: The solution is variable groove spacing control. If something loud comes in, you increase the distance and reduce it again if something quiet comes in. An additional solution is variable depth control. You don't need to cut as deep in quiet areas and at medium and high frequencies. (A shallow cutting depth of e.g. 20µm results in a shallow groove width of approx. 40µm). This is because the cutting stylus (~2x45°) does not move that far to the left and right, nor does it move that far up and down. However, if a loud bass (e.g.: 400Hz [+-sinus]) comes along, the stylus moves further in the diagonal (left-right, up-down). If the cutting depth is too shallow (low base contact force), the stylus first moves deep into the blank (e.g.: +40µm together with the set depth of 20µm = 60µm), but then beyond the surface of the record (minus -20µm). The same principle applies here too. You could set a cutting depth of 50µm from the start (making a groove width of approx. 100µm) - again a waste of space.

Side note: An elliptical equalizer (EEQ) should therefore also be used and the driver coils should be connected with opposite polarity. The EEQ "monoizes" signals below 75Hz/150Hz/300Hz, whereby the stylus only moves to the left and right and no longer performs the depth movement. Otherwise, as explained above, in the worst case a cutting depth of 150µm would be achieved, and that at 20Hz! The needle would jump out of the groove during playback!

What you have to pay attention to:
So if you have a cutting depth of only 20µm with "no" signal, you have to increase the cutting depth accordingly (if there comes a loud or low-frequency signal).
To do this, you have to know in advance (as with the groove spacing control) that such a signal is coming "soon" and then "slowly" increase the contact force. If you were to do this too quickly, you would already be cutting a sound. A low-frequency tone that does not belong there. Changing the groove spacing and cutting depth will of course produce a tone in any case. However, if you do it slowly enough, this sound will not be audible. As a rule, you should be informed in advance that such a signal is coming at least ½ turn of the disk. Depending on the disk speed, this means about one second.

And even if you have solved the problem of advance information, there is another problem with depth control. This is because a change in the contact force during recording also means a change in the cutting depth and therefore also a change in the required cutting force. The stylus (and therefore the driver coils) have to work harder to cut a signal when cutting deeper. Therefore, when the cutting depth and the required cutting force change, the power at the driver coils must also be increased quadratically. Therefore, such a function will only be possible using a cutterhead with feedback coils (or with a variable amplifier that increases the power accordingly depending on the selected contact force). A suitable FB compensation amplifier for cutterheads with feedback coils compensates for the increased force required.

As usual: one solution and ten new problems.

I will see. I'll just give it a try and see what happens. First of all, the control should move at all.

Greetings from Austria
Thomas

[diy_cutter]

Just read it, Thomas.

Very cool and detailed written! I was always interested in how this was implemented (variable groove pitch) in professional cutting recorders. For myself, I decided to deal with this when our cutting recorder records perfectly with a constant groove pitch.

But your solution with variable depth... Is this something new or did I miss some information? Has anyone already implemented something like this?

[farmersplow]

... But your solution with variable depth... Is this something new or did I miss some information? Has anyone already implemented something like this?

...is nothing new. But rare. It was already used in old Neumann lathes. I think it is very rarely used in the DIY sector, which is why there is so little information about it. To be able to use variable depth control, you also need variable groove spacing control. This is rarely done. You also need an FB cutting head, which is also rarely done. And then a suitable FB amplifier (also rare in DIY). All of this together is rather rare and only half the battle. Because there are still many hours/days/weeks of calibration work to be done.

I don't know who else has done it. I'd be interested to hear about it and their experiences.

Thomas

[farmersplow]

Suspension box FP-9
11/2023

The suspension box has now been reassembled. It now contains the mechanical lowering mechanism with lever and latching function. It also contains the mechanical and electrical release so that the cutting head can be raised again. Secondly, the coil for the GROOVE DEPTH CONTROL is also installed. Of course, the dashpot and the contact pressure sensor are also built in.

First the test for the GROOVE DEPTH CONTROL, because I'm very excited about that. I want to test whether the cutting head moves at all and with what force and speed it does so. The movement mechanism also has to fight against the dashpot damping. To do this, I have a transistor control (I press a button and control the voltage to the coil via the transistor), which I use to apply about 1 volt to the coil.
The reaction of the cutting head is shown in the following two videos:
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VIDEO 1:
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VIDEO 2:
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Now I test the electric release. To do this, I first lower the cutting head with the lever. The cutting head follows the lever movement in a damped form (because of the oil dashpot). Then the electric release is activated and the cutting head is raised.

VIDEO 3:
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Finally, I test the mechanical release. In the event of a power failure or other special situations, I have added the option of mechanical actuation. All I have to do is actuate the Release button (which I had already presented):

VIDEO 4:
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Now that everything is working well, I still have to integrate the functions into the programming. So back to the PC and programming. I'm putting off the challenge with the GROOVE DEPTH CONTROL for the time being. At the moment I'm satisfied that a basic movement is possible. As long as I don't have a feedback control, I'll put this function on hold.

Greetings from Austria
Thomas

[Thelatheofus]

Really nice as always !
Thanks to this forum there are some informations about the principle behind this kind of groove control mechanisms, but I never thought about how changing the depth too quick would cause an audible frequency by example. Now that I read it it seems obvious. So thanks for sharing your thoughts on the subject

[C-Pilote]

I checked the videos!
Nice work!

[farmersplow]

Really nice as always !
Thanks to this forum there are some informations about the principle behind this kind of groove control mechanisms, but I never thought about how changing the depth too quick would cause an audible frequency by example. Now that I read it it seems obvious. So thanks for sharing your thoughts on the subject

Thank you! I did another short post on how moving too fast can affect it (coming soon).

[farmersplow]

I checked the videos!
Nice work!

THX

[farmersplow]

GROOVE DEPTH CONTROL - SUPPLEMENT
11/2023

I wanted to find out a little more about the GROOVE DEPTH CONTROL before I got down to other (more important) things. And also because I claimed that changing it too quickly would result in a noise that doesn't belong there.

And so I asked myself whether I could actually cut music with my GROOVE DEPTH CONTROL – COIL alone? Of course, it doesn't make any sense because no precise cuts are possible and only depth cutting in mono is possible. The transmission arm and the entire cutting head would have to be moved to generate a signal.

But is it possible? In principle? Practically? It doesn't make sense, but it's an experimental forum!

So I tried it and attached a music signal to the coil of the Groove Depth Control. I sent the left channel of the sound card to the amplifier and then from the amplifier with more power to the coil.

I was afraid that the coil would burn out or the diamond would break due to too much depth. That's why I only cut quite quietly with IRIAA and set the high cut at around 4kHz.

The cut was interesting, I first had to feel my way around with the volume, but I could hear the music very quietly and distorted. The extraction worked well and there were no other problems.

Then I listened to the whole thing on the record player. It sounds terrible, of course. But you can even recognize the song. The very low frequencies in particular are extremely audible despite IRIAA. The higher the frequency, the harder it is for the GROOVE DEPTH CONTROL - COIL to keep up and from 2 to 3kHz it's absolutely over! The moving masses (~2kg) are already far too heavy.

For fun, here is a short excerpt of the audio recording for you

AUDIO : Music recorded with Depth Control coil only.

cutted only Downforce-Coil.mp3

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Do you recognize the song?
Here is the signal curve:
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But it did bring one insight: Very low frequencies are recorded excessively loud.
And therefore: The downward movement should take place very slowly, because “fast” movement (~20Hz) already makes a loud noise!

Greetings from Austria
Thomas

[farmersplow]

THX for over (unbelievable) 5,000,000 views

It was almost exactly three years ago that I started my project. I started reporting on it (with a delay) in July 2022. In the meantime, I have presented over 600 images and numerous videos and audios. I work on the project (including research and investigation) every day and have spent almost 13,000 hours on it since then. I wanted to share my knowledge and experience right from the start, because I think that we are a (small) community in which we should support each other in order not to die out.

With this in mind, I would also like to thank everyone else who has shared their projects, experiments and experiences.

And although there have been repeated setbacks and many things have only worked after lengthy trials, it has been a lot of fun and my enthusiasm is undiminished. Giving up is not an option for me.
But I can already see a light at the end of the tunnel and think that the project will be completed by July (this year, not just any year).
There's still a lot to do before then and if you're interested, I'll keep you posted.

Greetings from Austria
Thomas

[diy_cutter]

Thomas, thank you for all your hard work! And also for sharing all this with us!

[farmersplow]

Thomas, thank you for all your hard work! And also for sharing all this with us!

THX

[farmersplow]

VACUUM Part 1 - The side channel blower
11/2023

I also wanted to report on the extraction system. I have already mentioned this in another forum report, but I would like to complete it here. For me, only a side channel blower came into question. Firstly, only this generates a uniform vacuum because the rotary blower generates uniform suction pressure (unlike piston pumps). Secondly, this device is also relatively temperature-resistant, even if the air passage is very small due to the small suction pipe.
I chose this side channel blower (about two years ago):
https://www.doctor-san.eu/ventilation-luftbewegung/seitenkanalverdichter-filterboxen-filter/seitenkanalverdichter-110mbar-370-watt.html
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Technical data:
Pressure 110mbar
Vacuum 110mbar
Power 370 watts
Voltage 230 V
Noise level 53 dB
Air flow rate 80 m³/h
Weight 11 kg
Air outlet/inlet opening 39mm (1-1/4" pipe thread)
Dimensions mm approx. L/W/H 250 x 240 x 250


With this 80 m³/h air flow rate, you can easily operate three vinyl recorders.

This is how the appliance arrived. With silencer pipe at the air outlet.

Picture side channel blower with silencer:
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VACUUM Part 2 - The construction

I used 3D software to develop a sound-insulating housing. This also includes a control system that monitors the temperature of the pump and also cools it with a fan. On the other hand, the suction power should also be adjustable. This control system should function as a stand-alone unit but should also be able to be controlled by my record lathe (automated).

Exterior plan:
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Here is the planned control panel. As I said, it should be controlled automatically via my lathe. But it could also be controlled manually if required:
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Plan image underside:
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Interior layout plan:
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The idea of noise insulation:

The air is sucked into the side channel blower from the hose connection:

Diagram 1:
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After the air has been pressed through the side channel blower, it comes out at the other end. The silencer is fitted to this outlet. It takes away a lot of noise.
In the following picture I have shown how the air is passed through the housing. The air is routed from one chamber into the next chamber and then back into the main chamber area, where it can pass over the motor before finally being released into the open at an air outlet on the underside. All chambers are lined with sound insulation panels. (See picture)
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The outer housing panels are also lined with sound insulation mats. I have planned another air inlet at the rear. This has a fan that blows outside air over the motor and also flows out again at the lower exhaust air opening.
That's the theory.

Greetings from Austria
Thomas

[farmersplow]

VACUUM Part 3 - The practical construction
11/2023

For a test setup, I cut, drilled and glued plywood panels and lined them with sound insulation mats:
The closed housing is absolutely quiet. I don't have a dB meter with me, but it's about as loud as whispering.
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Unfortunately, the inside gets too warm and after 20 minutes of vacuum operation (inlet closed), the motor reaches temperatures of 60°C and the rotor bearing (max.) about 90°C! This is too warm and I had to install an additional fan as planned.
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This has reduced the temperatures to around (max.) 70°C. (Without the housing, the max. temperatures are around 60°)
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Further tests have shown that the temperature is constantly rising and after 30 minutes the motor bearing temperature has already reached over 85°. I then removed the mounting plate from the silencer, which stabilized the temperature at 75°. The noise development was only insignificantly higher.
To finally keep the temperature below 60°, I had to make a small adjustment. So I installed a "forced ventilation" in the intake area. An opening of a small size (half the size of a fingernail) was sufficient to draw in room air (20°C). The suction capacity (air volume) is still more than sufficient.
Now I just have to build the control system to complete the development. But I'm still thinking about changing the housing because I don't need the air deflection and can therefore build it much smaller.

Greetings from Austria
Thomas