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

[farmersplow]

Control panel (part 4)

Connect all the plugs and carry out the first tests. Something went wrong straight away! The balance and volume controls didn't do what they were supposed to do. It's been many years (decades) since I last planned balance controllers. It's only easy if you've done it before. Otherwise the controller does everything but what it is supposed to do. Connecting a balance control in combination with a volume control is much more difficult than it sounds.
But in the end I got the problem under control.
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Greetings from Austria
Thomas

[Semar]

So beautiful

[farmersplow]

Control panel (part 5)


The VU meter (dB display) did not work either! Not on either channel. Something was displayed, but the needle hardly moved. I spent at least a whole day looking for the fault and couldn't find it. The fault was me. I used an old circuit for dB meters and simply built it without thinking about it and testing it beforehand. It didn't work in the end. So I chose another circuit diagram and this time tested it on a small breadboard. What can I say, it worked perfectly. I decided not to look any further for the fault in the original circuit and to install the "new" one straight away. The PEAK LED's display worked straight away.
Now that everything is back in order, I can really play with the buttons. (It feels good).
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Here's a short video showing what it looks like in action. By the way, the sound comes directly from the cutterhead.
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Panel E 02 video kk.mp4

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The displays still need to be recalibrated, but that's another story.

Greetings from Austria
Thomas

[zdenek]

Control panel (part 5)


The VU meter (dB display) did not work either! Not on either channel. Something was displayed, but the needle hardly moved. I spent at least a whole day looking for the fault and couldn't find it. The fault was me. I used an old circuit for dB meters and simply built it without thinking about it and testing it beforehand. It didn't work in the end. So I chose another circuit diagram and this time tested it on a small breadboard. What can I say, it worked perfectly. I decided not to look any further for the fault in the original circuit and to install the "new" one straight away. The PEAK LED's display worked straight away.
Now that everything is back in order, I can really play with the buttons. (It feels good).
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Panel E 01.jpg
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Here's a short video showing what it looks like in action. By the way, the sound comes directly from the cutterhead.
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Panel E 02 video kk.mp4
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The displays still need to be recalibrated, but that's another story.

Greetings from Austria
Thomas

Can you cut this music with your equipment, only need five seconds from the middle of the recording, ok?
https://youtu.be/L4Z6Kp2Ma6w
https://www.youtube.com/watch?v=L4Z6Kp2Ma6w

[zdenek]

I'm sorry to say this, but I hear very high distortion and a narrow frequency response of your head, am I wrong?

[displacedsnail]

Very nice look to the whole device, congratulations on your progress so far!

[PLD]

Getting closer! Excellent!

[lulu]

Thomas,

I just went by this thread after a few months and I am blown away again. It is amazing. I hope you will get to your goals soon. and also thank you, you helped me with more than one problem I had with my diy machine. Maybe one day I'll get enough confidence to also share my machine here on the forum. Anyway, keep it up!

Lu.

Prague

[lucca2]

amazing work!

[farmersplow]

I'm back again (with new progress)

First of all, I would like to thank you for your letters and apologize for not responding until now.
It was a difficult time for me from July to October. Also with my project. I worked (almost) continuously and had a few setbacks. Sometimes I was desperate and then full of energy again. Not every experiment worked out as planned.
The cuts got better and better, then worse and sometimes I had to (almost) start again. But I'll get to that later.

I would like to respond to the unanswered comments:
Zdenek: I can cut the specified music, but I don't want to. And yes, there was a very high distortion because it wasn't calibrated yet.

Displacedsnail: Glad you like it so far. I'm always happy when others see it that way too.

PLD: Yes, I'm getting closer. But the closer I get, the more little things I notice. It's like a good hi-fi system. If the amplifier is the weak point and you replace it with a better one, you notice that the speakers are weak. And if you then replace them with better ones, you will hear the weaknesses of the pickup. And if you then improve it, then..... And that will probably go on forever!

Lulu: I'm glad you were able to do something with my posts. I'm looking forward to seeing you present your DIY machine. By the way, you once asked how the cone from a part affects sound and resonances! - So much in advance: it has advantages and disadvantages. Advantages are extremely low weight (no glue) and one-piece (no glued joints that can come loose). Disadvantage: Expensive and time-consuming to manufacture. If it becomes too thin, it develops natural resonances.

Lucca2: Thank you and glad you like it.

Greetings from Austria
Thomas

[farmersplow]

Cutterhead CH-9 improvements

I have continued to work on my cutterhead. First I tried to make the funnels even lighter.
I changed the entire funnel so that it also contains the holder for the thin phosphor bronze wire. Now this small part does not have to be installed and glued separately.
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The weight of 0.36 grams is already very low. If I compare it with the absorbent cotton (in which I store the cones), a cone weighs just half as much as the absorbent cotton ball. The old carbon cones from two years ago weighed 1.15 grams.

I then glued these cones precisely onto the drivers.
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But there are limits. If the walls become too thin, then the aircraft aluminum also begins to form resonances.

Then I got small resonance bumps in different frequency ranges that weren't there before.

In short, at some point it got worse again.

I then experimented a little with damping. I covered the surface with 2K glue, with resins, with varnishes and rubber coatings. Also in different combinations. Until I finally found something I was happy with.

The coatings had increased the weight again somewhat, but despite everything it was lighter (and more stable) than three months ago.
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Greetings from Austria
Thomas

[zdenek]

Hello, don't worry about failures, it's nothing. I went to a company that has equipment for $25k, it's modern equipment on a modern head, I asked these mastering people to cut me a test copper disc for 250 Euro. These people have discs for DMM, but the guy says to me: Sir, we don't record with this shit, we don't cut any grooves, we bought this shit just to show a potential client that we have a lathe machine for cutting vinyl records. When I asked this guy, it's usually like this, a client comes to us and says that he wants to press, for example, 1000 records, he gives us a file, and we have machines for pressing records, but not for cutting grooves, then we send the file to the mastering company, which has factory equipment from the eighties, where they make a matrix in copper, electroplate it and make a stamp, and we then put this stamp on our press and press the records in vinyl, that's all. I say, but please record something for me, I tell the guy, I pay and I want the recording from your machine. The guy from mastering took pity on me and cut a disc from my recording for 200 euros [that's how much the steel plate covered with copper cost alone]. I came home, put this beautifully cut something and I listen to it, DISASTER, Tragedy, what is this supposed to be, I think to myself and laugh to myself. Believe me Farmer, the recording is much worse than my pressings on CDR, zero bass, zero high frequencies, that's what it looked like with this equipment for 25k$...

[zdenek]

I will also add that I have read in brochures from the 80s of the last century that these German heads cost over ten thousand dollars a piece[as much as a new Mercedesin the 80s ], only a few companies in the world could afford this equipment. How much you have achieved is still good, it is always something than doing nothing at all, I am waiting impatiently for your further experiments, they are great Farmer!

[farmersplow]

Cutterhead damping

Then I took on the V-spring. Here, too, I experimented with different materials and sizes. I milled out a V-spring and then damped it with rubber compound.
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I then wanted to dampen the torsion bar. In addition to the external damping with shrink tubing, I also experimented with damping rubber.
I also used memory foam. I used this foam inside the torsion tube.
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Then I also rubberized the “complete package” torsion tube with V-spring.

Conclusion: The foam inside the torsion tube didn't help at all. But the damping rubber had actually dampened numerous resonances!

Greetings from Austria
Thomas

[farmersplow]

Cutterhead - New torsion tube

My constant urge to reduce the weight of moving masses has driven me to take this step. Because the dampers have shown that they have a positive effect on resonances but at the same time increase the weight again, I still see potential in the torsion tube.
My 5mm torsion tube has a weight of 0.74 grams.
An unmachined 3 mm aluminum rod of the same length weighs only 0.58 grams.
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Drilled and machined, the new rod weighs only 0.29 grams! So I have more than halved the weight of the old rod!
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However, it was quite difficult to produce this torsion bar precisely. But after a few attempts it worked quite well. Practice is helpful.
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Greetings from Austria
Thomas

[farmersplow]

Cutterhead - CH9 vers.67.58

I don't know exactly which version of this cutterhead I've tried. It feels like the thousandth.
Now, of course, the thinner torsion tube needs a new V-spring and everything starts (almost) from scratch again.
Lasercut parts are easy to order if you can specify exactly what you need. So I went back to the design program and designed a new V-spring.
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Compared to the “old” torsion tube, I like the new one much better.
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A first “fitting” looks very promising.
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And the weight, including the V-spring, is still very low.
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I have also added damping material to this unit (from experience).
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Greetings from Austria
Thomas

[farmersplow]

Cutterhead – Feedback Coil

The first tests with the feedback have already produced good results. Nevertheless, I wanted to get a little more out of the coils. If I have to make new coils, then I might as well improve them. I wanted to leave the ohmic resistance of ~10 ohms and the number of windings the same. But I have reduced the length and thus increased the number of layers. This of course increases the induced voltage and the signal is about 20% better.
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No matter. The coils do a lot of work either way.
Then I attached the coils (precisely positioned) to the drivers.
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I have damped the whole unit (again).
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I also coated the inside of the cutterhead housing with damping rubber.
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Greetings from Austria
Thomas

[Thelatheofus]

Really nice ! You make me want to try to build a cutting head again haha
Those torque tubes and drivers look amazing. What's your guess on the total weight of moving parts ?

I have the impression that the spring is the hardest thing to make. For the materials I get that the v-spring should be copper or bronze (just judging from pics) and the piano wire from steel. The thickness is a mystery to me and is probably what will need more testing. I tried the V-spring from 0.3mm copper and it seemed way too easy to bend, I don't think it puts the torque tube back to its place nicely (what I guess is its goal). Opcode66 used 0.6mm needles iirc for the piano wire. Here again I don't know exactly what type of steel would be the best choice.

I get why people (like flo with the early caruso, TKC's heads, zdenek's...) tried different options that involved less components, it is surely way easier to test different configurations when you have less components, and easier to troubleshoot.

I have a question about your feedback coils. If I understood correctly they need to stay still while the pushrod moves through them, which will generate a current. But in your pics it seems like they are a whole assembly, so they will move with the pushrod. Did I get this wrong ?

[farmersplow]

Really nice ! You make me want to try to build a cutting head again haha
Those torque tubes and drivers look amazing. What's your guess on the total weight of moving parts ?

Thank you! I don't know the exact weight. I estimate about 7 grams with both cones, drive coils, FB coils, torsion tube with V-spring and wires. The heaviest are the two driver coils at 5.4 grams.

I have the impression that the spring is the hardest thing to make. For the materials I get that the v-spring should be copper or bronze (just judging from pics) and the piano wire from steel. The thickness is a mystery to me and is probably what will need more testing. I tried the V-spring from 0.3mm copper and it seemed way too easy to bend, I don't think it puts the torque tube back to its place nicely (what I guess is its goal). Opcode66 used 0.6mm needles iirc for the piano wire. Here again I don't know exactly what type of steel would be the best choice.

Yes, the V-spring is a challenge. But at the end of the day, it should only hold the torsion tube in position. If the V-spring really acted like a spring, you would definitely have problems. In my head, the ‘spider’ membranes are so stiff that the V-spring doesn't have the task of holding the torsion bar in its basic position, but only offers the possibility of making a ‘V’ movement (for stereo).
I use a 0.8mm phosphor bronze wire.

I get why people (like flo with the early caruso, TKC's heads, zdenek's...) tried different options that involved less components, it is surely way easier to test different configurations when you have less components, and easier to troubleshoot.

Yes, that's right. But because I'm building a closed loop head, I unfortunately need more components. And they need to be stable. Hence the careful selection of materials and many, many, many tests

I have a question about your feedback coils. If I understood correctly they need to stay still while the pushrod moves through them, which will generate a current. But in your pics it seems like they are a whole assembly, so they will move with the pushrod. Did I get this wrong ?

You are wrong. The coils are firmly connected to the conical tube (of the driver coils) and move like the driver coils. There is a ring magnet in the housing through which the coils move. This generates the measuring voltage in the FB coils. The FB coils should be close to the diamond and the magnetic fields (from the driver coils and from the FB coils) should not cross.

Thomas

[Thelatheofus]

Ahhhh yeah, ok I'm silly. I'm glad I asked. I forgot that for electricity to be generated there must be a magnetic field moved around a coil. I got into the groove depth coil, and in this case it works with "just" a metal rod and a coil because the coil is electrified and becomes a electromagnet, so I thought it would work the other way around.

Yes, that's right. But because I'm building a closed loop head, I unfortunately need more components. And they need to be stable. Hence the careful selection of materials and many, many, many tests

By "more components" you don't mean the V-spring but the feedback coils by example I guess ? I don't get why a v-spring would be necessary for a feedback cutting head. From what I understand the goal before closing the loop is to get a "pyramid" frequency response (a constant steep on both sides of the main resonnance frequency). So I get the heavy dampening for the high frequency weird resonances, but I don't see how a v-spring helps with that.

Thank you! I don't know the exact weight. I estimate about 7 grams with both cones, drive coils, FB coils, torsion tube with V-spring and wires. The heaviest are the two driver coils at 5.4 grams.

Damn I didn't expect the drivers to be that heavy. Do you plan to try with smaller drivers someday ?

As always thanks for your pedagogy, I'm glad I can follow this thread in real time ! I wish I did it with the groove scribe topic, it's the only one on par with yours.