Deep Grooves Mastering - Opcode66 Transducer Project

[opcode66]

In response to plastic being too heavy. I seem to not have that issue. ROLANDJAYS, did you watch my video? Did you hear how well the transducer worked? The cutterhead body is essentially just a vessel for the transducers. If they work, the head will work.... That is fairly straightforward. My torque tube is no larger nor heavier than that of a Neumann SX cutterhead. Less than 1 gram.

Metal is heavier than plastic by the way... And, I got incredible results that simply can't be argued. Watch the video please. My design might be leveraging some techniques you may not have employed in your design. Possibly that accounts for the difference in results?

Besides, and I can't stress this enough, I am prototyping the parts in plastic people. The final head will be made in metal. Please read the thread.

All that is left to make is the linkage from the bobbins to the torque tube. Thanks to all who have been supportive and championing me along the way! Much appreciated.

[opcode66]

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[Stevie342000]

Looking good will have to wait for the test results and videos.

That's a lot of progress in one week. I see no reason why the body could not be plastic (with a bit of smoothing out) made to look like metal and a mix of other parts in metal i.e. torque bar and cutter coil parts.

Like the idea of slide in and slide out cutter coil mechanism, the proof will be in the testing and measurements.

Which from what I can see are not that far off.

[Ciuens]

Hello, this project is amazing.
Plastic is much lighter than aluminum, and can be lighter still with the setup of filling in the the 3d printer software.
I am following with enthusiasm.

[studiorp]

Project many interesting. Which could be the weight at the end ? If you can build a metal model fully working and with a cheap price, will be super .
Too I had built a prototype stereo some months ago, but without success.

[chaosbc]

I am myself working on a record lathe partly 3d printed since a while...it is not finished but I'm getting close...
I can easily imagine it with such a head.

[opcode66]

Cool!

[opcode66]

Worked out all the issues so far with all the parts you see. Spent time today figuring out how to make the linkage from the transducer bobbins to the torque tube. Using sewing needles set into the bobbin tip via heating the needle so it melts itself into the plastic a little and permanently sets into place. The needle is then bent to have an L at the end. The L of each needle fits into and X shaped depression (crossed slots) in the tip of the torque tube. This allows for pushing and pulling of the torue tube by each of the bobbins.

I also spent a lot of time on the torque tube and the holding block for the torque tube. The tube moves with even resistance in the directions desired. And it retuns to zero on its own.

Linkage will be finished tomorrow. Then, I will wind coils on the final bobbin prints, assemble everything, wire up the transducers, and test the head by itself on a table. If all goes well, I'll put a sapphire in it and try cutting lacquer.

However, I predict that I will likely have to make some tweaks once I try to hang the cutterhead on my suspension box. Some parts will likely need to be changed a little to insure it hangs properly. I also need to be insure that only the tip of the stylis is touching the disc. And no other part of the cutterhead is making contact. Might not be until the end of the weekend before I attempt to cut with this cutterhead on my Neumann. Rest assured, I will video document every step of the way.

[opcode66]

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[sunkingrecords]

Amazing!! Waiting for the results!

Miguel

[opcode66]

One thought that occurs to me is that this head is very light in comparison to my Neumann. Some pieces are very light in comparison to their metal counterparts. Less Mass means a Higher Resonant Frequency. Wouldn't it be fantastic if I could push the Resonant Frequency into a range close to or past audible (20K). I have no clue what the RF is currently. I will have to perform a number of frequency sweeps to really figure it out. But, it would be great to be able to control the RF via the design to the point where minimal pre-processing of audio is required. I.e. running it without a negative feedback pre-amp and no feedback coils.

[opcode66]

Linkage! Not perfect on this one. But, I'll get better at making them.

[Stevie342000]

One thought that occurs to me (which I am sure you have figured) is that the torque bar may need an end cap to stop horizontal movement of the L bars?

Aside from that looking good following you so far and looking forward (as so many of us are) to testing and seeing some measurements, videos etc.

[opcode66]

The slot for the pins is so small, it is a challenge just to squeeze the pin into its slot on the torque tube. Once in place, it doesn't move...

However, that being said, what I made was not a cap. It is just a plastic X that fits in after the pins to lock them in.

Life has intervened the past few days. Yesterday was Knobcon III The Return of the Synth here in Chicago. Spent most of the day there. Fantastic stuff people are doing these day with modular. Got some good ideas. Made some cool new contacts. Promoted for YouWantVinyl.com.

Had a few other things to do with friends. But, today is Cutterhead day... I have tweaked nearly every part of the design. I am currently winding drive coils while waiting for parts to print on the Makerbot. And, jamming to tunes. And, having a leisurely smoke outside in the glorious sun. Today a fantastic day in Chicago, IL, USA, Earth, Milky Way, Universe. I've added a number things to my design, including sorting out the pathway for helium from the back of the cutterhead, through the body sides, and up into the transducers.

Something else to note. I've included Thermisters into my design. Each transducer will have a thermister sitting right next to the coil. This will allow for realistic circuit breaking based on actual temperature readings instead of guestimating based on current flow. This will be an alternate to using a fuse. Also will be more accurate than bullshit implementation in the Neumann SEL circuit braking units. When my coils get close to being too hot, a very simple circuit will disconnect the drive coil lines.

While I'm on this topic.... I also have a design for an arcless large voltage AC relay switch. I'm going to be making my own. No snubber circuit required as in the Neumann SEL. And, completely arcless. They will be employing a special two way transducer that I've designed. The rest is a secret. When they become available, you can buy one and tear it down to find out how I'm doing this.

Regarding coil winding. I designed and printed a few gadgets in plastic to assist with this process. I'm not going to specifically detail them as I am now no longer going to be sharing the specifics about how I am making my coils. Sorry. But, its only fair to others who do this for a living. Needless to say, I've learned a fantastic amount about the art and technique. Being ambidextrous has been very handy. I can now complete a perfect coil in a fraction of the time it used to take me. And, I'm no longer using a jewelers loop. That gave me incredible headaches after a couple hours of work and it was extremely fatiguing. I think Flo said on the forum once something along these lines. Anyone can learn to do this work. You just need a lot of practice and a mountain of patience.

[opcode66]

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[markrob]

One thought that occurs to me is that this head is very light in comparison to my Neumann. Some pieces are very light in comparison to their metal counterparts. Less Mass means a Higher Resonant Frequency. Wouldn't it be fantastic if I could push the Resonant Frequency into a range close to or past audible (20K). I have no clue what the RF is currently. I will have to perform a number of frequency sweeps to really figure it out. But, it would be great to be able to control the RF via the design to the point where minimal pre-processing of audio is required. I.e. running it without a negative feedback pre-amp and no feedback coils.

Hi,

Really nice progress so far. Looking forward to seeing how this goes.

Have you measured the moving mass of your parts yet? Perhaps you are correct that they are lighter, but you also need to consider that plastic has a much higher compliance (or lower stiffness) for the same mass as aluminum (compare the Young's Modulus of the two materials). So you might end up decoupling at higher frequencies as compared to metal parts. This manifests as secondary resonances that will kill the performance of the head. You can bet Nuemann would have used plastic if it were the best material for the job.

If you intend to run the head open loop, you need to set the mechanical impedance of the head high enough such that it is not loaded down by the mechanical load represented by the lacquer. There needs to be enough stiffness to meet this condition. To some extent, this locks in your system RF. On the Neumann heads this is set in the 1Khz range and the and the open loop response of the head is affected by the load, but the feedback compensates for the added mechanical load. With great care, they are able to achieve 1Khz as the RF. Ortophon was able to push it up to 2Khz. If you imagine that you could reduce the moving mass to near zero, you could get away with very small return springs for a desired RF, but the head would have no ability to cut into the lacquer material (very low mechanical impedance). On the moving iron heads like the Presto, they set the stiffness very high and run a high system RF (around 8Khz) as compared to a typical moving coil head, but they have the luxury of being able to wind lots of turns on the drive coils as they are stationary.

The other issue I see is your magnetic circuit. I'm not sure if you will get the BL product needed to be efficient. The test you ran in the video was not very useful as I didn't see any return spring, so you were just pushing the raw coil and holder with no return force.

It will be interesting to see how the head performs once you get it up and running. I'm sure you are going to learn a great deal in the process.

Mark

[opcode66]

I've also considered ceramic for the bobbin part. For the time being, it is plastic because I need to get the parts worked out.

One thing the video doesn't convey is the amount of pressure I felt on my fingertip by the end of the bobbin. It was really pushing hard. Of course, I will video document my results. The last part is printing now. Had some alignment issues with my newly tracked Helium pathway. All is worked out now.

Everything is ready to be fully assembled. I rolled two new coils. The only thing left to do is link the coils to the torque tube and wire up the head.

[opcode66]

Codename "Bladerunner"

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[opcode66]

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[flozki]

hehe. nice so far. fast progress.
i dont want to slow your enthusiasm but for once my rare two cents on that thread:

payday is when you crank up the feedback for the first time.
before everything is easy. i always had great results with small speaker heads. fantastic results for what it is.its the last 10-20%
so we are looking forward to the video turning the FB knob on your SAL.

but i like the 3D printed heads. another dream you can download your new head. no need to send it for repair.
i was wondering how long it takes until someone comes up with that.

the circuit protection.
take another day to study the schematics.
time wasting to invnet the wheel. there is also a nice article explaining the system.
AES paper? Radio mentor? i cant remember but it was somewhere-

Something else to note. I've included Thermisters into my design. Each transducer will have a thermister sitting right next to the coil. This will allow for realistic circuit breaking based on actual temperature readings instead of guestimating based on current flow. This will be an alternate to using a fuse. Also will be more accurate than bullshit implementation in the Neumann SEL circuit braking units. When my coils get close to being too hot, a very simple circuit will disconnect the drive coil lines.

neumann circuit protection is not estimating temperature. it is reading the exact value!
all perfect. all fine. you can not do it better.
the only bad thing( but this is not the topic of that thread) on SAL are the power amps and the whole over enigneered neumann way to build things.
but the way they did, is the way to do if money and space is not an issue.