Open Source Lathes and Cutterheads

Anything goes! Inventors! Artists! Cutting edge solutions to old problems. But also non-commercial usage of record cutting. Cost- effective, cost-ineffective, nutso, brilliant, terribly fabulous and sometimes fabulously terrible ideas.

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jjwharris
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Re: Open Source Lathes and Cutterheads

Post: # 47860Unread post jjwharris
Mon Sep 18, 2017 6:23 am

After blank after blank and rebuilds i finally hit this tonight.

Managed to sort an eq and levels and I'm happy at last.
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Record Lathe Embossing Supplies - http://www.supplies.johnnyelectric.co.nz/

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jjwharris
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Re: Open Source Lathes and Cutterheads

Post: # 47861Unread post jjwharris
Mon Sep 18, 2017 8:36 am

I think I've nutted out the stepper noise, or rather, why it's more apparent and won't go away, the head is currently attached to the overhead with one bearing, it's centre of the head so it has a little back and forth, I'm thinking next step is to replace this with two bearing, to provide a little stability, sandwiched with two thrust bearings either side, I'll try model it up soon.
Record Lathe Embossing Supplies - http://www.supplies.johnnyelectric.co.nz/

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jjwharris
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Re: Open Source Lathes and Cutterheads

Post: # 47948Unread post jjwharris
Thu Sep 28, 2017 6:28 am

met Peter King yesterday, he gave me some very very very helpful advice in terms of needles and surface preparation.

EQ was made with FabEQ, played white noise, recorded the white noise, compared the original white noise to the recorded white noise and it came up with its own curve...

Now I'm here and I'm pretty chuffed.

I've noticed the cutterhead drag is slowing down the turntable, gonna try either bump up the turntable speed or slow down the songs?

I've attached the original mp3 and the version I embossed - I have a weird grounding issue with the turntable...it doesn't have a ground, so that's the hum.
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jjwharris
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Re: Open Source Lathes and Cutterheads

Post: # 47949Unread post jjwharris
Thu Sep 28, 2017 6:33 am

Ah shit, forgot to mention, my driver cones became decoupled resulting in distortion and me pulling my hair out for a bit, I took off the dome and fixed the funnels straight to the coil, doesn't seem to have any issues but I'm aware there could be a bit of rub going on...
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jjwharris
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Re: Open Source Lathes and Cutterheads

Post: # 48004Unread post jjwharris
Wed Oct 04, 2017 12:04 am

So heres my new design, bit rushed, shorter torque tube which should be lowered moving mass, expecting it to be 3 gram with the needle and unmodified transducers.

I was going to go without the V spring and replace it with a Vinyl Recorder style double pole thing made from .5mm tungsten rod, but I think the application without the correct tools will be a little too hard.

Torque tube is intended to be a m3 10mm brass screw, I'm not sure if that's going to be too short, I guess the frequency response will tell. the pushrods will again be 1mm tungsten rod, I really want to braze them to the torquetube but I've found it very difficult in the past to align them.

I'm thinking of making a 3d printed mockup to hold them in place, braze to the torquetube, then glue to the speakers. Only problem being that PLA and heat really don't mix.

The next step will be to wind my own drivers. On the lookout for a way to make my own turntable too, something like running an auxillary pitch motor to keep them up to speed when embossing.

I noticed Peter King's DIY heads don't have any form of v-spring, does this mean when embossing the V-spring is less integral?
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jjwharris
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Re: Open Source Lathes and Cutterheads

Post: # 48114Unread post jjwharris
Thu Oct 12, 2017 10:06 pm

I've got the new head together... It seems better. Getting some weird distortions but I've moved the drivers a little bit and it seems to have gotten rid of them.
I've attached photos of the head and a couple of samples of what I've been cutting.

Also installed a new stepper motor driver that I picked up off aliexpress and it's eliminated the stepper noise.

Still itching to build it again and have the torque tube even smaller.

I have a sneaking suspicion that the 8khz is the limit of the lathecut format, after reading about the soundscriber etc.
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Hanoi
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Re: Open Source Lathes and Cutterheads

Post: # 48123Unread post Hanoi
Sat Oct 14, 2017 6:06 am

Nice jjwharris, waiting for final Pro version! :)

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Hanoi
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Re: Open Source Lathes and Cutterheads

Post: # 48191Unread post Hanoi
Mon Oct 23, 2017 12:41 am

Hi John,
How's it going? Did you change the spring of transducer to plastic one, or you keep the original metal one?

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jjwharris
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Re: Open Source Lathes and Cutterheads

Post: # 48192Unread post jjwharris
Mon Oct 23, 2017 3:51 am

I still haven't assembled my next head, I'm currently using 3d printed springs in the head I am using, that should increase the resonant peak, however, I'm worried it moves the coil out from where it should sit which I why I want to try a tighter assembly with the original springs in place.
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handcut
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Re: Open Source Lathes and Cutterheads

Post: # 48199Unread post handcut
Mon Oct 23, 2017 6:16 pm

Hi,

From those curves it looks like you are experiencing the 6dB/oct falling response after resonance that is expected with a dynamic head. You have to compensate for this as well as the RIAA pre-emphasis. Yes, that is a lot of EQ - I was quite shocked when I first created a curve for our VR. Careful with with those coils though!

Nice work.

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jjwharris
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Re: Open Source Lathes and Cutterheads

Post: # 48352Unread post jjwharris
Mon Nov 06, 2017 2:36 am

cutting head version 4...I call it The Sir Ed Head.

No samples yet, but I'm pretty optimistic from the 30 seconds of a song I did cut.

Feel like I may have gone too much in the other direction and I might struggle to get my mids/lows back.
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jjwharris
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Re: Open Source Lathes and Cutterheads

Post: # 48355Unread post jjwharris
Mon Nov 06, 2017 4:43 am

So yup, looks like I need to lose some rigidity, gonna pull apart the other head and try make the next version of this. I'm very hopeful, thinking if i reprint the springs I may improve my results.

total moving mass is 2.2g per speaker, plus under 1g for the assembly. I can't get the screw/stylus holder/pushrods to measure on the scales.
Record Lathe Embossing Supplies - http://www.supplies.johnnyelectric.co.nz/

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markrob
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Re: Open Source Lathes and Cutterheads

Post: # 48362Unread post markrob
Mon Nov 06, 2017 9:30 am

Hi,

That last response looks really nice. Yes, you have things pretty stiff as the system resonance is way up in the 2Khz range. However, it might be a good thing in the case of an open loop head design. Increased stiffness implies that the head will be less affected by the cutting media. Just like a low impedance unregulated power supply would be less affected by load changes. The downside is that the drive sensitivity of the head will be lower. The trade-off is if you can drive the head to cut at sufficient levels without having it smoke. Your moving mass is on the high side. So that coupled with the stiffness, may have thrown away too much sensitivity. Some testing would need to be done here. In the case of a pro head with feedback applied, they can rely on the feedback to stiffen the head against load changes. This allows them to go with a very low mass design (1g moving mass or less) and limited stiffness. That might not be the best approach for an open loop head.

If you think about the open loop response of a moving coil head in the amplitude domain instead of velocity, the head is flat from DC to system resonance and then (theoretically) falls off at -12dB/Oct. This allows you to easily determine if the head can cut it at low frequencies. To test, just apply a DC current within the rating of the drivers ( in mono) and check the lateral deflection using a dial indicator. A typical pro head might be able to do +/-200um max (+/- .008"). If you are able to get near there, then you are probably ok. If not, then reduce the stiffness until you are able. On the other side of resonance the head response is mass controlled.

Hope that helps.

Mark

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jjwharris
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Re: Open Source Lathes and Cutterheads

Post: # 48393Unread post jjwharris
Tue Nov 07, 2017 3:32 pm

Hi Mark,

Thanks again for the input once again, your knowledge is invaluable.

I do not have access to a dial meter, but after a few cutting tests i have noticed that I've lost sensitivity, but as you say, the outcome is a lot more predictable. I have a new spring design I am planning to put into action which i think should free up those lower frequencies while hopefully not sacrificing too much stiffness and allowing me to emboss at louder volumes.

Just quickly, and this may be a somewhat basic question, but I do need clarification on it - when you say my moving mass is on the high side, do you mean everything attached to the moving coil including the coil itself or just everything infront of the moving coil?

Thank you also for your input on the arduino controlled turntable - I've been researching what you've said and am working with someone on a solution, looks like it will be a microprocessor but most likely not an arduino due to the low clock speed.
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markrob
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Re: Open Source Lathes and Cutterheads

Post: # 48394Unread post markrob
Tue Nov 07, 2017 4:04 pm

Hi,

I was saying the effective total moving mass of 3g might be a bit high. This includes the voice coil, wire, spider, push rods, torque tube, stylus holder, stylus, etc. Here is a link to some posts discussing effective tip mass for a pickup.

https://www.vinylengine.com/turntable_forum/viewtopic.php?t=30049

It can get quite complex. But at the end of the day its about how much force is required to move the cutting stylus while cutting. This reflects back to the current in the drive coil since this generates force.

BTW, there are some very inexpensive test dial indicators available. For example:

http://www.shars.com/products/measuring/dial-test-indicators/030-dial-test-indicator-0005-7

Also a cheap milligram scale is very useful:

https://www.amazon.com/American-Weigh-GEMINI-20-Portable-MilliGram/dp/B0012TDNAM

Mark

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Estrada
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Re: Open Source Lathes and Cutterheads

Post: # 56655Unread post Estrada
Mon Aug 31, 2020 6:27 am

Hey jjwharris, looks like this thread has been inactive for a while but was wondering how you are getting on with your project? I'm based in Wellington and I've just recently got my lathe operating (that I've owned for almost 15 year) and started embossing. Nice to know that there are other experimenters out there - besides Peter Kind of course.

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jjwharris
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Re: Open Source Lathes and Cutterheads

Post: # 56666Unread post jjwharris
Tue Sep 01, 2020 4:12 am

Hey Estrada,

I've kind of started again, there are a couple of topics;

https://www.lathetrolls.com/viewtopic.php?f=15&t=8775
Which is my current overhead design with turntable

and

https://www.lathetrolls.com/viewtopic.php?f=15&t=8851
Which is the Presto clone I'm trying to build. The current Presto clone is working, but I'm in the process of tightening up some tolerances to try and get a bit more out of it.

Ritter is based in Wellington too!
https://www.lathetrolls.com/viewtopic.php?f=15&t=7024
Record Lathe Embossing Supplies - http://www.supplies.johnnyelectric.co.nz/

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Estrada
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Re: Open Source Lathes and Cutterheads

Post: # 56706Unread post Estrada
Fri Sep 04, 2020 7:59 pm

Thanks for the reply, this is what I’ve been working on

https://www.lathetrolls.com/viewtopic.php?f=22&t=8287

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