Deep Grooves Mastering - Project Bladerunner

[opcode66]

Bladerunner 1.A

The tenth cutterhead build. The results of almost 4 months of engineering. I've come so far in so many areas working on this project. And, I think it is truly going to pay off. So many improvements I can barely list them all. Not the least of which are totallly re-engineered torque tube, new springs, completely new vacuum tube design and hidden cabling in the back. It used to look so mess in the back. It is now very clean.

Tomorrow I will test perform the 4th filmed test cuts. I will then rip the cuts and perform frequency analysis on them. All of this will be video documented. I will then put together a nicely edited video and upload. I already know what I'm going to use as program material. Looking forward to tomorrow!

[sbelleque]

When you see this kind of work, it is nothing short of inspirational.

[mrneedle]

Bladerunner 1.A
Looking forward to tomorrow!

that's one very cool cat good look tomorrow and looking forward to your results!

[opcode66]

Bladerunner 1.A Test Cut

A few things need to be tweaked. But, overall, good progress. And, closer to a good sounding cutterhead! Test cut, rip and analysis.

[opcode66]

That sort of buzzing in my recording is my 700 hz resonant frequency. With a little eq'ing i can get rid of it while cutting. Also, I put the wrong capacitor on my low pass filter (2.7 uF instead of 1.7 uF off a 4.7 Ohm 10W resistor). I didn't do the math myself and followed the instructions of someone who shall remain nameless. Not doing that again... My cutoff was at 12khz. That's what was killing my highs! So, much better cuts today!!!!!

[Self-lather]

Awesome, this is really making want to invest in a 3d printer.

[opcode66]

In some respects, I'm making this look a little too easy. I've spent countless undocumented hours learning the ins and outs of 3d design and printing on a Makerbot. I've wasted countless prints. Been frustrated sooooo many times. I've learned tricks to fool the machine into giving me what I want. Working in plastic has not been easy. But, I think I've been able to very rapidly prototype. So, that is fantastic.

Much better results today. No time to make a video. I already want to make Bladerunner 1.B because I have changes to the body that will improve things in general. Off to make new parts!

Here is a rip of today's cut.

Bladerunner 1.A 20-20K Sweep 11-14-2014.mp3

And Frequency Analysis on the sweep at the end. Not bad at all!

Bladerunner 1.A 20-20K Sweep.png

[opcode66]

[EpicenterBryan]

That sort of buzzing in my recording is my 700 hz resonant frequency.

Todd, is it possible that the slide in driver cartridges need something between them and the housing? Like some kind of non hardening liquid gasket material - something like "permagasket"? I wonder if something that stays flexible but could be spread on the surface while assembling to fill that gap may eliminate the big buzz / jump when things resonate. It can be cleaned off if the driver needs to be replaced. I'm not sure what the main solvent is and if it's compatible with the plastic you use but something like that may help. Perhaps even doing a skim coat with RTV while assembling? That might even do the trick.

Bryan

[opcode66]

I'm not particularly worried about it. It is due to the RF of about 700 hz. If you listen to the rip I posted above, you'll hear what happens when I cut with a Notch eq at 700 hz -3db. There is no longer any buzzing. When I implement my feedback coil, I will no longer have to EQ. The negative feedback will resolve this issue. All cutterheads have an RF. Mono heads using damping material. Stereo heads with feedback use feedback. Same result. To avoid exactly this issue. Nothing physical needs to be changed.

By the way, it is not the transducer cards that are buzzing. They are very snug. Extremely snug. I have to use the handle of a tool in order to pry them out. They are somewhat challenging to slide in and out. So, it is by no means the head. In fact, it isn't really buzzing. It is simply distorting. That is how the phono pre-amp sounds when over saturated.

[EpicenterBryan]

In fact, it isn't really buzzing. It is simply distorting. That is how the phono pre-amp sounds when over saturated.

Ok, I'm with you. Just was going by the audio in the YouTube video.

Bryan

[opcode66]

That is what the audio on disc sounds like. That is not what the head sounds like while cutting. Also, you can clearly see in the analysis of the audio that I have a huge increase in volume at around 700.

[opcode66]

I've learned a number of lessons over the past week. The buzzing sound was coming from a loose connection. The leaf springs (tabs) on the base of my torque tube were vibrating within the slots that they insert into. Gluing them solves the issue and kills the noise.

I also learned that it is called a torque tube for a reason. Without understanding that the tube does in fact torque.... Without accounting for and enabling this torquing.... You do not get proper vertical movement. Duh! And, you get a fair amount of crosstalk. I now understand how to resolve this issue in my design. I'm not saying how. #SecretKnowledge But, I will say that all of the other DIY head projects that I've seen are doomed to fail in this respect. You will never be able to kill the crosstalk and get good vertical excursion if you don't do one very important thing with the transducer design.

I've printed a couple of my harting clones. So, now, the cabling for my cutterhead has connectors on it. So, I can easily disconnect and work on the cutterhead without it being tethered.

Finally, I've come to understand through testing and research that you absolutely need to have your coil submerged within the permanent magnet (specifically the flux). So, I'm incorporating a washer style Neodymium magnet into my transducer cards. The bobbin will move inside the hole in the center of the washer style magnet. The net effect is a huge boost in the efficiency of the transducer and more excursion!

I'm making hot-rod transducer cards now. Expect some test video by weeks end. The sound should have more highs, better defined grooves, proper vertical movement, better overall volume, and minimized crosstalk. Then next week.... Bladerunner 1.B with major improvements to the body as well as the addition of heated stylus.

[EpicenterBryan]

I also learned that it is called a torque tube for a reason. Without understanding that the tube does in fact torque....

It has a rotational aspect to it, ie torque. But in a conventional sense it also supports the upward force from cutting.
The tube has to rotate as the L and R push rods try to do their thing. The real problem is that both R and L push rods also need flex at the stylus holder. When one pushes and the other retracts the same amount, the torque tube rotates. When both push rods extend, the torque tube goes down, but the union at both push rod connection must flex and change angle, or that angle change has to happen at the driver. With a DYI driver design, it messes up the geometry and the voice coils rub. So I think the key for a DIY is to have a very flexible union right at the stylus holder connection. For your version where you have feedback and can make what you need, I think having your push rods being spring steel (piano wire) of light gauge works fine. It gives the flex you need. If you shorten the distance from your driver to your stylus holder, drop the gauge of wire. It not only helps reduce moving mass, but increases the heads ability to deal with angular errors right at that connection point.

Bryan

[opcode66]

There is one additional critical factor that you haven't mentioned...

[EpicenterBryan]

There is one additional critical factor that you haven't mentioned...

Holds the stylus, and keeps it from pulling forward when cutting?
Share the #SecretKnowledge. Share the #SecretKnowledge. Share the #SecretKnowledge!

[opcode66]

Nope.

[The Shank]

hahaha!

[emidisc]

My guess the answer is springs! the ones that centralise the two parts of the driver and return it to its "normal" position ready for the next signal ie like the one on the surface transducers currently being discussed on the forum.........
But I can't imagine how these could be plastic? Surely only spring steel would suffice......

[opcode66]

Surely I'm cutting grooves with audio.... Surely you've seen my videos.... Surely I'm not faking it... Surely plastic works.

The plastic I'm working with is very solid when printed to a solid object. But, when printed thin, there is a range of thickness where it is actually flexible. Too thick and it does in fact break. But, thin and it is springy. Also, you must take into consideration that the movement that the springs need to counteract is measured in 1/1000's of an inch. That is not much excursion. Plastic has been working much better than even I expected.

But, you still don't have the secret knowledge. Has nothing to do with centering the torque tube after sound stops. The other DIY heads mostly seem to have some leaf springs at the base of the torque tube. That is not the critical flaw that I see in their design.