Hi Bryan,
Last week I tested the configuration with Mu Metal (Ciuens Shield, hehehe), but it still fails with the magnetic insulation of the coils. I have to run new tests with the coil feedback, perhaps increasing the impedance. The good news is that I got excellent results with the decrease of the springs. The resonance has been considerably attenuated and the total weight including the coil spring and the second was at 4 g.
Re: Project "Groove Scribe"- A DYI stereo 45/45 head.
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Re: Project "Groove Scribe"- A DYI stereo 45/45 head.
another cutting test. This time I used a good amplifier with 180 watts. Distorted, but got good response at all frequencies up to 16khz. No feedback or vacuum.
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EpicenterBryan
- Posts: 738
- Joined: Sun Aug 10, 2014 9:01 pm
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Re: Project "Groove Scribe"- A DYI stereo 45/45 head.
Hey Ciuens, that's impressive! Did you have to apply a bunch of EQ? Where do you think the distortion came from?Ciuens wrote:The good news is that I got excellent results with the decrease of the springs ...Distorted, but got good response at all frequencies up to 16khz.
Interesting. Were you able to see a difference by stacking a second layer (making the shield thicker)? Are you still seeing a big phase change or is that better?Ciuens wrote:I tested the configuration with Mu Metal (Ciuens Shield, hehehe), but it still fails with the magnetic insulation of the coils.
Re: Project "Groove Scribe"- A DYI stereo 45/45 head.
Yes, I had to apply a lot of EQ. The distortion came from the signal excess applied to the amplifier, hahaha. One tip, do not try to eliminate resonance with equalization, only attenuateHey Ciuens, that's impressive! Did you have to apply a bunch of EQ? Where do you think the distortion came from?
. On the other hand, managed to + 13dB loud. Compared to Maxi Single Discs 
I did not feel any difference. I think the MU Metal does not isolate magnetism generated by coils.I have not given up, then back to new tests.Interesting. Were you able to see a difference by stacking a second layer (making the shield thicker)? Are you still seeing a big phase change or is that better?
Re: Project "Groove Scribe"- A DYI stereo 45/45 head.
I can tell you two things that in combination kill a lot of em induction. I can. Or, just do a little research. Like for instance about how nuclear missile sites are hardened against em induction in computer equipment. HINT
The third factor I'll tell you. Distance. Remove the feedback coil as far from the drive coil as possible.
The fourth thing I will pnly hint at. It is how the coils in an SX cutterhead are made. Wont say more than configuration....
Just do some homework, all will be very obvious.
The third factor I'll tell you. Distance. Remove the feedback coil as far from the drive coil as possible.
The fourth thing I will pnly hint at. It is how the coils in an SX cutterhead are made. Wont say more than configuration....
Just do some homework, all will be very obvious.
Cutting, Inventing & Innovating
Groove Graphics, VMS Halfnuts, MIDI Automation, Professional Stereo Feedback Cutterheads, and Pesto 1-D Cutterhead Clones
Cutterhead Repair: Recoiling, Cleaning, Cloning of Screws, Dampers & More
http://mantra.audio
Groove Graphics, VMS Halfnuts, MIDI Automation, Professional Stereo Feedback Cutterheads, and Pesto 1-D Cutterhead Clones
Cutterhead Repair: Recoiling, Cleaning, Cloning of Screws, Dampers & More
http://mantra.audio
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EpicenterBryan
- Posts: 738
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Re: Project "Groove Scribe"- A DYI stereo 45/45 head.
I made an interesting discovery about the magnet structure on these drivers.
You are going to notice that there is an odd copper color to these parts. That's because of an experiment from a few weeks ago when I tried to copper plate this. The experiment lasted for about 20 seconds until it was clear that the acid was eating the front facing disc in the driver (which was not a washer as I thought, but a Neodymium magnet). Why did I do this you might ask? Well it has to do with a Faraday Ring and voice coils. My idea was to try to plate one in-place in copper. I was also trying to plate a reference piece of shim stock at the same time so I could measure how much copper was being deposited. Here is a link to some info on what a Faraday Ring does for those who are interested:
http://www.hifiakademiet.dk/User_files/fedd9fa85cbf2dee95f4281933f6e920.pdf
Anyway, in this first photo you see what is below the outer most disc. The lump of broken stuff is what's left of the magnet after breaking it off...
I had not seen this ring before. It was hidden under the outer magnet. Now it gets more interesting. I took a chisel to try to split the ring and see how far down it went and what it was made of. I half expected it to be Aluminum or something else non magnetic. In the process I was able to remove it and what turned out to be a washer (not a magnet)... As it turned out the ring and washer are both magnetic (but not magnetized) and are not the same material.
I used a compass and determined that the magnet that is still in the housing is North. Now look at the photo... a piece of the outer magnet that is still shiny (which was the side that was facing the washer and didn't get eaten) is also North, and the dark side (that was eaten by acid) is South.
So get this, the washer was in there so they could have two magnets both with the North facing each other (which you know is hard to do normally). And here you see clearly that the acid eaten South is facing out and both Norths are facing each other...
What does that have to do with the price of tea in China?
I'm not sure. But it does show that they were able to concentrate the magnetic field from those magnets right where they wanted it - right where the driver coils are.
Bryan
You are going to notice that there is an odd copper color to these parts. That's because of an experiment from a few weeks ago when I tried to copper plate this. The experiment lasted for about 20 seconds until it was clear that the acid was eating the front facing disc in the driver (which was not a washer as I thought, but a Neodymium magnet). Why did I do this you might ask? Well it has to do with a Faraday Ring and voice coils. My idea was to try to plate one in-place in copper. I was also trying to plate a reference piece of shim stock at the same time so I could measure how much copper was being deposited. Here is a link to some info on what a Faraday Ring does for those who are interested:
http://www.hifiakademiet.dk/User_files/fedd9fa85cbf2dee95f4281933f6e920.pdf
Anyway, in this first photo you see what is below the outer most disc. The lump of broken stuff is what's left of the magnet after breaking it off...
I had not seen this ring before. It was hidden under the outer magnet. Now it gets more interesting. I took a chisel to try to split the ring and see how far down it went and what it was made of. I half expected it to be Aluminum or something else non magnetic. In the process I was able to remove it and what turned out to be a washer (not a magnet)... As it turned out the ring and washer are both magnetic (but not magnetized) and are not the same material.
I used a compass and determined that the magnet that is still in the housing is North. Now look at the photo... a piece of the outer magnet that is still shiny (which was the side that was facing the washer and didn't get eaten) is also North, and the dark side (that was eaten by acid) is South.
So get this, the washer was in there so they could have two magnets both with the North facing each other (which you know is hard to do normally). And here you see clearly that the acid eaten South is facing out and both Norths are facing each other...
What does that have to do with the price of tea in China?
I'm not sure. But it does show that they were able to concentrate the magnetic field from those magnets right where they wanted it - right where the driver coils are.
Bryan
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EpicenterBryan
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- Joined: Sun Aug 10, 2014 9:01 pm
- Location: Eugene, OR USA
Re: Project "Groove Scribe"- A DYI stereo 45/45 head.
I revised the test platform and things are much more repeatable now.
The Renishaw 4mm ruby tipped ball styli arrived, and I printed a bracket to use two of them as a low friction V support point for the end of the carbon fiber rod. The bracket lets me move them up and down as needed.
I mentioned that I bought a Micro Seiki turn table to get the tone arm for the test setup... I printed some parts to make the tone arm stand alone. I also added 47K termination resistors at the tone arm wiring interface. I can switch out termination resistors at my preamp.
A few weeks ago while I was playing with the test jig that used an 80mm wide extrusion that was quite long, I realized that the hollow sections were resonating. I tried isolating the phono pickup but it proved to be problematic. I tried to use Sorbathane as a mount shock. Because that is very flexible, any slight reposition of the wires to the cartridge could change the adjustment of the contact force between the cartridge and contact with the carbon fiber rod. As part of the re-think of the measurement test bed, I decided to swap the 80mm base out with a shorter segment of 40mm extrusion. If I have time, I will design some end plates for the extrusion and fill it with lead shot or perhaps sand... But for now, I attached some material called "Poron" to the base to isolate it. It's a closed cell foam material I discover about 20 years ago and have a "hoard" of it...
So you get it... I changed stuff. And you might be asking how my crazy experiment went where I changed all the effective lengths of the driver springs so they were not the same? Here is the data now that I'm happy with the repeatability of the test jig.
But it gets better, not only did I use two different phono cartridges, but I also used two different phono preamps....
So here goes:
Both charts are done powering the drivers with 1W (measured at the driver).
This first chart is for the AudioTechnica AT3600 with 2g tracking force. The normal recommended range is 1. 5 - 3. 0 grams. So 2g seamed reasonable. The LEFT chart is with the signal going through my preamp and then into the IOdock LINE INPUT. The RIGHT chart is with the phono cart going directly into the MIC PREAMP input on the IOdock. The response is similar. As noted, my preamp had the termination turned off (since I added 47K resistors at the tone arm), and I can not find data on the input impedance of the IOdock MIC input but think it is much lower (like 1.5K or so).
This chart is for the Shure M95ed.
The normal recommended range is 0.75 - 1.5 grams. Here is where I screwed up. the LEFT chart is at 1.5 grams and was taken after I realized the right one was too high. The right one was at 2 grams...
The LEFT chart is with the signal going through my preamp and then into the IOdock LINE INPUT. The RIGHT chart is with the phono cart going directly into the MIC PREAMP input on the IOdock. The charts are again nearly identical even though the right one is tracking slightly too hard.
And when compared to the other phono cartridge, they again agree pretty well.
Now, let me also say that in-between these measurements I moved the driver out of position, and then re-positioned it to be able to check repeatability of the measurements. so even between two measurements with two different preamps on the same cartridge, the testing jig was disturbed and re-adjusted...
The take away is that I'm happy with the repeatability now.
Now it's time to try some other spring length mods...
B
The Renishaw 4mm ruby tipped ball styli arrived, and I printed a bracket to use two of them as a low friction V support point for the end of the carbon fiber rod. The bracket lets me move them up and down as needed.
I mentioned that I bought a Micro Seiki turn table to get the tone arm for the test setup... I printed some parts to make the tone arm stand alone. I also added 47K termination resistors at the tone arm wiring interface. I can switch out termination resistors at my preamp.
A few weeks ago while I was playing with the test jig that used an 80mm wide extrusion that was quite long, I realized that the hollow sections were resonating. I tried isolating the phono pickup but it proved to be problematic. I tried to use Sorbathane as a mount shock. Because that is very flexible, any slight reposition of the wires to the cartridge could change the adjustment of the contact force between the cartridge and contact with the carbon fiber rod. As part of the re-think of the measurement test bed, I decided to swap the 80mm base out with a shorter segment of 40mm extrusion. If I have time, I will design some end plates for the extrusion and fill it with lead shot or perhaps sand... But for now, I attached some material called "Poron" to the base to isolate it. It's a closed cell foam material I discover about 20 years ago and have a "hoard" of it...
So you get it... I changed stuff. And you might be asking how my crazy experiment went where I changed all the effective lengths of the driver springs so they were not the same? Here is the data now that I'm happy with the repeatability of the test jig.
But it gets better, not only did I use two different phono cartridges, but I also used two different phono preamps....
So here goes:
Both charts are done powering the drivers with 1W (measured at the driver).
This first chart is for the AudioTechnica AT3600 with 2g tracking force. The normal recommended range is 1. 5 - 3. 0 grams. So 2g seamed reasonable. The LEFT chart is with the signal going through my preamp and then into the IOdock LINE INPUT. The RIGHT chart is with the phono cart going directly into the MIC PREAMP input on the IOdock. The response is similar. As noted, my preamp had the termination turned off (since I added 47K resistors at the tone arm), and I can not find data on the input impedance of the IOdock MIC input but think it is much lower (like 1.5K or so).
This chart is for the Shure M95ed.
The normal recommended range is 0.75 - 1.5 grams. Here is where I screwed up. the LEFT chart is at 1.5 grams and was taken after I realized the right one was too high. The right one was at 2 grams...
The LEFT chart is with the signal going through my preamp and then into the IOdock LINE INPUT. The RIGHT chart is with the phono cart going directly into the MIC PREAMP input on the IOdock. The charts are again nearly identical even though the right one is tracking slightly too hard.
And when compared to the other phono cartridge, they again agree pretty well.
Now, let me also say that in-between these measurements I moved the driver out of position, and then re-positioned it to be able to check repeatability of the measurements. so even between two measurements with two different preamps on the same cartridge, the testing jig was disturbed and re-adjusted...
The take away is that I'm happy with the repeatability now.
Now it's time to try some other spring length mods...
B
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EpicenterBryan
- Posts: 738
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Re: Project "Groove Scribe"- A DYI stereo 45/45 head.
Wow, long time no update...
In the next week I'm going try out my latest idea for the driver mods.
Tonight I'll show you what I'm up to.
Based mostly on awesome inputs from MarkRobs's spring testing and what Ciuens has also shared, I have decided to re-think the spring all together. In this version, I'm trying to reduce the moving mass even more while at the same time keeping compliance in a reasonable range - not too soft not to hard...
In this version I'm trying to add dampening at the same time as eliminating some spring based resonance. The spring in this version is now really a diaphragm - one that is still flexible, but is as stiff as needed based on thickness of the printed material. This diaphragm is 3D printed in a Nylon type material. Details to follow.
I have decided to make Carbon Fiber discs that the Nylon diaphragm and push rods connect to. And the stock coil for the driver will attach directly to the carbon fiber disc as well. It's a bigger departure than buying something off the shelf than I wanted to go through but I think it has merits.
Here is a Cad view of the two options I'm planning to try.
One is a diaphragm, with counter sunk area to accommodate the thickness of the carbon fiber disc. The other one is the totally minimalist version which is very hard to print in this material.
The next phase is testing bonding agents between the Nylon and Carbon fiber discs. Fortunately there are several YouTube destruct videos that have eliminated several compounds. Tonight, I have tried one option that actually seams to work between the disc and the nylon diaphragm.
In this shot is a scrap disc, and a scrap diaphragm so you can see what they look like. The Wide disc is the side where the coil attaches. The other is where the push rod attaches.
More as time permits!
Bryan
In the next week I'm going try out my latest idea for the driver mods.
Tonight I'll show you what I'm up to.
Based mostly on awesome inputs from MarkRobs's spring testing and what Ciuens has also shared, I have decided to re-think the spring all together. In this version, I'm trying to reduce the moving mass even more while at the same time keeping compliance in a reasonable range - not too soft not to hard...
In this version I'm trying to add dampening at the same time as eliminating some spring based resonance. The spring in this version is now really a diaphragm - one that is still flexible, but is as stiff as needed based on thickness of the printed material. This diaphragm is 3D printed in a Nylon type material. Details to follow.
I have decided to make Carbon Fiber discs that the Nylon diaphragm and push rods connect to. And the stock coil for the driver will attach directly to the carbon fiber disc as well. It's a bigger departure than buying something off the shelf than I wanted to go through but I think it has merits.
Here is a Cad view of the two options I'm planning to try.
One is a diaphragm, with counter sunk area to accommodate the thickness of the carbon fiber disc. The other one is the totally minimalist version which is very hard to print in this material.
The next phase is testing bonding agents between the Nylon and Carbon fiber discs. Fortunately there are several YouTube destruct videos that have eliminated several compounds. Tonight, I have tried one option that actually seams to work between the disc and the nylon diaphragm.
In this shot is a scrap disc, and a scrap diaphragm so you can see what they look like. The Wide disc is the side where the coil attaches. The other is where the push rod attaches.
More as time permits!
Bryan
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Snug Music
- Posts: 299
- Joined: Sat Aug 15, 2015 5:23 pm
- Location: 28816 Stuhr / Moordeich LK Diepholz
Re: Project "Groove Scribe"- A DYI stereo 45/45 head.
Hi Brian, I have a question. I have seen that you have halved a tube and then glued over the Rods. ( standing wave! ) My question is: U glued this directly over the Rods or u cut the Rods in the middle? 
Thx for answere...Scotty
Thx for answere...Scotty
I'm still not a professional, but I learn pretty fast. especially with my eyes and ears!
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EpicenterBryan
- Posts: 738
- Joined: Sun Aug 10, 2014 9:01 pm
- Location: Eugene, OR USA
Re: Project "Groove Scribe"- A DYI stereo 45/45 head.
I glued them on top of the rods since they were an afterthought, and everything was already glued together.Snug Music wrote:Hi Brian, I have a question. I have seen that you have halved a tube and then glued over the Rods. ( standing wave! ) My question is: U glued this directly over the Rods or u cut the Rods in the middle?
Thx for answere...Scotty
I have hopes to get back to this in a few days. So many projects, so little time.
Bryan
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Snug Music
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- Joined: Sat Aug 15, 2015 5:23 pm
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Re: Project "Groove Scribe"- A DYI stereo 45/45 head.
Ok I understand! Have seen this even at the Neumann head are present in a conical type. Thank you for your quick response! You're doing a great job Brian. I want to stay tuned!
Thx....
Scotty
Thx....
Scotty
I'm still not a professional, but I learn pretty fast. especially with my eyes and ears!
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Snug Music
- Posts: 299
- Joined: Sat Aug 15, 2015 5:23 pm
- Location: 28816 Stuhr / Moordeich LK Diepholz
Re: Project "Groove Scribe"- A DYI stereo 45/45 head.
Hi Bryan, thanks for the good inspiration. I've now built a Lathe. The head is an inspiration to your work. Today I build it all together and make the first cut. I'm curious!
Thx..greetings from Bremen/west germany...
Scotty
Thx..greetings from Bremen/west germany...
Scotty
I'm still not a professional, but I learn pretty fast. especially with my eyes and ears!
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Snug Music
- Posts: 299
- Joined: Sat Aug 15, 2015 5:23 pm
- Location: 28816 Stuhr / Moordeich LK Diepholz
Re: Project "Groove Scribe"- A DYI stereo 45/45 head.
Here is my work...
Greetings
Scotty...
Greetings
Scotty...
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I'm still not a professional, but I learn pretty fast. especially with my eyes and ears!
Re: Project "Groove Scribe"- A DYI stereo 45/45 head.
hello everyone, I'm learning a lot from all the beautiful projects placed here, I would like to thank for sharing their experiences. I'm already working on my cutting head, and I wonder how the feedback system because not found yet more details of its operation.
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EpicenterBryan
- Posts: 738
- Joined: Sun Aug 10, 2014 9:01 pm
- Location: Eugene, OR USA
Re: Project "Groove Scribe"- A DYI stereo 45/45 head.
Hey guys,
I just wanted to drop in and let you know testing of the two new nylon spring / diaphragms starts tomorrow. There have been many distractions the last few weeks in my world... Fun distractions.
Thanks to all the guys who are sharing what they are doing with these drivers on this thread and in your own build logs! It's all some much fun to follow.
I realize I started the thread about these specific drivers and Groove Scribe, but it really belongs to everyone, everyone who reads it and everyone who shares what they are up to and what is working and not working! You guys are making great progress with your projects and we all are benefiting from you sharing things! Thanks so much for keeping Groove Scribe alive - and as a group effort the way it is working out. I really like the way this is going!
At some point several of us starting thinking these drivers might be a good solution for an off the shelf DIY project. And the more people playing with and sharing results have helped us all discover they need tweaks. Ultimately, can they be tweaked or should be abandoned? Everything I see that you guys are sharing is getting us closer. But it's the process and the willingness of you guys to share what you are up to that will ultimately help us decide. What a great website LatheTrolls is! And what a batch of great people to hang out with! I wish you all could come over for a BBQ and some cold beer.
Having said that, I have two coils / discs / nylon diaphragms and push rods ready for the test bed tomorrow!
This JB weld clear is what I think is going to do the trick on the union of the carbon fiber disc and the nylon diaphragms based on some YouTube videos. This is not something I could find in town, so I ordered it on Ebay. I also have a disc and nylon diaphragm that I glued with some Harbor Freight epoxy that has set for a week and I'll do a destruct test on the bond. That might be easier for some people to find...
And if anyone has missed the last update of Todd's Bladerunner project, be sure to check it out. Todd's newly designed drivers are truly impressive! Damn!
That's it for tonight. Rock on people. You guys are doing great work! Stay tuned for a go/no-go on the nylon diaphragm idea...
Bryan
I just wanted to drop in and let you know testing of the two new nylon spring / diaphragms starts tomorrow. There have been many distractions the last few weeks in my world... Fun distractions.
Thanks to all the guys who are sharing what they are doing with these drivers on this thread and in your own build logs! It's all some much fun to follow.
I realize I started the thread about these specific drivers and Groove Scribe, but it really belongs to everyone, everyone who reads it and everyone who shares what they are up to and what is working and not working! You guys are making great progress with your projects and we all are benefiting from you sharing things! Thanks so much for keeping Groove Scribe alive - and as a group effort the way it is working out. I really like the way this is going!
At some point several of us starting thinking these drivers might be a good solution for an off the shelf DIY project. And the more people playing with and sharing results have helped us all discover they need tweaks. Ultimately, can they be tweaked or should be abandoned? Everything I see that you guys are sharing is getting us closer. But it's the process and the willingness of you guys to share what you are up to that will ultimately help us decide. What a great website LatheTrolls is! And what a batch of great people to hang out with! I wish you all could come over for a BBQ and some cold beer.
Having said that, I have two coils / discs / nylon diaphragms and push rods ready for the test bed tomorrow!
This JB weld clear is what I think is going to do the trick on the union of the carbon fiber disc and the nylon diaphragms based on some YouTube videos. This is not something I could find in town, so I ordered it on Ebay. I also have a disc and nylon diaphragm that I glued with some Harbor Freight epoxy that has set for a week and I'll do a destruct test on the bond. That might be easier for some people to find...
And if anyone has missed the last update of Todd's Bladerunner project, be sure to check it out. Todd's newly designed drivers are truly impressive! Damn!
That's it for tonight. Rock on people. You guys are doing great work! Stay tuned for a go/no-go on the nylon diaphragm idea...
Bryan
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EpicenterBryan
- Posts: 738
- Joined: Sun Aug 10, 2014 9:01 pm
- Location: Eugene, OR USA
Re: Project "Groove Scribe"- A DYI stereo 45/45 head.
Holy smokes!
I think we are on to something.
Here is the curve for the full size diaphragm. Again, the diaphragm is printed with Taulman's Nylon Bridge. The center disc is 1mm think carbon fiber, the rod is solid 2.5mm carbon fiber.
One thing to note on this one is that I used epoxy at the connection between the disc and rod which added some mass that didn't need to be there. Dumb. The second one with the minimalist spring is using super glue so I may need to take this one apart and remove the epoxy...
But this is a great start to the day!
Bryan
I think we are on to something.
Here is the curve for the full size diaphragm. Again, the diaphragm is printed with Taulman's Nylon Bridge. The center disc is 1mm think carbon fiber, the rod is solid 2.5mm carbon fiber.
One thing to note on this one is that I used epoxy at the connection between the disc and rod which added some mass that didn't need to be there. Dumb. The second one with the minimalist spring is using super glue so I may need to take this one apart and remove the epoxy...
But this is a great start to the day!
Bryan
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Re: Project "Groove Scribe"- A DYI stereo 45/45 head.
wooooooooow. My God, 2479 Hz in the main resonance? Bryan, that is impressive. You know what to do to eliminate or decrease the phase shift?
Ciuens
Ciuens
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EpicenterBryan
- Posts: 738
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Re: Project "Groove Scribe"- A DYI stereo 45/45 head.
Ciuens, don't get too excited yet! We need to dive into Marks previous posts and think about this all a bit. I hope he will chime in...Ciuens wrote:wooooooooow. My God, 2479 Hz in the main resonance? Bryan, that is impressive. You know what to do to eliminate or decrease the phase shift?
What we have done is messed with 3 things at the same time. It's always best to do one thing at a time so you know what really changed things... but it is what it is.
- 1). Increased stiffness and raised the resonant frequency. This surely will reduce the output sensitivity requiring more power as I recall.
2). Decreased the moving mass, extending the HF response. This is a really good thing if the data is correct.
3). Added dampening effectively by reducing the spring in the spring mass relationship. I have no clue how to account for that. I think this may be a really good thing.
At head: 1.89v RMS (0.76W at 4.7ohm)
At phono cartridge: 1.2mv.
Cartridge specs: Shure M95ED, output 4.2mv at 5cm/s 1khz.
So I think the actual movement being generated at 0.76 watts is 1.42cm/s. But, that's at the driver rod. In my version of groove scribe, my rod connections are Behind the stylus. Not because I'm smart, just because I have presto style styli. That means that where the stylus is located (in front of the rod connections) it has a mechanical multiplier because of the distance down the torque tube from the driver connection. Also, I only have long shank styli, so that also has an extrusion advantage but a HF disadvantage due to increased mass and such. So I really don't know how this will work until something is built.
But I have other tests to run.
We all certainly have seen that response gets better as we get moving mass down. We have also seen the resonant frequency move up as we stiffen the system. But now we also see this new variable where the spring part of the equation is reduced by the material used.
So much more messing around to do.
If anyone has a 3D printer and would like to experiment with this Nylon Bridge stuff, drop me a PM. I have two full reels of it I'm happy to share with people at no cost as long as you share your results on the forum. Offer valid until October 1, 2015. International guys will have to kick in on mailing costs... I'll need to figure that out. I'll also share my printer settings that worked the best.
The stuff is tricky to play with and chances are that it may clog your nozzle. So be sure you have extra nozzles, extrusion tubes and everything else ready to go before you use this stuff.
Bryan
Re: Project "Groove Scribe"- A DYI stereo 45/45 head.
Hey,
That response is looking really nice. You seem to have a good handle on things. One odd thing. I think you might have the polarity flipped. The phase display starts out at -90 degrees at low frequencies and transitions to +90 after resonance. It should be just the opposite (+90 at low frequencies and -90 after system resonance.
What is the distance from the drive coil to the phono pickup? The extra phase lag could be due, in part, to the sound propagation delay from the driver to the pickup. It could also be due to the driver L/R time constant. One way around that (if it is the source of the lag) is to drive the head using a constant current source rather than a constant voltage. That can be done easily with a second feedback loop around the power amp with a small current sense resistor in the ground return of the head.
In any event, it looks like you should be able to close the loop beyond 8 Khz with a bit of lead lag compensation.
Mark
That response is looking really nice. You seem to have a good handle on things. One odd thing. I think you might have the polarity flipped. The phase display starts out at -90 degrees at low frequencies and transitions to +90 after resonance. It should be just the opposite (+90 at low frequencies and -90 after system resonance.
What is the distance from the drive coil to the phono pickup? The extra phase lag could be due, in part, to the sound propagation delay from the driver to the pickup. It could also be due to the driver L/R time constant. One way around that (if it is the source of the lag) is to drive the head using a constant current source rather than a constant voltage. That can be done easily with a second feedback loop around the power amp with a small current sense resistor in the ground return of the head.
In any event, it looks like you should be able to close the loop beyond 8 Khz with a bit of lead lag compensation.
Mark
Re: Project "Groove Scribe"- A DYI stereo 45/45 head.
Bryan, I believe we are close to getting a great cutting head with these transducers. Really the mass reduction makes all the difference in the results, especially at high frequencies. The key will be to get the best compromise between stiffness x level of power.
Mark, why are phase shift after resonance?
What is lead lag compensation? I'm getting some results with my feedback coils, + - 25db reduction in the main resonance (550Hz) but only up to 1.5kHz. Above this frequency, the feedback sum rather than subtract. This is phase shift the blame?
Ciuens
Mark, why are phase shift after resonance?
What is lead lag compensation? I'm getting some results with my feedback coils, + - 25db reduction in the main resonance (550Hz) but only up to 1.5kHz. Above this frequency, the feedback sum rather than subtract. This is phase shift the blame?
Ciuens