Project "Groove Scribe"- A DYI stereo 45/45 head.

[sakuszi]

possible that others have achieved the desired effect, but I gave it up immediately with these transducters . I bought MM6 and is now very well

[EpicenterBryan]

This is not good news, but easy to solder the cable, already did that, good links are telephone copper, very flexible.

Yes - not good news at all. Re-connection of the black wire went fine. But it looks like I overheated the solder connection for the red wire when I decided to replace the connection. Now the coil no longer connects to the solder pad and it can not be fixed - and I have tried everything... even under a microscope. But that's not a really bad thing. In disassembly, I have found several issues and will learn from them.

First, I removed the entire right driver down to the stylus holder. Then I discovered that the left driver "Super Glue" (CA) connection to the stylus holder failed. That may have failed when I had to slightly bend that connection as noted in a prior post. But it gets worse... I also discovered that the "Super Glue" (CA) connection between the stylus holder and the torque tube (an aluminum cap screw) also failed, which allowed the stylus to potentially go out of perpendicular with the surface of the disc - even though the V spring at the end of the torque tube is designed to prevent that.

The lesson learned here is to make the stylus holder / connection points to push rods / and torque tube one piece or use a glue other than "Super Glue" (CA) to join those parts.

Also in Postmortem disassembly I believe the final segment of 1mm Phosphorus-Copper is too stiff. I'll need to re-evaluate that. So all is not lost other than having to start over with new drivers and internal guts - but things were learned and that's the most important part of the process. The end result I hoped to achieve long ago - but if it were easy I would not have learned as much. And although this process has had ups and downs, I hope readers have learned something as we all go through the process together. We are all in the same boat.

These drivers seem to have had the greatest impact in the development of a successful "DIY" feedback head that we've seen so far.
Look at Cuiens and his ZEZ, good results using a modified version of this driver and then quite amazing results with it's smaller sibling.

I'm sure his work was informed by this thread to some extent.
The work here shouldn't be dismissed, it is valuable and significant.

Thanks for the comment Sillitoe. Yes, the smaller version that Cuiens has been messing with do look more promising. They too need to be modified, so are similar in that respect. And the smaller size will naturally mean that the head can be smaller - getting more record time per side. As far as this thread impacting Cuiens thread and vise-versa... Absolutely both ways! We have both shared things publicly. That's the great thing about LatheTrolls! We all benefit from sharing what works, and what doesn't. This is an awesome place to hang out, and a great batch of people. We should do a week long party this summer...

How about my place in Eugene, Oregon? Who is in?

Bryan

[EpicenterBryan]

Here is the update:

I started prepping 2 new drivers. This is the 3rd set I have purchased over this project from the same supplier. All 4 of the previous drivers had aluminum coil formers. In this batch one has a Mylar coil former.

IMG_4532.JPG

It turned out I was able to salvage one of the drivers from groove scribe so I'll go ahead and build up the Mylar unit as a spare, but will use the aluminum one to match the other driver. I was able to salvage the driver by heating the push rod with a mini torch and pulling it out in 2 segments with needle nose pliers. And I didn't even damage the feedback coil! It still shows the correct resistance! Yay for the home team! Then I ran a 2mm drill bit through the center to clear out debris.

IMG_4533.JPG

Now for the interesting discussion. I was puzzled by the lack of channel separation in the actual test cut. I picked that music because it had interesting left and right audio that was in the higher frequency range so I didn't have to worry too much about vertical movement without messing with the mix.

In a quick E-mail exchange with MarkRob a term I didn't recognize "VTA" was mentioned as a possible issue. Mark had an interesting comment that I'm sure he will be OK with me sharing.

Keep in mind the stereo separation comes from the vertical motion of the head (L-R). The fact that it was mostly mono indicates that the vector sum of the two drivers is not quite happening as you would expect. I wouldn’t have expected that given your design. Maybe it’s a VTA issue. However, my understanding is that this would affect the distortion and high freq response of the vertical channel. So you might have good separation at low frequencies and much reduced at higher.

I've spent several days reading about it and I do think that is the source of reduced channel separation. It has to do with geometry and it is related to the vertical movements which represent the difference between the left and right channels (L-R). Those vertical movements are the heart and sole of stereo channel separation and why we are even messing with this!

And I discovered a tread right here on Lathe Trolls that I hadn't read that discusses cutting angles as it relates to VTA! You dudes are so sharp!
Here is the thread:
http://lathetrolls.com/viewtopic.php?f=1&t=6369&hilit=vta


Up until now, my only cutting has been with either a Presto or Grampian mono head using the associated long or short shank stylus. These heads are mono, and only do lateral movements. I have built my home brew stereo heads so they could use the same stylus. And at the same 0 degree cutting angle relative to the disc surface. The head is 90 degrees to the lathe mount, the torque tube is parallel to the head body, the cutting stylus is perpendicular to both the torque tube and the disc to be cut.

There lies the decrease of stereo separation in my DIY head, and possibly in yours. Perhaps not in yours if you are smarter than I am!

My first thought was to make a 15 degree shim to change the angle of my head / torque tube / stylus to go backwards like shown below:

IMG_4536.JPG

Then the stylus would have the 15 degree negative back angle my lathe can not adjust to. But I have no clue if the cutting stylus design could possibly "snow plow" into the blank material ...

So I'm going to need to look into things like head angle, torque tube angle relative to the head, and angle of the stylus mounting related to the torque tube. And ultimately if a simple Presto style stylus could even be used assuming it could be mounted correctly such that the other variables are accounted for in a DIY head.

I think it is more involved. I think the geometry of the stylus movement needs to be such that that the stylus remain perpendicular to the disc, but the arc relating to stylus movement appears as if the angle of the stylus moves through an arc such that the angle is 15 degrees from the origin of rotation.

My head hurts.

Bryan

[Snug Music]

Here is the update:

Now for the interesting discussion. I was puzzled by the lack of channel separation in the actual test cut. I picked that music because it had interesting left and right audio that was in the higher frequency range so I didn't have to worry too much about vertical movement without messing with the mix.

In a quick E-mail exchange with MarkRob a term I didn't recognize "VTA" was mentioned as a possible issue. Mark had an interesting comment that I'm sure he will be OK with me sharing.
Keep in mind the stereo separation comes from the vertical motion of the head (L-R). The fact that it was mostly mono indicates that the vector sum of the two drivers is not quite happening as you would expect. I wouldn’t have expected that given your design. Maybe it’s a VTA issue. However, my understanding is that this would affect the distortion and high freq response of the vertical channel. So you might have good separation at low frequencies and much reduced at higher.

Hey Bryan, yes .. I also read this post. The 15 degrees are there really influential on the channel separation. I had the Stylus also attached only at 90 degrees, but then noticed that the stereo field is in mono. After I changed it and the stylus, the movement made in the return angle came when recording the stereo field for retribution. The geometry has influence on the stereo field really huge! I can sympathize with you properly, I felt the same way.
I have also headache and was depleted.
Rock on bryan, you can do it !!!

Best regards
Scotty

[EpicenterBryan]

The 15 degrees are there really influential on the channel separation. I had the Stylus also attached only at 90 degrees, but then noticed that the stereo field is in mono.

I ran across this photo of the Souri head and noticed the angle of the stylus. I rotated it to see what that angle is. Guess what? It's 15 degrees...

143339.jpg

15 degrees.jpg

I'm not sure it's that simple though.

Bryan

[Snug Music]

ortofon.jpg

I ran across this photo of the Souri head and noticed the angle of the stylus. I rotated it to see what that angle is. Guess what? It's 15 degrees...
I'm not sure it's that simple though.
Bryan

YES! are 15 degrees! Saw this photo also.
So my stylus is also like that of Souris Head hubcaps ... lol ...
But somehow logical, I work a lot as a DJ and I have several systems such as Ortofon Good, it's the needles have a back angle. Previously I have since never thought it over.

best regards
Scotty

[EpicenterBryan]

Here is the update for tonight.

I've got two new drivers in the works. These should be ready to install push rods with feedback wires and get coated in another day or two.

IMG_4538.JPG

I'm still looking into the possible VTA issue, so that will have to wait. But, there were also lessons learned from the past that didn't get fully integrated into the most recent attempt. Did they get learned? Perhaps not if similar errors were made again!

These drivers and this head configuration is missing a key element. An element I thought about and made provisions for when I started working on the aluminum body. But only 1/2 of what is needed as it turned out. And it wasn't implemented because I'm either forgetful, or didn't learn a lesson I should have learned.

I mentioned in a previous post about the brass standoffs I installed in the head body and that I was going to make a V-spring out of very small diameter phosphor bronze tied to the push rod at the driver. I didn't do anything about that and in my rush to do a test cut with what I had working at the time we heard the result. Not so good on channel separation!

Now that I'm back tracking and trying to learn from what went wrong (besides messing up the head), I realize that there was no centralizing spring (or diaphragm) at the other end of the driver to insure it only goes in and out exactly centered, which translated to exactly 45 degrees in the 45/45 system.

My first thought before totally taking apart the head, was to scab in an extra centralizing diaphragm like a NinjaFlax end cap demonstrated in this after the fact photo. The idea was to make something like this that could go over the magnet, but be cut 1/2 way through the center (not like shown which is solid) and the feedback wires could be brought out before heat welding the NinjaFlex cap closed and then glued to the push rod output from the driver. It was a good idea, but would be at best a band-aid.

IMG_4537.JPG

So I decided to go back to what should have been done in the first place. That meant I had to remove everything from the head and drill two holes for additional stand off points on each side like this. Here you now see 4 connection points for an X centralizing spring for each driver:

IMG_4539.JPG

I had to go with females rather than male stand offs since there was little room in the center.
Although I have not decided yet on whether I'm going to go with NinjaFlex X springs, or a different material for the X springs, you can get the idea from one of my earlier posts about the olive can driver / feedback idea that also used an X spring as seen below:

IMG_4542.JPG

All this stuff is connected. We can learn from every failure, and every success!

Bryan

[sakuszi]

in direct metal mastering knife is positioned at an angle of 90 degrees to the plate, and the channel separation is excellent. I think that 15 degrees angle of the knife is the reason why the hardness of the material, so it is a few degrees to several degrees, but this has nothing to do with separation of channels [at least in a small dependence].
For the separation channels L R corresponds mainly, the difference brought stereo signals out of phase L R, it is in opposite phases. Too much opposed phase LR is tiring to the ear, the ear, not nice to listen to music, it is better in phases mono. You agree Brayan?

[The Shank]

in direct metal mastering knife is positioned at an angle of 90 degrees to the plate

wrong.



1st post here, congratulations Bryan for all your progress.

[Snug Music]

in direct metal mastering knife is positioned at an angle of 90 degrees to the plate, and the channel separation is excellent. I think that 15 degrees angle of the knife is the reason why the hardness of the material, so it is a few degrees to several degrees, but this has nothing to do with separation of channels

hey Sakuszi .. which is not quite true what you say.
DMM is not at 90 degrees !!!
I have an old (not yet repaired!) Neumann 68 and had (as Diepholz is the same for me around the corner! (PALAS)) seen as cut. And this will NOT held at a 90 degree angle!
Best regards
Scotty

[sakuszi]

in direct metal mastering knife is positioned at an angle of 90 degrees to the plate

wrong.



1st post here, congratulations Bryan for all your progress.

What wrong? a knife diamond in the DMM is perpendicular to the plate is equal to 90 degrees to the copper plate

[sakuszi]

in direct metal mastering knife is positioned at an angle of 90 degrees to the plate, and the channel separation is excellent. I think that 15 degrees angle of the knife is the reason why the hardness of the material, so it is a few degrees to several degrees, but this has nothing to do with separation of channels

hey Sakuszi .. which is not quite true what you say.
DMM is not at 90 degrees !!!
I have an old (not yet repaired!) Neumann 68 and had (as Diepholz is the same for me around the corner! (PALAS)) seen as cut. And this will NOT held at a 90 degree angle!
Best regards
Scotty

SM , do you have any photos ?

[sakuszi]

you have to ask them, maybe I'm wrong ... http://trade.mar.cx/DE1047495

[Snug Music]

you have to ask them, maybe I'm wrong ... http://trade.mar.cx/DE1047495

I found this one, check it out:

https://books.google.de/books?id=riMJ5Uo8fZgC&pg=PA393&lpg=PA393&dq=dmm+cutting+stylus+angle&source=bl&ots=Y6_hH0mcA0&sig=JlcfOxRuI2tWowx5mW1H1gXXNjs&hl=de&sa=X&ved=0ahUKEwiXmfm5l8_LAhUKJ5oKHTaNBbEQ6AEILjAB#v=onepage&q=dmm%20cutting%20stylus%20angle&f=false


Scotty

[The Shank]

you have to ask them, maybe I'm wrong ... http://trade.mar.cx/DE1047495

Because I know it and I've seen it, why should I ask?

[Snug Music]

you have to ask them, maybe I'm wrong ... http://trade.mar.cx/DE1047495

Because I know it and I've seen it, why should I ask?

hey Steven I am fairly in your opinion, I see the same!


Regards Scotty
Yay-Media / Snug Music

[sakuszi]

I read here on the forum that the knife perpendicular to the plate in the DMM, but according to this description is 5 degrees, it is best to ask these people what they cut the DMM for example GZ records etc

[Sillitoe]

You could also ask The Shank!
http://www.myshank.com/modules/blockblog/blockblog-post.php?post_id=4

[sakuszi]

beautiful image DMM GZ VINYL knife! THANKS
I suggested this patent

[EpicenterBryan]

Back to the drawing board.

Looks like I'll have to move the x spring support points as far toward the center of the drivers as I can.
These ninja flex springs had to be shaped this way for the screws at the top of the head to be inserted.
Also notice in the bottom photo how little space there is to get the feedback wires out.

IMG_4544.JPG

IMG_4545.JPG

This one worked better but I couldn't fit it in because the two Xs interfered with each other at the top of the head.

X spring.jpg

Rats!