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

[inspector77]

WOW, Congratulations Brian, amazing improvement!

[emidisc]

Sounding very very good to my ears... well done and please keep us posted

[Bahndahn]

Brilliant!! Great work Bryan, I'm inspired!

[studiorp]

Yes, I am agree with you , sounds very good, compliments !

[markrob]

Hey,

Really great job! I think you are well on your way. Do you have an estimate of the head sensitivity at 1 watt (in cm/sec)? As you stated, you are probably being very conservative in the power you are applying to the head using you program material. I'm sure can can push it a few db higher with no ill effect, but it would suck to burn out the head given the amount of time you put into the construction.

If you are interested, I can send you a paper that will show you how to measure the internal coil temperature of your drivers using the tempco of the copper wire in a bridge arrangement in real time. I used it to get an idea of how much difference using ferro-fluid in the gap made with the drivers I used. Its very similar to the method Neumann uses to protect the SX drivers. Just pm me with your email.

Mark

[flozki]

nice one. i gonna drop in
a 5cm/s vinylike testtone record if you mail me your adress.
it wont make it for under the tree.
but would be great if you play back that.for 10seconds and then then with same setting you add your groove scribe recording in same file.
and make that uncompressed file available.then its possible to compare.

and if you put a 500mA slowblow in series for a quick test. just go a little bit under the point where it starts lightning in the dark.you wont destroy your drivers and. then you are fine.
if you dont trust you can do it first with 315mA SB fuse. that definitely wont kill the drivers.
should be quite loud.

[EpicenterBryan]

Hey inspector77, emidisc, Bahndahn and studiorp : Thanks for the nice comments!

And to markrob Ill send you a PM regarding the temperature measurement paper. I would love to take a look at that.

I do have a total newbie question for you though. Am I to measure the distance between the two extreme valley locations for one cycle on the 1K groove then multiply by 1000 to get seconds? There is a graticule in my scope but the lines and the numbers are very hard to read. It's a Spencer. There are long lines, and short ones between them but I'm not sure what the scale is. Here is a picture. I'm not sure if the scale shows up. Can you determine anything from this? If not, do you have a suggestion on how I can measure it? Is there a fine scale I can buy and lay on the record to make the measurement with the scope?

IMG_3161.JPG

[EpicenterBryan]

would be great if you play back that.for 10seconds and then then with same setting you add your groove scribe recording in same file. and make that uncompressed file available.then its possible to compare.

Sure, I would be interested in doing that. I'll PM you my address. You should already have it, I received 2 of your Caruso boards recently.

and if you put a 500mA slowblow in series for a quick test. just go a little bit under the point where it starts lightning in the dark.you wont destroy your drivers and. then you are fine.

Great idea. I don't think I have ever watched a fuse glow before. There is a first time for everything!

Bryan

[studiorp]

Hey Bryan, have you thought to build a little series to sell inside this forum ?
I think that here there is many people that want have a little stereo head mounted on own lathe .

[Jccc]

really awesome results. i believe adding a fuse to the head will protect the head from blowing out and you can even push the audio signal just a tad bit more to get even better results the fuse will blow before the coils burn up and then you can actually see how far you can push the audio signal before distortion.

[EpicenterBryan]

really awesome results. i believe adding a fuse to the head will protect the head from blowing out and you can even push the audio signal just a tad bit more to get even better results the fuse will blow before the coils burn up and then you can actually see how far you can push the audio signal before distortion.

Thanks Jccc.

I'm on the way to the electronics store to get some fuses.
Thinking back, and after calculating power, I did have one situation when setting things up I forgot that the power amp was still on and I saw over 7 volts for a few seconds until I got the amp shut off. That works out to over 6 watts. I checked the drivers and they did have a slight smell to them. Unfortunately I was not cutting at the time.

[IRF80]

Brian you are a legend! Well done and thanks for the vids, I love the input from you, Mark and Flo.

I need to get back on my head but time and money (more time) are limited.

[emidisc]

Bryan
Regarding the calibration of your microscope perhaps placing a a standard vinyl disk (of the same rpm )under the scope would give you a reasonable idea of the divisions on your scope?

Emidisc

[opcode66]

You would have to know the depth of cut and lpi of the record to be able to use it to make comparisons to you scope.

[dimi751]

Hi Bryan,

Fantastic video ! Excellent result with this cutter head, I can't believe with such low watts these transducers you are using provide such results. I always think the bigger the watts the better vibration to stylus looks like this isn't the case with your diy design Great job Bryan and I also like this Track you playing

Dimi

[EpicenterBryan]

I thought I would go over some of the components today. It will need to be split across more than 1 post.

As you know, the drivers are surface transducers. The part number is SPK-TRANS-L. I got them from ABRA Electronics Inc. http://www.abra-electronics.com/ . A pair was about $50 including shipping. These have two non threaded mounting holes unlike some drivers that look similar so if you get them somewhere else look closely at how you can mount them.

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The drivers have a threaded M5 hole in the center. It was a bit troublesome finding a screw that wasn’t steel or stainless especially in a small town. Ideally, I wanted aluminum but nylon would also work from a weight standpoint. I did find that a US 10-32 thread was close enough to work so that may be an option for some people. I found some nylon ones at True Value Hardware. Eventually I ordered M5 nylon screws and some other things that would work.

Something I found that would work are prop shaft adapters for model airplanes. These are available in several forms and diameters. One uses a collet with either 3 or 4 grabbers, and another style had a hole and set screw. My thought was that it would make it possible to disconnect the push-rod to replace the driver. But the collet style with 4 fingers could be modified to be the stylus holder, push rod connection and torque tube.
If used on the driver, all need some extra threads cut, or the spacer would have to be used which increases the weight. Other mods could be done to cut the weight if desired but that’s more work.

The Aluminum button cap screws were nearly impossible to find. Ultimately I found a windshield mounting kit for a motor cycle on e-bay that had 6 of them! It was simple enough to drill a 1mm hole in the center for the push-rod. Then you need to cut it short so there are only 3-4 threads left. Here is a shot of the options.

Driver Screw Options.jpg

My first attempt at a stylus holder / push rod connector once I decided to use solid 1mm push-rods worked well and was very light but took some doing. I ended up buying a rotary stage and 3 point chuck to hold and turn it to specific angles. I started with a threaded aluminum stand off with 6 sides. I milled a section of it into 8 sides, each face 45 degrees from the other. Then I was able to drill the stylus hole near the front, and the two push-rod holes 45 degrees each direction relative to the stylus hole and cut it to length leaving enough threaded area at each end for the set screw and threaded push rod at the rear. I also offset the two push-rod holes by 1mm, and changed the driver mount so the drivers were also offset by 1mm to ease instillation.

Alunimum holder.jpg

The first attempt used 1mm solid carbon fiber push rods. The swarf on the first cut looked funny, and there was an odd dust in all the grooves although everything looked aligned. The test response was really bad too.

Then I found a web page that had a really good graphic that depicted the required stylus movement for a 45/45 head and I had the eureka moment. I’ll go into that graphic in another post because it was that important for it to sink in. Anyway, I did a mock up of a v spring, and a torque tube connected to it, screwed the ends of the spring into the edge of a table and played with it. Sure enough, that’s the way it had to work to keep the cutting stylus exactly perpendicular to the disc through all movement of the tube. I also realized that some spring in the pushrods is desirable especially at the torque tube connection. So I took the head apart and scrapped the guts since it was all glued.

So the next stylus holder idea really needed to incorporate a new torque tube and had to incorporate the piano wire connection at the rear as well. I’ll go into details on all this later, but let’s talk about the stylus holder / push rod connection first. What I used was carbon fiber tubing from Midwest Products – Stock # 5734 – 5.3mm OD x 3.4mm ID. A few things to note: Carbon fiber is hard to cut. I used a diamond Dremel cutoff tool from Home Depot. Also, I used a respirator when drilling and cutting the carbon fiber. They say to wear gloves but I didn’t.

Now how to hold the rod at the correct angles while drilling? I tried several things and failed. One thing I did that worked OK was to 3D print a 2 piece jig that clamped around the rod. You will have to look close at the picture, but the big end would get clamped in a vice to drill the stylus hole. Then notice the smaller square on the other end of the jig? I would clamp that end to get 45 degrees on either side of the stylus hole for the push rod connection. Now for the kicker. Carbon fiber is tough to drill. All my 1mm drill bits were standard HSS and this stuff will dull them with just a few uses. The real issue is at times you could be drilling where the fibers are especially hard and a bit this small has a tendency to drift. When using this jig you can’t see that the bit has drifted so although I ended up with one that was pretty good, I just wasn’t happy. So I ended up using the rotary stage and supporting the end that I was drilling. One hole still wouldn’t drill exactly where I wanted and I had to nick a slot in the tube with the Dremel tool to get it started. I also had the exit hole delaminate the fiber on several attempts. Perhaps it was a dull bit?

Carbon Drill Jig.jpg

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[EpicenterBryan]

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The next trick was coming up with a way to use a set screw for the stylus. I tried filling the end of the tube with JB weld, then drilling and taping. That just wouldn’t work – not enough material left. So I ended up super gluing a nylon nut on the end (my aluminum ones hadn’t arrived yet).

Now for the torque tube extension and piano wire. What I used was Midwest Products – carbon fiber Stock #5720 – 3.2mm OD x 1.5mm ID tubing. The wire came from the inside core of a guitar string and turned out to be 0.45mm (0.017”). I just ran it through the tube, bent one end over and inserted and glued to the stylus holder.

IMG_3111.JPG

Next up - the V spring. What I used was 1mm (0.004”) stainless steel shim stock. This is the same as what you find in a standard feeler gauge set, so you could sacrifice a set and pick what ever one you think will work for you. I cut strips of it using a heavy duty paper cutter. Then, I took a piece of paper and taped two pieces of the shim stock to the paper to get a 90 degree angle and spot welded the intersection in several spots. Then cut it to the size that fit the body. Drilling it was trickier than I thought it would be and I really distorted my first attempt. Be sure to clamp it down when drilling because it will slice you if the bit grabs and it spins.

V-Spring welding.jpg

V-Spring Weld.JPG

The V spring was attached to the body at 2 points, and the torque tube goes through the spring. A sort segment of 5.2mm OD x 3.4mm ID was added to the end of the torque tube to provide more surface area to glue the tube to the spring.. To secure the piano wire at the end of the head body I used a Du-Bro catalog 137 1/6th” cullet, and washer and glued it to the body.

IMG_3119.JPG

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[EpicenterBryan]

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The push rods I ended up using were music wire stock #497 from KS Metals – 1mm diameter. As an afterthought I added a short segment of 3.2mm OD x 1.5mm ID tubing in the center of each pushrod to encourage flex to occur at either the driver or the torque tube and not in the center. I was worried about a standing wave developing and causing a drop in response here or there. I don’t know if it was needed but I’m glad I did it. But I had already glued everything, so I took a razor blade and split the tube in half - and glued each half one at a time to the rods.

Link Brace.jpg

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The last detail is that I used some Sorbathane here and there that I bought on E-bay. I cut some strips and put some between the V spring and body, and around the piano wire. I also added 4 pieces on the springs on both drivers. And I put some here and there inside the body. The 2 pieces near the spring are also touching the side of the spring.

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There are several things I would like to do including making it a bit smaller so I can get closer to the center of a disc. I would also like to make the left rear more open so I can get a swarf pickup tube in there. But I’m happy with this one so I’m just going to start on a new one – most likely with an aluminum body. But I also want to mess around with some options for feedback. The project list never ends. But the days start getting longer starting today!!!

[EpicenterBryan]

Hey Bryan, have you thought to build a little series to sell inside this forum ?

No, but my hope was to provide enough details that if a guy is handy he would be able to make one too. Only if it worked that is. The most recent update has part numbers so it should help.

[EpicenterBryan]

Brian you are a legend! Well done and thanks for the vids, I love the input from you, Mark and Flo.

I am only a legend in my own mind. And don't forget Todds great inputs too!