JE-1D Version 356

[jjwharris]

I've made another attempt a Presto Clone.

I run three machines, so made them in sets of three. The first two ended up with a resonant frequency of 7khz, this last one has hit 10khz...I'm still trying to figure out exactly why. I think it could be the tensioning of my springs, but needles to say, I'm very happy with the results. I might need to upgrade my amplifiers as I am struggling to power the heads. I've attached a sample and some photos.

I managed to make a jig to bend the omega style springs, but ended up with a resonant frequency down at 4-5khz, so as a last ditch attempt I tried straight piano wire. It seems to have worked in my favor. I can only imagine it's to do with the neodymium magnets

It looks like it goes up to 20kHz (although my playback turntable leaves something to be desired, I've had the test record (thats the red response) tested on a friends turntable and it came out flat. This is all tested with my embossing needles, so it's not a cut record.

Big thanks to Fela for helping with the dimensions, and opcode's presto assembly videos on youtube were a massive help. Also the multiple threads about winding coils on here.

(Swallowtail is a BJM track, here; https://www.youtube.com/watch?v=WqP_U6YuiTU which is also the source I used to cut the record)

It's all a bit messy, but I need to get these machines back up and running and into business.

It seems like my amplifier might be the bottle neck at the moment, it's 100w and I don't think it's quite cutting it, I've got plenty of headroom for current, and no audible distortion, so it would be nice to push the volume a bit higher.

[Dogtemple]

nice work, sounds good too. I would be very happy with that.

after making a stereo head i'll probably have a go at making one of these. love the idea of a rugged mono head

[Fela Borbone]

Congratulations!
Well done!

[jjwharris]

Interestingly enough, the other two heads ended up with a resonance around 7khz, they also have a much higher cutting level.

I took the first one apart and it looks like the knife edge was out of alignment, adding stiffness to the system. I think I'm happier with the lower resonance as even though the 16khz+ range is harder to achieve, I can't hear it because I'm old and more volume is a happy tradeoff...

I'll try get another sample up when it's all dialled in.

[Dogtemple]

Are you making the knife edge for this? Presumably you make all the parts from scratch but just wondering as the edge may be from a pre existing part

[jjwharris]

The majority of the tricky parts are laser cut steel. The rest of them are essentially just aluminium stock - the error I made early in was thinking that I would just mill everything into the correct shape. The aluminium parts are 15*10mm, 10*10mm and 3*50mm stock. It makes the whole process a lot easier.

I have a DRO on my mill, but it's poorly mounted, and can often mis-register. Todd mentions the Presto heads were somewhat inaccurate, I kind of took that to heart and ran with it, so I ended up printing and gluing templates to the aluminium stock and used that as a guide.

There are a few changes I would make in future.

The pole pieces are two pieces of 3mm steel plate, I've joined them with a quick arc weld - I'd love to track down a spot welder if I were to make them again. I would also design a slot in them to move/rotate the pole pieces into place - there's a tiny airgap between the armature and pole pieces which was my biggest issue with my last build.

The armature is just a blank T shape, the groove is made with a router bit tilted to 45 degrees in my mill. The stylus hole is made on the lathe, then the piece is rotated 90 degrees and a 2.5mm hole is made to accept the tip of the stylus mounting screw, I pre-drill the M4 screw which holds the dampening. (So pre-drill a 2.5mm hole, not all the way through, but leaving enough at one side to accept a M2 thread. Then that threaded rod is held in the lathe and there's a couple of quick welds to attach it.

The knife edge is just a blank laser cut rectangle, Initially I made them to 60 degrees, and made them before I fixed them into the aluminium. However once I assembled the heads, I noticed from reference photos the edge seems closer to 45, and that the knife edge wasnt quite holding the armature parallel with the pole pieces. It worked out better remilling the knife edge while mounted in the aluminium.

This entire process makes me want to try and make a Presto/Grampian hybrid as I'm wondering if the knife edge and springs could be replaced with a torsion rod set up, while keeping the pole pieces and coils.

It would make the entire construction much more simple, and hopefully would create a cutting head that is more consistent.

(That said, these three heads sound very very similar with very minimal EQ)

[markrob]

Hi,

Really nice job! I know you've been on this for quite awhile, but all of the hard work has paid off!

Mark

[jjwharris]

Thanks Mark!

As always your help and advice has helped me massively!

I've got a couple of other projects I need to look into, but I would like to take the time to build more of these, perhaps with hand-wound coils and aluminium formers.

[jjwharris]

This is another cut I've done... I'm really happy with it. I've got a grado red2 cartridge on the way, so hopefully that can illuminate more of what's going on and maybe give me the 'true' 10khz+ response, as I'm under the impression that my current cartridge starts falling at that upper range.

I was having issues with EQing the head to pink noise - I ended up EQing this head to a song which I also had on a pressed record. This seems to have given me the best results...

https://soundcloud.com/johnny_electric_nz/hans-pucket-i-dont-know-what-to-get-you-for-christmas-dec-2021-embossed-lathe-cut

[Dogtemple]

I’ve not been able to see a lot of the other diy project outcomes due to all the broken links in other threads but this has got to be up there at the top/one of the best diy efforts. It’s really inspiring. Well done.

[jjwharris]

I was hoping to start selling these at the end of this month - Unfortunately I've put 5 models together and they all deviate from where I want them to be.

I'm currently redesigning some parts (and looking a bit more closely at magnetic fields) Most of this was manually milled, but I'm going to be getting most of the aluminium parts CNC'd and hopefully end of Feb I should be sending out some test units. If anyone is interested send me a DM.

[grooveguy]

That embossing from December sounds remarkable. What stylus and blank was that? Particulars, please. Bravo!

[jjwharris]

Hey grooveguy!

They're 1.5mm poylcarb blanks from PSP, in NZ (The same Peter King used!)

And I'm making the stylus myself, based from eposlabs work with .5mm tungsten tips, though the geometry is a little different - I was intending to have available for sale at the end of Feb, but time has got away on me!

I might try get something out this week.

The packaging is nearly done and I've been road testing them - I started at 65-75g embossing weight and over 14 hours cutting time / (200+ 7" sides?) that weight had to be increased, with the extra weight the bottom end needs to be attenuated a bit.

That said, even after 14 hours the noise floor didn't increase much, but the attenuation of the bottom end mean there was essentially a volume drop.

I've noticed they do have a very slight 'run in' period. After a few sides the top end seems to extend and the surface noise decreases.

I do have a theory that I may be able to hone the cutting edge a little more.

[grooveguy]

Good info, thanks jjw! I have one of Epos' styli that I just haven't had the time to evaluate yet, but am getting to the point of being able to devote more effort to disc recording and would certainly love to try yours as well. A good number of you embosser-guys have shown very promising results, despite 1947 research saying that embossing can never deliver anything like the quality I heard in your sample (https://www.dropbox.com/s/ayy9vtn09mrxrs5/Embossing%20at%20High%20Frequencies.pdf?dl=0). My one attempt was onto polycarbonate with a sapphire microgroove playback point at a 20 degree lean. Response was good, but the level was a good 8dB below a real cut into a lacquer. Do let me know if I can purchase one of your styli, and keep up the research!

[jjwharris]

I've sent you a PM!

I think the results I've had with mono cutting heads have certainly been better and more manageable than with the stereo builds I've done. My theory is that the extra stiffness of the assembly does lend itself well to the extra weight required for embossing.

It does make me wonder if I'm unknowingly tweaking things further away from the original Presto design because of the neodymium magnets and more powerful amplifiers available today.

I've since purchased a crosley style turntable to try and pull back my levels - while the December embossing played fine on my turntable with anti-skate it did have a tough time tracking on the Crosley, so there certainly is a physical limitation of the volume an embossed recording can be tracked at.

[jjwharris]

It's been awhile...

I'm heading into production with this one - Hoping to have it for sale along with the stylus' soon.

I've got cases on the way and the majority of parts are now all CNC cut.

Only just got the final-ish version together tonight, so haven't had much of a play with the EQ - this is recorded with a fairly basic iRIAA / Set for the previous head. The hope is this set of heads all sound nearly identical.

One sample is the pressed record, the other is the embossed lathe cut.

There was a little issue with the magnet/dampener clamp, but that will be fixed next week hopefully. The actual ring dampener also will follow the Presto design.

I think I'll keep the green damper, as a nod to Soundscriber blanks.

[grooveguy]

Hey, JJW, most commendable progress on this. Thanks for including the MP3 of the source track for comparison; your lathe cut sounds quite promising indeed. I was expecting more of a difference between the cut and the embossing, your embossing stylus geometry must be just about optimum. The embossing even sounds a bit brighter. Can you give us the TT speed and the recording diameter? Just wondering what groove velocity gave you this good result. It also looks like your stylus must be pretty near vertical, too; can you confirm this and let us know what lubricant and heat you may have used? I'm anxious to get hold of one of those styli!

[jjwharris]

Hi GG!

I embossed the track on a 10" record at 45 rpm - the pressed track is at 33rpm.

I would say that the embossed track was closer to the 9" mark, whereas the pressed record is close to the 11" (second track on the album)

I use bulk shellite as the lubricant (https://www.bunnings.co.nz/diggers-1l-shellite_p0309654) which I believe is a lighter fluid. That said, I have tried filling a zippo lighter with Shellite before, and it evaporates much more quickly than brand name 'Zippo' fluid.

The stylus is quite far from vertical, and the tip is greater than 90 degrees.

I found that when the tip was ground to 90 degrees, the record was more difficult to track, with no audible improvements.

The embossing angle is around 76°, that's 'leaning back' from 90° vertical. I experimented with having the stylus close to vertical but there was increased surface noise, the angle is very similar to Peter King's embossing angle.

I do need some testers for the stylus - I was hoping to get the packaging done by Feb this year, but it was a folded ordeal and I never really got it right. The new packaging is smaller, and more robust (and the stylus click into place!)

298140423_581322096703290_1817066039428914521_n.jpg

[grooveguy]

Okay, thanks for all that; makes good sense. I'm not sure I understand how your springs provide any flex at all without the omega bend, it seems like they'd be compressing rather than flexing. But the implied increased stiffness probably accounts for the HF response extended past that 7-8kHz point you mentioned before. Do please keep me in mind for a stylus when you begin selling them. -Jim

[jjwharris]

My next design will be a similar armature and pole piece design, but I'm toying with the idea of designing the armature to allow for torsional flex, this should mean it's easier to set up and there are less parts to fail. One of the challenges will be fitting it into the existing case footprint, as the minimum order I could get was 100 cases.

I'm more than happy to send you a head to loan/test along with some stylus - There aren't many people cutting or embossing with mono cutting heads in New Zealand, let alone cutting lacquer.

It's possible this design is more suited to embossing than cutting. I'm under the impression the tradeoff of straight vs omega springs is less volume for an extended top end/flatter EQ curve.

This would work in favor of embossing, where volume/groove excursion is the limitation, as if the volume is too loud, the record will skip. Whereas if cutting a groove the extra volume can be utilised.