"Brother Singer" Cutterhead

[sifis1983]

Hi,

I try the plastic pieces for my coils. I made cone shape, as mark suggests me. I just glue them with super glue in the center of the coil former.
It was difficult to attach them without any distortion but I made it.

coil1.jpg

cutterhead1.jpg

The problem now, is to attach the brass rods to the torque tube. A sine wave is good enough only from then transducer, but when I attach them to the torque tube I can listen distortion. I don't know if this happening because of the bad connention to the tube or not the accuracy of 45 degrees of my design. Maybe both.

Could you suggest a more precise method of the connection on the torque tube???

Anyway, I try the cutterhead to see what happens.
This is the result:

CUT white noise FAB12 2nd Try.mp3

This is a cut with sapphire stylus, no heat and no suction.

The signal chain is wav file - 2 FAB fitler in series (trying to make flat the response of my head) - Izotope Imager (to make mono bass under 150Hz) and a high frequency limiter after 10kHz.

You can listen now that finally that I have high frequency response till 14k approximately.
This is makes me happy for now,
BUT, there is a lot of harmonic distortion in the "tones" part of the audio. I believe this is because of my bad connection to the torque tube.
Also, as you can listen there is a lot of wobble in this cut, because maybe of not enough torque of the Technics Sl100 mk2. I don't know if the 1,5Kg/cm is good enough for this application. I try to keep the downforce weight as low as I can, but this causes a lot of skips, because the grooves are too shallow.

Do you believe that I can achieve better results with technics turntable? Or should I try a turntable with more torque? Numark TTX for example?
Is the downforce weight of cutterhead matters to avoid this terrible wobbles? The blanks are 1mm thick. Maybe I should try 2mm blanks for better contact on the platter.

Another query: Is the swarf affects the distortion of the signal?


Also, I must say that I have no dBmeter to measure the level of this cut. The only thing I do, is to use my multimeter in the output of my amp.
The amp was set to full. (150W at 4Ohm).
In the white noise part there 13,5Volts approximately. In 1kHz it is 1Volt. If I go louder to the 1kHz, the harmonic distortion is bigger.

multimeter white noise.jpg

Is this 13,5 volts are too big signal?

I was thinking to try the small adafruit transducers (3W @ 4Ohm), as Ciuens try them in the past. As I learn from here, less mass means less power.

Anyway, next step is to built a more rigid lathe, to continue my tests. And of course, I will try another cutterhead with more precise design (especially in the connection of the brass rods to the tube). Also I have to start thinking about the suction part of my project.

Thanks for reading this,
Any comments or suggestions are welcome,

Happy Easter,
Sifis

[sifis1983]

Hi,

Finally, after too much experimentation, many cutterhead builts and many cuts, I ‘m very happy to announce that I have cut some music into plastic that sounds decent to my ears!


Firstly you will hear white noise, followed by 1kHz tones and then a part of music.

Here is the result of the cut:

Brother Singer CUT.mp3

The music source is a wav file of “James Brown - Payback”.


However, there are still some problems.
So, I will need help from you guys, so to measure things…


1st and major problem is that I have harmonic distortion in my 1kHz reference tones.

BS CUT Harmonic Distortion.png

As far as I know, harmonic distortion is created from bad connection of the drivers to the “torque tube” or just the “ringing” of the plastic enclosure of the head. Maybe I should try aluminum torque tube and pushrods.
Any comment on that?

38812340_1759447754103657_7125215693112344576_n.jpg

2nd. I have notice some “flutter” in the 1kHz tones. I’m cutting with a downforce weight at about 6-10gr in a standard platter of a Technics SL1200 MK2. I’m using 1mm cork as a mat and a record stabiliser 400gr, in the center of the blank disc. Should I try rubber mat maybe ? As far as I know the constant torque of the platter affects wow and flutter problems. I’ cutting on 2mm blank discs from Steven, which are heavy enough, in comparison with the 1.5mm commercial vinyl records. (However these blanks are great! )
Any suggestion on this ?

38736444_299566384128580_8409033588854489088_n.jpg

3rd. Stereo separation. I’ve attach 2 pics of the 1kHz tones (left + right) from Ozone 5 Imaging.
It seems that there is approximately 15dB difference...
You can see also the Vectorscope that there is a good portion of signal to each channel.
Do you believe is good enough for a dynamic head?

BS CUT Left channel 1kHz.png

BS CUT Right channel 1kHz.png

Any comments or suggestions are welcome.

Thanks in advance,
Sifis

[soeffingodly]

Well done sifis! Wish I had more technical/practical knowledge to assist you further. Keep at it!

[markrob]

Hi,

Looks like pretty nice results. 15 db is not too bad on separation. Are you sure you have your VTA (vertical tracking angle set properly)?

The harmonic distortion measurement seems wrong. I measured the second harmonic about -30dB below the fundamental which calculates to about 3% (not horrible). Have you measured your playback system using test record? Some of your problems may be due to tracking error in playback and/or misalignment of the path of the cutter. It would be good to get a feel for where your playback system sits.

Even order distortion (e.g. second) is not due to ringing. It is due to an asymmetrical transfer function of displacement of the stylus by the vs the force generated by the driver. There are a few reasons for that to happen (e.g. non-linaer spider spring). This will manifest by the shape of the positive peaks of a sine wave appearing different than the negative peaks. In the case of odd order distortion, the displacement is symmetrical, but not linear (think S curve shaped transfer function).

Also, it would be good to calibrate your cutting setup so that you know what drive level results in a recorded velocity of 5 cm/sec RMS lateral. Again a test record should help here. Flo produced a nice one recently.

As far as wow and flutter, the SL1200 is marginal for cutting as it was designed for playback and its torque rating is limited. Not much you can do here. See the recent thread on the VR external motor solution. There a a mod to increase torque on the 1200, but its not a panacea. A few years ago, I posted a software wow and flutter app. Not sure if anybody ever tried it as I never received any feedback on it. I am in process of updating it for my own use and will post once its available.

Mark

[sifis1983]

Hi,

Thanks for your kind words soeffingodly!

Thanks for your help once again, Mark.
Your comments always give me more “food” to read more and search many things about cutting records.

Well, no I don’t measure my playback system. Neither the VTA. (is the VTA could produce problems at stereo image or harmonic distortion?)
I will use some stereo expander plugin, to see if I can get better results.
Also, I can notice some problems in sibilance frequencies, but I’d never use a de-esser.
Do you believe a de-esser is necessary for dynamic heads ?

I’m going to buy a test record and make measurements of my playback system.
Should I just measure the 5cm/sec from test record and then try to “reach” this level at my cuts ?
Also, a lot of reading about reference levels… ( I can measure 0.250 Volts approximately in my 8ohm drivers, when playing the 1kHz sine wave - I don’t know if that means something…)


I test my signal to a digital oscilloscope plug-in, but I can’t notice any disorder to the shape of my sine wave. Neither on positive or negative peaks (see pic - I don’t know if this plug-in is reliable). I can’t understand what you mean about not linear displacement…

oscilloscpe sine wave.png

Very interesting thread the one with the external motor of Technics SL1200mk2. Really got me into reading again… Of course I would like to see and test your wow & flutter app!


Anyway, I will be back with more experiments and results very soon

Sifis

[markrob]

Hi,

Because the distortion is pretty low in value (< 3%), it can be hard to see the deviation in the shape of the sine wave on playback. That is why looking at a spectrum plot is better at determining the THD. Also, note that the playback spectrum has both even and odd order harmonics present, so the it is even harder to see the non-linearity via the wave shape. I found a link to a presentation that has a good explanation of how the transfer function affects the harmonic distortion spectral content.

http://www.pmillett.com/etf_sod.htm

The Wow and flutter meter I created is found in the old post:

https://www.lathetrolls.com/viewtopic.php?f=15&t=6002&hilit=wow+and+flutter+meter

[tragwag]

just an off hand observation - you need something to hold the disc to the platter while it's cutting.
a cheap solution is a 1/4" rubber grommet, push it over the center spindle on top of the blank.
a more permanent solution is the heavy weight/hold down from MyShank:
https://www.myshank.com/en/accueil/141-record-clamp.html

the 1200 will have some audible wow and flutter, but the clamp will help couple the disc

[sifis1983]

Hi,

tragwag, your suggestion about using rubber grommet is amazing! thanks for that!

Mark, I read about transfer function. Very interesting paper.
Also, I have tried the “wow&flutter” app. I can measure a 1005hz - 1006Hz in my 1kHz signals, that is pretty constant I think, but I can’t understand how to use the app further.


So, I found a test record and I made some measurements. Yes, there is harmonic distortion in my playback system. There is mostly the 2nd harmonic (even harmonic).
Below you can see in the analyzer, a sine wave from the test record in 5cm/sec lateral (right channel). The signal is coming from the outer grooves. The level of the signal in my recording process, is -3db (RMS).

Harmonic Distotion - Test Record - Outer Groove.png

My cut in previous post was at very low levels. I tried to cut “louder”, so to reach the level of the test record.
There is a lot of harmonic distortion when I’m doing this... Even if I reach -10dB approximately (RMS). (I didn’t try to reach -3dB as the test record … )

However I have to mention that I’m cutting at 33 1/3 - in a 5’’ blank.
So, inner groove distortion, affects my signal, for sure.

All I do is to give more gain, from my source (which is “operator” soft synth in Ableton), not the power amp. At the moment I use Inter M R300 so, I have about 100W amplification in my 8ohm drivers.

Sine wave result -10dB CUT.png

sine wave from 23RD CUT.mp3

So, I realise that my head, can’t cut a “normal” groove (without distortion) above a “level”.
I will need to do some more cuts to find that "level", today.
Also, I will cut at 45 speed in a 5’’ blank, so to see if there is a difference.
However, as far as I know, lathe cuts with dynamic heads, can't reach the level of "commercial records". Am I right here?




Another thing.
As I was trying to cut louder signals, my white noise part, is starting to have different response in some frequencies, along the time. I have tried many cuts to finally realise that the problem was coming from my drivers. I can hear the head, start resonating along the time. I believe that there is some weird response of the drivers when reach its limits. I use 0.5A fast fuses and I have blown some during tests. (luckily my drivers are still alive).

Do you believe this is a mechanical/electrical problem? Or it’s some weird response after too much processing in the digital source ? (fab filters - stereo imager - deesser).

Noise filtered along the time.mp3

Any comments, suggestions or advices are welcome.

Sifis

[Vice Fiori]

have a "easy" way to help you with the wow/flutter:
got a stepper motor, connect with a good driver and a signal generator pwm module (if you want stay out from arduino).
make a wood disk platter (mine i even make witth a suction)and a wood pully, put the motor in a distance and ad a 3mm rubber "chain" in motor/platter.
add a rubber matt on platter/wood platter to not slip and another on wood platter/blank disk to not slip too (if you´re not make a suction system) and corse, still use the rubber you use to fix the blank.
turn on the motor and calibrate the speed until you got a right speed on your optical rpm counter, than turn on the turntable and it will help to keep the torque speed..
it help me a lot and i have 0 wow/flutter to start at end of the disk (i need use more speed on motor as i use a hard suction system and it got me to use more torque.

resonance is a mess, i remember one time the head play and got the sound all over the head, go to the rest of the lathe and come back, sound like a whistle sometimes but not come to the sound, but i remember if i put my hands on the head in certain points it´s gone and i cant hear anymore, try to play a sound you can hear the resonances and try to put your hands on the top part of the head and see what happen. think thats why souri use that black liquid tape all over the head.

the better thing i find to calibrate the head sound is:

-record a pink noise without any eq and only a inverse iriaa, try to got a best volume without distortion (analyzer going to show you ressonances, but not distortion levels);
-record back this track on vinyl for your computer
-while you play your record you got back, turn off the invert riaa, got a EQ and start to fix everything to keep the flat as possible (to got this more easy i use GEQ modern from WAVES and make a sidechain in my pink noise generator to compare in same place and correct the best i can)
-as correct, use this eq on your output and turn on back the invert iriaa and record another pink noise.
-record back on computer and verify.
-use a mixer you have sure when your music vinyl got 0db, record a sound and start slowly put volume and playback at same time until you got 0db.

About you sounds, try to use a variety of, keep only in james brown going to try to come to the perfection, but not going to help you at all, because you going try and try keep the perfection for this particular sound, when you going to another can be different sometimes, try old music, rock, old house and new electronics, you´re going notice diferences. james for exemple have a real crispy and hot voice pre recording, and going to show you more distortion because of this. old electronic music going to show you smooth bass and high sibilances on vocals, rock going to show you how your mid´s going do play.

well i know it not going to help and maybe you´re doing that, just talk about my experience and what start working for me, i see too much people trying just one kind of music and genre, and when switch to another style start to have even more doubts about, because, remember when you in this vinyl place, people going to ast your services about a lots of things, from classical rock, to electronics, to lofi noisecore.

I stop with it for a while now so i try to help with i have, because i start to have problems that it´s better not discuss and a massive pain in almost entire body from all stress that i won.

[Vice Fiori]

about the digital thing, that time i want a more lite and small things to work and start to think on digital amps (i know, it´s trash compare a analog system), but you, mark or someone try to use? have a nice result? i think that time to use a tda 7498 100x2 amp

[sifis1983]

Hi,

It's been a long time since I have an update to my thread.
Until now, I 'm very happy with my cuts and "Brother Singer" lathe & cutterhead works fine for me & I love it.

I recently install to my lathe an oil dashpot, that I have made.
The reason I decide to use an oil dashpot is because I ruined my diamond stylus too fast, in comparison with others in this forum.
(I have cut only about 20 hours of music...)

As far as I know, the vertical movement in my lathe was uncertain (due to any tiny imperfect flatness of the rotating blank) and the whole suspension of my cutterhead was "flowing" without any damping mechanism.
Also, I have to mention that the last cut I've made, was a 3xLP bad recording session from a live show, that I realize later that the phase correlation was close at 0 (or sometimes -1), therefore I had big vertical movement - (of course I had the signal in mono under 200hz).
I suspect that's the reason that I ruin my diamond stylus fast. If someone knows more about phase correlation of a signal and its relationship with the vertical movement, I will be glad to hear it.

So, the goal is to achieve a longer lifetime in diamond stylus and of course a uniform depth of cut.

I make some cuts with this setup and it seems that the grooves are nice & clean, but I don't know if my dashpot helps.
Υou can check this small vid I have made to show the movement of the cutterhead and dashpot.
https://www.youtube.com/watch?v=W6Dema1uBlA

The dashpot I use a 14mm tube and a 3mm rod with a rubber washer at the end of the rod. The oil that I use is for trumpet valves. I don't know if the density of this oil is good for damping purposes, but It seems that I have a smooth viscous damping in my suspension.


Could you please suggest any method to test my dashpot so to check if it works as it should?

Thank you in advance

[sifis1983]

Greetings to all the community,

Hope you are good & healthy and continue cutting beautiful records

This coronavirus quarantine gives me time to restart sketching and build a new dynamic cutterhead.

I will use body made from steel - for attaching the drivers & the extra housing probably will be plastic.
Also, I will try to attach the little aluminium perfume funnels precisely to the center of my drivers with an extension of 0.7mm brass rods for pushing & pulling the tube that holding the stylus.

The reason that I’m writing is that I’m in a dilemma concerning the built of the “torque tube” and the the V spring on the backplate of the head.

I see many professional cutterhead creators here that are seperate these two parts. I can see many V springs from brass (?)-(or a gold plated kind of material) with a hole in the center so to accept the tube (just like the neumann head). Till now, I use a Vspring & tube 3d printed united, as one part.

neumann what is going on here.jpg

So my queries are :

1st. How can I be sure that the tube it will perfectly align at 90 degrees if I attach the tube to the V spring at the back?

2nd. Tube and V spring connection.
I see very often that a “grey” glue is used for this connection, but I really don’t know what kind of glue is this (something like a “liquid electrical tape” or SUGRU https://sugru.com/about glue maybe ? )
Also, many people use a rubber grommet or “O-ring” rubber material at the back of the tube. I can’t understand how this can be achieved and where exactly the rubber grommet is attached… before the V spring of after ? How the rubber damper allows motion in any direction in relation with the connection on the V spring?
What can I win (or lose) doing this?

3rd. Till now I attach my 2mm brass rods at the body of the torque tube as you can see in the picture below.
Many professional builders attach the push rods at the front of the tube in an X-shape at the top/front of the tube.
What’s the reason of that ? Is it just for making a shorter - and consequently “lighter” tube ?

brass rod notch.jpg

brass rod front X notch.jpg

Of course I know that I'm asking too much - as always ... hehe

Any comment, suggestion or advice will be appreciated.

Thank you
Sifis

www.loficoncept.com