Vintage Pick-Up to Cutterhead Experiment

[Soulbear]

Hi Trolls,
A few days ago I had a discussion with Lathe Trolls member grooveguy. During the course of our exchanges I mentioned some "Vintage" Thorens Pick-Ups I had purchased, having read somwhere (Don't Ask Me Where, I Just Can't Remember!!) that essentially they are of the same Construction as A "Cutterhead" On one of the Covers of said Thorens Components they are described as "Graveur" meaning Engraver (Cutterhead) or "Lecteur" meaning Reader (Pick-Up)

Thorens D200 Front-Veiw.JPG

What I also mentioned to grooveguy is that I'd not to date, done anything with these items. Well today that changed, my Curiosity got the Better of Me, and I went and Dug One of Them Out. I've now had a Cursory Play-Around with one of them (The Thorens D200) though I've not as yet Removed the Cover to give the Internals a Visual Inspection. Sometime ago I bought a Poltz Freres Lathe which had a Pierre Clement Cutterhead with it. This Pierre Clement Cutterhead has an "Unusual" DC Resistance of 23 Ohms, making it neither a "Standard" 8 Ohms ish! Cutterhead, or of the 500++ Ohms High Impedance Variety. I subsequently Hand-Wound a Transformer to Drive the Pierre Clement Cutterhead, this one :-

P.C. Head Custom Transformer.jpg

P.C. Head Custom Transformer1.jpg

I made the Primary Winding 8 Ohms ish, and the Secondary Winding 23 Ohms ish figuring the "Turns Ratio" would take care of itself and end up about 3:1 and Just about Right to Drive the Pierre Clement Cutterhead from a "Standard" Amplifier. Now back to today, I measured the DC Resistance of the Thorens D200 and found it to be around 200 Ohms. With a Resistance that High, I felt there was no chance of getting a Meaningful Level of Audio Signal through it, from a "Standard Amplifier" for "Testing Purposes" but felt its Resistance was Too Low to Warrant Maybe Trying to "Drive" the Pick-Up with one of my 100 Volt Line Transformers either. What I did Try However, is Driving the Pick-Up as a Cutterhead, from the "Custom Made" Transformer I'd made for the Pierre Clement Head :-

Thorens Pick-Up To Cutter Experiment.3gp

Well now, as the Old Saying Goes "What Can't Speak Can't Lie" I've done my usual "Trick" of Mounting a "Dummy Stylus" then Pressing the Stylus Onto the Resonant Chassis of My Gas Fire. Once Again Appologies for the "Dire Quality" of My Video's, when She's next home from Uni, I must get the Daughter to Show me How to use my "Touch-Screen" Camera Phone!! With a Small Flashlight Gripped between my Teeth, my Basic Camera Phone in One Hand, the Thorens "Cutterhead" in my Other Hand (Please Trolls Just Don't Ask what I Pressed the Pause/Play Button of my Stereo With Te He!!! ) The Audio Signal caused the Stylus to Vibrate Very Strongly Indeed, at least on a Par with "Propper" Cutterheads I've Tested, and I could Hear the Music Track being Played Really Well. I did find However, that I did have to "Turn Up" the Amplifier Volume Control Quite High, so Perhaps I could Possibly "Drive" this Thorens "Better" After All, via a 100Volt Line Transformer?? MMMmm Food for Thought!! It would appear that what I'd Read about Thorens Pick-Ups and Cutterheads being of the Same Construction, might Very well turn out to be True!! I'll at sometime Try and "Open Up" the Thorens D200 for a Visual Examination, but at "First Glance" this looks to be a "Good Prospect" and "Promising Alternative" to Lathe Trolls having to "Fork Out" Silly Bollocks Amounts of Cash, for what are (Looking at the usual Sale Channels) seemingly well Overpriced "Cutterheads" At least I think it's Worthy of a "Closer Examination" I hope other Lathe Trolls Agree
Regards Soulbear

[markrob]

Hi,

Sounds promising. You would think that a device designed to be a pickup would use more turns of smaller gauge wire to increase the recovered signal. So it might not be able to handle the drive power. But its sure worth a try.

The turns ratio should be around 1.7:1 for an impedance ratio of 3:1 (they are related via the square root). Even though you measured 23 ohms DC resistance, the impedance at 1 Khz is likely closer to 100 ohms or more So your ratio probably did come out closer to 3:1 after all. At the end of the day the goal is to force current into the coil. That determines the force . You have to fight the inductance, DC resistance, and back EMF to make that happen. If the resistance is too large, you will burn too much heat as you froce more current thorugh the head.

Mark

[dubcutter89]

Nothing new at all (but to find something new in the field of mechanical sound recording is very hard...)

I have several books that recommend the reader to use a pickup for "amateur recording" - there were even some brand recommendations, but it sure was not that Thorens... Personally I would also go for a more common cheapy pickup as it will loose most of it's collectible status if modded for cutting, but on the otherside.... I once also looked at some of those old disc scratchers and of course they would make a solid base for recording device, but never finished that project.

But there are some differences: It might even be a moving coil thing (as Neumann R5 and others back then) which is not really what you want. But of course a look inside would bring some info. Also pickups normally have low stiffnes. Moving Iron cutters have higher stiffnes to push resonance frequency up and to overcome disc loading effects..

Anyway good luck with your project!
Looking forward to look inside!

Lukas

[Soulbear]

Hi Mark,
Thanks for the input, the 3:1 Ratio from my "Home Brew" Transformer was an effort to Specifically "Better Drive" the Pierre Clement M1 Cutterhead, In that regard I considered it from My Perspective a (Very Subjective) "Decent Outcome" in that I got Greatly Improved "Sound Levels" when Testing the Pierre Clement M1, when compared to Driving the M1 Cutterhead Straight from an Amplifier. In the Test of the Thorens "Pick Up" to "Cutterhead" Experiment, I was reluctant to use a 100 Volt Line Transformer Initially, not wanting to "Burn Out" the Thorens. I then got to thinking that I'd bought the thing speculatively to do such a Test, so "What the Heck" I was however, Buoyed somewhat by the Successful Result of the First Test with my "Home Brew" Transformer. I've just in the past Half-hour or so, Gone Ahead and this time Driven the Thorens D200, via an Eagle Brand MT-40Watt 100V Line Transformer. Here's the result :-

Thorens Pick-Up To Cutter Experiment2.3gp

Sadly I have to accept that really I could now do with an Apprentice to Assist Me, as the Video does not really do Justice to what I heard when doing the Test. Whilst trying to do 6 things at once, I don't know if I had a Finger over the Camera Phone's Microphone when making this Test, thereby seriously reducing the Recorded Volume. What I can say, is that I got about the Same "Sound Levels" as in the First Test, with the Amplifier Volume Control in a much much Lower Setting. I Just Hope this Experiment Might Spark a Bit of Discussion, and Perhaps Encourage other Lathe Trolls to Have a Closer Look into this "Possible Alternative" to the Extortionate Prices being asked for Cutterheads Nowadays.
Regards Soulbear

[Soulbear]

Hi Lukas,

I have several books that recommend the reader to use a pickup for "amateur recording"

I hope you can dig out the Literature where you read this information, and let me know the Title of It. I don't mind admiting that it's "Driving Me To the Point of Distraction" trying to remember where I'd read about these "Pick-Up/Cutterhead "Shared Construction" details.

Looking forward to look inside!

Me too, the Problem is that there's No way to Hold the Screws which come through the Front Cover as they're a Grooveless Chrome Rivet Head Type thing. And at the back Thorens must have had a Service Tool of an Especially "Thin Walled" Box Spanner or Socket Spanner to fit into the Nut Recess on the Back Plate, I can't get a Socket in There!! :-

Thorens D200 Back Cover.jpg

See What I Mean??
Regards Soulbear

[Soulbear]

Hi Trolls,
I have just recently been revisiting this subject with a modicum of success!!
Hopefully other Trolls may find it of interest, and as a way of obtaining a Mono Cutterhead for
very little cost. I hope to share the results of my endeavours with other Lathetrolls when I can
find the time

Cosmo -1.jpg

However, just to pique your curiosity I though I might share this Photo ^^^^ just to whet your appetites

Regards
Soulbear