Copper Wire for FAIRCHILD 541 A Mono Cutterhead???

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Copper Wire for FAIRCHILD 541 A Mono Cutterhead???

Unread postby Gus » Mon Feb 13, 2017 8:34 am

Hi,
I would like to rewound my FAIRCHILD 541 Mono Cutterhead from 500 Ohm to 8 Ohm i have available one reel of Enamelled Copper Magnet Wire of AWG 30 and one reel of AWG 32 what is better to use for rewound AWG30 or AWG32 and why?

Thanks in Advance!

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Re: Copper Wire for FAIRCHILD 541 A Mono Cutterhead???

Unread postby markrob » Mon Feb 13, 2017 11:20 am

Hi,

If you really want to wind to 8 ohms, you would have to measure the AC impedance at a specified frequency (e.g. 1 Khz). I don't think that is necessary, since most modern solid state amps can drive a pretty wide range of loads. The best bet would be to use the finer gauge wire and fill the bobbin(s). That will give you the largest length of wire in the magnetic field and therefore more force generated for a given current. Next measure the DC resistance and make a note of it. If its in the range of 3-7 ohms, you'll probably be able to drive it fine with your power amp. If its too high. Try winding the larger gauge and see where you land. If its too small, you would need to go a bit smaller in gauge. At the end of the day, the power handling is limited mostly by the I squared R loss in the winding. The current in the head also determines the force generated on the cutter stylus. So its a trade off. Once you get the winding in range, it would be good idea to determine the operating level in voltage drive a 1Khz that will produce a 5 cm/sec recorded velocity. Most heads are able to do that with a watt or so drive. So, at 8 ohms, you would be looking at 2.83 Vrms. That would be a good place to start. The actual power to your rewound head might not be exactly 1 watt at 2.83 V drive, but it will be in the ballpark.

Hope that helps.

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Re: Copper Wire for FAIRCHILD 541 A Mono Cutterhead???

Unread postby Gus » Thu Feb 16, 2017 3:25 pm

markrob wrote:Hi,

If you really want to wind to 8 ohms, you would have to measure the AC impedance at a specified frequency (e.g. 1 Khz). I don't think that is necessary, since most modern solid state amps can drive a pretty wide range of loads. The best bet would be to use the finer gauge wire and fill the bobbin(s). That will give you the largest length of wire in the magnetic field and therefore more force generated for a given current. Next measure the DC resistance and make a note of it. If its in the range of 3-7 ohms, you'll probably be able to drive it fine with your power amp. If its too high. Try winding the larger gauge and see where you land. If its too small, you would need to go a bit smaller in gauge. At the end of the day, the power handling is limited mostly by the I squared R loss in the winding. The current in the head also determines the force generated on the cutter stylus. So its a trade off. Once you get the winding in range, it would be good idea to determine the operating level in voltage drive a 1Khz that will produce a 5 cm/sec recorded velocity. Most heads are able to do that with a watt or so drive. So, at 8 ohms, you would be looking at 2.83 Vrms. That would be a good place to start. The actual power to your rewound head might not be exactly 1 watt at 2.83 V drive, but it will be in the ballpark.

Hope that helps.

Mark


Thank you Mark!
Thank you Mark!
Finally I re wound my Fairchild with AWG 32 my multi meter reads DC Resistance 5.2 ohm, also the magnet recharged,and i replaced the rubbers who are placed inside the tubes,cutterhead connected with 300 w power amp and it sounds very loud and crispy
i'm waiting to receive a new one sapphire to test it.

DSC_0521.JPG

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Re: Copper Wire for FAIRCHILD 541 A Mono Cutterhead???

Unread postby grooveguy » Sat Feb 25, 2017 2:09 pm

Hey, Gus,

Looks like you did an excellent job there! I used to have one of those heads; it cut a pretty decent-sounding groove. One comment: from what I see in your video, there appears to be a huge gap between the armature and pole pieces, at least as near as I can tell looking through the little glass window. When I rewound and rebuilt mine, I think I used two thicknesses of typing paper on either side of the wedge-shaped armature... much closer anyway. But you seem to be getting good action from the stylus with a low AC drive voltage.
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Re: Copper Wire for FAIRCHILD 541 A Mono Cutterhead???

Unread postby Gus » Sun Feb 26, 2017 8:52 pm

Thank you for your thought Grooveguy!
Here is a quick and dirty, recordings of my rewound cutterhead the first file is the original, the second is with 32AWG wire, and the third with 30AWG i think the second file have better fidelity, but the third sounds loudness please ignore the noise of my cuts.I'm new to cutting... i had spend 3 years to embossing with polycarbonate and steel needles.






Last edited by Gus on Sun Feb 26, 2017 9:04 pm, edited 1 time in total.
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Re: Copper Wire for FAIRCHILD 541 A Mono Cutterhead???

Unread postby grooveguy » Sun Feb 26, 2017 9:04 pm

Gus, did anything else change besides the wire gauge? The original cut sounded better-balanced to me; the two subsequent ones seemed to lack bass and the response was skewed toward the presence region; a bit shrill around 3kHz, I would think. Are you cutting into PVC on all of them? What stylus are you using?
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Re: Copper Wire for FAIRCHILD 541 A Mono Cutterhead???

Unread postby Gus » Sun Feb 26, 2017 9:09 pm

grooveguy wrote:Gus, did anything else change besides the wire gauge? The original cut sounded better-balanced to me; the two subsequent ones seemed to lack bass and the response was skewed toward the presence region; a bit shrill around 3kHz, I would think. Are you cutting into PVC on all of them? What stylus are you using?


I'm using sapphire on pvc 0.2mm flexi sheets...

the lack of the bass i think is for two reasons the first is because the cutterhead is not centered with the platter,and the second reason is because i used a cheap Chinese tube preamp who cut everything below 80hz because the buzz problems of Chinese cheap tubes.
I will try again without preamp and with my cutterhead centered.
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Re: Copper Wire for FAIRCHILD 541 A Mono Cutterhead???

Unread postby Gus » Mon Feb 27, 2017 8:00 am

grooveguy wrote:Gus, did anything else change besides the wire gauge? The original cut sounded better-balanced to me; the two subsequent ones seemed to lack bass and the response was skewed toward the presence region; a bit shrill around 3kHz, I would think. Are you cutting into PVC on all of them? What stylus are you using?


Please ignore the previous examples i've forgot to turn on the riaa preamp :roll:

Here is the sound files with riaa preamp on,i think the 32AWG have a little better response on high freq.
my examples have surface noise, because i cut too deep.







Please let me know your opinion.
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Re: Copper Wire for FAIRCHILD 541 A Mono Cutterhead???

Unread postby grooveguy » Mon Feb 27, 2017 4:09 pm

Aha! There you go. I'm assuming that the first MP3 is the source material and the other two your cuts. Very good; on first listen it seems that you have a proper EQ curve and it sounds just fine.

When you say 'sapphire' stylus, can you be a bit more specific? One thing that's happened during the course of my 60+ years cutting records is the demise of Audio Devices, Capps and MicroPoint, all manufacturers of cutting styli from days gone bye-bye. In the late 1950s/early 1960s a new sapphire Audiopoint ran around $6, and a very good custom Capps microgroove stylus, pre-wired for heat, was about twice that. At the same time, those of us who were cutting more for fun than profit would cut both sides of a 45 for about $4, and a 12" for $10 or $12. Blank lacquers were on the order of a couple of bucks to maybe $5, with 'stale' ones often discounted 50%. Trolls have been very resourceful in finding material to cut or emboss into, but a serious cutting stylus has become prohibitively expensive for those of us who do not turn a profit with a wear-and-tear factor built in to cover expendables. Just want to make sure I'm not overlooking more modestly-prices sources of recording styli.

You're certainly on your way with a good-sounding system, Gus; keep it up and keep us posted.
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Re: Copper Wire for FAIRCHILD 541 A Mono Cutterhead???

Unread postby Gus » Mon Feb 27, 2017 11:37 pm

grooveguy wrote:Aha! There you go. I'm assuming that the first MP3 is the source material and the other two your cuts. Very good; on first listen it seems that you have a proper EQ curve and it sounds just fine.

When you say 'sapphire' stylus, can you be a bit more specific? One thing that's happened during the course of my 60+ years cutting records is the demise of Audio Devices, Capps and MicroPoint, all manufacturers of cutting styli from days gone bye-bye. In the late 1950s/early 1960s a new sapphire Audiopoint ran around $6, and a very good custom Capps microgroove stylus, pre-wired for heat, was about twice that. At the same time, those of us who were cutting more for fun than profit would cut both sides of a 45 for about $4, and a 12" for $10 or $12. Blank lacquers were on the order of a couple of bucks to maybe $5, with 'stale' ones often discounted 50%. Trolls have been very resourceful in finding material to cut or emboss into, but a serious cutting stylus has become prohibitively expensive for those of us who do not turn a profit with a wear-and-tear factor built in to cover expendables. Just want to make sure I'm not overlooking more modestly-prices sources of recording styli.

You're certainly on your way with a good-sounding system, Gus; keep it up and keep us posted.


I have an old Sapphire, (Capps) and experimenting to cutting pvc & polysterine sheets of 0.2mm, but i think you can experimenting, with Apollo sapphire too.

Here is my last experiment, i fill the bobbin with 30&32Awg as a pair, the total DC resistance is 3.4 ohm.

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