The Secret Society of Lathe Trolls

What happens if you use a fixed frequency at the 10Khz resonance point? Does that excite the lower main resonance? What does this sound like? Can you post a sample of the cut?

Hi, The uncorrected plot looks how you would expect the open loop response to react. Not sure what is going on as far as your first post. Perhaps there is some extra energy in your program material that is in time to, but not generated by the hi-hat. Have you tried creating a test tone that only has...

Hi, All heads have a main system resonance formed by the moving mass and the stiffness of the suspension. That's your 300 Hz resonance. In a feedback head design, that resonance is removed by the servo action. In an open loop design, you can add damping material to help tame the resonance and use EQ...

Hi,

You read voltage across the heater leads, not current. To read heater current, you would need to pit your meter in series with the heater. I'm not sure you are making the measurement correctly.

Mark

Hi, I'm glad this is working out for you. I've been working to improve and add some features. Most important is the ability to add replaceable styli that can be purchased from vendors like Mike at recordlatheparts.com. I've found that cutting off the short length of the stylus that extends past the ...

Hi, You want the current meter to have the least impact on the signal going to the head. Since its in series with the head, that means you want its impedance to be as low (close to zero) as possible. 0.065 ohms is very low and would not have much impact on your audio. You also have to select a meter...

Hi,

Yes, you don't want to introduce very much extra resistance between the amp and the head. Its also possible that if the meter uses a rectifier to convert the AC to DC that it might cause some unwanted effects on the signal. It may be hard to find analog current meter that fits the bill.

Mark

Hi, I would not lose the fuse. That is still your protection (as limited as it is). Adding current monitoring is a nice thing depending on the meter type and if you understand how to interpret the readings. If you decide to make a current reading you can do it by breaking one of the leads to the hea...

Hi,

I think that would probably be too much of a leap. By that time, you would be better off designing a lathe from scratch. You get quite a bit of mechanical stuff with the PO80 that would need to be scaled up.

Mark

Hi, I actually sent a file with with white noise to the on-line mastering app just to see what it was doing. There was some high frequency EQ going on. They kept it mild given the limited power on the PO80. I think there was some compression added as well. I rolled my own set of electronics (you can...

Hi, I don't have much experience with the stock head. I am using my head, electronics and cutting software, so its hard to compare. I am also using CD blanks for all my testing. Because of the extreme amount of high frequency EQ and peak power I am using, I drive my head with a 50 watt amp which can...

Hi,

If you want to preserve that style jack and plug, here are the specs:
Mark

Hi, I see. A couple of options for you: 1. Add a digital panel meter to the exiting VR box to allow you to read the motor voltage digitally. My concern with this approach is that the repeatability might be poor. The voltage will be very repeatable, but the actual motor speed will probably not be (es...

Hi, I don't own a VR, but I did work on and repair the pitch section of that unit for a friend. IIRC, the pitch control was just an LM317 adjustable regulator circuit with a provision made to allow the voltage to be adjusted via a pot and/or via an external voltage control. At first glance, you migh...

Hi,

If you are just looking for dimensions, this pdf may be all you need.

Mark

Hi,

On the cheap, look into template faceting. Since you are making simple geometry, you only need a few templates and a lapping wheel setup. You can DIY a machine for very low cost.

Mark

Hi, Any idea on how much he is asking for the generator? Might be out of my league, but I've been interested in the CD-4 format. I have been working on a software decoder for CD-4 and would love something like this to help with the reverse engineering and testing. Do you think it would be possible t...

Hi, Yes. I think you have the idea. I'm doing a bunch of hacking to the PO-80. I've updated the motor on mine with a small NEMA 14 stepper and Arduino based controller. Its not quite ready for prime time yet, but keep an eye out in the thread I've been posting to on this subject. I'm also looking to...

Hi,

Instead of removing material, you basically empress or indent a groove. Does that make sense?

Mark

Hi, I flip the stylus 180 degrees and emboss on CD-R blanks rather than cut. They stylus lasts quite long and the blanks are cheap. You will have to make a simple adaptor to reduce the center hole of the CD-R to the standard record hole diameter. I 3D print them. Here is an STL file I created that w...