The Secret Society of Lathe Trolls

I am playing with a Yaskawa coreless direct drive servo motor SGMCS-05B3C11 as a direct drive on a 14 inch platter, 5nm =~ 50kgcm of torque which should be fine. One thing I did find is that the servo driver seems to chop at 6kHz, which given the very low running torque can wind up audible in the ai...

Yea doing it from scratch is a serious LEARNING experience, especially if mech eng of the fairly serious sort is not really your thing. Lots of precision parallelism over annoying distances and fun with vibration management (I am on Rev 3 of my build, hint epoxy granite is your friend for stiff, wel...

Don't forget that the material you are cutting is plastic and so deforms under the cutting forces and then springs back to some extent. This argues that for a 15 degree RIAA standard rake on the disk you probably want more then that on the cutter and this is usually a mix of the angle of the torque ...

An ioniser might help.

You want one that makes both kinds to reliably to this, but they are tried and tested technology in the electronics industry for static control of insulating surfaces.

I think the RF present in the output of (particularly NOS) R2R DACs when combined with the bipolar inputs on something like a 5532 sometimes has rather 'unfortunate' effects, mostly down to slew rate that possibly explains some of the dislike of that part in this application, as well as why such DAC...

That's jfet input isn't it? Probably better from an RFI perspective if the inputs lack solid filtering, but the noise impedance is also going to be way higher then the bipolar parts, so it will want a different feedback network for best performance. I certainly don't want to be designing audio that ...

There are some detailed drawings in the AES Disk cutting anthology of the (IIRC) Capps styli, and I think there is at least one drawing in "Basic Disk Mastering" by Boden.
You got someone able to make these?

Are you sure those opamps were properly stable? I have heard some weird things from such (You always have to listen, it is a critical part of testing a design), but it always seems to come down to instability or running the thing into clipping (Recovery from this is often NASTY, just a trade off wit...

The noise of the semiconductors is all too often dwarfed by the noise of the resistors! You have to be very careful if you want the noise of a decent opamp to dominate over the Johnson noise of the resistors that surround it. Possible to bollox it? Sure, anyone can screw it up, and most designers wi...

Loose the old mercury relay, we got better ways to skin that now. Skyworks have an isolated gate driver that is made for switching a pair of back to back mosfets, and will do it in microseconds that is just ideal for speaker protection applications, which is really what we are discussing here, cheap...

So modulating laser power while maintaining SLM with good coherence length operation? Sounds frankly gnarly, unless you do something like use an AOM or Pockels cell to do the modulation with the laser itself running at constant power with the usual precision thermal management. Even then, holography...

Just remember that heat pump efficiency drops as delta T increases, and Carnot was a right bastard. Might be something to be said for lowering the mass that is cycled to lower the energy transferred from the steam to the cold water? We don't have to use 1970s steels today! Just thinking I don't actu...

The phase change gets you very rapid heating (Steam into a cold heat exchanger will condense and that give up a LOT of energy) which is kind of what is wanted for a fast cycle time, with a thermo fluid you only get the energy from the temperature drop, not the (far greater) energy from the condensat...

One thing I found is that any kind of recirculating ball linear bearing is the kiss of death, you really want something more in the line of a linear cross roller slide, but getting one long enough can be a challenge. Same goes for ball screws, good for precision machining, but NOT the right thing in...

You can eliminate a lot of the gain stages in eq and limiting by going digital for that, but the power amps sort of need to be actual amplifiers, and anyone running a feedback head needs to close that loop in the analog domain simply because the group delay thru a set of ADCs and DACs will destroy a...

CD4 was cut at half speed IIRC, which does of course nothing to help with the geometric limits but does significantly reduce the current required in the cutting head coils. There are three limits on the amplitude you can cut up there: One geometric imposed by the back angle on the cutting sapphire (...

It was NOT a CNC Lathe, it was an old school manual toolroom machine (And frankly rather knackered). Look up Hardinge HLV for a picture of the kind of thing. I cut a small disk (hence the limitation due to centre height), could have done a cylinder I suppose, but I have nothing to plat those back. T...

For shits and giggles I cut a record on a Hardinge HLV, turned up a mandrill to take the blank with a stub to fit in a collet, and mounted the cutting head in a tool holder, then use the power facing mode to cut the groove. Speed was a bit 'iffy' and the headstock belt on that machine is showing its...

There is a bit of a trap with bronze self lubricating bearings, they only really work if the surface speed is high enough, which is possibly not the case here, you might do better to organise lubrication of the bearings rather running them dry. I got stuffed good and proper trying to use a sintered ...

The old school approach when setting up playback decks on rather 'mobile' surfaces in raves might work well here. What you do is use 3 or 4 sorbothane hemispheres (Squash balls cut in half) under a paving slab with the deck placed on the slab. Your basic mass/spring/damper sort of thing really. The ...