The Secret Society of Lathe Trolls

are you saying that using an EE has a side effect of (subjectively) reducing the bass impact? If the Bass is out of phase of course it does, that IS rather the point after all. However the EE is classically a first order network so it tends to have an effect way above whatever you have dialled in a...

I cobbled something together in C, that pays attention to the timing of the platter encoder pulses from my platter drive to make the delay track precisely.

A few thousand lines of C (Mainly in the delay lock loop), not too bad.

The thing is a fix for the technical limitations at low frequency, but it does effect the sound obviously, so you only use it if you have to, bit like the acceleration and velocity limiters. These things are necessary because both the lathes and the replay doings have some hard geometric and mechani...

Does the depth gauge reflect what is happening? How about the current in the depth control coil? If you cut a test with the damping test mode engaged does the resulting groove look right both at larger, smaller and at the diameter where the problem exists? If you cut with the depth control disconnec...

Remember the surface that the stylus contacts is the wall of the groove not the surface of the blank, washing is probably carrying muck from the original surface down into the groove when the stylus can see it.

So Some of you may remember my more or less accidentally acquiring a NSK brushless DD servo motor about a year back to experiment with. Turns out the driver really did not consider speed to be a first class citizen and was all about positioning, which is fine as far as it goes, but not really what w...

You kind of have to separate the "Head blows because of corroded coil connection/Glue/Mechanical failure/Electronics issue" from "Head blows because of overload", the first being something which apart from a serious maintenance regime you can do little about, the second being something that you have...

Bear in mind that when those cards were designed, good quality trimmers were expensive (and unavailable in the case of caps for audio useful values!), and even the good ones were sometimes of dubious reliability. There is something to be said for fixed resistors if you cannot just use 1% parts and a...

Are you sure that Ignus slide is going to be quiet enough? I have one of those and find that the noise level when running it at any speed can be disturbingly high, I suggest you try manually finding on a worst case spiral and making sure it does not raise the noise floor objectionably. I would sugge...

On the subject of the oil friction drive, don't forget that we have low speed coreless motors now, which were not really a thing in the 70s. Coreless means zero cogging, which is what that oil coupler was really trying to cut down, I have a Yaskawa example coming, expect I will need custom electroni...

Disconnect the cartridge and meter each of the tonearm wires to the arm tube, something may be shorting.
Also meter the arm tube to the ground connection point, sometimes you discover wonders here.

Groove depth is always just under half groove width if the cutter stylus is in even reasonable condition, as the stylus has a 90 degree tip (With a typically 1 micron rounded point, hence the just under).

If you are not running a feedback head, then the odds are that the curve you need will not be all that close to IRIAA, so in the first instance I would do it in software until you figure out what you need.

Feedback heads are typically mechanically very under damped with much of the damping being due to the error amplifier circuit (In pursuit of more sensitivity at high frequency). Non feedback heads are typically heavily mechanically damped to try to take out the worst of the generally massive mechani...

It matters from a noise and headroom perspective as well as an 'what exactly are you limiting' one. Generally the elliptical eq goes in first, just because why not? This is really part of the transfer console for me, not the lathe. Then I would typically high pass, apart from anything else, this wil...

What does your cutting chain look like at the moment? A SAL 74 copy of some form? Open loop you could do the valve amp thing, not really sure I would, but you could, but it will not work like you think if running a feedback head. I could maybe see something like a vari mu desser being an interesting...

Be very careful here, if it is a reasonably good copy of a VMS80, it is probably running a feedback head, in which case you really, really need the amp to have a flat frequency and phase response. In addition the operation of the circuit breaker cards requires a small DC offset at the output of the ...

Yea, I was kind of assuming that the doings to make the IRIAA output effectively velocity were post all of this (either feedback or a mess of post EQ if running open loop). Do not that any limiting MUST be placed outside the feedback loop as anything in the loop will just be automatically equalised ...

Yea, but mine came from ebay.... Nice gear generally, but as you say this application is just a little out there. I did actually contemplate a setup with a strain wave reducer (Yay for zero backlash!) actually driving the turntable directly, at 50:1 a reasonable mass of flywheel on the high speed si...

Interesting, I was rather planning to use one of these for the carriage drive in my machine, thru a 50:1 harmonic drive reducer, which has a fair amount of friction to help damp the thing. Time to look elsewhere i guess. The number of servo drive system vendors who do not do speed rather then positi...