‘Mapping’ a head analog?

[Big Al]

With the news of new lathes becoming available recently, I see a lot of mentioning of having to ‘map’ the heads of these machines,
which as far as I know involves a plug in EQ (more often than not Fab Filter).

I am aware that this is to tame the resonances
of the head.

If I wanted to cut a record (dub) with these machines and wanted to stay in the analog domain, would this be possible using outboard hardware parametric EQ to achieve the same results as a plug in?

How was this done in the past pre DAW?

Was it just built into the design of the electronics of the lathe?

For example how is this ‘mapping’ done with a Neumann SX or Scully?

Obviously theres a million amazing records cut on these machines and the EQ in mastering is usually used to tame / enhance the song being cut, not to tame the resonances of the head?

If this is the case, then is it too expensive or technically challenging ( or both! ) these days to design a cutting head / lathe with the resonances already dampened, without having to resort to digital plug ins to ‘map’ and fix these problems that couldn’t be solved in the design / build stage?

[Big Al]

Adding to this, my experience with the 1980’s portable lathes here in Japan the heads are pretty resonant and when ‘mapped’ and the resonances tamed, usually with some extreme EQ’ing they sound a million times better than ‘stock’ !

So I’m guessing that technically its challenging to design / engineer the taming of the resonances in the analog design of the lathe?

[spinnertownblanks]

When using 320 styli on a mid level lathe, you often need around 20db of clean gain in the top end of the EQ. Most consumer level graphic EQs can’t handle this, and even if 20db is available it usually adds noise. So software is easier.

Professional lathes have custom electronics with matching hand wound driver coils, but at say mid level, like the Vinyl Recorder there are also so many variables to account for and software is simply just the cleanest, easiest option. Mid level lathes generally do not adhere to the iRIAA curve either.

[spinnertownblanks]

But…. For sure you can totally do it all analogue. I’d digitally map your head to find its mechanical resonances and frequency response, then just copy those settings over to an analogue graphic EQ and see how you get on. The graphic EQ you choose is the biggest factor in this scenario.

[Big Al]

Thanks for your reply!

Yes good point, and noted that if a lot of gain is needed then in some cases software EQ can be less ‘noisy’, although in my experience good quality ‘professional’ analog hardware EQ is usually more powerful and sounds ‘better’ than software for boosting, so there may be less required to achieve what’s needed.

Have to experiment at some point as it could be good with the right hardware EQ!
Be interesting to see if the end result sounds better or not!

Anyway aside from needing to do this (which once done and setup works well) its great that there are more options for mid level lathes than Souri’s becoming available now!

[spinnertownblanks]

Yeah professional analogue is always great, just make sure it is clean, mapping is about matching the heads frequency response and no colouration, cleanest possible signal.

[markrob]

Hi,

Older mono moving iron heads are quite a different beast as compared with open loop moving coil stereo designs such that its much easier to flatten the response. In a moving iron head the drive coil is stationary, many more turns of wire can be employed resulting in the ability to produce higher forces to the stylus. This allows the head designer to make the armature very stiff. While this throws away some efficiency, it allows the main resonance of the head to be moved from the 1-2Khz region up to 4Khz and above. Some of these head designs then physically damp that resonance resulting a starting response that is smooth (some heads used the main resonance peak as part of the IRIAA curve). The best of these type heads like the Presto 1C/D and Grampian tend to be quite flat out of the box and therefore only need simple EQ, easily done with analog electronics. Most, if not all, professional moving coil head designs are of the feedback type. Feedback flattens and mechanically stiffens the head. The "textbook" response of an open loop velocity frequency response of a moving coil head is inverted v shape, with the tip of the v at the system resonance. This is not too difficult to EQ to flat electrically, but it turns out to be quite difficult to make a head of this type using off the shelf tweeters and/or exciters without adding secondary resonances. On top of that, the main resonance needs be set lower (1-2Khz) or you would be unable to get the head to cut at required levels without burning up. Lowe stiffness results in the head response being more dependent on the physical loading of the stylus to the cutting medium. This leads to the need to do some pretty radical EQ to flatten the response. This is certainly doable in an all analog design, but it can become painful if you need to work with embossing, cutting, and different media. If you look at the very popular VR lathe, I believe the EQ supplied is a simple analog unit. IIRC, that head design has quite a bit of physical damping material applied in an attempt to kill some of those resonances. I see that some users drop the supplied EQ and do the mapping as described. This a a big and complex subject and I had to simply things, but hopefully you get the idea. Let me know if you have any questions and I'll try to answer with my abilities.

Mark

[Big Al]

Thanks for the technical overview Mark.
Appreciate the insights!

And yes it is a complicated subject, but thankfully we have a range of tools at our disposal now to help us achieve the end result, which at the end of day is what’s important, how the music sounds when the disk is played back!

[leemichael]

Digitally mapped heads combine both the RIAA curve and the flattening of the resonances.

Personally if I was going down the analog route, I’d add an external RIAA circuit in a box and then you’d only need a handful of parametric EQ channels to do the rest!