Cryogenic treatment of guitars warning

[salvarsan]

And Salversan, would you like to do the testing on the Strat and humbucker pickups?

No.

What do you want me for when you can do it yourself so easily?

Collect parts, number them, test them, cryo treat, test again, note changes.

Tools:

• 5000 count digital volt-ohm meter, for DC resistance to 1 count per 1000 precision
• Extech LCR meter, or other.
• Air core coil, 3/16" diameter bore, 0.75 inch long, 500 winds (about 2.5 layers AWG42)

Using the Extech at 1kHz, measure the coil's inductance for each slug and magnet rod placed in the coil bore.

This method is sensitive enough to distinguish between different A5 rods from the same batch.

I guarantee that it will see even minute inductance changes in a steel slug, whether from cryogenic treatment, annealing, hammering, or brief exposure to a magnet. Of course, this also means that the steel parts should be degaussed if they show any residual magnetic field.

[salvarsan]

I can find a handful of companies that explicitly advertise cryo treatment services.

Controlled Thermal Processing Inc

300 Below

Nitrofreeze

Solar Atmospheres


I will contact them tomorrow to find out about minimum put up charges.

-drh

[ScottA]

I've gotten to the point that I try not to poo-poo anything out of hand, unless it's totally ludicrous (which it many times is).

You can hear some pretty subtle things, although I do think they should be measurable. Oftentimes, the trick is doing the right measurement, or looking at the data the right way.

I'm not saying I think this stuff is real right now, but I do think it's worth investigating.

[Diablo]

The type 400 magnetic steels are interesting but you need to remember that their average permeability is roughly 1/5 that of soft steel (1010 or 1018).

There's a reason why the Zephyr pickup poles have 430 stainless with a pure nickel core -- delivering enough field to the guitar strings. Neither the stainless nor the nickel will magnetize permanently, as do soft steels.

I'm tired now so someone else will need to figure out how a low BH hysteresis affects the pickup signal.

Soft steels do not magnetize permanently - by definition, magnetically soft materials are easily magnetized and demagnetized. Steels which are physically soft are also magnetically soft. As you lower the carbon content of steel, they become physically softer and magnetically softer. You can make a cheap permanent magnet out of steel - load it up with carbon and heat treat it for high hardness.

[Diablo]

Copper wire isn't going to respond at all to cryo treatment. At least the copper won't change because it's essentially pure copper. No transformations upon cooling or heating back up to room temperature. Maybe the insulation on the copper won't like the cryo treatment and will crack? Is the insulation coating flexible enough at cryo temps, and does the coefficient of thermal expansion match copper closely? If not, expect the coating to crack.

[Chuck H]

I'm on your side re the copper. Copper alloys can be transformed. Copper cannot. There's are transformations that will happen to the pole pieces though. I don't see how it can make a damn bit of difference, honestly. The magnet is the power that operates the pickup. About the most one can shoot for is more or less magnetism and AFAIK we're not suffering from an inability to control that now. There's also the actual shape of the magnetic field I suppose. If it can be made more uniform, or something, by treatment, that could have an affect. Though I doubt it will be significant. Still... You don't get anything if you don't try.

[Mike Sulzer]

The magnet is the power that operates the pickup.

It is the vibrating string that powers the pickup. The permanent magnetic field is there to magnetize the string; the permanent field at locations other than the string does not matter.

[eschertron]

It is the vibrating string that powers the pickup. The permanent magnetic field is there to magnetize the string; the permanent field at locations other than the string does not matter.

I'm following this thread with interest now; my high-school understanding was that the string caused perturbations in the field around the permanent magnet, those changing flux lines caused an electric current to flow in the pickup wires. A magnetic field generated by the string wasn't part of the model as I envisioned it.

[Rick Turner]

Copper can't be transformed by cryo?

Effect of cryogenic treatment on thermal conductivity properties of copper

OK, this is mainly about thermal conductivity, but change is change.

Cryogenic Treatment of Materials: A Cryo Central resource from the CSA

and:

Machine Tool Cryogenic Treatment : Texas-Machine Tool International

Note that this is about reduction of residual stresses, and I would imagine that drawing magnet wire does induce stresses in the copper.

or:

Machine Tool Cryogenic Treatment : Texas-Machine Tool International

My point is that there are reports of change to copper with cryo treatment. I'm not saying whether these changes are good or bad for pickups, but rejecting the possibility of change without doing the testing is a rather Luddite-like reaction to scientific curiosity.

[salvarsan]

It is the vibrating string that powers the pickup. The permanent magnetic field is there to magnetize the string; the permanent field at locations other than the string does not matter.

Looking at a string over a magnet in the FEMM modeling software is instructive, too. The magnetic energy distribution in the string is a dipole.

[Rick Turner]

Salvarsan, I'd have thought it to be somewhat tri-pole (NSN or SNS) with a single coil, and more dipole with a humbucker.

Also, if the permeability of strings is an issue (and it might prove to be...), then cryo treated strings may respond differently than non-cryo treated strings. It's that old A to M conversion thing again and lots of carbon: Piano wire - Wikipedia, the free encyclopedia

[ScottA]

There's are transformations that will happen to the pole pieces though. I don't see how it can make a damn bit of difference, honestly. The magnet is the power that operates the pickup.

The properties of the pole piece are the single most important part of the pickup. I think this is probably the biggest hole in the general understanding of what drives pickup response.

Consider this: I can take the same coil and drive it over most of the tonal map by changing the pole piece. If I take the same pole piece and change the coil, I can only achieve a fraction of that response. The pole piece, more than anything else, defines the "voice" of the pickup.

What you might consider to be relatively subtle changes in the pole piece response can have a discernible effect of tone.

[salvarsan]

Cryogenic Treatment Services

I've attempted to contact the four providers previously listed.

300Below and Nitrofreeze answered their phones and quoted minimum order sizes. You can meet a 10 or 18 lb minimum order by bulking it with other parts, perhaps brake rotors or drill bits, they suggest.

Both remarked that they already serviced at least two secretive pickup makers, one of whom always asks that the parts box be perforated but not opened. We had a good laugh at their secretiveness. This is more anecdotal confirmation that Cryo treatment is of audible value.

To all the nay-sayers on cryo treatment of pickups, < insert embittered vindictive caustic profane exhortation here >.

Can someone else contact Controlled Thermal Processing and get a quote on their minimum order size? The $6.50/lb is attractive but I doubt that it is a minimum.

Controlled Thermal Processing Inc
No phone contact, no info on minimum orders.
$6.50/lb, 2nd Day Air shipping from MA, IL, CA

300 Below, Illinois
Minimum $150/18 lb., every Tue, Fri.
says they handle at least two secretive pickup makers

Nitrofreeze
Minimum $50/10 lbs, processing every Friday, return ship every Tuesday

Solar Atmospheres
No phone contact.
Submit job for online quote.
handles Large Industrial Quantities, to judge from the walk-in cryo chambers.

[Mike Sulzer]

Variable reluctance is a derived concept. It works fine, but it is far from the physics, and makes the physics harder to understand. How does something "perturb" the permanent field? Only by another field; and fields add. The permanent field need not be from the pole piece. Suppose you replace the pole piece with one with the same permeability and conductivity but no permanent field. You can then make the pickup work by holding a magnet over the strings. You must use a magnet to magnetize the string, one way or another. (Of course the string retains very little permanent magnetism when you remove the magnet, but the magnetization can be permanent or temporary; it matters little.)

I'm following this thread with interest now; my high-school understanding was that the string caused perturbations in the field around the permanent magnet, those changing flux lines caused an electric current to flow in the pickup wires. A magnetic field generated by the string wasn't part of the model as I envisioned it.

[Rick Turner]

To enhance what Mike just said (and to chime in on another thread re. electromagnetic charging of the strings), in the 1930s there was a lap steel sold with an amplifier that had a circuit to send DC up to the pickup coil. You'd switch it on and then off, and it would magnetize the strings. In the off position, the coil was the pickup. The magnetism didn't last long, so you'd have to periodically recharge the strings.

The variable reluctance model may come into place with those tiny Roland magnetic hex humbuckers. They get mounted so close to the strings that the strings may act as a moving magnetic "keeper" between the north pole coils and the south pole coils. Those are pretty cool little units. Pun intended...

And it is the string indeed that drives the alternator here...

And "I don't see how it can make a damn bit of difference, honestly." is not the kind of statement that accompanies an open mind, especially given the clear evidence that cryo affects properties important to the permeability of steel. With pole pieces, it all about permeability. It's kind of like saying that the conductivity of magnet wire makes no difference.