The slot on Gretch Filtertrons

If you look closely ...

...some Gretsch pickups have a slot in the middle of the pickup cover. Why?

Let's look up US patent 2892371


"A slot 14h extending between slots 14a in the top wall 14 constitutes a gap for inhibiting circulating currents in top wall 14 around slots 14a. "

Lenz’s law, in electromagnetism, states that an induced electric current flows in a direction such that the current opposes the change that induced it.

This means that the pickup cover of an electric guitar generates a signal that opposes the signal of the guitar pickup. The slot in Gretsch pickups reduces the induced currents (called eddy currents) that cancel out some of the guitar signal. Mostly the high frequencies.

Cheap Telecaster neck pickups have brass pickup covers that cut a lot of high frequencies, some folk cut slots to kill the eddy currents:

The covers reduce electromagnetic interference, which is good, and slotting the pickup covers reduces signal loss. Gretsch seems to be the only pickup manufacturer who actually slotted their pickup covers.

Jump to 2:23 to see how slots cut in the pendulum reduce eddy currents and magnetic braking:

A Flutter Renting app

 A Flutter Renting app I wrote. Some resizing needed, but it connects to Firebase and you can navigate around.

Ibanez MT-10 Mostortion kit for $40

 Update: The kit arrived. It is a Zendrive, not an OD-1. So more changes will be required. I might build it as a Zendrive to compare with my Rumble Drive. If it isn't better than the Rumble drive it will become a Mostortion.

Zendrive -> Mostortion conversion schematic:

This is the AliExpress Landtone Boss OD-1 with tone control kit (it says OD-1 on the PCB in the photo, that's how you know Edit: apparently not), almost exactly the same as a true bypass tube screamer. If you replace the tone control with a 3-band passive EQ and add an extra clipping diode, you get a Ibanez MT-10 Mostortion, which is out of production. The Danelectro Roebuck Distortion Pedal is a clone for $200. So this kit is good if you want a cheap copy that you can easily modify to suit your needs.

You need to be able to solder and to relate the schematic to the PCB. Some components will change, some will disappear, and the tone controls will have the new components soldered directly to them.

You drill 2 extra holes in the enclosure, and add new treble, middle and bass pots. Solder the new caps and resistors to the pots, since the PCB don't know what they are. Some components change, and the non-inverting input after the tone control is different. Replace 3 clipping diodes with 4 new ones and replace the opamp with the MOSFET opamp. Order the semiconductors and a bag of metal film resistors separately. And the capacitors, plastic film for the tone control caps, tantalum or electrolytic for the 1uF cap.

Here is the new schematic:


$25 for the kit shipped, $15 for the new pots and semiconductors.

Aion has a custom PCB with nice instructions, as does AMZ. For the extra $10 you get better instructions than you do here.

It's Alive!

Hot Harmonics

 My Hot Tubes/ Craig Anderton Tube Sound Fuzz variants from the '90s. Nowadays I would get the cheapest Aliexpress booster pedal (Kokko FBS-2), and tack the last 2 stages of the "Basic" arrangement onto the output. That would be about $US 20, and an hour's work.

Hot Harmonics:

"Basic" Hot Harmonics:

Hot Harmonics

This is the "House Pedal" - an overdriver/distortion/fuzz/octave up pedal. It's not a just a tweaked copy of something else, although it functions as a simplified Electro-Harmonix "Hot Tubes". No opamps, just a standard 1-FET booster to drive the CMOS inverters. Overdriven CMOS inverters actually sound a bit like a tube guitar amp, moreso than most opamp diode clipper circuits. I think. It's all the mind anyway.

A lot of distortion and volume from this thing, and I've reduced the gain from R.G. Keen's "Hot Tubes" schematic. I don't think the EH Hot Tubes was this hot (it used a CD4049BE, this may be the reason). The EH Hot Tubes is a guitar amp simulator. You have 2 inverting asymmetrical clipping stages, a tone control and a symmetricial clipping stage. This is a crude model of a push-pull guitar amp.

It does seem that the manufacturer of the CD4049UBE chip used makes a big difference. It's worth trying a couple of manufacturers. Harris (CD4049UBE H9801) and ST Microelectronics (HCF4049UBE W990A9828 MALAYSIA) work for me. I plan to try the CD4069 next (Ed Rembold's suggestion).

You can replace the input transistor with your favourite volume booster, a tube screamer, or an opamp as in the Guitar Player Anderton Tube Sound Fuzz. It does actually sound a bit like an overdriven tube amp. 


The Basic Hot Harmonics has about 15 components, which is almost as minimalist as it gets. There is no FET preamp stage, so the CMOS gain has been increased. Like a Fuzz Face, the pickup loads the input, reducing high frequencies (which is good). Turning the volume control down to about 7 takes nearly all the distortion away, giving a bright rhythn guitar sound.

It doesn't sound like a Fuzz Face of course, more of a "amp at 11" sound.

See also the Slow Finger on Aron Nelson's page.



The brothers Blues

 And Eddie.

You can't go back

Back to my parent's house, now my house, for my Dad's funeral.
Soda bread, fish and chips.
I'm never going back to my old school. See you in hell.

Parental wallpaper.

Anti-Angry Mob Doorstop

When you get shamed for hoarding more than one can of baked beans, you will need something to delay the enraged horde as you unlock your magical defence items. This is a piece of wood with a wedge on one end. You have to have an immovable object at t'other end, in this case a handy wall.

3d files:

Space Crusade Scout rules

Scout squad for Space Crusade:

Sgt Reeves and the boys back from retirement

Sniper*1w 1r1w711
Heavy bolter2r2w511
Bolter/combat knife2w2w711
SGT: Bolter/Chainsword1w 1r2w716
*Sniper with thermal imaging, can shoot an enemy through 1 square of walls. Shooting the target reveals it.

They can chose the orders and equipment cards of any Space Marine chapter. Campaign advancement is the same as Marines.

The scouts are fast but vulnerable to gunfire,  so they get extra actions, cover and going prone, loosely based on Advanced Space Crusade.

Rules: A roll of 1 cannot kill a scout in H2H. A commander is a scout for rule purposes.

At the start of each turn, Roll 2 red dice to get the Squad's Extra Action points, each point may be used for an "Extra Action"

Extra Actions:
1) One reroll on one shooting attack (aimed fire attack), not overwatch.
2) Enter overwatch, may fire once during enemy turn when a moving enemy halts, before it attacks.
3) Throw a grenade (3x3 square, 2w) in addition to firing, not overwatch.
(You can make up more actions, such as first aid with a 1 in 6 chance of saving a marine killed on the previous turn)

You show a scout is in cover by placing it on the line between 2 squares. Unless an attacker can shoot at both squares, the scout is under cover from that attacker, and gets +1 to armor. This action costs 1 movement point. Next turn, the scout can start to move from either square.

Prone: Move 1 square, and turn mini over. Defender gets a +1 armor if shot at, may only roll 1 die in H2H.

Comment: The scouts are very different from Marines, and they borrow from Advanced Space Crusade, so that adds interest. They are worth shooting at by Orcs and Chaos Marines, since they are good at H2H. They can shoot more than Marines, although they have only 1 heavy weapon. The sniper can reveal a suspected dreadnought, and stay well away from the enemy.
You could use Eldar as scouts, the extra speed and skills make sense.
The scouts are easily available on EBay, and you can google the 3D printer files. "Scout Sniper" and "SM Scout" on TinkerCad. Also "Space Orc".

Simple 3d replication of objects

Make a sort of 3D object
From a photo, convert to svg, 2 contrast settings

High contrast svg
Combine 2 svg versions in TinkerCAD

You now have the 3d item at the top, which you can 3D print. It isn't very realistic, but it has a style of its own. I used Paint .Net to process the photos, and Inkscape to convert to .svg.TinkerCAD can import the .svg files.