Herculean DIY Autoformer wiring.

 They say a picture is worth 1000 words... well how about how about around 180 wires and 820 solder connections?  Brad from the Boston contingency wired 6 of the 28 position autoformers up for Caroll's home theater system.  I often joke that more than half of the $200 autoformers I have sold sit partially wired in a box on a shelf and this picture might explain why.

New Stuff.

Sheltering at home has lead to a few new things in the intact arsenal.  First is a low ratio Speakerformer.  These units offer 1dB-6dB of attenuation in 1dB steps and the shunt resistor is changed with each setting to keep the impedance the crossover sees a constant 8Ω or 16Ω.  These will handle 20W of input and are designed for crossover frequencies of 100hz and above.

Next is something that fits in the middle ground between the Elmaformer and the basic autoformer modules.  Many customers have been asking for an alternative to the plastic shaft found on the entry level units without the cost of the Elma switched version. These are based on a 23 position Blore Edwards switch and offer a good compromise between cost and performance.

It should be noted that all of the autoformers are wound identically to each other and the only difference between the various versions are in switch type.

Tannoy Redux

A decade or so ago, I played with some nickel cored versions of the Tannoy crossover parts for Arthur Loesch.  Recently, Chris from Jupiter Condenser had me do a complete set using his 0.99999 pure cotton served copper wire.

The cotton serving takes up a fair bit of the winding space compared to typical magnet wire insulation so some creative license was needed to keep the parameters identical to the original.  Luckily, the higher perm of the 80% nickel cores made this easy!

In the original design the ~0.5mhy inductor was air cored and had a rather high DCR and was in series with a ~4Ω resistor and I needed to juggle the DCR and and resistor values to net the same end result.

Since the theme here was 80% nickel, it only seemed appropriate to use that to my advantage for the above choke and sneak a few lams into the typically air cored inductor above to keep the family character.

Emia Manual

We are slowly moving Emia into the 20th century and just added a new Manual Autoformer as an entry level product.  It is dual mono and does 0 to -52.5dB in 2.5dB steps.  Two inputs and parallel outputs adorn the back and that funny knob in the center does a penalty free balance of 1.25dB and 2.5dB left or right.  Moving beyond the need for a 2.5dB shift the mono aspect will allow for any offset desired in 1.25dB steps.

It is essentially a 5-1/2" cube with enough mass to be stable and to really put things over the top it ships in a hard case.

Speakerformers

Resistance isn't futile... It is downright evil!  One of the big offenders in the resistance camp is the humble L-pad so here is a magnetic solution.

This particular unit goes from -6 to -16.5dB in 0.5dB steps which is perfect for padding that horn down to the bass.  The "coarse" steps are 1dB and the toggle allows for a 0.5dB trim.

Of course it resides on a permalloy core and allows the end user to select the desired impedance presented to the crossover by selecting the shunt resistor.

Wiring is simple with the same 3 connections as an L-pad.  More info to come!

Family Portrait

 I now have finished versions of 4 different types of "turnkey" autoformers that wire up with three connections per channel (In, Out and Ground).

The Elma Switch versions have Deep gold plated circuit boards for the switch contacts which then directly connect to the pins on the autoformers.  They come in 24 and 47 position versions and can be stacked for stereo or balanced operation.  The single 23 position mono unit  can be wound with any taper that is desired and the version with 3 switches pulls another trick out of the bag.

This version consists of a pair of 23 stepped units that attenuate form 0 to -52.5dB in 2.5dB steps for left and right and while 2.5dB is a bit coarse for a balance control the center knob comes to the rescue with the ability to shift the balance left or right over a 5dB range in 1.25dB steps.  This in conjunction with the independent 23 position controls allow for any shift to be set in 1.25dB steps.

I'll be updating the Intact Autoformer page in the next few days with priced and clickable purchasing options.

Boxing Day

Seems like an appropriate post Festivus day to pick a winner and pack something up.

If Moko sends me an address this year they will head his way.  Otherwise Random will pick someone else.

Festivus Present.

We wish you all a happy and healthy Festivus and for your audio enjoyment here is a pair of new toys.

They are 23 position autoformers that wire with a simple in out and ground connection just like a pot.

These have an audio like taper with a few 3dB steps then a bunch of 2sB steps and finish off with a few larger steps for that late night listening.

Air your grievances below and random.org will decide who will find them under their festivus pole early next week.

Silver Elmaformers

This is a new version of the elmaformers which uses a 47 position switch and seamlessly goes from -51.25dB to +5dB in 1.25dB steps.  It is essentially a linear version of the Chapman remote modules.

 It all starts with the weakest link and that is the pesky circuit board.  This isn't your everyday board but one made with .9999 silver and the traces are cut on a CNC milling machine.


The 4 deck 47position Elma switch mounts directly to the board and the wiper contacts are the silver of the board.  I have already run some boards through 20,000 switch rotation cycles without any issues so I am confident in the longevity of the units.

The silver boards are very time consuming to produce and will be reserved for the silver wound units.  For the more pedestrian copper wound units I am getting quotes for the hard gold boards per Elma's spec and will have them in the very near future.

Elmaformers

It is such a task for people (including myself) to solder the $400 autoformers to a switch so I am doing a circuit board that wires them directly to an elma switch.

While not being the smallest of finished items, it fits together nicely and can stack for as many decks as needed which makes true balanced operation a breeze.

This is a simple two deck "proof of concept" on proto boards with a 24 position switch that can have any desired taper you choose.  They will wire up lust like a traditional pot with In, Out and Ground connections for each deck.  I am so happy with the results I am planning another version on the 47 position switch that can have 1dB steps.