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.
Went to the "Secret Land of Walter" last weekend to have some fun with some friends. On the agenda for the weekend were some Tungar Supplies for his 4 RCA 1428's so I brought a few boxes of parts to complete the task.
Then some basic supplies were added and we were off to the races.
The kitchen table was taken over for a short period while Carroll and his helper whipped things together and tested things out.
After all was well they went upstairs for the in system test.
Then finally things were buttoned up for some music for the distinguished guests who many of which were there in spirit only.
and a member of the press came in and requested some Reggae... I begged him not to leave.
Art and Herb also did their thing for Stereophile and Art just added some more. FWIW... the table was a 501 and the creation of Ijaz Khan. The armwand is dymondwood (think panzerholz with parallel grain structure) and the cartridge a 103 with a line contact/boron cantilever combo and a new (much) softer suspension which tracks at 1.3g. I promise the field coil will be done by next time around.
Hey... where have jeffrey and dave been??? Well the answer to that is busy. To add at least a little content to this miniscule corner of the web, here is one of the small things I have recently made.
This is a "keeper" board that attaches to a pc mount bobbin and holds a schottky bridge and a pair of caps for a choke input filament supply. The chokes are dual bobbin and wound with flat wire for choke input duty and have split windings so one leg goes in the + side of the supply and the other in the ground. The PC mount bobbin allows for a nice way to hold the needed parts and the whole thing is supported by the mounted choke.
The ultimate use of these boards is for providing DC to some coleman regs and here is the resulting waveform when drawing an amp and a half of current. Yes that is a 60mv p-p 120hz sine wave
One of the biggest problems with rolling your own SUT is shielding them to get them quiet. In the very near future I plan on offering two options to help the cause of the DIY'er for shielding. One is a Steel box that has holes for RCA jacks and a ground lug. This can be lined with mumetal and copper foil for an effective enclosure. The other is a deep drawn mumetal can that can be placed end to end for a final shield. These can then be put inside a steel box for complete shielding.
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.
So I receive a belated holiday present from a friend and it comes in a box with cyrillic letters on it so I get a bit excited. When I open it, my first thought is why the hell did Fred get me an ugly red sweater?
Upon closer examination I quickly realize that there is something hiding inside that sweater.
Ahhhh, now I feel much better but I am still really confused why this sweater used as packing has no armholes. This naturally brings me to the conclusion that this isn't a sweater but a Soviet Era method of packing valuable tubes. (take that eimac!) While the boys were having fun playing with the "armless sweater" their mom comes in and asks why there were playing with a skirt? We all need to go out and mow the lawn now.... or work on the car.... or something.....
Just got these back from a vendor and they need a new home. They are the current modules and have a cheap pair of interconnects soldered into them for a quick audition. I'm leaving them as is and it is up to the lucky winner to decide what to do with them.
Leave a comment below with an identifiable name and Random.Org will pick a winner in a few days.