Friday, May 25, 2018

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.

Friday, May 4, 2018

LCR Tape EQ


Just finished up a LCR tape EQ for a customer in Hong Kong.


Single ended input and output with 40dB of gain and three different EQ filter options. (NAB, 7.5ips IEC and 15ips IEC)  This follows the basic topology of our phono with permalloy output transformers and power supply chokes.


In this instance the customer needed a balanced input so I built an active Balanced to SE gain stage based on a pair of 2SK170's loaded with an 80% nickel transformer that brings the overall tape gain up to 60dB.


Wednesday, April 4, 2018

Tarragona Audio

Pictured below are 14 pieces of lovingly hand crafted nickel for an all out design of a microphone preamp by our good friend Peter in Berlin.


This device is unique because unlike the typical professional "buffer it all and let god find the music" approach of some, Peter harkens back to the days of yore when transformers and inductors were the proper tools to use and what something sounded like actually mattered.


The 14 permalloy pieces consist of 4 - DC carrying output transformers that load active devices, 2 - level control autoformers, 2 - tapped filter chokes, 4 - nickel power supply chokes, an input transformer and a phantom power choke.  No caps exist outside the power supply and at the next ETF I will lobby for some filament supplies.  As it stand, i think it is awesome and if given the choice between using transformer loaded Fet's and chokes or tubes and caps I think peter made a wise choice.

full details of this design can be found at Tarragona Audio

Friday, February 16, 2018

GM70, Silver and Nanocrystalline

Just finished these up for a GM70 amp Jeffrey is building for a customer.  They are wound with 0.9999 pure silver wire on big nanocrystalline cores.


The silver winding wire is brought out for direct connection to the circuit.  While I am a firm believer that it is the amp designers responsibility for the ultimate packaging aesthetic, I do have some 125mm cubed aluminum covers that will cover them if needed.


After many years of insisting that doing multiple taps only adds to the compromises I want to avoid in a design, I have finally come up with results that I deem acceptable.  Below are the plots of a similar transformer wound with the ability for 4, 8 and 16 ohm taps.


For behavior below 100hz I look at the inductance plots to make the best choice of inductance vs. current for the intended application and set the air gap accordingly.  The plots below were taken with the equivalent of a 16W excitation voltage @ 50hz.  Pink would be suitable for a parallel 300B,  Brown an 845 or GM-70 and something inbetween green and blue could be chosen for a 211.



dave




Thursday, January 25, 2018

Nickel and Amorphous L1's

These just came out of the oven both for Choke Input power supplies.


The bigger one is on an amorphous core and weighs in at 14 pounds will find service in a GM-70 amp.  18Hy @ 250ma for a 1000V B+  The smaller pair are on 49% nickel and measure in at 100hy @ 20ma.
Autoformer for size reference:-)


Friday, December 22, 2017

Random says 17

and the winner is Hamingredient.

please contact me by email with which ones you want and where to ship them.

Happy Festivus to all!


Thursday, December 14, 2017

FFM..... festivus filament modules

It's beginning to look a lot like Festivus with all the airing of grievances and dancing around the Festivus Pole of late.   This must mean is time to give something away.  The newest thing in our bag of tricks is a simple LC filament module that can provide up to 2A or 3.5A of DC current.

Originally designed to power coleman regs, these modules give you a nice easy way to mount and wire a source of low ripple DC from an AC input.


All of the sordid details of what they are and what they can do can be found HERE

Air your Grievance in a comment below (with your name) for a chance at a free pair shipped to you as a Festivus Miracle.  As usual... in a few days Random.Org will pick a winner.

Enjoy!

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