I have spent quite a lot of time to find a good transformer maker who can build something “beyond ordinary”. That means something standard (or a bit above standard) is no longer interest me. I spend hundreds of emails to talk and ask – from East to West. Some of the manufacturers are able to build what do I want, but they are not able to convince me that they know what they are doing instead of just like agreeing what I’m asking – that gives doubt on me. Some other manufacturers simply just insist to build based on what they have (and they know) – that’s good, but simply not what I want.

After spending hours to chat, email, and browse, finally I meet Ken from J&K Audio Design. Previously, he was the owner of DIY Audio Guide. Later then he decides to run his transformer business. One thing that interests me is his “bravery” in playing with “fire” (means high quality materials). I rarely see someone who really cares about power transformer – like I do – and I see that on him. After several emails back and forth, I finally come into conclusion to order something special (probably really special) from him. He probably have said silently that I’m crazy…

Not quite sure if he agrees with me, but probably this custom power transformer is also his first ultimate power transformer. He categorized this as Level 4. Normally he tells me that he build only up to Level 3 (and that’s also quite rare).

Beside ultimate materials used, this power transformer also designed with all techniques used in designing output transformer. I can guess some of his techniques, but will not explore more here. At first, Ken tells me that it’s useless to use output transformer design in power transformer. He agrees that  I will gain some benefit but (probably) not much. Power transformer is designed to run at lower frequency, while output transformer is designed to have widest bandwidth (completely agree with this). So probably just not worth with the cost to apply output transformer’s style as it will require more precision work and longer working hours – which translated to higher bills on me.

But sometime when we have reached certain point, going back even an inch will be regretted for the rest of our life… So be it! Be something that probably no one has gone before.

This custom power transformer is expected to upgrade my current Z11 power transformer for my Aikido PreAmplifier. It will be a split transformer for High Voltage and Filament.

I will not spend too much time talking here. Below are some pictures from him. You should upgrade your camera, Ken! 😉

First picture, precision CNC machine is working to create custom size bobbin.

CNC Precision Cut Bobbins

It will be a separate power transformer for Filament and High Voltage. So we will have two custom made bobbins. Separate transformer will allow me to slowly warming up the heater of the tube first. Yes you can use separate secondary on same transformer like on my earlier transformer, but I don’t prefer to switch in high voltage DC line (well, one can excuse to put the switch in Ground, though!).


The core material is Super Hi-B. Super Hi-B is higher grade than the original Hi-B core. From the initial measurement, we can get over 75% extra inductance by using this Super Hi-B core. Imagine many people are still using ordinary H or M or Z core in output transformer, now I will be using Super Hi-B core in power transformer.

I have good experience upgrading from H core to Z core power transformer – with same winding from same manufacturer. The result (again, you can call it as a placebo) is I do like the Z core one.

Super Hi-B C Core length

The stripes on Super Hi-B core is done by laser cut. We need to match the stripes in order to make sure the core is factory matched and aligned in right direction (the core itself is grain oriented type). Ken also says that the laser cut stripes helps to reduce Eddy current.

There are some numbers written on the side of the core to identify the “pair” or each C-Core. I believe the Core is from Nippon Steel Japan.

Super Hi-B C Cores with laser direction stripes

The windings are done. I would say that the winding is done in neatly fashion and carefully done. The tension also one of the factor that is carefully taken care by Ken as part of Level 4 design architecture.


Teflon film used to seal between layers. Will take more effort to do it, but as this is “no compromise” design, so there will be no excuse then…


Finished windings. Nothing much to say here, but simply a neatly done job. More to state of the art project for me.


Super Hi-B core is plugged to test the transformer. I think the job is half done now. There are some more to go – the most interesting part: the potting session! Again, you should upgrade your camera, Ken! 🙂