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Saturday, July 26, 2014

Biggest Output Transformer

What you are going to see is going to amaze you... 
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hold your breath...

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 witness this spectacular...
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while most people are still talking about double C core...
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quad C core is already being done here...
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and when people are considering quad C core, something grander is already cooking...
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and the next is actually a 6th C core!!!
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and not just that...
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it is a GIANT 6 C core output transformer!!!
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that weights 15.6KG a piece!!!
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it can be used with any tubes that you fancy...
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a vacuum tube amplifier that can match solid state amplifier in terms of power...
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isn't it wonderful?
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now, we present you the biggest output transformer
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everything just pales compare to it
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the largest, monstrous output transformer!

The biggest Output Transformer?
 An EI66 EI transformer is place beside this biggest output transformer for size comparison. See how big this mother of all OPT is? 

Is this the largest Output Transformer?
Is this the biggest? You tell me!

The above is made for FU33 tube, single ended output transformer.
Primary 10K, secondary 4-8 Ohm.
It can withstand 1500V supply.
Primary DC current of 200mA.
6000 rounds of primary with Teflon insulation.

Above is just an example of what it can do. Many other variations can be done with this core, like for example: power choke, plate choke, PP or SE output, interstage (erm... I don't think anyone will do this), and many more.

If you dream of some monster project that you want to try, now is the time to do it. It will not be cheap but it is one in this world. We only live once! Treat it as a gift of your lifetime! 

Contact us now on what you want to do before it runs out. Fulfill your fantasy today. It does not come as close as this today.

J&K Audio Design



805 Output Transformer

New stock arrival - Amorphous SiFE C Core from Japan.

This size is good for 805 vacuum tube amplifiers. It's good to be made as power supply chokes or anode chokes too. A pair of double C core 805 /  845 output transformers Precision Wind would be ~USD$990 for such cores, potted in good quality transformer potting compound, with measurement data provided, not to mention, matched pair. *Custom designs will be priced separately.


C Core that comes in sealed adpack.
Meticulously packed. Salute to Japanese workmanship spirit!
Paired C core with alignment marking for best coupling.

The brand new cores are much more expensive than refurbished cores because brand new cores are perfectly matched and comes in perfect condition with electrical properties know. Refurbished cores conditions might not be as good and therefore reflected in the lower price.

Below is an example of output transformer built with this core.
10K Output Transformer for 845
The core window utilization is very high, and therefore if possible, we do not recommend more than 2 taps to be configured at the output as there is no more space for wires to fit into the core.

Potted 10K Output Transformer


Primary impedance: 10K Ohm
Primary DCR: 275 Ohm
Primary inductance: > 50H (measured at 100mA, 20Hz at 5Vrms)
Primary DC current: 120mA max (100mA recommended)
Secondary impedance: 4 - 8 Ohm
Weight: 13KG per pair

Actual measured frequency response is as follow (excellent!):
* 20Hz (-0.26dB) - 1kHz (ref) - 20kHz (-0.31dB)
* Using 845 tube biased at 900V 80mA at 1W output power.
* Matching - DCR <2%, primary inductance <5%

Below is another pair made for KT88 Push Pull tube amplifier.

KT88 Push Pull Output Transformer
7.5K PP Output Transformer
Push Pull C Core Output Transformer


J&K Audio Design
26 July 2014

Sunday, July 13, 2014

Audiophile Z11 Power Transformers

These are special custom made audiophile Z11 power transformer for tube amplifier (filament supply). It is not cheap but definitely is worth the investment. The wires used are UK made silver plated OFC with Teflon insulation.

The secondaries are drawn out directly using the same wire materials instead of via solder-tags then with other types of wires. For those that might not be aware, there is a reason for such designs. Different wires have different characteristics impedance. Once you go though a change of materials, that equals to change of characteristics impedance - see below:

On DC world, it looks like this:





* Wires A - connector - wire B

On AC world, especially on high frequency operation, it looks like this:
* Wire A (impedance A) - connector (impedance C) - wire B (impedance B)

What happens when the impedance change? Reflections, attenuation, boosts, and all sorts of artifacts of impedance mismatch. This will indirectly affect the signal integrity of the music signal. At audio signal range, it should be negligible but every little things matter.

It's better to take every precaution possible, and therefore the birth of this special made audiophile Z11 power transformer.

Of course, we will not forget to share some pictures! Enjoy!

Z11 audiophile tube filament transformers

Teflon insulated silver plated OFC

Audiophile Power Transformers


Till then.

J&K Audio Design
13th July 2014


Monday, July 7, 2014

Back from holidays!

J&K Audio Design is back from holidays! 

The most memorable night to remember - reunited with the venerable Jo Ki and TL Koo at Jo's place for a very short listening session - excellent setup! I wish I could stay longer but I needed all the energy to stay awake in a 3-day course in Kuala Lumpur, Malaysia. 

My favorite picture of the year!

J&K Audio Design 
7th July 2014

C Core Power Transformers

A pair of Hi-Hi-B double C Core power transformers are being completed and to be delivered soon! This gentleman has taste as he realizes the importance of supplying stable and good quality power source from the power transformers to the sound!

The best thing for power transformers is still to pot it and protect it with potting compound instead of letting the core rusts and deteriorate over time. Do not worry about the temperature generated as J&K transformers are designed to work at lower temperature.

Transformer submerged in potting compound.

Solder-tagged and ready to ship.
We are still waiting for it to fully cure before it is be subjected to the harshest trip it will make in its' whole lifetime - via the postman to the owner!

Hi-Hi-B Double C Core being placed into the enclosure - perfect fit.



Final look and test before being packaged.
J&K Audio Design
7/7/2014