Check back regularly or subscribe for updates. Email us at, or fill in the form on the left.

Monday, August 30, 2021

J&K Balanced Ultra Isolation Transformer

J&K Ultra Isolation Transformer measured! 

If you are looking for an isolation transformer, look no further. We are one of the very best isolation transformer producer in the world. 

Below is one of a more unique Ultra Isolation Transformer we produced recently. What is Ultra Isolation Transformer? Read here ->  

Again, we have 3 grades:

  1. Level 1    - standard isolation transformer
  2. Level 2    - advance isolation transformer
  3. Level 2.5 - near ultra grade isolation transformer 
  4. Level 3    - ultra isolation transformer
Level 3 must be potted for us to fully utilize the isolation technology we have. For those that does not have the real estate to house these beauties, Level 2 is the raw unpotted version in metal frame but with as much Level 3 ultra isolation transformer technologies as possible. 

Below is a step-down double barrel shotgun Level 3 Isolation Transformer that a customer ordered. 

  • Specified input: 0-220V-230V (230V tap is used below)
  • Specified out: 110V-0-110V (balanced power) 
  • Dual unit of isolation transformers in a single chassis with 2 totally isolated outputs 
The voltage shown is on the high side as the input mains at my area is on average 246Vac. 

J&K Balanced Ultra Isolation Transformer

Dual ultra isolation transformer in a single chassis

Simple EMI tester 

Measured input noise level - long yellow bar, 376mV AC noise

Measured output #1, 0 yellow bar, 8x lower AC 38mV noise

Measured output #2, 0 yellow bar, 8x lower AC 45mV noise

J&K Ultra Isolation Transformer Test

Check out the video taken when we measure the unit. The audible AC noise can be heard, and you can see the significant reduction from input to output. Imagine how much improvement it can bring to your audio setup!

Posted by Ken Loo on Sunday, August 29, 2021
Till then, take care and stay safe!  

J&K Audio Design


Monday, August 2, 2021

Output Transformers Sales - 211 PSE or 845 SE or 212 SE (50W)

Sales! Sales! Sales! Clearing out storeroom. We will clear out storeroom once in a while and here's what we found idling. 

Level 3, 50W Single Ended Output Transformers

Primary: 5K

DC: 150mA - 180mA

Secondary: 0-4-8 Ohm 

Core: Hi-B / Nickel (Permalloy) Hybrid 

Potted with solder tags (126mm x 126mm x 150mm H) 

Original price MY$6,900 / U$1,725 per pair 

Sales price MY$5,715 / U$1,290 per pair (25% discount!) 

Suitable for 300B SE, 300B XLS SE, 211 PSE, 854 SE or PSE, 212 SE (limit to 180mA), KT120 SE, KT150SE, KT88 SE, KT90 SE, EL156 SE, EL152 SE, EL153 SE or any big power tubes. 

Saturday, June 19, 2021

J&K Ultra Isolation Transformer Testimony

We've received another follow up "glorious" testimony from Steve from SMC Audio

Thank you for your kind words and time to write us this testimony! 


Hi Ken,

I have been meaning to write you about the final outcome of the custom power amplifiers I built using your 800VA Level 3 Ultra Isolation Power Transformers in silver but I have been so busy I haven’t been able to find the time. I still intend to write something more formal but I thought I’d send you this note for the moment.

It seems to me that you are more tube-oriented, while I have chosen to wrestle with the issues of solid-state design and finding ways (hopefully) of delivering the beautiful musicality of tubes without some of the practical issues. I feel that I’ve made good progress towards that goal and I’ve been able to make a lot of people happy with my amps. These custom amps gave me the opportunity to try some new ideas and to “push the envelope” of performance, and I could not be happier with the results.

A friend asked me “How do they sound?” and I told him that I could not explain because I no longer had any words that were up to the task! And it’s true…these amps went to a whole new level of performance that I’ve never heard from anything previously. I’ll have to come up with a new way to describe what I hear from them. The usual adjectives simply fail to convey the experience of hearing the music these deliver, although I will say that “holistically, organically whole and complete” comes to mind. I’ve never heard any other amps as satisfying as these, and think that your transformers are an important part of that equation.

Thank you again for your hard work in making these a reality.

Best regards,

Steve McCormack

End quote. 

Enjoy the pictures. Man, they look so magnificent!  We're sure it sounds as good as it looks! 

P/S: J&K does not pay for reviews. Therefore you will not see our stuff being published in mags or paid reviewer sites. Paid can be in forms of advertisement fees as well. All are testimonies are from real user that paid real money for them - that speaks the most! 

Till then, take care everyone.

J&K Audio Design 


Sunday, June 6, 2021

Output Transformer for EL86

Hope everyone is doing well out there! It is approaching 2 years since COVID19 outbreak started and yet, our country is experience the 3rd (or 4th, I don't really know!) full lock down to control the spread of the virus. Blame the government? Blame to foolish citizen for our own demise?

Life goes on, online, not in the physical world. Since we can't do much in the factory, we can focus our energy to generate some post to past time. Apologies for those that ordered - we are truly sorry for not being able to churn out the irons on time. 

Now let's talk about tubes --> EL86. Huh? Not EL84? Typo? No... you've read it correctly --> EL86. It is a low impedance output pentode suitable for audio use. It is very similar to EL84, just that it has a higher maximum current tolerance and lower Ra or Rp (plate impedance) compared to EL84. The output transformer designed for EL84 may be usable but is not that suitable or optimum.

Why we choose to bring up EL86 instead of EL84? NOS EL84 is quite expensive now and is being used in commercial amplifiers. EL86 on the other hand, is not, and NOS is cheap and plentiful. I myself have collected some for personal usages, such as Mullard, Telefunken or SIemens made NOS EL86, which are such beautiful and excellent sounding tubes. Due to such low price, fake EL86 are rare, unlike fake EL84, plentiful!!! 

I do not like Pentode sound personally, but luckily, EL86 can be triode connected. 

DHTs are pure blood
IDHTs are half blood
Pentodes are muggles

Just joking... Meanwhile... 

With the low impedance of 650 Ohm when triode connected, output transformers used for 6080 tubes, or 2A3 tubes, can used. Such 2A3 or 6080 SE OPTs usually have primary impedance of ~1.5K to 2.5K which suits EL86 perfectly. The triode connected EL86 calls for 170Vp with bias current of 74mA, which most SE OPTs happily fits. For connoisseurs, they can custom make SE OPTs for perfect fit to optimize the bandwidth and primary inductance. 

Primary impedance: 1.5K to 2.5K

Primary DC current: 70mA-80mA

Output power: ~2.5W (recommend a 10W OPT) 

For those that needs a bit more power, then can happily purchase more tubes and have PSE or Parallel SE. Exotic NOS EL86 are plentiful anyways, use as many as you like! Also, maybe you can run it near maximum to have even higher power. NOS are made to last and won't be as fragile as modern tubes. 

On top of being a power tube, EL86 is a decent driver tube too since it can churn out quite a lot of current for grid current hungry tubes, or large transmitting tubes. Due to the low plate voltage, one may need to use a step-up interstage transformer to get the required V-swing to drive the output tube to full power. 

It is not as warm and pure as true triode, or true DHT (direct heated triode), but the tonality is still good, and one gets to play with multiple types of exotic NOS brands such as Telefunken, Mullard, Siemens, and such. They are many, many times better than modern day new production tubes. In addition, we have to mention the jaw-dropped faces of the visitors when they get to know that you're using Telefunkens or Mullards or Siemens that they paid loads of hard earned cash for (I wonder how much ECC802s cost now for real NOS Telefunken) while you just paid peanuts for it, and have another dozens of different NOS pairs in a box as spares. 

I'd say, why not! Now, it's time to go back to my den and have a bunch loads of beers to endure the MCO while we can. Nuh, just kidding. We'll still try to catch up with work while we can. Also, we will find another tube to introduce in the next round. 

Stay safe everyone and enjoy life. 

J&K Audio Design


Friday, April 30, 2021

Ultra Isolation Transformer Upgrades - Ubiquitous Ground Technology

It has been quite some time since we update everyone on our J&K ultra isolation transformers. It has become better, and better, and better! We may be quiet on all fronts (FB, blogger) but we are still very active in the background. On top of our custom audio transformers, one of the other bestsellers is our J&K ultra isolation transformers that have received countless recommendations and praises.

On second half 2021, we are rolling out new grounding design for our J&K ultra isolation transformer. We call it Ubiquitous Ground Technology. Ubiquitous Ground Technology further removes or reduces the noise at the output and ground with a unique winding winding and grounding method. The noise immunity of the already super quiet output of J&K Isolation Transformer is further enhanced to an ultra low level. 

Some of our users prior to this announcement have been enjoying them since we've incorporated them in some of our recent products, free of charge. With the Ubiquitous Ground Technology being finalized and matured, we are proudly introducing it now! You can now specify to add this to your ultra isolation transformer orders. It comes with a small fee but it is definitely worth it. 

On the other hand, we would like to take this opportunity to mention the option for our J&K Ultra Isolation Transformers that we did not mention in the past - ultra low impedance transformer design. This is suitable for users in area prone to surges and spikes in their power line. It is more for protection than sound - for safeguarding and protection mostly. We usually do not offer it since it is not a small cost adder. Ask is if you prefer to have it in your order. 

P/S (important): just a note, customers have always asked us to oversize the transformers to provide more headroom. Oversizing is not bad, just that it sometimes creates other problems such as over-voltage when unloaded and also higher inrush current. So, when you order, in case we forgot to ask (apologies - we're just too busy with orders and manufacturing honestly) please indicate the actual usage so that we can adjust the winding ratio to give you more accurate desired output voltage since unloaded/lightly loaded transformers may yield higher output voltage.

Due to manufacturing being overloaded with OEM orders and everyone in J&K being overloaded, we're increasing our lead time to 4-8 weeks for custom orders, depending on design, quantity ordered, and the load at manufacturing line. 

Please plan and order early if you are in a rush. Do not order from us if you cannot wait. We do not want complications arising for long lead time - we do not want that either but it is just life. We are hiring additional technicians but it takes time to train them up PROPERLY before they can be deployed to the production line. 

We noticed that some commercial companies have been copying our design ideas from our blog posts. Shame on your but we treat it as compliment and acknowledgement to our advancement in isolation transformer technology. 

J&K Audio Design


Friday, April 2, 2021

Custom order lead time

Dear beloved customers, we are officially increasing our custom order lead times to about 6-8 weeks due to our manufacturing lines being overloaded with OEM orders. 

Orders will still be processed according to the time they are received. Just that OEM orders are large and will take quite some time to be completed, and therefore those that come after it will be impacted. We have been seeing quite a number of large OEM orders and do not see them subsiding any time now. 

We hate to say that but it is hard to get experienced hires to help with production. We are planning for hires but it won't be so soon before they can join the workforce since they would need to be fully trained first. 

We are working our best to get the orders moving. If you plan to order something from us, please plan ahead of time and order early.

Kindly be informed. 

Thousand apologies.

J&K Audio Design


Search This Blog

Product Lists

Product Lists

Level 0: link 1

Level 1: link 1, link 2, link 3, link 4

Level 2: link 1, link 2, link 3, link 4, link 5, link 6, link 7, Link 8, link 9

Level 3: depends on type, size and complexity. Email us for details.

Iso-trans: link 1, link 2

Power-trans: link 1

* Finished amplifiers, DACs, audio gadgets, upgrades and repairs - this is not our core business and we do it out of passion. We do not have fixed models, fixed price and we customize for each individuals. The sky is limit of creativity.

* Our product lines are always improving and increasing. If you do not see what you want, contact us!

* Please email for volume discounts, distributor and OEM pricing.