Different types of Hi-B cores

It has been a while! We're still alive but have been busy with various industrial or corporate projects than consumer sales. 

Why do we always promote Hi-B? Hi-B has lower core loss, lower exciting current, and noise. This enables transformers with higher efficiency (smaller size), and larger capacity per same volume (compact). Hi-B also have lower hysterisis loss + better magnetizing characteristics + lower eddy current loss compared to ordinary GOSS. This in return, results a lower noise and better efficiency transformers. On top of that, the Hi-B that we chose employs special glass-film and phosphate coating to improve interlaminar insulation and better handling of tensile stress in the rolling direction. These are not BS but can be proven in the electrical characteristics of the cores. 

So, GOSS cores, stand aside. And non-GOSS cores, stand even further way please (pun intended)! 

Nah, we all know this, why do you bring this up again? Well, we want to let you know this as some often are confused what core we use in our products versus the others, and what our different grades of materials means to the quality and price. Here goes nothing:

0) Non-GOSS - nuh, we don't really want to use this unless budget is really a concern. This is your standard offerings you get from others - go get from them! 

1) Standard GOSS - the standard grain oriented silicon steel, which is widely used in signal or output transformers, or high efficiency power transformers. We likey. Our standard offering in Level-1 and Level-2 products. 

2) Hi-B - improved over GOSS, with higher degree of crystal orientation than GOSS. It offers higher permeability and lower iron loss. Widely employed in our Level-2 and Level-3 products. 

3) Super Hi-B - improved Hi-B, with laser beam irradiation on the surface to refine the magnetic domain, as some have ordered from us in the past, named widely as SHIB cores. It is a grade above Hi-B. It has even lower loss and lower magneto-restriction. 

4) Ultra Hi-B (new, well, not really new but just not mentioned in our blog) - now this is the ultimate, for now, before alien technology comes in. This adds more post-processing to the core where the surface (facial treatment!) are further treated, magnetic domain-refining, for those experts readers. 

Just for fun, take a look at the properties below: 

We did not list out all as there are just too many, and the properties improve from lower grades to higher grade version - you get what we mean, right? 

Note: non-GOSS are added just for fun and comparison. El-cheapo's - don't bother asking us to make it for you unless you can order 100 sets or more of the non-GOSS variants. :p 

As how the world operations, higher quality cores have more limited ranges and therefore not all applications can use the higher grade cores. We shall decide per the application how to best suit the desired use. 

Till then. You guys take care. We need to go back to submarining to focus on churning out more irons. 

J&K Audio Design

26/5/2024 

 

Output transformer primary inductance

Output transformer primary inductance - warming, long topic with some simple maths. LOL. 

What's the best primary inductance for an output transformer, or even an interstage transformer? Often, we get customers asking for insanely high primary inductance as they read over internet that there should be at least 10H for a 1K primary impedance. 

High primary inductance is good but with conditions that the capacitance and the leakage inductance remained the same (which is kind of difficult to achieve since these parameters are conflicting).

Leakage inductance is proportionate to the number of turns (square of it in fact). In order to reduce leakage inductance, one must decrease the number of turns. Then, that reduces the primary inductance! This can be overcome by different winding techniques (interleaving for one, or use different core materials for another, and many more), but those also will introduce different parameters that one need to consider. Yes, it is kind endless - balance is the key.

Let's do a oversimplified calculation for easy understanding.

Required load = 8,000 

Primary impedance of SE OPT = 15,000

Primary inductance of SE OPT = 90H 

Reactance of primary @ 30Hz = 2piFL = 2 * 3.142 * 30Hz * 90H = 17,000

(30Hz is the reasonable low frequency limit)

Real load with the OPT = reactance of primary // reflected load resistance 

Required load = 17,000 // 15,000 = 8K 

1K primary impedance needs about 6H in this case. 

So, one needs an OPT of 15K primary impedance with 90H primary inductance for very good low frequency response, as required by the driver tube specifications. The stronger the tube (lower Rp - plate resistance), the lesser the requirements on the output transformers. 

Now this is not that difficult, isn't it? Of course, if one needs to extend the low frequency to 20Hz, which we think is a bit over, then the primary inductance may need to increase. One simple way of increasing the primary inductance is to increase the primary turns, and/or use a larger core (or core with different electrical parameters - I would not say better here since different core has different intended usages, more may not be the best a lot of the times).

Increase turns, will increase the capacitance and leakage inductance. This will affect the high frequency response since it is sort of like a filter. The more turns, the higher the leakage inductance. Also, the turns number affects the flux density and we do not want to exceed the amount stated for the core size/material. Not forgetting to mention, the transient response of the OPT will need to be taken care off too by controlling the leakage inductance. If you see ringing, that's one of the artifacts of high leakage inductance. It may cause distortion or early overloads if not taken care. 

We can use different winding techniques to help with the above but there's just so much those techniques can do before reaching the limits. 

Of course, in circuit design, there are other parameters that will come into the picture that will affect the OPT primary inductance requirements, which is out of topic for now. And... there are many more that comes into the picture that we do not have time and space to list out all. 

This also shows that universal transformers isn't such a great idea, is it now? Go figure. Go tailor made! 

Rgds,

J&K

Ultra Isolation Transformer for AV show

Greetings everyone. 

Hope everyone is safe and sound. We all have been through hell, from Alpha to Delta, and now the almighty Omicron. We will get through this together! We'd like to dedicate this song to everyone! 

https://www.youtube.com/watch?v=-n3sUWR4FV4 

We have a little story to share today actually. A friend / customer went to an AV show some time ago. He was amazed on a setup in a room. The sound was very clean, pure, relaxed, effortless, and less distressed as compared to other setup he listened to. He went around busy-bodying and found a little secret gadget hidden behind the scene. 

Guess what...? We're delighted to see that it is actually none other than our Ultra Isolation Transformer, connected to their front end electronics. Unfortunately, we cannot share the pictures of the setup, nor the name of the room and details, as he couldn't get the authorization from the setup owner. 

Nevertheless, there is no copyright in sharing news, and here we are. 

https://jandkaudiodesign.blogspot.com/2020/09/the-best-power-transformer-for-audio.html 

For additional details, 2 units were used, 1 with single Ultra Isolation Transformer inside, the other with 2 Ultra Isolation Transformer inside. The one with single transformer is used for the tube amplifier. The one with 2 Ultra Isolation Transformer inside was for the front end gears - CDP and digital player, cascaded for absolute performance for noisy environment. 

Usually one Ultra Isolation Transformer is enough for home environment. Cascading may make the sound too "dead", but if the incoming mains are just too dirty, such as in AV shows, or condos, then, perhaps this would be a good solution. 

We have a variation of this connection, which is to do as below, where user can try both double-isolation and single isolation. 

Or even this below if one has skills to do the switching correctly, or with qualified DIY skills.

P/S: Not everyone knows our blog. Information is there for those that do their homework. One that reads, follows and employs this tactic, will have an edge over the others. I guess that's how it works in stock trading too. Take action now! 

Till then, everyone take care! 

Time to get some rest. We've just been too busy lately. 

11/28/2021 

J&K Audio Design

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! 

Quote:

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 

20/6/2021

Price Increase of Ultra Isolation Transformer

Howdy everyone,

We are very happy that we received a lot of praises on our Ultra Isolation Transformers and Ultra Isolation Power Transformers (for tube audio and solid electronics) on HIFI and industrial applications. They are considered one of the best, if not the best transformer to be used for audio applications. 

Our Ultra Isolation Transformers price has been stagnant since a few years ago. Unfortunately due to materials / commodities prices increase (some had increased over 10%, as well as labor rate rise, we have to revised our Ultra Isolation Transformer prices. 

FYI - our Ultra Isolation Transformers (or Ultra Isolation Power Transformers) takes 8-10x longer time to produce compared to standard transformers. It is a very labor intensive job and making a perfect one is not a simple feat. So, please bear with us if your Ultra Isolation Transformers or Ultra Isolation Power Transformers take longer time to produce. 

https://jandkaudiodesign.blogspot.com/2020/09/the-best-power-transformer-for-audio.html

https://jandkaudiodesign.blogspot.com/2017/05/ultra-isolation-power-transformer.html

https://jandkaudiodesign.blogspot.com/2021/01/j-ultra-isolation-power-transformers.html

Thank you for your patience and support in advance.

Several of our experienced designers and workers are overstretched, overworked, and complained about the burden on them to always being pushed for deliveries. Our experienced staffs are not young (I'm getting old too!) anymore and and we are expanding our human resources slightly but still no drastic huge hiring to keep the quality of the personnel hired and have quality job done for our customers. Therefore, lead time is still rather long. 

Please plan ahead and order early if you need anything from us with lead time of 4-8 weeks. Else, please look elsewhere if you need rushed orders. We do not wish to have any arguments down the road if you feel that your orders take too long to deliver - we have pre-warned you here again. 

Enjoy your audio! 

Rgds,

J&K Audio Design 

28/3/2021. 

Repair transformers

Hello everyone! 

It has been a while since we've posted! COVID-19 lands us in a really bad condition. Crippled operation. Stunted supply chain. Work from home. Movement restrictions. Anything that you can think of, can happen. Anyhow, life goes on!

Today, we want to share a lesson learnt from a customer of ours to you about transformer repairs. Hope that you do not land in the same situation when you want to repair your transformers, be it transformers for tube amp or transformers for solid state amp.

Customer has a faulty preamp output transformer. He heard of us, and approached us for a quotation. Our price seemed too high for him and he turned down our service to repair his preamp output transformer. 

After a month or so, I can't really remember, he came back, confirming that he would want us to repair the preamp output transformer for him, and he will be sending a pair, including the OK output transformer.

We told him - we only need 1 piece, the damaged one. We can and will reverse engineer it if it is not too badly burnt, and rebuild it according to the original design/methods.  

He said, he insisted that he needed to send us both the OK and NOK units. I asked, why? He sent the damaged transformer to another person for repair and it came back still damage - producing distorted sound. Now he needs to send it to us for another round of repair. And since the damaged unit had been tempered and may no longer follow the original design, we have to have the OK unit as a reference to rebuild the damaged preamp output transformer 

Ah ha!!! 

Now do you see the problem? Now we have to dismantle the OK preamp output transformer in order to know the design and rebuild TWO preamp output transformers now. Repair charge is DOUBLED now since we have to work on two units unfortunately.

Moral of the story - pay for quality, do it right the 1st time. In the long run, it may save you more money - for not resending it for another round of repair, for not paying for 2-3rd time of repair, for longevity of the transformer, for getting back the original sound, for peace of mind!

Only send to reputable repair center for your beloved transformers - J&K Audio Design, your faithful repair guy next door. We may charge higher for the repair because we really, really reverse engineer your transformers, and rebuild them based on the original design, use good quality wires, and original materials when available. In addition, most importantly, you get peace of mind that it is in safe hands and you will get it back to be as close as original.

We've repaired tonnes of super high end transformers that cost as much as a car. We've repaired transformers from 1940's to 2000's. We know almost all the designs. We know what we are done. 

Thank you and that's all for this time! Stay tuned folks!

Take care and stay safe! 

J&K Audio Design

28/11/2020

  

The best power transformer for audio!

The best power transformer for audio has just gone even better! Our Level 3 Ultra Isolation Power Transformers design has just been improved and enhanced with even better isolation properties and grounding techniques to achieve even lower noise than before. 

For those who are unaware of what Ultra Isolation Power Transformers (UIPT) are, here are 2 main pages we talk about our ultra isolation transformer or ultra isolation power transformer. If you have not tried it, you have to die-die (as we say it in locally) try one. The performance is Heaven and Earth apart from the ordinary on-the-shelf stuff.  

There is a price to pay but the ROI is well worth it. It is much better than just upgrading power cords or add more 3rd party gadgets to lower noise floor. 

Why do one use Ultra Isolation Power Transformer (UIPT)? In short, UIPT is a combination of power transformer with ultra isolation properties. You get the lowest noise and darkest background out of this by just 1 UIPT instead of the usual isolation transformer then power transformer combo. 

https://jandkaudiodesign.blogspot.com/2017/05/ultra-isolation-power-transformer.html

https://jandkaudiodesign.blogspot.com/2016/06/isolation-transformer-bandwidth.html?m=1

For those who are not a follower of our J&K Audio Design page, please take a few minutes to visit our FB page, give us a "Like" and subscribe to our page: 

https://www.facebook.com/groups/jnkaudiodesign

All the best for audio! 

J&K Audio Design

4/9/2020

Output transformer preamp transformer

Thanks to one of our great and frequent customer, this article is born.

Before we start our lecture, take a look at this picture below of Tamura A-4714 signal transformer. Do you see any peculiarity about this Tamura A-4714 signal transformer? 

Sorry, right guess does not win any prizes here. LOL! 

Yes, it is an output transformer. Yes, it is a pre-out / pre-amp output transformer. What? Two types in one? Yes, two in one! 

Based on the limited information available, it is a signal transformer with primary of 5K that is capable of ~50mA of DC current, and a mixed secondary of 150 Ohm + 150 Ohm + 6 Ohm.  

1. Application 1 - use it as a power amplifier output transformer capable of ~3W output.
2. Application 2 - use it as a pre-amp output transformer with either 150 Ohm (secondaries in parallel) or 600 Ohm (secondaries in series) output impedance.
3. Application 3 - use the additional tap as a feedback tap to reduce distortion, as seen in some innovative designs in very old designs. It may be present in modern designs but I rarely see one. 
4. Application 4 - use both! 

How to design the circuit - hmm... maybe next time. There are plenty of sample circuits online. If you buy one from us, maybe I shall consider spending more time to teach you how to do so. 

Now this sort of signal transformer is kind of fun, right? If you're undecided if your tube is going to be used in either applications, order this transformer! You can decide later and still have the right transformer to use - now ain't that cool! 

Of course, buyers be warned - universal design is a compromise. A dedicated transformer will be better, minimalist, as we always preach. For the fun of it, I see why not. Also, the user said it is one of the good transformers he owns. So, I believe, we can do better than that! Challenge accepted! 

Good old used or NOS Tamura A-4714 could still be found occasionally in eB*y or all sorts of online sellers out there. If the A-4714 fits what you need, perfect. If you need something that is out of ordinary, custom made, then you know who to look for - J&K Audio Design! We can make it to any primary and secondary taps that you need. So far I've not seen new ones being made - I may be right for now, and wrong later. You can check Tamura website and see if it is there. 

The sky is the limit! Seriously. We can use almost ALL sorts of cores available in the world. And we have 3 types of magnet wires to choose from - ordinary John Doe OFC, to exotic OCC Copper and OCC Silver cable wounded output transformers. Oh ya, any voltage (as high as your dare) and any DC current for the primary too (1A? No issue, been there, done that!). 

So, for those under-decisive souls out there, your savior is here!

Do I have an actual picture of it? Nuh... it looks the same like every output transformers out there - bare naked or potted. They all looked the same. You want special casing? Hmm... maybe we can do so now - since we've found a LOVELY LOCAL vendor here. He's a bit busy though - so expect longer lead time if you need a fancy output transformer case. 

Meanwhile, take care and stay away from being infected with COVID-19. Stay safe at home. DIY more audio amplifiers. Buy more transformers from us!

J&K Audio Design
22/6/2020 

Shunt Reactor

People has been talking about the evil artifacts, such as, noises the active regulation brings, for example, those using a toroidal transformer with a motorized carbon brush, or even relays to switch to multiple taps in the transformer, to adjust the voltage when there are elevated mains voltage or brown-outs. Or, some audiophile just despises in-line or in-series regulators, saying that they choke the sound of their system, or restricts the dynamics  

So, is there a more elegant way of regulation other than the active way? Is there a way to regulate with passive components? Is there a shunt type of regulation device that can help with regulation? When it comes to transformer, or anything with a core and wire, ask us! 

Well, there is! And, it is called Shunt Reactor! 

Shunt reactor is used in industrial applications, more than home environment, where it is an absorber of reactive power to increase the efficiency of energy transmission, or to compensate (or consume) the reactive power generated by capacitive loads line capacitance - Ferranti effect). 

An inductive load consumes reactive power. A capacitive load generates reactive power. We have too MANY capacitive loads connected to our power line right now, especially with high power amplifiers that uses a lot of capacitors. Even an OPEN POWER LINE generates reactive power. 

The shunt reactor is normally connected permanently to the power line, or sometimes are switchable, or adjustable (VSR - variable shunt reactor) to cater for different daily-hour power draws or seasonal dips and peaks of power draw. 

In layman terms, shunt reactor automatically stabilize the voltage levels. minimize over-voltages. 

Usually the shunt reactor is permanently connected, or switched by a circuit-breaker (circuit-break is required ***important***). Several shunt reactors with different can be connected in parallel, or switched in and out to adapt to different power line conditions. 

A simple connection diagram of the shunt reactor is as above - across the live and neutral lines. For balance power, you will need two units of them to work in tandem. 

WARNING: It is dangerous and LETHAL mains / live AC voltages you are working on. Do it at your own risk. It is for qualified electrician only. WARNING. 

What consists of a good shunt reactor design? 

• Air-gapped core - constant impedance, reduce loss, avoid saturation, promotes linear energizing, and minimize remanent flux in the core (flatter hysteresis B-H curve, lower inrush current) 
• High inductance - high energy storage and resistance to changes 
• Low DCR or thick wire gauge - quick charge and discharge
• High grade core - minimize power loss, lower vibration and noise  

A shunt reactor may look like a transformer, but it is intended to consume or compensate reactive power, where as transformer is to convert one voltage to another, or one impedance to another. Shunt reactor has only one winding. Transformer has 2, and above for the conversion. 

Since it is switched on all the time, losses becomes important to avoid high electricity bill and heat. What are the major losses in a shunt reactor?

• Copper losses in the winding - wire 
• Core loss - iron core loss 
• Eddy current losses

Therefore, it is critical to minimize losses, and have a good shunt reactor design for better reactive power compensation / voltage regulation. 

Now, are you ready to DIY a shunt reactor device and use it in your home environment? 

J&K Audio Design
2/5/2020 

VA versus WATT

Often users ask us, how do I estimate the size required for the power transformers the circuit requires? How do I know if the power transformer size is sufficient for my circuit, for my amplifier or for my equipment? 

To them, it is always Watt that they heard mostly and learnt in secondary school, or even university. How do they use Watt versus VA? What is the best method to power transformers? What are the differences between VA and Watt? Some often see that we usually up-rate the transformers per the Vdc and Idc they use on their tube amplifier and they wonder why. 

How do I properly size my power transformers? How do I properly size my isolation transformer? 

First, we've to know what is the distinction between VA (Volt-Amp) and Watt. For equipment, the power consumption, or the actual power drawn by the equipment, is usually expressed in Watts. For transformers, usually they are rated in VA, which is also known as "apparent power", and is simply Vac x Iac. 

For resistive loads, such as bulbs with filament, heater with heating elements, and many more, the VA rating and Watt rating are the same - this is because the "Power Factor" is 1.0. For power supplies with capacitor-input, choke input supply, switch mode power supply (SMPS) and etc, the "Power Factor" is <1.0, such as 0.6 - 0.8, and therefore the VA rating and Watt rating will be different. Google for "power factor" if you're unsure what it is - we will postpone this for another article - hold on first. 

The Watt rating has to be divided by the "Power Factor" to get the actual VA rating required for the equipment in use. Or, the VA rating must be multiplied by the "Power Factor" to get the Watt rating.

Alright, enough with the theory, cut the crap, how do I order the d*mn transformer? 

Ok, ok, here's the simplified version, easy for non-technical people to follow. It's not super accurate, but is good enough for ordering use: 

Example #1: Consider the case of a equipment that consumes 260W from the wall on average. 

If we conservatively assume (yes, assume, since we do not know what's inside, we will take the worst case) 0.6 Power Factor, then the calculation would be as follow for the transformer VA to order: 

VA = 260W / 0.6 = 433VA

(Some will use rule of thumb of doubling the VA required versus the power consumption in Watts.) 

I would expect users to do some additional de-rating as well since transformer is not a perfect device - there may be losses. Also, if it is an amplifier, then the power consumption may actually be more since amplifier is dynamic, drawing different power at different point of time due to the volume versus music nature, which is dynamic and unpredictable. Therefore, double or triple of that is nothing surprising for amplifiers. 

*** If you prefer cool-running transformers, de-rate it further - do note that de-rating requires readjustment of the primary/secondary ratio since the secondary voltage will be higher than normal when under-load. *** Inform us if so when you're ordering, so that we can set the right voltage for you. 

Example 2: Order power transformer for an amplifier. Assuming you need Vdc of 400V at Idc of 200mA, using a bridge with capacitor input power supply (important note: different circuit calls for different formula). 

Vac = V-average-dc x 0.9 = 360Vac

Iac = Idc x 1.61 = 0.322A

VA = Vac x Iac = 116VA 

If you do not know the calculation method, you can go for simple calculation:

P in Watts = Idc x Vdc = 0.2 x 400 = 80W

Power factor = 0.6 

VA = 80W / 0.6 =  133VA

Above is just for a single winding. If there are multiple windings in a power transformer, add them all up, and add additional margins for multiple windings since efficiency will drop further with more windings in a single transformer. 

Some will use rule of thumb (again) of doubling the power (Watt) required for the VA rating, for a quick check. 

Do not forget to take losses into consideration, which is not included in this guide, especially tube rectifier / diode drops. D.C. regulator requires voltage margin for stable operations too and is dependent on the type of circuit used. Also, consider mains voltage drop/hike too in your calculation. Some will add additional buffer for lower operating temperature since there shall be copper losses and core losses that will generate heat and cause temperature to rise. 

Alright, here's your calculation example for how to order a power transformer, and how to differentiate VA and Watts during transformer ordering. Keep this in mind when you order. If you do not know how to calculate, let us know and we can help you estimate. 

J&K Audio Design

26/4/2020  

:

Value for money output transformers

Best bang of the buck output transformers! Value for money output transformers! Good sounding output transformers! Good things need to repeat 3 times!

Hope everyone is well in terms of the COVID-19 outbreak, as well as the current stock market correction period. In such treacherous period of time, what’s better than staying home and do some self-improvement reading, market research/analysis and new product design!?!?

Who’d like to have a best bang of the buck output transformer? Please raise your hand! We’ve surveyed the market of output transformer makers, list out some of the popular names such as Lundahl, Tango, Hammond and etc to analyse what’s good, and what’s to be had.

The picture shows our rating based on our own criteria – take it with a cup of salt.

What are the critical parameter for output transformer?

1. Primary impedance ~2.5K to 3.5K (common impedance for most tubes)
2. Primary DC 100mA at minimum (suitable for 2A3, 300B, KT88, KT100, KT120 till KT150)
3. Primary inductance of ~6H per 1K Ohm (for better low frequency loading/response)
4. Secondary 0 – 4 – 8 Ohm (suits most speakers out there)
5. Output power 30W (decent, but not too low)
6. Frequency response of at least <20Hz and > 20kHz (for full HIFI bandwidth)
7. Tolerance of +/-1dB (where human ears could hardy differentiate a 1dB difference)
8. Decent headroom/core volume >= 1KG per 10W SE
9. Decent price <$150/pc

With all the above criteria in consideration, we have come up with 2 output transformer designs to satisfy most users needs. We cannot do an All-In-One output transformer as the design trade-off is just too much.

Therefore, one (JK Fighter P-OPT) is designed more for Pentode (KT88, EL34, EL84, KT120, KT150, and etc).

• Higher primary inductance to cater for higher tube Rp (Pentodes in general)

The other (JK Fighter T-OPT) is designed more for Triode (50, 300B, 2A3, 45, 71, R120, 300BXLS, PX4, and etc).

• Lower primary inductance to cater for lower tube Rp (genuine Triodes in general)
• Additional 16 Ohm secondary for high efficiency speakers  

For those that wish for a warmer sound, they can use JK Fighter P-OPT with Triodes or even Pentodes. For those that want a more high fidelity sound, JK Fighter T-OPT is the one to go.

Expected availability ~June 2020. If you’ve feedback on the design for improvements, or you happen to be looking for one for your design(s) – let us know before we finalize the design. Email us! If they are valid and genuine, and doable within the budget, we will include them.

To keep the price low, they are all fixed design. If you need to customize, it will have to be on standard customize price. Custom made version will be more expensive, and will have better dynamic headroom too.

We have no plans to release Push-Pull versions since those have lower demand. If there are a lot of queries, or even OEM requests, we may consider doing so – let us know.  

Thank you for your support!

Take care everyone! 

J&K Audio Design

28/2/2020

Voicing of output transformers

Howdy everyone! 

After repairing and measuring sooooooo... many vintage and modern output transformers from no-name to legendary brands, we've had a good grasp on how they voice the output transformers, from the materials used, winding techniques, etc... to the sizing of cores.

If you're going after a certain tone, you can let us know and we can wind towards that. Else, we will do the best for each level (Level 0 to Level 3) of grading for our transformers, using the wide bandwidth winding method, with sufficient dynamic headroom for all sorts of music, including faithful 20Hz reproductions. 

Our Level 2-3 output transformers are usually specified to ~10Hz @ -3dB region (or lower if required or paid for), and therefore anything at 20Hz is of no issues at all. We're not that worried on the high frequency response side as that's something easily manageable and easily achievable. We'd tend to just limit it at ~60k-75kHz to avoid unnecessary side effects but if one still want 100kHz, just let us know. 

Just a refresher to all perhaps, we do offer OCC Cu, OCC Ag magnet wire transformers now, that we previously do not (maybe 2 years ago), due to the wire price, amount of orders and scarcity of such materials. Now, we can say that they're pretty common. 

On the other hand, we have to keep the transformer repair price to at least U$200/pc and above. The amount of work involved are just too labor intensive and charging below that is just PAYING YOU TO REPAIR FOR YOU.  

Each transformer requires around 1 week to complete. Say if we pay a technician to do so, at U$15/hour for 5 days, that would be whopping U$600 labor charge slapped onto the repair price. You see what we mean now? 

Anyhow, we'd like to thank everyone that supported us so far to lead us till today. You're such a gem! 

And, apologies for those that had hiccups in their projects. We will keep on improving ourselves and keep on serving you guys better.

J&K Audio Design
8/9/2019. 

Audiophile Toroid Transformer

Good day folks.

Our Toroidal transformer is excellent, but is still not as good as the EI transformer counterpart. We still like to use EI transformer for most of our audio applications but sometimes Toroid / Toroidal transformer is still needed for high power applications or for equipment with limited real-estate, and requires smaller transformer to be used. 

We have been researching on this for quite some time and we have finally found several parameters to improve on the Toroidal transformer performance. These brings the Toroid / Toroidal transformer closer to the EI transformer, not 100%, but close enough! 

1. Usage of higher grade 0.23mm lamination thickness Toroid / Toroidal core
2. Usage of grain oriented silicon (Hi-B)
3. Laser welded full strip of silicon steel from a full roll to ensure no air-gap present
4. Special formula of Nitrogen / Hydrogen during silicon steel cooling process to improve magnet properties 
5. Double shielding technique, 50 (non-potted) and 95% (potted) reduction in magnetic interference

Results? Toroid / Toroidal transformer that works substantially quieter, and sounds absolutely HIFI. 

Try it now! 

J&K Audio Deign
27/3/2019

General transformer problems

General transformer problems?

Temperature is too high

- Short circuit in the winding, at primary or secondary. Once shorted, the current will be high and cause rise in temperature. If this continues, not only the insulation layers will be burnt, and the adjacent winding will be burnt due to high temperature, and the vicious circles continues, until the whole transformer is burnt. This high temperature happens whether it is loaded or unloaded. The only fix is to remove the bobbin and remove and replace the burnt winding(s), or all altogether.

- High temperature may happen at small transformers and goes un-noticed, where there are a lot of turns in a single winding. If the adjacent magnet wire got short-circuited, since the voltage is low, wires are long and thin, the temperature may not reach the exterior, but it will not work for long. 

Note: When there are shorts in the transformer, the no-load current will be higher than normal.

- Magnetic flux density (B) set too high - especially when using unknown transformer core/lamination. If B is set too high, causing the turns to be lesser than ideal. With reduced primary turns, the no load current will be too high, causing increase of transformer temperature. Even if secondary are unloaded, the transformer temperature will rise high. If you reduce the primary voltage up to a certain point, the temperature will be at normal temp, for such kind of transformers.

- Overloaded transformer - self explanatory

- Magnet wire is too thin - high DCR causing more power dissipated at the wires.


Electrocute feeling when touching the core

- If one touches the core and feels a slight tingle or eletrocute feeling, this is due to parasitic capacitance between the winding and core. You can measure a certain Vac value on the core with respect to ground. This may be resolved by adding grounding to the core or mount it at a grounded plate.

Magnetic flux leakage is high - causing noise

-When powered on, the field generated by the winding should follow the path formed by the core, and should have low magnetic path resistance, to enable a high efficiency transformer. Due to various reasons, if the path is not smooth, leakage form where magnetic flux to goes through the air instead (magnetic flux leakage). That could happen to uneven surface between the cores (gap), or cores not tighten enough with the E/I lamination, or the air-gap laminate is too thick, and various other reasons.

- If the transformer works alone, the impact is not much and may not be noticeable. If it is mounted in jam-packed equipment with lots of sensitive electronics, the magnet flux leakage will be detrimental, causing AC hum to the adjacent components (therefore, giving EI transformer a bad name). 

- To check for magnetic flux leakage, one can wind a 200-300 turns of wire on an iron nail, connecting it to a high impedance sensitive headphone, and move this to a powered transformer with magnetic flux leakage, and see if there are audible hum generated in the headphone. 

- To avoid this, the lamination must be even so that the interface is as close as possible. This is even more important when using refurbished cores. It has to be clean enough and polished to ensure the closest interface. OTOH, transformer designer should not design it close to the maximum magnetic flux density. Also, the copper band will come in handy to prevent such leakage from affecting the environment. Distance may help too since the density drops as it moves further away from the transformer. 

Noise when powered

- Ringing / hum when powered - this could be due to loose lamination. Lamination could get loose in many ways - abuse, drops, not tightened enough, and etc. Low grade core with un-eveness in the cores (not flat enough).

- Short circuit in the transformer, where there is high current flowing., causing the lamination to rattle, and heate up. 

- Misaligned lamination - you can see the un-eveness alignment of the lamination when the whole transformer is constructed. Such zig-zag lamination will cause noise. This should be easy to see externally. 

So, you have been empowered now with the knowledge to know the general transformer problems. Choose wisely. 

8/5/2018
J&K Audio Design

Transformer selections for isolation transformer

We've seen some fully built isolation transformers appearing on the net that is quite close to what we're offering. I guess, imitation is a kind of artless! We'd like to emphasize: get only the originals, for peace of mind, for quality, and most importantly for excellent sound (pun intended)!

What's the recommended isolation transformer for my application? We've replied this question for countless times. Therefore, it is time for a post! 

Q&As:

High power SS amplifiers, home theater amplifiers (>200W class AB, or >40W class A)
* Do not use isolation transformers unless necessary, where you are having noise, sibilance and over-voltage issue that requires some step-down.
* Isolation transformers that you can consider using are toroid (for the size / efficiency 

Lower power SS amplifiers, all tube amplifiers
* EI isolation transformers, or Ultra isolation transformers (quieter, cleaner, better!)

Sources, such as CDP, DAC, preamp
* EI Ultra isolation transformers (highly recommended), standard isolation transformers 

Toroid vs EI
* Toroid has better efficiency and therefore is more suitable for high power applications. But, toroid has higher bandwidth and therefore is not a good filter / isolation device. Toroid has more noise that leaks through primary / secondary compared to EI.
* Most importantly, EI sounds warmer, cleaner, better bass definition, less sibilance, and better body when compared to toroid. EI is the one to use if the power required is not extremely high. 
* Toroid has lesser radiated magnetic field compared to EI and may be acceptable to use un-potted but once EI is potted in metal case or have comprehensive copper bands , it will have similar behavior on radiated noise.

Grades of cores
* For toroid, we only use the highest grade silicon steel toroid core from Japan, that is only available up to 3.5KVA for now. 
* There are lower grades toroid cores with higher VA out in the market that are less efficient and have high mechanical hum. We don't use them. 
* For EI, there are several types available too. We only use Z9 for higher end units (lesser loss, runs cooler, sounds better), and Z11 for standard units (still pretty high end compared to others out there).
* The H-grade EI cores are much lower end and we try not to use them unless budget is really a concern. 

Potted vs un-potted
* Definitely potted if possible 
* Potting dissipates heat better, is mechanically damped, protects the transformer from moist/rust, avoids misalignment of the cores (EI) from abuse, and etc

Input and output taps
* If step-up or step-down is required, multiple input/primaries can be made and users can select them based on incoming mains condition
* Secondary can be multi-tapped too but is not recommended. Try with only multi-tap primaries first, such as 250-240-230-0 or 120-110-100-0 (and etc combos) to tailor to various input mains levels. 
* Secondary is recommended to be configured as balanced, aka balanced-power, such as 120-0-120 for 240Vac, or 65-0-65 for 110Vac, and so forth.

Multiple isolated outputs
* Instead of all equipment sharing the secondary and cross-pollute one another, we can build isolated secondaries in a single isolation transformer so that one can still enjoy the benefits without paying too much for dedicated isolation transformer per equipment
* Secondaries can be of multiple similar or different voltages, similar VA or different VA, balance or un-balance power (there is a limit of how many secondaries are available, try to keep to 20 taps total). 
* Extreme example is as follow
-- Primary: 250-240-230-0, 2KVA total
-- Sec1: 120-0-120, 500VA (for 240Vac for British gears)
-- Sec2: 65-0-65, 500VA (for 110Vac USA gears)
-- Sec3: 110-0-110, 500VA (for 220Vac China gears)
-- Sec4: 50-0-50, 500VA (for 100Vac Japan gears)

Standard isolation versus Ultra isolation
* Ultra isolation transformers have multitudes better noise isolation properties than standard isolation transformers 
* Ultra isolation transformers size is ~2x of standard isolation transformer to fit all the additional secret sauce and is 50-80% more expensive


Magnet wire options
* OFC (standard)
* OCC Copper (recommended for high end gears and golden ears)
* OCC Silver (for millionaires and billionaires)

Outputs
* Wire/lead out with OFC
* Wire/lead out with OCC copper or OCC silver
* Wire/lead out with original magnet wire (not for small transformers with thin wires)
* Solder tags (be warned to not over-solder, or use too high power soldering irons)
* Binding posts 

Sizing or over-sizing isolation transformers (important)
* We are already oversizing the core for cooler operation and better sound, if you want further oversizing, please inform us.
* If is oversized, output voltage may be much higher when lightly or un-loaded 
* Inform us the estimated usage so that we can custom to reduce the output voltage (ex: rated voltage at 50% load or 25% load) - VERY IMPORTANT
* Over-voltage due to light load will burn your equipment, be warned! 
* We have often seen buyers of on-the-shelf isolation transformers to suffer from over-voltage issues since the on-the-shelf isolation transformers VA are higher than needed/used.
* Multi-tap primary may help to reduce the output voltage too, such as connecting the incoming mains of 240Vac to 260Vac input tap of the transformer will effectively lowers the output voltage. 

DC Blockers
* Highly recommended for toroid isolation transformers, and recommended for EI isolation transformers
* Removes DC from the mains, transformers run cooler and have less noise electrically and mechanically
* Price varies depending on the components used, long life electrolytic capacitors are recommended since these caps pass current constantly when equipment is switched on - do not skimp here 


Soft-start
* Not required for EI isolation transformers or toroid isolation transformers with <500VA capacity.
* Recommended for toroid isolation transformers >500VA 

EMI/RFI filter modules
* Optional, may be good or bad, very system dependent, add at your own risk
* Can be placed at input or output of isolation transformers
* Results will be 50-50 (option, have dual secondaries, one with and one without) 


Due to the higher grades of core being used, prices to produce these isolation transformers are higher compared to those out there. Don't use industrial grade core products to compare to ours! Low-ballers, please save your energy.

8/5/2018
J&K Audio Design