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 

Difference between audiophile isolation transformer versus technician isolation transformer

Do you know the difference between audiophile isolation transformer (or medical isolation transformer) versus technician / electrician isolation transformer?

If you do not know, then you are in for a very severe shock, both mentally and electrically. Both of them have a very distinct difference for different usage model - and it is related to safety and noise isolation. 

If you are ordering or going to use an isolation transformer in your system, you need, you DEFINITELY MUST know this, or else, you are risking your equipment and you're risking your life it there's a fire. 

J&K single ended isolation transformer, secondary is not grounded by default. 

J&K balanced isolation transformer, secondary center-tap is grounded by default. 

For J&K customers, if you're unsure on how to use them, email us.
For J&K customers, if you need to convert to technician / electrician isolation transformer, email us. 

For followers, please wait for our write-up before you do anything drastic.

We do not have the time to quickly do the write-up yet unfortunately. Watch this space if you value your life and equipment. 

Take care! 

J&K Audio Design
3/6/2020 

Retrospective - feedback

It has been 7 years since we started our blog, and much before that, the off-line presence through ordinary website, traditional brick and mortar business, and via words of mouth. 

Over the 15 years of history, we have changed our business models multiple times, tried aggressive expansion, worked with partners and vendors for different strategies to sell design or sell products, cooperate with our valuable customers to develop and fine tune our products and product lines based on feedback of our customers. 

We would like to say:

Thank you! 

To our customers. To our partners. To our fans and followers! You guys rock!  

And, we would love to continue to hear from you on how we can improve ourselves to better serve you, and help you with your projects! So, please use the form on the LEFT PANEL of this blog, and send in your feedback, criticisms, ideas, proposals, topic for discussions, anything at all! 

We may have hiccups along the way due to a lot of reasons - we would like to take this opportunity to apologize on them. If you see any issues at all, please work with us and we would always try to satisfy your requirements and fix the issues for you. 

That aside, apologies - we do not want to buy pipes or buy construction materials. We also, do not have any dead or distant relatives that have a bunch of monies waiting to be inherited. We prefer hard earned monies instead. So, spammers, stay away please. If you think we are gullible, think again. 

If you like (or dislike) our services and products, and do not like to write emails, please leave a comment in our blog page below! 

If you have new product ideas, we would love to hear from you! We can work with you to market your business. 

Till then, take care and stay safe everyone! 

J&K Audio Design
21/5/2020 

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 

Partners

We're always open to partners to help us expand our business and product coverage. 

If you are specialize in certain technology, or handcraft, or any work that is related to HIFI or audio industry, please contact us and tell us more how we can cooperate and benefit one another.

You can be - equipment manufacturer, gadgets maker, or even transformer manufacturer, we can work something out to benefit ourselves, as well as our customers. 

Examples:

1. You are amplifier manufacturer - we can cooperate by supplying you transformers. 

2. You are HIFI gadget designer - we can cooperate by sharing technology and product ideas. 

3. You are CNC house, or capable of metal stamping, bending and such. 

4. You are a supplier of parts (electronics, electrical, irons, pre-fabricated chassis, transformer cases, transformer frames and etc). 

5. You are transformer manufacturer - we can cooperate by covering one another product gaps. There are some product segments that J&K do not cover, we can pass those business to you, or act as bridge; and vice versa. There are some geographic regions that is too far to ship J&K products to (too expensive, or not covered), and vice versa, we can leverage each other's network. 

We had outsourced some of our low end transformers to our partners previously as the pricing that our customers looked for were just too low for us to manufacture here. If we like your audio gadgets, we may even help you market it under your brand, or under our brand. 

6. You have idea on transformer design that you would like to design (by us, or by yourself), manufacturer, and sell (by yourself or by us), we can work out a deal.

Ideas are limitless! Complicated or simple. 

Email us and we shall discuss more. We are open to all ideas - no ideas are stupid ideas. 

J&K Audio Design
28/4/2020 

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  

:

COVID-19 Update

Hope all are well, alive and kicking! 

Movement Control Order has extended but we've slowly begun our operations and catching up with the orders in the past few months - we'd like to take this opportunity to apologize for the hiccups in production. 

Kindly send in your new orders to avoid long delays as materials shortage won't be something that can be resolved in a short term as most materials manufacturers have stopped operations, or in a 50% or less capacity, same with us. 

Take care and live strong!

J&K Audio Design
26/4/2020 

Halt operations from 18th MAR till 31st MAR 2020 due to COVID-19.

J&K Audio Design has to halt operations from 18th MAR till 31st MAR 2020 due to COVID-19 outbreak measures from the government.

Apologies for all the delays. We still check and respond to emails.

Take care and stay well everyone! 

J&K Audio Design
19/3/2020 

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

Vacuum Tube Repair

Good health to all J&K readers, supporters, and most importantly customers! 

Just a little update on the COVID-19 outbreak - latest news is that some of our suppliers will resume work on 24th FEB 2020 - hope that situation improves that much to enable them to resume production. 

Now back to our agenda here - vacuum tube repairs, or vacuum tube revivals!

I believe, transformers repair is nothing new to our followers. We've repaired hundreds, if not thousands of them over the past many years. 

Another critical part of the solution chain would be on vacuum tube repair and revival, especially on those exotic NOS tubes that cost quite a considerable amount of money. We now offer vacuum tube repair or revival service to our customers through our long time partner (a tube maestro). 

Do note that not all vacuum tubes can be repaired or revived. Some are dead for good. For some that are still having some life in it, or failed prematurely, or even fail as DOA, maybe they could be repaired. In some cases, some even be buying those expensive exotic NOS tubes that are dead at a dirt cheap price, and sending them to us for repair! If by any chance those dead exotic NOS tubes can be repaired, they could save thousands of dollars comparing to buying good exotic NOS tubes. Those that are worth repairing are those Western Electric signal or power tubes, Genelax / Gold Lion signal or power tubes, or even any old big power tubes that worth fortunes. 

Since repairing or revival could a 50-50 or worse kind of odds, one may need to weight the pros and cons before sending for repair. Vacuum tube repairs or vacuum tube revival starts at U$100 per piece, and could be more depending on the type of tubes and illnesses. 

Loose base, no connection at tube pin due to broken wire or cracked solder, or broken pin can be easily repaired by base replacement or re-connection internally at the base. Broken filament, could possibly be repaired, on case by case basis. 

Here are some things to be considered before sending vacuum tubes for repairs or revivals: 

1. Are they worth the trouble or worth the price? Repair price could be more than buying them new or  or buying NOS. 
2. Mechanically broken vacuum tubes are not repairable - such as broken glass or vacuum loss (inside appears all white). 
3. Severely broken tube internally (massive internal structure failure, broken plates for example).

For other cases, please send us some pictures and descriptions and we shall see what we can do. 

Examples for some cases on vacuum tubes that could possibly be repaired:

1. Crackling noise
2. Keep blowing fuses 
3. Filament shorted 
4. Internal pins shorted 
5. Open connections 
6. Intermittent operation
7. Missing base / base repair / base replacements
8. Oxidized tube pins / internal wires
9. Weak tubes 
10. And etc... can't list all since there could be other illnesses 

Contact us, if unsure.

Now, go dig your storeroom and see if there are any vacuum tubes you'd like to be repaired. Better still, go ask all your tube audiophile friends for used tubes, broken tubes that they do no longer use, and see if they are worth repairing or reviving! They could save you a fortune, or make you some good money after being repaired! 

Tubes that are worth repair, for example, could be 212, 4212, 211, 4211, 4300B, 300B, 2A3 single plate, 2A3 double plate, 801A, PX4, AD1, 53KU, 52KU, U52, EL156, KT88, KT66, Telefunken, Western Electric, Genelax, and various other expensive exotic tubes. 

Vacuum tube dealers, sellers, shops owners - if you have tubes that you think are worth repairing, please contact us and we may be able to repair them for you for re-selling later. The same 3 rules above apply. 

Start digging! You may encounter a few gold mines! Don't let the exotic tubes go to waste - recycle them! 

J&K Audio Design
18/2/2020 

Corona Virus

Some states or regions in China, including places where some of our raw materials vendors are located, were mandated by the Chinese Government to remain close until 10^th February, 2020. This is to prevent wide spread of the Corona virus, and is one of the precautionary measures to avoid further spread of the disease and threat to the nations.

This has affect the continuous supply of raw materials needed to produce our products. This may have some impact to the production and may delay delivery of some shipments. We are could and are still in contact with the raw materials vendors for the latest update of the situation.

As of now, most of our raw materials vendors will resume production on 10^th February, 2020. Given the uncertainty of this matter, we’re still actively monitoring the situation.

Kindly contact us if you’ve any concerns. Thousand apologies for the inconveniences caused.

J&K solid wood chassis

Happy 2020! Business as usual. Hope everyone is well, and still actively and passionately pursuing the DIY audio hobby! 

While working on transformers design and orders, we received an order for solid wood chassis with 3mm copper top, for his tube amplifier. 

Some said that the wood chassis looked like Chinese kung-fu tea tray... I can't argue with that. It does! 

Enjoy DIY!

J&K Audio Design
13/1/2020