Toroid Ultra Isolation Transformers and Toroid Ultra Isolation Power Transformers

Happy 2025 to everyone! 

There aren't nothing much to blog about after many years of research and development of various types of audio signal transformers and power transformers. In order to show that we're still alive and kicking, and most importantly, based on feedback and popular demands for higher and higher power transformers, we proudly introduce Level-3 Toroid Ultra Isolation Transformers, and Level-3 Toroid Ultra Isolation Power Transformers. 

In the previous years, we only focus on manufacturing and perfecting our EI based Level-3 Ultra Isolation Transformers. In the past 2-3 years, we have added new technologies to our Level-3 Ultra Isolation Transformers, such as these below additional / optional enhancements: 

1. Special grounding method, called Ubiquitous Ground (UG), coupled with primary and secondary shield;
2. Ultra Low Impedance (ULI) version for better power delivery and transient response;
3. Ultra Low Noise Design (ULND), by doing the inverse method as audio transformers, where bandwidth is limited between primary and secondary, to filter out those unwanted signal, aka, noises; 
4. Additional Permalloy Shield (APS), if environmental noises, either being aggressor or victim, are crucial. 

EI Level-3 Ultra Isolation Transformers are still the best of the best, but the EI transformers size are prohibitively large when it exceeds 1500VA and we seldom entertain requests to produce larger EI Level-3 Ultra Isolation Transformers. 

With the current trend of more and more high power audio amplifiers being marketed, which was a rare case decades ago, the demand for high power isolation transformers have risen significantly, where the EI Level-3 Ultra Isolation Transformers' limit of 1500VA could no longer be sufficient. In addition to that, international shipping of high transformers are expensive and we need more efficient, smaller size, lighter weight power transformers and isolation transformers for international customers. 

Therefore, the Level-3 Toroid Ultra Isolation Transformers, and Level-3 Toroid Ultra Isolation Power Transformers are born. In nature, toroid transformers are more efficient (lower magnetic flux leakage and better utilization of core), produce less electromagnetic interference (EMI) (due to the donut-shaped core design). 

Available sizes are from:

10VA to 3000VA where the largest 3000VA weights about 20KG with diameter of 250mm and 120mm height. 

Toroid cores transformers are much more efficient than EI core transformers. 3000VA EI would weight over 50KG. The Toroid Level-3 Ultra Isolation Power Transformers and Toroid Level-3 Ultra Isolation Transformers can have the same additional / optional enhancements (UG, ULI, ULND, APS) that are available on the Level-3 EI brothers. 

If power requirement is not high where 1500VA is still sufficient, the Level-3 EI Ultra Isolation Transformers and Level-3 EI Ultra Isolation Power Transformers are still the best, as naturally, EI core transformers have narrower bandwidth compared to Toroid core transformers, and with the way EI are assembled together, enabled us to implement more noise isolation and cancellation techniques. 

Either ways, you can't go wrong with either the EI or Toroid Level-3 Ultra Isolation or Isolation Power Transformers. They're much quieter, lower noise electrically and mechanically, stable, lasting, lower temperature, and many more, than the generic power transformers and isolation transformers out there. 

Reach out to us using the contact form on the left panel or drop us a PM in our FaceBook page if you need more information. 

Hear the unheard.

J&K Audio Design

9/2/2025

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 

 

J&K Audio Design Transformers

Howdy everyone! Happy New Year 2022! Hope everyone is safe, healthy and wealthy! 

A lot had happened, including COVID19 that visited us recently, but we are definitely moving on and kicking, although a bit slowly. OMICRON is still in full swing here and one can never be too careful! 

That said, things are still going on in the background. We've just had some great comments from a customer that just took delivery of his DAC filled with J&K audio coupling transformers and power transformers:

• Level 3 Ultra Isolation Power Transformers (dual mono) for the tube I/V stage and 
• Level 2 Isolation Power Transformers (split bobbin, dedicated transformer for all power rails with a total of 6 transformers) for the DAC digital / receiver stage.
• Level 3 signal coupling transformers, OCC Silver wired, 1+1:1+1 (150+150:150+150)
• Level 3 Hitachi Finemet tube pre output transformers, 10K:600

J&K transformers may not look the best, but they definitely functions extraordinarily, AND MOST IMPORTANLY with full of emotions (that's what music is all about!), heart and feelings.  

Check out the comments he sent to the WhatsApp chat group with a few other audiophile friends: 

Names are removed to protect confidentiality of the owners. Please pardon the language used as it is local rojak style REAL conversation, not fake and paid reviews. J&K do not pay for reviews. We only publish reviews from real paying customers. 

Thank you for all the support all these years. 

Signing out. Take care and stay safe!

J&K Audio Design

23/1/2022 

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 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 -> https://jandkaudiodesign.blogspot.com/2016/06/isolation-transformer-bandwidth.html  

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

8/31/2021

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. 

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

3/4/2021

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. 

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 

tweeter attenuator transformer

Mids highs attenuator transformer - useful tool for final tuning of mids and tweeter to match listening room conditions, seating distance, and woofer / mids / highs volume level. It can be useful during crossover design phase too, to try with different attenuator taps / levels before deciding on the final attenuation levels. 

For those speakers with bi-wire or tri-wire connections, one can even use this to attenuate or boost the mids and highs if one feels that the highs / mids / bass levels are mismatched with their listening room or listening taste. 

100W Transformer Attenuator

Tweeter attenuator transformer

Attenuator / booster transformer

Tango has made some in the past, model Tango SA-300. 

For ours, we can custom it from 30W to 300W, or even 1KW if required. Pictured above are the 100W version, with total DCR of about 4 Ohm end-to-end, 11-steps at 2dB per step. Other configurations can be made per customer requirements. 

Users can choose the output format (potted, bare frame, stand), cores (Hi-B, Amorphous, Permalloy, NanoCrystalline), wires (OFC, OCC Cu, OCC Ag), taps (10-step to 33-step), power (10W - 1KW), and anything that the user needs.

Applications #1 - attenuate
- connect two ends to amplifier output
- connect the middle steps and return step to the mid/tweeter
- choose the steps to select attenuation levels

Applications #2 - boost 
- connect mid step and return to amplifier output
- connect the higher steps and return step to the mid/tweeter 

- choose the steps to select boost levels

Reference prices for mid/tweeter attenuator transformer: 

30W version
- OFC - U$150/pc 
- OCC Ag - U$490/pc
- OCC Cu - U$260/pc
- Amorphous / Permalloy / NanoC core upgrade +U$50/pc
- other parameters, please email

100W version
- OFC - U$260/pc
- bare frame 
- other versions, please email

* 10 step at 2dB/step (other steps quantity and step size can be made) 
* Potting adds U$30/pc.
* 200Hz and above (mid-high use only)
* Full frequency range unit can be made too 

For bare version, we can only use OFC magnet wire with adhesive property to ensure the wires stay aligned and together during and after winding. For other type of wire, those without adhesive properties, they need to be potted to ensure the coils do not move around. 

For full range version, also known as unity-coupled-transformer, it can be made too. These transformers are used for speaker impedance matching purposes, as well as to gain some "tube sound" by using it as "output transformer" in solid state amplifiers. 

One can connect the amplifier to the 8 Ohm tap, and the right output impedance is chosen to match the speaker impedance. These are useful to drive low impedance speakers, or difficult speakers that have huge dips in the impedance. Or, if one is using 16 Ohm or 4 Ohm speakers, and only have 8 Ohm output tap at the output transformer, they can connect the amplifier to 8 Ohm tap, and use the 16 Ohm or 4 Ohm tap to connect to the speakers.

Tips:
1. If attenuation can be done earlier at the signal chain, do it earlier, such as attenuate the signal at the source (DAC output) rather than at the destination (amplifier output). In such application, TVC (transformer volume control) can be used. 
2. Transformer coupling is better sounding that Autoformer coupling (our findings), YMMV though. Experiment and find out yourself which is better in your application or taste. 
3. Fixed attenuation with single tap will be better than multi-tapped autoformer/transformer. Simpler is better - this rule does not change. Multi-tapped autoformer/transformer offers the flexibility for tuning or matching on-the-fly. This will be good during designing, experimenting, or tuning phase, or even for users that try to tune the system for different type of music / speakers / rooms / taste. Single tap transformer/autoformer could not be as flexible. 


J&K Audio Design
9/28/2019

Western Electric transformers

Hi guys,

Merry Christmas and Happy New Year! 

We've an important announcement to make.

Western Electric cores are running low on the market. We're working on a customer order and got a shock. A lot of these cores are swooped by some vendors and make them to sub-par transformers - what a waste. As a result, these Western Electric cores are no longer abundant and choices are very limited. 

If you intend to use Western Electric cores to make transformers, please be quick and order soon. In future, we may need to buy those sub-par ready made transformers to obtain those nice Western Electric cores for rewinding to something much better.

We've made some in the past, as you can see below: 

http://jandkaudiodesign.blogspot.com/2016/01/western-electric-output-transformer.html
http://jandkaudiodesign.blogspot.com/2016/12/western-electric-we-618b.html
http://jandkaudiodesign.blogspot.com/2016/01/western-electric-transformers.html

There are still some original WE cores, untouched at decent price. Make a move quick before it is gone. The WE1048 that used previously are no longer available at our previous source. What a sad news! 

Apologies to break such a news at such time, but I think it is a good news that we discover it early. Else, it will be as rare as the 1950's - 1960's WE 300B tube. 

25/12/2018
J&K Audio Design

Autoformer Volume Control

Autoformer Volume Control, or Transformer Volume Control

We think that AVC, or TVC are one of the many great things that happened in audio industry in the past 10 years. The sound signature brought forward by AVC, or TVC can be stated as - better fluidity, warmer, wider bandwidth, and more analogous.  

For those that are unaware (not following us on Facebook, it is a good time to do so now!), we've found a new casing to house our TVC (Transformer Volume Control), or AVC (Autoformer Volume Control). 

Here are some pictures of the casing. The matte version is still available if one still want those. 

Some past articles on TVC and AVC. We can do both, but TVC is preferred due to various reasons, but we can still do AVC if customer prefers AVC. There's no right or wrong in audio, just what one prefers. 

Our preference:

** brushed pot -> stepped attenuator -> digital volume control -> AVC -> TVC 

http://jandkaudiodesign.blogspot.my/2016/10/transformer-volume-control-tvc.html
http://jandkaudiodesign.blogspot.my/2016/12/transformer-volume-control-review.html
http://jandkaudiodesign.blogspot.my/2017/04/j-transformer-volume-control.html
http://jandkaudiodesign.blogspot.my/2014/06/autoformer-volume-control.html

Some tips on using TVC / AVC: 
* low output impedance source is preferred but not 
* use a very high quality switch - it make or breaks the AVC / TVC
* durability of the switch is very important - you will be switching them quite frequently
* encased / sealed switch is preferred over open casing type
* step down type of TVC will have lower output impedance and will be capable of driving heavier loads compared to AVC 
* invest on good low melting point solder and good soldering irons - very swift soldering, with low melting point solder is preferred - TVC / AVC are made with very thin wires and are very fragile 

Hear the unheard! Sail the uncharted! 
Long live custom made audio! 

J&K Audio Design
9/19/2017

GM70 Output Transformer

For most of users out there, with usual modern loudspeakers, the efficiency normally falls around 90dB +/- 6dB. Such speakers require considerable power to drive and control the loudspeaker to a satisfactory level. Tube power of ~20W and above are usually preferred, and in order to get such power for tubes, one would need to go for push-pull or PSE design, if not, to turn to high power tubes such as 805, 211, 212, 845, 833 and such.

NOS high power triode, and/or even pentode are hard to find nowadays. Even if they are available, prices are most probably sky high, such as RCA 211, RCA 845, or United 211, not to even mention the exotic ones such as Western Electric 211 tubes. GE VT4C or GE 211 can still be found, but even so, their prices have soared since. 

What other inexpensive alternatives do we have? Well, we still have one option left, the GM70! It will only cost you about U$60-100 a pair, depending on the year made, and also the type of plates, either graphite, or copper plates. GM70 copper plate versions are rumored to be warmer than the GM70 graphite plate variety, but, YMMY. GM70 copper pate version is almost 2-3x more expensive, and are getting rare as collectors start to hog those tubes.

One can even design a tube amplifier that's 845 and GM70 compatible. Both tubes accepts load resistance of ~5K to 10K, with similar plate current. Output power varies slightly but is not of utmost importance here. GM70 has higher plate dissipation, and therefore the amplifier should be designed as such that it does not exceed 100W at all time.

845 Data

GM70 Data

The most ideal load resistance for both could be ~7K - 8K to get decent power and distortion figure. One just need to ensure a few things, no biggie, simple stuff (if you dare to build >1KV stuff, this is nothing to you!):

* Have separate filament supply to cater for different requirements
* Different tube sockets side by side for GM70 and 845
* Switch on cathode, or CCS cathode load to regulate the plate current


Which GM70 output transformer should we use? Of course, none other than from J&K Audio Design! We have recently designed one for our customer for his GM70 single ended amplifier. 

Here are the GM70 output transformer details:

* Power: 37W (20Hz)
* Measured frequency response: 20Hz - 20kHz +/- 0.23dB
(5Hz - 45kHz +/- 3dB - tuned to have higher/better loading at low frequency)
* Primary: 7.5k Ohm, Secondary: 0-4-8 Ohm (other primary/secondary - please request)
* Core: NanoCrystalline (aka Finemet) double C core
* Primary DCR: 235 Ohm (B-P, 20C)
* Secondary DCR: 0-4 Ohm (0.2 Ohm); 0-8 Ohm (0.29 Ohm)
* Primary inductance: 61H
* Max Primary Current: 120mA
* Efficiency: 0-4 Ohm (>93%), 0-8 Ohm (>94%)

(In circuit measured with Shuguang 211 at 1W. Full power response will be similar. Customer that wishes to have more high frequency response - please request at ordering or we will tune based on our house sound/voicing.)

 
* Matching: primary DCR +/-0.1 Ohm, inductance +/- 1.5H (<5%)

The above are made with NanoCrystalline double C core, which are a difficult material to work with on such power level. Such glass cores are usually for high frequency usages, and for 400Hz power supplies. NanoCrystalline core excels at high frequency, and significant compensation is required to augment the low frequency response. Using a larger core helps but that increase the magnetic length significantly (causing high frequency loss), and various other problems. Using them at full range applications is super challenging. Try asking other winders for it.

The rewards, after overcoming such obstacles, are of course very fruitful - micro details, dynamism, real sense, directness, purity, tonality are outstanding. If one can consider using OCC (Ohno Continuous Cast) copper cable with it, the results will be even more significant. The purity of sound with OCC + NanoC is out of this world.

If one is looking for purely at specification perspective, EI Z11 would be a better choice where we can get a much wider bandwidth than NanoC. The voicing of EI Z11 will be different than the NanoC. 

Enjoy life, enjoy music.

J&K Audio Design
6/5/2017