Flexibility of custom isolation transformers

Why do we custom isolation transformers? Flexibility is the key advantage, among the others. Here we list a few options and actually there are more than meet the eye. 

Above i a multi-tapped primary and a balanced power output. User can connect to either one of the input based on their input primary voltage. User can also select to boost or buck the output voltage if the user connects to a higher or lower tap to achieve the desired output voltage.

Other than input voltage adaptation, and output voltage tuning, custom isolation transformers can have multiple inter-isolated outputs by having separate secondaries with different (or the same) VA to cater for different gears that have different power consumption, and input voltage requirements. Inter-isolated means the secondaries are shielded from interfering from each other rather than affecting each other for quieter operations, on top of being shielded from the primary / incoming mains. 

Above is a super flexible isolation transformer where user can fine tune to 16 combination of voltages, step-up, down, or equal. The step can be 10V-step as what's shown above, or 5V-step, or 20V-step, up to user's requirement. 

Balanced outputs can be tuned too, not just unbalanced outputs. User can have +/- 110V, or +/-120V, or others. Just let us know. 

Other than the above, another example would be to have multiple secondaries with multiple VAs and voltage requirements, connected to several output sockets so that user can connect to source, pre-amplifier, power amplifier, DAC, AV equipment, and etc. Outputs can be balanced or unbalanced, or both. 

Another even more extreme case is, in a single chassis fully built isolation transformer system, internally it can have multiple physically separated isolation transformers, each supplying to a single socket to the external world. This would save space by taking up only 1 rack space than multiple, and yet have the beauty of each equipment connecting to a separate isolation transformer. 

The possibilities are limitless. Take the advantage now and reach out to us in the left panel contact us form.

Hear the unheard!

J&K Audio Design

9/2/2025

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 

 

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

Balanced tube filament winding

Balanced power for mains has been known for ages and it brings tremendous improvement to the sound of many audio setups, especially with our Level 3 Ultra Isolation Transformers or Level 3 Ultra Isolation Power Transformers custom made for audio amplifiers. 

Balanced LV filament winding

Why do we still want to bring this up then? 

Take a look at the above schematic. What can you see different from the ordinary tube amplifier schematic with tube rectifier design? Yes, the filament winding as a center-tap and is balanced. 

Since we manufacture a lot of custom made power transformers, we do not see the the common usage of balanced filament windings for tube rectifier filament supply. It is quote common for the B+ / HT supplies, but not the LV filament supplies. LV filament supply is often quoted as 5Vac or 6.3Vac, but not as 5VCT or 6.3VCT with a center-tap, which is also a balanced winding? 

Why not? Since it is custom made power transformers, one should consider balanced LV filament windings as well to gain all the benefits of balanced winding and the noise cancellation/immunity properties it brings. 

Till then. Take care everyone! 

J&K Audio Design

1/5/2022 

Surplus transformers for sale

Howdy everyone! Greetings from J&K Audio Design team. Hope everyone is safe and sound. 

We're clearing out stocks again! There are just too many old stocks lying around that are taking out our storage space. If you are flexible in terms of transformers, we have some surplus power transformers and audio (input/output) transformers to let go at discounted and very decent prices. Email us your needs and we will search around to see if we have something close. 

Below is a pair of the recent surplus pair of Level-1 0.35mm GOSS 400VA power transformers we have. 

Primary: 0-240-250, G (electrostatic shield).

Secondary: 3.15-0-3.15@14A; 270V-0@1.15A.

400VA each, sell in pair.

Good for high power amplifiers with 6.3V filament tubes. Copper shields. Teflon lead outs. 15KG packaged and ready to go anywhere. MY$1100/pair (U$260), as is.

Till then, take care everyone.

J&K Audio Design

23/4/2022