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Saturday, May 25, 2024

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


Sunday, July 31, 2022

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! 



Thursday, June 30, 2022

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


Friday, April 22, 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


Saturday, January 22, 2022

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

Saturday, November 27, 2021

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! 

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. 

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. 

J&K Audio Design

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

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

Iso-trans: link 1, link 2

Power-trans: link 1

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

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