We can make anything that you can dream of. We are experts in arts of transformers making. We build all sorts of budget to exotic high end tube amplifiers. Just shoot us an email at jnkaudiodesign@gmail.com or fill in the form below. Email us even if what you want is not mentioned in our website. With regards from Penang, Malaysia!

Friday, April 29, 2016

NOS Riken Carbon Film Resistors

Life of an audiophile is difficult. Life of an amplifier design is even MORE difficult. As we all know, a lot of the legendary vintage audio equipment are made with carbon composite or carbon film resistors, and that's one of the reason why they carry such a tonality that modern equipment do not have.  

We are building a batch of preamp for customers, and they specifically asked for NOS Riken Carbon Film resistors due the unique sound signature it carries. As we all know, carbon film or carbon composite resistors tend to drift in value over time due to temperature, humidity and run-in. Matching them is really pain in the a** and expensive task. We have to buy a huge batch of resistors just to match very few pairs.

Riken (Japan) RM2 2W NOS Carbon Film Audiophile Resistors
Tolerance: 5%
Size: 8mm D x 18mm L
Originality: Japan

Sound characteristics
* musical, warm, golden tonality, atmospheric, smokey, live-like, relaxed, full with emotion
* less precision, less detail in layering and imaging quality
* fuller at mid-bottom, full of energy 





This is a great resistor for tonality! It is comparable to the famous AB (Allen Bradley) resistors. It is great to be used as cathode bias resistor, grid resistors, or places where heat or power dissipation are lesser. You can still use that at hot places or as plate resistors, but you need to over-rate it substantially to reduce the temperature caused aging effects, or pre-age it by running it in first before matching. If all are considered, this is one helluva resistor for tube amp use!

4/29/2016
J&K Audio Design 

Saturday, April 23, 2016

New arrivals

Life and work are so time consuming that we hardly have time to blog! 

Just to let you guys know that, we are still alive, and we have been busy in the back. Here are some additions to the family, at a small volume, and extra charges of course.

- long grain crystal OFC magnet wires for OPT for limited models of transformers
- vacuum + oil immersed / sealed transformers
- pure silver wire transformers 
- hybrid Permalloy cores for output transformers 

Email for details. 

J&K Audio Design
4/24/2016

 

Sunday, April 17, 2016

J&K NanoCrystalline OPT User Review

David from Singapore is one of the proud users of our Level 3 Nanocrystalline Preamp Output Transformer. Recently he has just ping us to share with us his creation. We wait for his full review on the transformer. Meanwhile, please enjoy the little pics he sent us in Whatsapp recently. 

We are always happy to hear back from our customer pools and will share their pictures and stories here in our blog. If you have anything to share, just drop us an email!




He uses Bendix 6900 in his WOT preamp. Nice work David! You can find out the details of this Level 3 Nanocrystalline Double C preamp output transformer details in the below link. 

Enjoy!

http://jandkaudiodesign.blogspot.sg/2016/01/balanced-preamp-output-transformer.html

4/18/2016

Saturday, April 16, 2016

Transformer Cores

Manufacture / processing

The SiFe / silicon steel are purified, refined, melted and rolled into sheets / coils for further processing. Careful and precise control is needed at every stage if high quality, consistent magnetic properties are needed, and that's where cores from reliable manufacturers are only used in high quality transformers to ensure the materials are meeting specifications and consistent. If you get them from unknown source, then good luck with the outcome!

The silicon steel is rolled at controlled high temperature in high gauge coils, and further rolled at cold temperature to the ultimate desired gauge and further annealed. The silicon steel are usually cold reduced and further processed to develop their grain orientation if needed.

The silicon steel (for transformers use) are produced to meet magnetic property specifications rather than specific chemical composition. Magnetic properties are of utmost importance for transformer use, although it is highly dependent on the chemical composition and processing control.

Transformer cores is made up of a few ingredients:
- silicon: primary alloy, to increase volume resistivity, to reduce eddy current, help in attaining the desired grain structure of steel, reduced hysterisis component for lower core loss, avoid phase change in the orientation processing
- aluminum: ~<1% added for metallurgical effects, and affect the grain structure
- manganese: ~<1%, added for metallurgical effects, and affect the grain structure
- others: other impurities such as carbon, sulfur, nitrogen

What we are generally interested are High Silicon Steel (~M15 to M47) and Grain-Oriented Silicon Steel (~M2 - M10), for power and audio transformers use. The silicon steel are normally supplied in specific gauges, and for transformers, are usually 0.64mm, 0.47mm, 0.35mm, 0.27mm, 0.23mm and 0.18mm.

Oriented and non-oriented silicon steel
Oriented - crystal structure having magnetic properties that are better in a given direction 
Non-oriented - not oriented intentionally oriented but will still have very minor orientation magnetic properties due to process methods.

Grain orientation
Fully controlled processing are required to produce grain oriented silicon steel. After hot rolling, cold reduction with intervened annealing will be needed. The steel grains/crystals are elongated and oriented during the rolling. Further final mill annealing will be needed for secondary re-crystallization to grow the crystals to a final desired size. The end results is that the silicon steel will be most easily magnetized in the grain direction/orientation (parallel to the direction of rolling).

Advantages of grain oriented silicon steel
* increase permeability at high flux densities with reduced core loss (M15-47 >> M2-M6)
* higher efficiency / energy-efficient / less heat
* cost reduction 
* size / weight reduction
* reduced ampere-turns ratio

Lamination Thickness
Thickness of the silicon steel lamination influences the core loss under mains (AC) and audio applications due to the eddy current component of the core loss. Therefore, for mains (AC) and audio use, we need to limit the maximum thickness to <=0.64mm and below. Higher lamination thickness will increase the exitation current and increased eddy current + skin effects.

Skin effects (caused by eddy currents within each lamination) causes crowding of magnetic flux out of the middle thickness section of the lamination. The eddy current produces counter magnetomotive force that caused this effect, where only a portion of the lamination cross section will be effective in carrying the flux - a great loss and may cause early saturation due to such effects.

Although so, not all applications requires the thinner lamination. All are case by case bassis and sometimes using thinner than needed is actually wasteful and brings no benefits.

4/17/2016












Magnetic Cores for Audio

As manufacturer of transformers, we can run away from magnetic cores. Magnetic cores are made of combinations of characteristics and properties. We we use mostly are the soft magnetic core materials, or so called electrical steels. Deep understanding of the electrical and magnetic properties will enable us to produce the end product with the right specifications.

We would need a big huge textbook to cover all the fundamental aspects of magnetic materials. We would only glide through the surface in blogs of course, for a general idea and high level understanding. What we focused on are those in lamination form, wound or stacked magnetic cores, for transformers used, primarily at mains frequency (50-60Hz) or at audio frequency (20-20kHz, or more!). 

We usually call cores for such application silicon steel, or SiFe, or iron silicon alloys. A lot of people call them silicon steel, or electrical steel. The magnetic properties / characteristics make them well suited for power or audio frequency usages. 

Core Loss

Primarily, a lot of the classification of silicon steels are by core loss. Core loss is usually the most important factor for us choosing a particular silicon steel for a certain application. Core loss is the electrical power loss in the form of heat in the core when subjected to AC magnetic force. 

There are several types of core loss, or a sum of all the different losses - hysteresis loss, eddy current loss within individual lamination, and inter-lamination.

We used to have so many types of grading since we have many steel manufacturers all over the world. The one I use the most is Z-prefix, commonly used in Japan and Asia, like the most common Z11 wit 0.35mm lamination. There is another standard, using M-prefix by USA (American Iron and Steel Institute) to grade the core loss. 

Grades

AISI grades the silicon steel by M-prefix followed by a number. M = magnetic material. Number = grade of the core, and also the relative core losses of grades within a class. The Number was a representative of the core loss of that grade but it was no longer applicable in modern days due to advancement of the silicon steel properties. 

Classes

Silicon steel are categorized into several classes generally. The classes are based on the primary magnetic properties of the material, the form, and the differences between the grades of the materials produced. 

Non-grain-oriented
Magnetic properties are same in any direction of magnetization in the plane of the material.

Grain-oriented
Magnetic properties are strongly oriented with respect to the direction of the rolling/annealing. The rolling/annealing process produces a crystal structure that are grains aligned so that the magnetic properties are far more superior in the rolling direction. 

Non-grain-oriented: M15, M19, M22, M27, M36, M-43, M-45, M47
Grain oriented: M2, M3, M4, M6

To be continued... 

16/4/2016