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. With regards from Penang, Malaysia!

Thursday, January 28, 2016

Marantz 8B Output Transformers

One of the issues of cloning legendary designs like Dynaco ST70, Marantz 7/8/8B and so forth, are the difficulties in getting the original output transformers to go with the design. Due to age, the originals output transformers are hard to come by, and most of them time, in very bad condition or damaged. 

On top of that, buying replacement output transformers from other makers, that do not follow the original design, the tone, quality and taste of the original design is lost, or deviated further away. Worse is that some of the original designs / schematics do not specify the primary/secondary winding in detail where it is impossible to remake.

Well, we have good news for you. We've repaired many famous and legendary output transformers in the past. We've reverse engineered it for our customers, kept the design data so that we could reproduce the same exact copy if future customers that want to restore or rebuild their classic machines, using the original cores, or with modern cores.

A few of them are Marantz 8B output transformers with the feedback secondaries, or WE 543A input transformers and etc. 

Let us know what you need and we shall check if we have it for you.

Do note that we do not support piracy. We do not clone modern designs for profit. These are just for restoration/repair purposes only, or for extinct and out of print designs only.


Thursday, January 21, 2016

Balanced Preamp Output Transformer

Are these requirements what you are looking for in a preamp output transformer? 
  • Sounded as good as measured or specified in datasheet?
  • Balanced or single ended configurable preamp / linestage output transformer? 
  • For medium high current driver tubes like 5842, 6C45, 5687, 6900, E182CC? 
  • Flat frequency response from 20Hz to 20KHZ?
  • Install and forget? Worry free reputable source? 

We have the answers to above all. Here's our Level 3 Nanocrystalline Double C 6K medium current balanced preamp / linestage output transformer.

Frequency response (in circuit measurement, standard 20Hz - 20KHz)

(150Ω+150Ω balanced out): 20Hz-0.66dB—1KHz0db—20KHz-0.23dB
(150Ω single ended OUT1):  20Hz-0.65dB—1KHz0db—20KHz-0.2dB
(150Ω single ended OUT2):  20Hz-0.65dB)—1KHz0db)—20KHz-0.16dB
(600Ω single ended OUT1):  20Hz-0.62dB—1KHz0db—20KHz-0.31dB
(600Ω single ended OUT2):  20Hz-0.62dB)—1KHz0db)—20KHz-0.31dB

Core: Nanocrystalline SiFe Cut Core
Primary DCR: 359.9Ω360.2 B-P9℃)
Secondary DCR, E-OUT1: 17.617.6)Ω
Secondary DCR, E-OUT2: 18.418.4)Ω
Primary inductance: 51.6H51.1H)(DC bias at 25mA20Hz5Vrms
Primary DC (absolute max)
50mA (recommended≤30mA

Notes & tips
* P & OUT1 is in phase
* Suitable for tubes with Rp ~<2K
* Higher current version is available for tubes like 45, 2A3, 300B as drivers 
* Play with different configurations to tune it to your likings
* Measurement is done with 10K load, results will be better with higher loads but still very good with lower loads like 1K or 5K.

Here are the measured results with single 5687 tube. 

7Hz - 75kHz -3dB

7Hz - 65kHz -3dB

7Hz - 90kHz -3dB

7Hz - 65kHz -3dB

7Hz - 80kHz -3dB

If you do not find what you need at our website, contact us. We are expert in customized transformers for various applications. Tell us your desires and we will make it happen.

J&K Audio Design

Saturday, January 16, 2016

Power Factor Correction

Recently, a few buddies of mine have been very interested in products that will improve the mains power. There are many products of such nature, like isolation transformer, mains regulator, power factor corrector, power bank, and etc. Isolation transformer, mains regulator and power factor corrector are widely understood, but what is power bank? Can we really store power?

One of the gist of better power transmission is power factor correction. This has been widely used in industrial or commercial buildings to correct the phase relationship between voltage and current to achieve better (close to 1) power factor. Power factor of 1 means there is perfect alignment of voltage and current phase to achieve perfect 100% power transmission. Power factor of <1 means there is a phase shift between Voltage and Current, and power delivery is less than idea.

The phase relationship of the Voltage and Current is dependent on the electrical equipment connected on the load. Say, if we fixed the Voltage phase as reference (as usual, we always need a reference point), there shall be loads that shifts the Current forward and backward in relation to the Voltage phase. In general, inductive load will shift the current backward since inductor prohibits current flow (high impedance to current change), and capacitive load will shift the current forward, in relation to Voltage. Resistive load, is phase neutral - does not shift the current in relation to voltage.

Most solid state uses very big capacitor bank and therefore causes current to advance in phase in relationship with voltage. On the other hand, tube amplifier uses a lot of chokes and transformers, with low capacitance but high voltage capacitors, therefore current will retract in relationship with voltage.

Current / Voltage Phase Relationship

How do you correct this relationship? Simple! The answer is already there! If the current advances in relationship with voltage, use inductor to pull it back, and vice versa! This is called power factor correction (PFC)in lay man's term! One of the difficulties with power factor correction is that how much is enough and how much is too much? There is NO benefits in over-correcting. A close to 1 power factor will not only make your system sounds better, but saves you money too!

In industrial designs, usually a micro-controller is used to monitor the current versus phase relationship, and change the compensation in a controlled feedback loop. Less complicated system can use fixed PFC, like switch mode power supplies with PFC integrated.

PFC works, but can passive PFC like the above work for your system? Yes, it can, but not always the case since everyone's systems are different! Once would have to get the right PFC factor right to have the optimal correction and optimal sound. A one size fits all solution does not work. If it works, you are lucky, or it is just sound changes instead of optimization with over or under-corrected power factor.

In the next article, we shall come up with a simple user configurable power factor correction device. Once can flip switches to change the PFC factor to customize it to their own systems. It might be hard without measurement devices but at least one can still use their ears and that's what matters!

J&K Audio Design


Friday, January 15, 2016

Western Electric Transformers

Imaging Star Wars music playing at the background - "Imperial March"

Attack of the WE chokes and OPT fighters... The force is strong with this one... Once tried, there's never going back.

WE choke

Original WE core

Fleet of WE fighters
Western Electric Output Transformers

We often hear people saying that WE output transformers is good in mids, smooth and warm but lack of high and low frequency extension. That is because they do not understand the Western Electric core as well as we do. 

In order to have high primary inductance, one has to have more turns in the primary, and that reduces the high frequency response, and vice versa. It is not easy to achieve a balance between the two and often people gave up with less optimal results. We do not. We aim for the best!

Take a look at our WE OPT primary inductance specifications below, and also the bandwidth. We are not all talk and no results. 

Primary inductance: 114H112H)(DC bias at 10mA20Hz5Vrms
Bandwidth:7Hz – 60kHz at -3dB
Audible bandwidth is almost flat: 20Hz (-0.76dB) — 1 KHz (0db) — 20 KHz (-0.41dB)
More pictures added (1/21/2016)


J&K Audio Design