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Saturday, February 18, 2017

Audio Transformer Repair

Audio Transformer Repair

If there's something strange in your neighborhood.
Who you gonna call? Ghostbusters!

If there's trannies burnt in your neighborhood
Who you gonna call? J&K! 

Nothing beats getting back the original sound, original look, and original material for your beloved audio gears collection! We repair any audio transformers - be it input, output, interstage, power transformers or chokes. We do not repair SMPS chokes though - get a new SMPS for Pete's sake!

4pc of damaged vintage input transformers were sent to us for repair recently. It was cleaned up and rewinded with traditional Kraft paper with old-school technology, following the generation when it was manufactured. It is fully restored back to the older days glory! 

The in/out wires are following the original color coding as well!

If your transformers, be it power, input, output, interstage, or anything at all, are damaged, don't forget to drop us an email to have them restored! A close to original vintage gear, at anytime, has much higher value than those with damaged or non-original components on it. 

Spend now and you will be rewarded financially, or in terms of audio enjoyment.

J&K Audio Design

Sunday, February 12, 2017

Solid State Power Amp

Introducing our very first solid state power amplifier!

We're working towards getting more write-up on our solid state amplifiers but that will take some time. For now, we will share some brief specifications, and later, detail write-up on the design methodology will follow to introduce more about our solid state amplifier technology.

We are using chassis from Breeze Audio. If you do not find the chassis that you like, let us know.

Alpha 1 - U$490

- Class AB dual mono stereo power amplifier
- MK1, 45W / 8 Ohm (high power version, made for high efficiency speakers)
- MK2, 26W / 4 Ohm, 13W / 8 Ohm (high current version, made for low impedance single driver speakers and general use)
- Ultra high bandwidth: 8Hz - 100kHz @-3dB
- THD 0.02%
- J&K sound tuning, absolute darkness and quietness
- Purist & minimalist design, for high quality high efficiency speakers, or high efficiency single full range driver

Beta 1 - U$890

- Class AB dual mono stereo power amplifier
- MK1, 85W / 8 Ohm
- MK2, 76W / 4 Ohm, 38W / 8 Ohm
- Ultra high bandwidth: 8Hz - 100kHz @-3dB 
- THD 0.005%
- J&K sound tuning
- Purist & minimalist design, for high quality high efficiency speakers, or high efficiency single full range driver 

Gamma 1 - U$1290 / unit

- Class AB dual mono stereo power amplifier
- MK1, 180W / 4 Ohm, 110W / 8 Ohm  
- MK2, 200W / 2 Ohm, 100W / 4 Ohm, 50W / 8 Ohm
- Ultra high bandwidth: 8Hz - 100kHz @-3dB 
- THD 0.005%
- J&K sound tuning
- Purist & minimalist design
- High current high power version for driving low impedance, difficult speaker loads, such as Dynaudio, Maggies or ATC. 


Delta 1 - U$1990 / unit

- Class AB dual mono power amplifier
- 520W / 1 Ohm, 260W / 2 Ohm, 130W / 4 Ohm, 65W / 8 Ohm
- Ultra high bandwidth: 8Hz - 100kHz @-3dB 
- THD 0.005%
- J&K sound tuning
- Purist & minimalist design
- Ultra high current high power version for driving low impedance, difficult speaker loads, such as Dynaudio, Maggies or ATC.



- Upgrades available, such as up-sizing power transformers, upgrade coupling capacitors (Mundorf, Duelund, and etc) and power supply capacitors, upgrade internal wiring, mechanical hardware (speaker binding posts, RCA, IEC), customize add-on features such as volume control, remote switching, DC blocker, EMI/RFI filter and etc.
- High quality components, high precision resistors, low ESR/high current capacitors, oversized high quality power transformers, and etc. 
- Traditional linear power supply with high energy storage are used for low noise operation. 


- For higher output power, from 250W up to 1kW, please write us.
- SMPS option is available upon request for PA or high power version.
- Can be made as mono-blocks, 2 channel, 3 channel, and 4 channels, or depending on the power and size.

Design methodology

J&K Audio Design continuously, and relentlessly seeks for improvement and advancement in every aspects of our product design. The best technology, methodology, metrology, know-how, experiences and materials science, are always applied to our products and design, whenever possible, and applicable, towards giving the best audio results.

Why did we say “when applicable”?  In audio, it is all about tuning and applicability. One cannot throw all the best parts available in the world, and expect the end results to be out of this world, to be remarkable. You cannot. That is not how audio design works. Just like in the culinary world, everything has to be in the right proportion, the correct ingredient, the right processes, the correct steps, to produce the best taste and texture to the creation. It is just the same as designing and manufacturing amplifiers, which is out topic today.

We have seen many, many excellent recent, and vintage amplifiers being made by great designers all over the world, all since the invention of audio amplifiers, starting from vacuum tubes (we love vacuum tubes, we still do), until all the various classes (A, AB, D, H, T, all DHT, PP, SE and etc) of solid stage silicon based amplifiers today. There is not “the best” amplifier, period. All are made with different end in mind, for different markets, different applications, different segments, and different people!

Our team, and our panel of HIFI enthusiast’s beta version testers have been ear trained to prefer vacuum tube sound. Those lush, warm midrange, extended highs, absolute transparency, taut but not overly excessive bass frequency, and many more traits associated with vacuum tube amplifiers.  In order to achieve such decent quality in vacuum tube amplifier, significant cost is involved, to have the right design, component, and materials deployed. As a result, cost might be overbearing for some, and may need to seek a cheaper alternative to achieve similarly closed performance.

Therefore, our quest to design such amplifier started.

We explored different designs, different classes, different materials (FET, bi-polar, jFET, MOSFET, and etc), discrete versus integrated circuit, different power supply designs, different topologies, different components (R, L, C, wire type, chassis, transformer and etc), and many more parameters that constitute to sound reproduction. This takes up considerable time, money and resource, and finally, we found the solution! Initially we were quite fond of class D switching amplifiers, with the efficiency, and capability to pack a very low footprint per Watt ratio, but the load dependent bandwidth due to the LC filter at the output stage turned us off.

The design we found, and offer now, is an integrated chip solution. It offers super wide bandwidth, easily range from 10 Hz – 100 kHz (ultra-low frequency contents <10Hz, are restricted per board design to minimize noise and wastage of power – increase efficiency and power handling), with flexible and scalable output power, from low to very high power, from low to high load impedances, and from low to high supply voltages. With integrated chip solution, signal path are the shortest, component count are the lowest, meeting our purist and minimalist design ideology, and that minimizes the loss from PCB material, PCB trace inductance/capacitance/resistance, PCB joints, and solder quality impact. 

I wish we could do a point-to-point wiring method using OCC (Ohno Continuous Cast) copper, with this solution, but the time and cost to manufactur such amplifiers would be too significantly expensive compared, unless customers request and are willing to pay for it, in a custom solution format. 

In addition, integrated circuits minimizes interferences from external environment, especially for the sensitive front-end circuitries, and short internal traces enable very fast and short signal transfer, and tightly controlled feedback or control loop for absolute signal integrity and transient response. All the complex and sensitive circuitries can be packed and shielded in a small integrated circuit. With current advancement in silicon wafer process technology, device deviation, or skew are tightly matched or controlled up till micron level. Part to part variation is kept to a very, ultra-low figure that matching integrated circuit behaviors can be expected consistently.

J&K Audio Design is not that large in volume until we can order customized audio integrated circuits from big time manufacturers such as TSMC or UMC where they produce chips for large scale manufacturing houses for the PC or mobile phone segments. We are just leveraging the effort and millions of dollars of investment made by such huge conglomerates to our benefit.

Out of the box, such integrated circuits may not be working at the optimized circuit, or being properly treated in their partnering components, such as the passive components, and the power supplies supplying the important energy to power the chip. We, work hard to complement the already very excellent performance, to raise it to another sonic level, under achieved in the mass-produced electronics gears or gadgets.

The scalable nature of the integrated circuits enables us to customize the output power to match the segment the amplifiers are designed for, whether is to power high efficiency speakers, or power hungry huge floor-standers. With careful selection of design and components usage, we tailor made the amplifier to match the speakers, with excellent results.

The integrated circuit is designed with intelligence to sense the output power required, and determine if extra output transistors are required to be turned on to deliver the extra power, thus still keeping to the minimalist and purist path where single chip produces the power until further requests at larger loads. Such switching or crossover may introduce noises but due to the internal circuitries built it, such traits are minimized and of very little effects.

Still, we recommend high efficiency speaker users to go for the version optimized for high efficiency speakers. The higher power versions, are, for more difficult loads. The sonic character is the same. Only the output power and current delivery are scaled up for high power versions. Such scale up in components, with more component count, with larger PCB size, may cause unwanted stray and leakage currents, inductance, and capacitances, attracts EMI/RFI and other interferences, add in more coloration, which may be detrimental to the sound.


The J&K Audio design amplifiers combine the benefits of integrated circuit with audio technology to bring users the best listening experience.

As you would have noticed by now, branding, marketing, paid reviews, and packaging expenses are kept to a very minimum, while research and development, prototyping, component technology and product quality are our utmost priorities. Therefore you will not see much reviews being published on magazines or websites, but true word of mount from our real world, satisfied customers. That is what really counts.
J&K Audio Design

Thursday, February 2, 2017

DC Blocker Review

Again, Gong Xi Fa Cai! 

We woke up this morning to find this wonderful news from a J&K Audio Design Audiophile DC Blocker user in Hong Kong. Another Hong Kong user used J&K DC blocker and introduced it to him on an online forum (refer link below):

His mono-block power amplifiers had issues on hum and he asked us to custom make two cost-no-object super high end audiophile DC blocker with Furutech inlet and outlet (NCF type), audiophile capacitors, and with 6N OFC cables. 

FI-06 NCF (R)


The Furutech GTX-S NCF and FI-06 NCF are really something! Build quality is top notch. The material felt solid and damped, unlike those cheapskate plugs from the general stores. It costs a bomb but is worth it.

After adding in the DC blocker, not only the hum from the toroid transformer at his Constellation amplifier is gone, the performance is improved as well since the transformer is no longer saturated with DC and can work optimally / normally. 

See a screen capture from our Inbox:

Ivan posted in a HK forum too, as follow (with pictures too!)

Quotes (can translate with Google Translate):

"效果應該是預期(是期望才對),初插上15分鐘,有如冇開機的靜。 半小時後播上第一隻碟,弱音更現,低頻更深,好聽好多多多。相信經長假期慢火煲練應可更溫純。"

" 我先要針對Amp hum 這問題, 乜都要試。 這對DC Blocker真真有料到, 昨晚開足七小時, Amp机身微暖, DC Blocker机身溫度涼爽如未用上的。聲音似用上Centaur II, 聽至零晨一時, 細細聲也很清晰細緻。直得一試。"

For some background, you can read it here. We can custom make it to any format, any quality you need, based on your budget.

Ivan: thanks for sharing your feedback! 

Till then, take care guys! 

J&K Audio Design

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* 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.

* Our product lines are always improving and increasing. If you do not see what you want, contact us!

* Please email for volume discounts, distributor and OEM pricing.

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