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Tuesday, December 27, 2016

HIFI Repair

Is this a trend or what - manufacturers not willing to repair their gears after warranty period is over, even if customers are willing to pay? Please share your experience in our comments section.

We occasionally take in some damaged HIFI equipment to repair, as a good will to get the gears alive again, or helping friends and customers, as a favor. This, however, has led us to discover some unhealthy trend that the after sales and service of certain manufacturers and distributors are as good as none.

Some HIFI equipment requires special parts and PCB to be replaced in order to get them alive again, such as the controller board for smart power management system for a battery backed power supply regulator, label masked off parts, special custom made integrated circuits (IC), and such. These parts are not available outside, except the creator/manufacturer themselves. 

To our dismay, multiple mails and phone calls are often, not successful to get their responses to entertain our requests, or even our customers' queries! What kind of customer service is that?

The most recent one, is to ask for just a replacement power transformer (willing to pay!) since the specifications is not made known to us, and the owner wanted the original part. Nadah... distributor is wiling to entertain for a few mails but at the end, nothing. Manufacturer just kept quiet since day one. Bravo service, really! Oh ya, your design sucks too, cramping all the parts in a small chassis, including a big hot power transformers, with very minimal venting. No wonder it failed, and failed twice - the unit has got the original power transformer replaced once, with a badly done job. I guess the repair guy could not get replacement part and just substituted with anything he can find on hand.

It is not that we are asking for free parts and free service! Our friends and customers are paying a hefty price tag for the HIFI equipment they purchased! It is their right to get replacement parts at least, if sending in for repair is not an option. Nadah... not even a reply of email sometimes, or sometimes a wait of eternity is presented to us, on the requests.

Gosh... even a little entity like us, provides better service than them! Shame on you!

Now you guys have 1 more thing to consider before buying any HIFI equipment - ask around first on the after sales service, the durability of the equipment, and how helpful is the seller/distributor!

Just venting out... thank you for listening, and share your good or bad experiences with us, in the comments section!

J&K Audio Design

Friday, December 23, 2016

WE 618B Input Transformer

Western Electric 618B Input Transformer 

One of the benefits of offering transformer repairing service is, you get to analyze all the various exotic, excellent sounding, conservatively built, extraordinary designs in the past! Then, those knowledge and know-how can be applied to our products, combining the old school engineering with modern technology = best of both worlds. 

Below is the WE 618B Input Transformer that our Thailand customers ordered, to compare with another WE 618B clone from Japan.

Permalloy EI Core

Cloth Wire are used

We can make ANY transformers! We can contract manufacture too (ODM), building the transformers you need for your on the shelf products.

Contact us for more details!  

J&K Audio Design

Friday, December 16, 2016

6C33 SE Output Transformer

Nanocrystalline 6C33C Double C Core Single Ended Output Transformer – for 6C33C tube, custom made for Melquiades 6C33C SE amplifier.

We have made this pair last year but didn't have the time to post it at our blog. Since there's a recent request to make 6C33 OPT, we took the opportunity to publish the specifications here. The user was concerned that there might not be sufficient bass if he chose Nanocrystalline (aka Finemet) core for better mid-high resolution. 

Worry not, friend. People often have that misconception as many of the amorphous core they used in their amplifiers are not optimized. Amorphous core output transformers require different design method compared to ordinary orient Hi-B / Z11 cores. Using the same formula for both will just end up with emphasized / tilting towards the mid-high frequency response, giving the amorphous core a bad / false reputation - of being detailed but lack of low frequency extension and mid-bass impact.

For those that have used our NanoC output transformers, they would have find that our OPT are balanced in low-mid-high (no BS, just look at the measurement below), and yet rich with harmonics and flavor instead of being overly colorless and flat. That's how a properly design amorphous based OPT should sound. Switching to Permalloy / nickel core adds more silkiness in the highs, and produces a golden tone to the mid-range. 

Optimize your 6C33C SE amplifier now by getting a pair of J&K 6C33C OPT home! Let your creation shine like a star!

  • Power: 40W(20Hz)
  • Actual in circuit frequency response (360mA)
    • 20Hz(-0.36dB)—1KHz(0db)—20KHz(-0.19dB)(12 Ohm tap, 1W)
    • Note: measurement conditions, 6C33C, plate voltage 150V, plate current 360mA, fixed bias, secondary load with resistor, at 1W.
  • Full bandwidth: 
    • 7Hz – 70kHz +/- 3dB @ 360mA
    • 5Hz – 100kHz +/-3dB @ 280mA
  • Primary impedance: 650 Ohm (can be 1K-1.2K too)
  • Secondary impedance: 0-6-12 Ohm (or 4/8, 8/16)
  • Core: Nanocrystalline Cut Core (aka Finemet)
  • Primary DCR: 18.1(18.3) Ohm (B-P, measured at 29degC)
  • Secondary DCR: 0-6 Ohm (0.28 Ohm), 0-12 Ohm (0.4 Ohm)
  • Primary inductance: 3.26(3.4)H @ DC bias of 360mA, 20Hz, 5Vrms 
    • Primary inductance can be increased if the air-gap, primary inductance, core size are varied, tailored according to applications.
  • Primary current (absolute max): 600mA (recommended <= 360mA)
  • Efficiency: 0-6 Ohm (>92%), 0-12 Ohm (>93%)
  • Matching results:
    • DCR <2% (actual <0.2 Ohm)
    • Primary inductance <5% (actual <0.14H)
Measured at 360mA

Measured at 280mA primary current

Measured at 280mA primary current
Look of the potted OPT before the cover is being added. Properly sized core is required to strike the right balance between low and high frequency response at rated output power.

J&K Audio Design


Thursday, December 15, 2016

Transformer Volume Control Review

Greetings. We have made a pair of TVC (transformer volume control) for a very nice and patient customer some time ago, and he has been very nice to provide us with his review and also measured data on our TVC. 

For those that are unaware of what it is, you can refer to the links below:

As you can see from the measured data, bandwidth is RULER FLAT from 20Hz - 20kHz, and low frequency -3dB point is at 10Hz, more than most speakers can reproduce. Channel matching is spot on. Most importantly, it sounds absolutely terrific! Do not hear it from us, try it yourself. 

We'd like to THANK Lasse for sharing the pictures and providing a review for us!


Hi Jolin,

I like the TVC's. They are made with tight tolarenaces regarding channel balance and frequency response from each step. 

I used Sommercable Carbocab 225 (6N copper in compressed carbonized plastic layer and polypropylen insulation) to wire all the taps, which I find very good cable especially compared to it's price. I use Oyaide Tunami cabling otherwise almost everywhere.

The sound quality is the best I have heard, beating the crap out of S*** TVC's and the original TVC's of the Coincident Statement Line Stage. Compared to my previous TVC's the sound is much smoother. The sound of the TVC's is very liquid, refined and microdetailed also at low listening levels. I'd say with Permalloy core they hit just the right spot with Finemet transformers, very very good combination of transformer cores in my opinion because the Permalloy is so smooth and Finemet is so transparent, airy and wide bandwidth. I believe they are "the" core materials in those attributes, and when combined 25% permalloy/75 % Finemet the result "does it all" for my liking.

Please find a picture of the installed units attached. I did not take other pictures than that, I'm sorry and now I have put on the stainless steel covers which block the view of the transformers. The freq response of each step has now "normalized" and is identical in each step. Funny how that changed slightly in the burn in process also.

Thank you for the (snipped - our little secret)!

Best regards,



Do note the measurement is made by Room EQ Wizard software. It is limited to 48kHz sampling frequency only and therefore the accuracy for such sampling rate is <= half of the sampling frequency before Nyquist effect kicks in. So, everything after 24kHz is not faithfully measured. The TVC bandwidth is definitely much much more than 20kHz.

Suppose the highest frequency component, in Hertz, for a given analog signal is fmax. According to the Nyquist Theorem, the sampling rate must be at least 2fmax, or twice the highest analog frequency component. If the sampling rate is less than 2fmax, some of the highest frequency components in the analog input signal will not be correctly represented in the digitized output.

TVC measurement - left channel

TVC measurement - right channel

Screen capture of email sent to us
Coincident Statement Line Stage

Update on 12/21/2016 (thanks to Lasse that provided the supplementary information).

* The measurements are from the whole modified Coincident Statement Line Stage preamp. The preamp has been modified with J&K TVC and Noguchi FM-10K-600CT output transformer. Very simple & great sound, zero feedback. 

* Also the sound-card's input/output is not DC connected and the loop back measurement has attenuation at the bass (-3dB @ 7,5Hz).

J&K Audio Design

Sunday, December 11, 2016

2016 Retrospective

Greetings everyone! Hope everyone is doing well, enjoying better music and HIFI in 2016!

In a blink, we're almost at the end of 2016! We would like to take this opportunity to thank our customers, friends and family for their support on our journey along the way. We would like to apologize if we have offended anyone or have a long lead time for our products.

Highlights for 2016
  • MADE NEW FRIENDS! Especially a few folks from Bangkok, Thailand; Silicon Valley, USA; Hong Kong, Singapore, Malaysia, Taiwan, and from Russia with love! We enjoyed your company, and also your sharing of your projects, knowledge and ideas! Long live friendship!
  •  -----------------------------------------------------------
  • EXPANSION - we've gone a bit to aggressive due to the rise in orders and made the wrong step to hire technician and that regrettably screwed up on a few power transformers projects due to new hires mistakes and miscommunications. 
  • We were deeply very sorry about those cases. Please let us know how to make up to you.
  • After much consideration, we have reverted back to our business model, limited experienced engineers and practice: good stuff have to wait! We apologize in advance for the long lead time - that's how good stuff are made. 
  •  -----------------------------------------------------------
  • PROGRESSION and MATURITY in winding technology - for those that notice, our product specifications and outlook have changed over time. We've been improving (and increasing the varieties) our products in the background and keep on exceeding our own expectations. Things just keep getting better, such as OPT winding methodology, isolation transformer improvement, materials/equipment upgrade, and such! 
  • We've built quite some massive OPTs again this year, such as 212 SE OPT, 212 PP OPT, 212 PPP OPT, GM70 OPT, GM100 OPT and such that had gone into several very, very high end amplifiers.
  •  -----------------------------------------------------------
  • MATERIALS TECHNOLOGY - previously we were mostly limited to various SiFE, amorphous and Nanocrystalline (aka Finemet) cores. Now, we have added some Permalloy (nickel + iron) cores to our product line, with some 1 time-of special cores that come and go, such as Cobalt or Western Electric cores, for connoisseurs with special unique tastes.
  •  -----------------------------------------------------------
That pretty much sums up what we have gone through in year 2016. Long live the spirit of DIY and self creation! 

Thank you again!

J&K Audio Design

Blog comments

Hi guys,

We used to get alerts from Blogspot whenever there are new comments posted at our blog. It's funny that some time ago, Blogspot stopped doing so and we could not keep track of what have been posted in our blog, if there are questions or not pertaining to the topic of interest.

If you've any questions, comments or help needed on our posts, please drop us an email and we will attend to it at the shortest time possible. For those that have posted comments at our blog, if you do not see any response, we apologize and urge you to resend those comments to us at our "contact us" form. 

Apologies for mistakenly being "arrogant".

Thanks again!

J&K Audio Design

Friday, December 9, 2016

Western Electric WE 618B

Western Electric 618B Input Transformer 

One day, we've been chatting casually with one of our customers about Western Electric sound, and transformers. They're interested in the WE 618B, that is sky high in price for an original pair - U$6,500 - U$7,000/pair (wow... that's crazy!).

We dug our repair logs years ago and found that we have actually repaired them before, and we have recorded down all the winding details, plus the core physical dimensions too. With that, we will be able to recreate a WE 618B faithfully with modern EI Permalloy cores. If one can supply us the WE Permalloy core, that would be even better, closer to the original.

* Clone with new EI-35 Permalloy core, or you supply original WE 618B / similar WE cores
* Recreate following exactly the original WE 618B winding method (we repaired before)
* Potted in square case, bare or framed in standard end bells.
* U$890 / pair (compared to U$6,500 a pair the original)
* Lead time ~4 weeks

Original WE 618B - how it looks like. I'm sorry, I do not have the original casing, or casing that look alike. If you can supply me, I can put it in. Meanwhile, I will try to source for something similar.

J&K Audio Design

Hacker Alert

Hacker alert!

We have been alerted that a hacker (or more) with the name of Aleksandar Tsankov has access to our email database and has been phishing data and/or money from our customers.

Please take note that there is only one official email account for J&K Audio Design. Any other emails pretending to be J&K are fakes! If the reply does not sound right, it is not right! 

We suspect that he might have either hacked our email account (unlikely), or hacked our blog "Contact Us" form. Or perhaps our customer has malware on his/her computer that the data got sent to the hacker while he fills up the Contact Us form?

We are investigating all these possibilities now. Meanwhile, just be extra careful. If you have gotten funny emails from us, please use the Contat Us form to resend it for reverification, just to be safe.

Many thanks to our customer to alert us about this very unfortunate incident. 

Buyer beware!

Here below an email from Aleksandar Tsankov:

Hi **** (removed for privacy),
My previous answer to your questions was not delivered to you by some reason that's why I'm resending it again from my personal e-mail account - sorry for unwanted delay.
Fitted with 33000 uF capacitors the Blocker can handle 10A current. The input IEC inlet is also rated at 10A max. current.
According to negative impact on the sound quality, till now I do not have such feedback from my clients. On the contrary, some of them reported improvement of the sound. Of course I do not claim that the Blocker will improve your sound quality at any time - its purpose is to block DC offset in the Mains network.
Yes, I can ship my stuff to Hong Kong.

Best wishes!

End Quote.

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

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