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
12/27/2016

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.

http://jandkaudiodesign.blogspot.my/2016/12/western-electric-we-618b.html

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!  

12/24/2016
J&K Audio Design

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!

Parameters

• 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
12/16/2016

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:

http://jandkaudiodesign.blogspot.my/2016/10/optvc.html
http://jandkaudiodesign.blogspot.my/2016/10/transformer-volume-control-tvc.html

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!


QUOTE:

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,


Lasse

END QUOTE. 

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 f_max. According to the Nyquist Theorem, the sampling rate must be at least 2f_max, or twice the highest analog frequency component. If the sampling rate is less than 2f_max, 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
12/15/2016

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
12/12/2016

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
12/12/2016

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
12/10/2016

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:

Quote:

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!
Alex

End Quote.

Ground box trial

We have 1 unit of 3io's Blackbox in New Zealand now for trials. If anyone of you nearby would like to give it a try, please contact us asap.

http://jandkaudiodesign.blogspot.my/2015/03/3ios-blackbox.html
http://jandkaudiodesign.blogspot.my/2015/03/3ios-blackbox-ground-box.html 
http://notanotherhifiblog.blogspot.sg/2016/08/grounding-for-better-j-audio-design-3io.html
http://notanotherhifiblog.blogspot.my/2016/08/grounding-for-better-j-audio-design-3io.html

It's quite easy to use - just plug it to your mains, or connect it to ANY ground point of your HIFI system. The best is at wall plug ground, or power distributor ground.  

Hear it to believe! 
J&K Audio Design
11/2/2016

OPTVC

OPTVC - Output Transformer Volume Control (OP TVC)

What is OPTVC? What is the difference between TVC and OPTVC? Please read on.

What we're going to share today is something special for the purist. We're not the first but definitely this is something not very common.

It is the simplest form, purist approach, preamp with volume control!

Before we go there, here's how a traditional TVC (transformer volume control) looks like.

TVC

Below two pictures are how traditional simplest single stage tube preamp with volume pot look like, with or without output transformer (just remove the OPT and replace with a resistor). There are lots of components in this simple preamp.

For parafeed preamp with OPT: 

• Volume pot
• Load resistor
• Coupling capacitor
• Preamp Output transformer

Parafeed output tube preamp

Traditional tube preamp WOT

To make things simpler, we go with traditional non-parafeed preamp with output transformer above. We still have:

• Volume pot
• Preamp Output Transformer

It has become quite simple already, right? 

The resistive brushed (yucky) volume pot in front can be replaced with a TVC to significantly improve the sound, and below is how it looks like. It is still not as simple we want - we still have TVC + Preamp OPT, two components.

We can simplify it further!

• Remove the TVC at input!
• Replace the preamp OPT with a OPTVC - output transformer volume control! 

Now we are left with only the OPTVC and the triode! That is what we call TRUE simple tube preamp!  (Don't try this with normal TVC! This requires a special type of TVC!)

OPTVC on a simple Preamp

The simplest, the PURIST-EST design! The tube uses the TVC as a load, with multiple (23-24 step) secondaries as volume control! That's it! No more additional volume pot at the input. We are left with ONLY 1 transformer in the circuit. The preamp OPT is combined with TVC to become what we call OPTVC - Output Transformer Volume Control!

The differences between TVC and OPTVC are:

• TVC usually has low primary impedance for direct CDP/DAC drive
• OPTVC needs high primary impedance for tube loading 
• TVC has no core air-gap, therefore DC at primary is not permitted
• OPTVC has air-gap, and DC loading is permitted 
• OPTVC requires significantly larger core due to DC loading

The compounding effects of having two signal transformers, where the high and low frequencies are attenuated twice, are now gone! You get the benefits of both TVC and preamp OPT in one shot! 

Compounding attenuation example, for a design with traditional TVC + preamp OPT

• preamp OPT has -3dB at 20Hz
• TVC has -3dB at 20Hz. 
• TVC + preamp OPT = -6dB at 20Hz

The compounding effect of 2 transformers is actually making it -6dB at 20Hz, a much steeper slope than what we thought. That applies for high frequency attenuation too!

You SAVE MONEY on spending 1 less component, either an expensive volume pot, or an expensive preamp OPT! What's saved can be used to get an ultimate OPTVC and you actually have lesser coloration since component count and signal path are significantly shorter/simpler/lesser! 

Copper OPTVC (Output Transformer Volume Control)

• Primary: 5K (other values, please ask)
• Primary DC: 10mA (standard, other values available)
• Secondary: user defined impedance (600 Ohm usually as preamp)
• Matched pairs, potted - must 
• 23 steps U$690 OFC
• 23 steps U$890 OCC (Ohno Continuous Cast) Copper
• 33 steps U$990 OFC
• 33 steps U$1190 OCC Copper
• 44 step U$1290 OFC
• 44 step U$1490 OCC Copper

Silver OPTVC (Output Transformer Volume Control)

• Primary: 5K (other values, please ask)
• Primary DC: 10mA (standard, other values available)
• Secondary: user defined impedance (600 Ohm usually as preamp) 
• Matched pairs, potted - must 
• 23 steps U$1090 OCC silver wires
• 33 steps: U$1390 OCC silver wires
• 44 steps: U$1690 OCC silver wires 

If more steps are needed (49, etc) please email us. 

Order a pair of OPTVC now, and experience the magic of simplicity!

Note: price for silver wire based transformers will change according to silver commodity price fluctuations. Price posted is valid for 2 months upon posting. Please email us for latest quotation for silver versions. 

Hear the unheard! 
10/18/2016
J&K Audio Design

Transformer Volume Control TVC

Transformer Volume Control, TVC

Transformer Volume Control (TVC)

What is the best attenuator in the world? There are many types available, such as digital chip based (PGA2310), analog brushed pot, discrete stepped attenuator, digital relay switching stepped attenuator, DSP based attenuator, Autotransformer Volume Control (AVC), and finally transformer volume control (TVC), which is our favorite. 

It is not the widest in terms of bandwidth but it has the best tonality, body, and harmonics that we look for - musicality in another term. Transformer volume control (TVC) became quite hot about 10 years ago but somehow it went rather lukewarm these few years. We heard some rumors or complaints on the durability of the unit being manufactured due to switch connectivity as that is one of the crucial component of the TVC, where mechanical connectivity will affect the outcome severely. High quality switchers such as Elma, Seiden or some milspec switchers will be desired in TVC application to ensure no mechanical issues arises after prolong (or even short) use.

No matter what, it is still a gem to be discovered if you have not ventured into TVC world. The sonic characteristics / benefits are not something other volume pots can reproduce easily. 

Different types

Low Level (signal, not quality) Input Transformer Volume Control (TVC) - install after source (CDP/DAC)

• LLI TVC OFC - U$690 / matched pair, potted, 23/24 step
• 23 step OCC - U$890
• 33 step OFC - U$990 
• 33 step OCC - U$1090
• LLI Silver TVC - U$1090 / matched pair, potted, pure 4N Silver wires, 23/24 step 
• 33 step - U$1390
• Notes
• Amorphous or Permalloy double C core
• 2Vrms @ 20Hz

High Level (signal, not quality) Input Transformer Volume Control (TVC-XL) - install after preamp (SS or tube)

• HLI TVC OFC - U$790 / matched pair, potted, 23/24 step
• 23 step OCC - U$990
• 33 step OFC - U$1090
• 33 step OCC - U$1290
• HLI Silver TVC - U$1190 / matched pair, potted, pure 4N Silver wires, 23/24 step  
• 33 step - U$1490
• Notes
• Amorphous or Permalloy double C core
• 5Vrms @ 20Hz (other input level / sizes at different pricing) 

Variations / Upgrades / Notes:

• Options: balanced input, higher input level (bigger size), fully built in chassis version, higher/lower number of steps, with gain (step-up) options, and etc.
• If higher signal level input is not required, 2Vrms @ 20Hz version will have better performance than 5Vrms @ 20Hz version in terms of bandwidth. Do not use truck engines in your sports car! 
• These guys are hard to manufacturer - order early as they have long lead time (1 month generally).
• Others not mentioned, please email us.

Application notes:

• Grounding at primary or secondary depends on application. 
• If it is going to act as a standalone preamp, secondary should not be grounded, and therefore it also acts as an isolation transformer to remove ground loop. 
• If step-up (gain) is required, the load must be light to prevent bandwidth loss as output impedance will be increased with step-up. 
• KISS rules - keep it (the design) sweet and simple, and it will serve you better. 
• The load on the secondary will make or break the signal integrity. If you have a scope, try with different values of load on the secondary. If not, ask us for help, and mention it (the load) when you order and we will optimize for you.
• High quality 23/24 step switch is a must. Cheap pots will be just a waste of time.

Milspec 24 Step Switch

Notice how thin those secondary wires are? Utmost care is required when soldering these wires. We tried to sell bare format TVC transformers (cheaper) but chose to do potted version instead. The success rate is too low for DIY folks for getting the soldering and order correct. Therefore, we chose the potted with solder tags format for easier handling and better re-usability.

Fully built TVC

This is a fully built TVC, with SE and Balanced input. It uses a special XXL double C core to handle very high level input (>5Vrms).

Double C Core TVC

A closer view of the double C core Transformer Volume Control.

Function Generator / Signal Generator

Every unit is characterized and matched before being assembled. Usage of function generator / signal generator is unavoidable. This function generator is capable of generating low distortion sine/square/triangle/saw-tooth 20Vpp of output for us to fully test the TVC for all the operating corners.

Testing Transformer Volume Control

  TVC test setup - function generator and high bandwidth oscilloscope.

TVC Output Waveform

One of the sine wave test - testing the input capability of the TVC - determine how large the signal can go before distorting.

TVC Primary Inductance

Matching of primary inductance. Take note of the 4 pictures here with the LCR bridge (green display). The LCR bridge is actually measuring the same TVC, but with different core air-gap. You can see that the primary inductance actually varies substantially with different core air-gap, from 50H to 187H. 

We are actually working on a next generation of MIND BOGGLING, FIRST IN THE WORLD NEVER BEING SEEN TVC EVOLUTION that is to be released very soon. The primary inductance measurement work is helping us to characterize the behavior of the EVO TVC to be made for a special purpose application.  

Stay tuned for very recent announcement - monitor or subscribe to our blog in order not to miss this special product.

Transformer Volume Control Primary Inductance

Low primary inductance - if cores left untouched - huge air-gap.

Core Air Gap Affecting Primary Inductance

Primary inductance surged to 187H if cores are tightened to almost 0 core air-gap. The difference is day and night, >100% change from 51H to 187H. The gain of primary inductance is not free though, something has to be sacrificed. Do remember what we say always, there is no free lunch in transformer design. All the parameters are working against one another.

Reduce air-gap, increase primary inductance

If we press the C-cores by hand, that's what we get! Interesting, right? This is like designing and characterizing single ended output transformer, where the size of the air-gap determines the maximum primary current / capacity of the SE output transformer. The gap has to be made exact with up to micrometer to have exact matching between pairs, and for accurate primary current loading capacity determination.

TVC Primary DCR

Matching the primary DCR.

Matching TVC

Since both units are winded at exactly the same methodology, matching is easier and the electrical parameters are very, very close. It was 771 Ohm and 772 Ohm between 2 units! That is like 0.1% matching!

TVC Design

Notice how thin the secondaries are? These are special Litz Teflon OFC magnet wire. These wires are giving us lots of headache in terms of winding (ultra thin, fragile and slippery) and soldering (very high soldering point to melt the insulation, no mechanical stripping allowed, it will break!), although they are, very very good in performance.

Double C Core TVC

TVC Winding

Transformer Volume Control

That's all for today! Thank you for reading. If you have any questions, email us for clarifications. Our customer service is always willing to help.

Hear the unheard!
10/16/2016
J&K Audio Design