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Monday, January 13, 2020

J&K solid wood chassis

Happy 2020! Business as usual. Hope everyone is well, and still actively and passionately pursuing the DIY audio hobby! 

While working on transformers design and orders, we received an order for solid wood chassis with 3mm copper top, for his tube amplifier. 

Some said that the wood chassis looked like Chinese kung-fu tea tray... I can't argue with that. It does! 

Enjoy DIY!

J&K Audio Design

Sunday, November 24, 2019

J&K custom services

What does J&K have in store? Some may ask. Our blog touches too many things.

Well, let us tell you now in a very brief way. The best answer, is still to email us what you need, and we shall see if we can satisfy your needs, or solve your problems. 

J&K main services 

1. Transformers (custom made) of all sorts - power transformers, chokes, isolation transformers, input transformers, output transformers, interstage transformers, speaker crossover / attenuator, solid state output transformers, headphone transformers, and etc. 

Materials we have now: OFC, OCC Cu, and OCC Ag (silver); single and triple insulated magnet wires; various types of insulation materials for different purposes, and etc. 

2. Transformer repair / rewinding / rebuilding - we can repair almost all types of transformers, such as power transformers, input transformers, output transformers, interstage transformers, special transformers and etc. All except SMPS high frequency switching transformers. We had repaired or rebuilt tonnes of vintage and modern transformers from famous brands, such as AN-JP and AN-UK, Western Electri*, McIntos*, Peerles*, Alte*, Marant*, Jadi*, Dynac*, you name it, we have almost repaired it. 

*** Thanks to J&K Services #2, we've learnt so much from reverse engineering those vintage and famous transformers for repair purposes. If you need your J&K transformers to mimic certain vintage and famous transformers, we can do so too. We'd prefer our own house sound if you build from now, but if you need to restore vintage amplifiers, we would recommend to follow their way to preserve the house sound, or brand sound. *** 

J&K side lines 

3. Equipment repair services / modifications / upgrades.

4. Fully built audio gears, such as integrated amplifiers,pre-amplifiers, power amplifiers, isolation transformer, balance power isolation transformer, audio gadgets or audio modules, active crossover, DC blocker, noise filter, ground conditioner and such.

5. Special projects - email J&K and tell us what you need, or what's troubling you, and we can custom the solutions for you, or refer you to our partners to sort out your problems if we cannot do so. We've built such a wide network of friends, customers and partners along the way in this line. 

We pride J&K / ourselves to provide top rate quality products and services. Therefore, please excuse or please forgive us if it takes some time to get your project(s) finished. We tried not to increase our staff abruptly just to get more businesses (been there, done that, and suffered due to such) as good quality staff are had to find and train up. 

If you need an item done urgently, J&K would recommend you to please plan it far ahead to avoid rushed work. 

Thank you all again for your businesses along these years! 

P/S: you may find that we're slow on the blogging as time is really short on our hands. We do have very occasional posts in our Facebook page on the projects on hand. So, please visit our FB page more frequently!

Till then, take care and enjoy being alive! 

Tuesday, October 1, 2019

J&K lead time

Hi guys,

Plan your orders ahead of time please. Custom projects take a long time for planning, sourcing, executing/manufacturing and verifying the designs and creations. 

We cannot accept expedited orders. (*** Maybe yes if you are our in laws. :p ***)

Orders are placed in queue per the order they come in. 
  • Custom transformer duration is ~1 month, depending on complexity, quantity and time of order. Some may be faster, some may be longer.
  • Transformer repair duration is ~1 month, depending on complexity, quantity and time of order. Some may be faster, some may be longer.
  • Custom finished project duration is ~2 months, depending on complexity, quantity and time of order. Some may be faster, some may be longer.
Please try not chase us for delivery. Please try to understand that we are trying to keep the quality high by not rushing orders, and by not over-expanding the human resources and compromise quality. 

If you are in a rush, please order and pay early so that we can place your project(s) in the order queue early. 

Last minute rush orders will not entertained. (*** Maybe yes if you can consider paying 10x of normal price. :p ***)

Thank you for your cooperation.

J&K Audio Design

Friday, September 27, 2019

tweeter attenuator transformer

Mids highs attenuator transformer - useful tool for final tuning of mids and tweeter to match listening room conditions, seating distance, and woofer / mids / highs volume level. It can be useful during crossover design phase too, to try with different attenuator taps / levels before deciding on the final attenuation levels. 

For those speakers with bi-wire or tri-wire connections, one can even use this to attenuate or boost the mids and highs if one feels that the highs / mids / bass levels are mismatched with their listening room or listening taste. 

100W Transformer Attenuator

Tweeter attenuator transformer

Attenuator / booster transformer

Tango has made some in the past, model Tango SA-300. 

For ours, we can custom it from 30W to 300W, or even 1KW if required. Pictured above are the 100W version, with total DCR of about 4 Ohm end-to-end, 11-steps at 2dB per step. Other configurations can be made per customer requirements. 

Users can choose the output format (potted, bare frame, stand), cores (Hi-B, Amorphous, Permalloy, NanoCrystalline), wires (OFC, OCC Cu, OCC Ag), taps (10-step to 33-step), power (10W - 1KW), and anything that the user needs.

Applications #1 - attenuate
- connect two ends to amplifier output
- connect the middle steps and return step to the mid/tweeter
- choose the steps to select attenuation levels

Applications #2 - boost 
- connect mid step and return to amplifier output
- connect the higher steps and return step to the mid/tweeter 
- choose the steps to select boost levels

Reference prices for mid/tweeter attenuator transformer: 

30W version
- OFC - U$150/pc 
- OCC Ag - U$490/pc
- OCC Cu - U$260/pc
- Amorphous / Permalloy / NanoC core upgrade +U$50/pc
- other parameters, please email

100W version
- OFC - U$260/pc
- bare frame 
- other versions, please email

* 10 step at 2dB/step (other steps quantity and step size can be made) 
* Potting adds U$30/pc.
* 200Hz and above (mid-high use only)
* Full frequency range unit can be made too 

For bare version, we can only use OFC magnet wire with adhesive property to ensure the wires stay aligned and together during and after winding. For other type of wire, those without adhesive properties, they need to be potted to ensure the coils do not move around. 

For full range version, also known as unity-coupled-transformer, it can be made too. These transformers are used for speaker impedance matching purposes, as well as to gain some "tube sound" by using it as "output transformer" in solid state amplifiers. 

One can connect the amplifier to the 8 Ohm tap, and the right output impedance is chosen to match the speaker impedance. These are useful to drive low impedance speakers, or difficult speakers that have huge dips in the impedance. Or, if one is using 16 Ohm or 4 Ohm speakers, and only have 8 Ohm output tap at the output transformer, they can connect the amplifier to 8 Ohm tap, and use the 16 Ohm or 4 Ohm tap to connect to the speakers.

1. If attenuation can be done earlier at the signal chain, do it earlier, such as attenuate the signal at the source (DAC output) rather than at the destination (amplifier output). In such application, TVC (transformer volume control) can be used. 
2. Transformer coupling is better sounding that Autoformer coupling (our findings), YMMV though. Experiment and find out yourself which is better in your application or taste. 
3. Fixed attenuation with single tap will be better than multi-tapped autoformer/transformer. Simpler is better - this rule does not change. Multi-tapped autoformer/transformer offers the flexibility for tuning or matching on-the-fly. This will be good during designing, experimenting, or tuning phase, or even for users that try to tune the system for different type of music / speakers / rooms / taste. Single tap transformer/autoformer could not be as flexible. 

J&K Audio Design

Saturday, September 7, 2019

Voicing of output transformers

Howdy everyone! 

After repairing and measuring sooooooo... many vintage and modern output transformers from no-name to legendary brands, we've had a good grasp on how they voice the output transformers, from the materials used, winding techniques, etc... to the sizing of cores.

If you're going after a certain tone, you can let us know and we can wind towards that. Else, we will do the best for each level (Level 0 to Level 3) of grading for our transformers, using the wide bandwidth winding method, with sufficient dynamic headroom for all sorts of music, including faithful 20Hz reproductions. 

Our Level 2-3 output transformers are usually specified to ~10Hz @ -3dB region (or lower if required or paid for), and therefore anything at 20Hz is of no issues at all. We're not that worried on the high frequency response side as that's something easily manageable and easily achievable. We'd tend to just limit it at ~60k-75kHz to avoid unnecessary side effects but if one still want 100kHz, just let us know. 

Just a refresher to all perhaps, we do offer OCC Cu, OCC Ag magnet wire transformers now, that we previously do not (maybe 2 years ago), due to the wire price, amount of orders and scarcity of such materials. Now, we can say that they're pretty common. 

On the other hand, we have to keep the transformer repair price to at least U$200/pc and above. The amount of work involved are just too labor intensive and charging below that is just PAYING YOU TO REPAIR FOR YOU.  

Each transformer requires around 1 week to complete. Say if we pay a technician to do so, at U$15/hour for 5 days, that would be whopping U$600 labor charge slapped onto the repair price. You see what we mean now? 

Anyhow, we'd like to thank everyone that supported us so far to lead us till today. You're such a gem! 

And, apologies for those that had hiccups in their projects. We will keep on improving ourselves and keep on serving you guys better.

J&K Audio Design

Tuesday, August 6, 2019

Vintage transformers repair

Greetings folks. Life has been busy, and therefore it translates to the lesser and lesser post we have.

Recently we've heard some horrendous news where there are repairers that swaps valuable vintage transformers for el-cheapo newly built transformers.

Just beware!

We'd never do so. Everything that is salvageable, will be reused, especially the cores and the bobbin.

Just look at the multiple posts of vintage transformers that had been repaired by us, and are being used now all over the world.

They are rebuilt with the utmost care to preserve the original design, original sound and tone.

Use our service with confidence.

Check out the multiple postings in our FB page!

Cheers! Signing out!

J&K Audio Design

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Product Lists

Product Lists

Level 0: link 1

Level 1: link 1, link 2, link 3, link 4

Level 2: link 1, link 2, link 3, link 4, link 5, link 6, link 7, Link 8, link 9

Level 3: depends on type, size and complexity. Email us for details.

Iso-trans: link 1, link 2

Power-trans: link 1

* 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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