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Sunday, August 20, 2017

Potting Transformer

Potting transformer - we've received news from our chassis vendor that they've some new transformer case / transformer cover for order. It just so happens that we have two Level 2 - 600W power transformer for solid state amplifier waiting to be potted. We're about to use the standard build transformer cover but this one is just too nice to pass.

Above is what our casing vendor sent to us - handsome! Casing are very solid as well, and is perfect for our power transformer.

Trying the size of the transformer versus the transformer cover - just nice!

Placing the transformer inside the casing, getting ready to pour potting compound into the casing.

Some pre-work, sealing the joints prior to potting the transformer to prevent compound leakage.

Wallaa! Potting is done. Notice that the magnet wire are first covered with wax cable.

A typical day in factory. Hope you enjoyed the pictures.

J&K Audio Design

Saturday, August 12, 2017

Greetings everyone! Yes, we're still alive, although we have been quiet on our side.

Apologies for not being able to post as frequent as before. Time is really running short at our hands. Lead time is getting longer as our custom made department is fully, well, overloaded with orders from everyone.

That helped us to put bread and butter on the table for some of our technicians, support workers, and suppliers. Thank you very much, guys! Your support is very, very appreciated.

Today, we'd like to share a short review from our supporter in USA! He'd purchased quite a number of ultra isolation power transformers to replace the transformers inside his existing equipment, as well as the ultra isolation transformers as external use for power filtration.

Here's Rich's review on our ultra isolation transformer below in his home theater! Yes, ultra isolation transformers are not just for audio (HIFI), but can be for home theater too!

We're very happy to hear that he's enjoying our ultra isolation transformers! And thank you (Rich) for allowing us to share your write up.

Some background reading for new readers, if they're unaware of what they are all about:

You can order transformers in such a way from us (I know, it's a lot of options but it is all worth it!)
* power transformers with electrostatic shield (standard in market)
* ultra isolated power transformers or pure ultra isolation transformers (size is almost same as transformers 2x the rating)
* upgrade OCC (Ohno Continuous Cast wires)
* upgrade from EI to C or double C cores 
* core upsize (operate at lower flux density, size will be much, much larger!)
* bare with frame, or upgrade to end bells, or potted in casing (recommended for low noise operation)

Why all these options? All for better sound of course! And it does matter.

PS: We've users that paired our transformers OCC power cords and they find huge improvements. That's why we are offering OCC in our power transformers, chokes and isolation transformers now instead of just purely for the audio transformers such as output transformers, input transformers, TVC and interstage transformers. Instead of the 1-2 meter of OCC at the power cord, now you get hundreds of meters of OCC in the power transformers. Imagine the improvement you would get!

J&K Audio Design

Sunday, July 23, 2017

Custom Made Amplifier Chassis

Custom made amplifier chassis - costly but well worth the money, if HIFI rack real estate is low, and gears outlook uniformity (consistency) is an important criteria for you.

If you followed every post of our blog, you would have noticed it, that one of our customers owns a pair of AudioNote Conquest (300B PSE). His AN Conquest broke down moons ago after the 300B failed on him. It was sent in for overhaul and upgrade. Unfortunately (or fortunately?!?!) the output transformer compartment was too small, or else, a pair of Level 3 NanoC OPT from J&K would have gone inside. His looked something like this (pic taken from the internet).

Now he's come back for more, to build a custom ultimate J&K modular DAC. Modular means - the DAC receiving and decoding stages, are separate from the IV conversion stage, or the gain stage (tube based, of course) for some DAC chips with V-out. The fun part of this J&K modular DAC is that, for those that buy our DACs, are able to swap around and play with different DAC and output modules by exchanging between themselves.  We have some here in our local community that are already playing with that. They have TDA 1541, AD1865, AD1862, ES9038, and etc.

Back to this guy with AN Conquest, due to his limited HIFI rack real estate, has a very limited and specific dimension reserved for the DAC. The DAC is going to share the space used for his AN Conquest, and therefore the shape (and outlook) of the DAC will have to mimic his amplifier for consistent outlook. 

We usually purchase ready made full aluminum chassis from our vendor to keep the cost down. In this case, those ready made ones do not match the size and look that he's looking for. We will have to custom make one just for him, following closely the AN style. It's not cheap, but ART is priceless. It has higher WAF (wife acceptance factor) too!

- Top: 2mm copper plate, polished, clear paint
- Base: 2mm mild steel, powder coated, matte
- Front plate: 8mm hairline brush aluminum
- Holes: CNC

 Wala! It's done!

We hope to post more pics when the DAC is finished. Just a head's up on what's coming on this DAC:

* PCM1702 dual mono 
* Separate Level 2 & 3 power trans for PSU, Super Hi-B for analog, EI Z11 for digital
* Western Electric output trans for tube based IV stage
* Telefunken RGN1064 tube rectified, 6J5G NOS triode gain stage
* Western Electric choke for PSU / B+, with full Mundorf film capacitors

* Mundorf electrolytic capacitors for DAC stages, with capacitance more than a power amp
* Mundorf Silver Gold wires all over
* WBT silver solder + WBT sockets

Like I say, it is one helluva tube DAC...! 
J&K Audio Design

Saturday, June 17, 2017

Tube Tester Transformer Repair

Restoring your vintage tube testers? Found out that your tube tester has burnt transformers? No problem at all! Look for J&K Audio Design. We will get your tube tester transformers repaired in no time (well, in some time actually since they're quite difficult to repair due to massive output taps).

We even retained the original outer layer of "skin" to enable builder to easily recognize the taps.

Tube tester transformers

Repaired tube tester transformers

tube tester transformers
We can repair all of them, be it Hickok tube tester, B&K tube tester, Sencore tube tester, WE tube tester, Teletest tube tester, Heathkit tube tester, or any other tube tester you can find. As long as they are having transformers not potted in epoxy, we can repair them.

So, what are you waiting now? Time to get those tube testers, whether it is damaged or not, for your tube amplifier DIY hobby. Maybe you're lucky enough to get one damaged one at dirt cheap price, and just spend a little to restore them to their previous glory.

J&K Audio Design

Monday, June 5, 2017

GM70 Output Transformer

For most of users out there, with usual modern loudspeakers, the efficiency normally falls around 90dB +/- 6dB. Such speakers require considerable power to drive and control the loudspeaker to a satisfactory level. Tube power of ~20W and above are usually preferred, and in order to get such power for tubes, one would need to go for push-pull or PSE design, if not, to turn to high power tubes such as 805, 211, 212, 845, 833 and such.

NOS high power triode, and/or even pentode are hard to find nowadays. Even if they are available, prices are most probably sky high, such as RCA 211, RCA 845, or United 211, not to even mention the exotic ones such as Western Electric 211 tubes. GE VT4C or GE 211 can still be found, but even so, their prices have soared since. 

What other inexpensive alternatives do we have? Well, we still have one option left, the GM70! It will only cost you about U$60-100 a pair, depending on the year made, and also the type of plates, either graphite, or copper plates. GM70 copper plate versions are rumored to be warmer than the GM70 graphite plate variety, but, YMMY. GM70 copper pate version is almost 2-3x more expensive, and are getting rare as collectors start to hog those tubes.

One can even design a tube amplifier that's 845 and GM70 compatible. Both tubes accepts load resistance of ~5K to 10K, with similar plate current. Output power varies slightly but is not of utmost importance here. GM70 has higher plate dissipation, and therefore the amplifier should be designed as such that it does not exceed 100W at all time.

845 Data

GM70 Data

The most ideal load resistance for both could be ~7K - 8K to get decent power and distortion figure. One just need to ensure a few things, no biggie, simple stuff (if you dare to build >1KV stuff, this is nothing to you!):

* Have separate filament supply to cater for different requirements
* Different tube sockets side by side for GM70 and 845
* Switch on cathode, or CCS cathode load to regulate the plate current

Which GM70 output transformer should we use? Of course, none other than from J&K Audio Design! We have recently designed one for our customer for his GM70 single ended amplifier. 

Here are the GM70 output transformer details:

* Power: 37W (20Hz)
* Measured frequency response: 20Hz - 20kHz +/- 0.23dB
(5Hz - 45kHz +/- 3dB - tuned to have higher/better loading at low frequency)
* Primary: 7.5k Ohm, Secondary: 0-4-8 Ohm (other primary/secondary - please request)
* Core: NanoCrystalline (aka Finemet) double C core
* Primary DCR: 235 Ohm (B-P, 20C)
* Secondary DCR: 0-4 Ohm (0.2 Ohm); 0-8 Ohm (0.29 Ohm)
* Primary inductance: 61H
* Max Primary Current: 120mA
* Efficiency: 0-4 Ohm (>93%), 0-8 Ohm (>94%)

(In circuit measured with Shuguang 211 at 1W. Full power response will be similar. Customer that wishes to have more high frequency response - please request at ordering or we will tune based on our house sound/voicing.)

* Matching: primary DCR +/-0.1 Ohm, inductance +/- 1.5H (<5%)

The above are made with NanoCrystalline double C core, which are a difficult material to work with on such power level. Such glass cores are usually for high frequency usages, and for 400Hz power supplies. NanoCrystalline core excels at high frequency, and significant compensation is required to augment the low frequency response. Using a larger core helps but that increase the magnetic length significantly (causing high frequency loss), and various other problems. Using them at full range applications is super challenging. Try asking other winders for it.

The rewards, after overcoming such obstacles, are of course very fruitful - micro details, dynamism, real sense, directness, purity, tonality are outstanding. If one can consider using OCC (Ohno Continuous Cast) copper cable with it, the results will be even more significant. The purity of sound with OCC + NanoC is out of this world.

If one is looking for purely at specification perspective, EI Z11 would be a better choice where we can get a much wider bandwidth than NanoC. The voicing of EI Z11 will be different than the NanoC. 

Enjoy life, enjoy music.

J&K Audio Design

Saturday, May 13, 2017

J&K Isolation Transformer in High End Setup

We've recently flown a unit of fully built high end J&K Isolation Transformer to USA. The user is kind enough to allow us to share his setup pictures with our followers. J&K Isolation Transformer is used to power up 2 stereo Nord One SE UP NC500DM amplifiers. 

It is such a lovely setup. It gives us a sense of Zen and peacefulness when we looked at his setup. Well done, sir! J&K Isolation Transformer's silver fascia matches will with the color scheme of his whole setup too!

Speakers used in the setup are Analysis Audio's flagship, Amphitryon:

The speakers were purchased without a crossover. The owner employs active digital crossovers and and DSP with his preamp (pre-processor), Trinnov's flagship, Amethyst:

The speakers are bi-amplified (2 stereo amplifiers), using Nord Acoustics - Nord One SE UP NC500DM Stereo Silver:

Each amp uses a pair of Hypex Ncore NC500 modules.

For vinyl, he uses vintage Micro Seiki RX-3300, with SAEC arm. Cartridge is Transfiguration Proteus. He uses Audio Note SFZ step up transformer and Audio Note phono:

Enjoy the pictures!

* EI isotrans - better for front end, low power amplifiers, preamplifiers, sources
* Toroid isotrans - better for medium-high power gears

J&K Audio Design

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