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Sunday, October 15, 2017

Isolation transformer effectiveness

Many had asked us, you have so many types of isolation transformers, which should I choose? 

Instead of repeating ourselves again and again (not that we're not willing to, but just to save everyone, and our time), here goes the effectiveness rating, from our perspective, from low (bad) to high (good), with some comments:
  1. Toroid isolation transformer (for HT, audio OK too but not warm and clean as C or EI)
    1. Up to 3.5KVA for highest grade toroid core (other grades with higher KVA are available but not recommended)
    2. >3.5KVA, go for parallel toroid for lower impedance 
  2. C core isolation transformer (for audio and HT) 
    1. Up to 1KVA (bigger size, can be custom made, up to 3KVA)
  3. EI isolation transformer (for audio and HT)
    1. Up to 3KVA
  4. C core ultra isolation transformer (for audio and HT)
    1. Up to 1KVA (bigger size, can be custom made, up to 3KVA)
  5. EI ultra isolation transformer (for audio and HT) 
    1. Up to 3KVA
Some articles about ultra isolation - article 1, article 2

OCC copper magnet wires (Ohno Continuous Cast) transformers are available for #2 to #5. OCC comes with a hefty price tag though. 

Benefits of OCC - lower DCR, better dynamics and clarity. We often use OCC for our output transformers, but for true audiophiles, those that hear a difference with high grade power cords, this is definitely better, and higher ROI compared to using OCC based power cords. 

Options:
* Balance or single ended outputs
* Multiple-taps isolation (explanation below) 
* Potting/frame
* Multiple shielding (electrostatic, primary/secondary, secondary/secondary
* Can be made as power transformers with isolation/ultra-isolation for SS and tube amplifiers

Multitap-isolation? 

What is multitap-isolation? Normal isolation transformers have only 1 single set of outputs, say:

- Primary: 0-240V-G
- Secondary: 120V-0-120V (balanced)

Multitap-isolation is as follow:

- Primary: 0-240V-G
- Secondary 1: 120V-0-120V (balanced, isolated/shielded from 2/3)
- Secondary 2: 120V-0-120V (balanced, isolated/shielded from 1/3)

- Secondary 3: 120V-0-120V (balanced, isolated/shielded from 1/2)

This way, instead of having multiple gears connected to a single secondary, each output is connected to 1 set of secondary to make 3 sets of ISOLATED outputs. This way, the CDP, tube preamp, and DAC (for example), are isolated from one another as they are connected to different secondary windings instead of connected altogether in a normal isolation transformer unit where all the outputs are connected to a SINGLE secondary. 

This is a MUCH better isolation scheme than normal paralleled output on-the-shelf isolation transformer unit. Yet, it is more cost effective than having 3 units of separate isolation transformer, which is the ultimate way one should do it, eventually perhaps.

Go go go, custom made audio!

J&K Audio Design
10/15/2017


Type 50 Amplifier

Supercharger amplifier with type 50 tube, anyone? Want to listen to how a pure type 50 tube amplifier really sounds like without other tubes to color it? Well, Sakuma style is a good example, using 50 to drive 50. Due to the scarcity of type 50 tubes, let's not waste the 50's. 

Note: One can use ANY power tube to replace type 50 tube in the below example, DHT, IDHT, pentode, tetrode, or any power tubes, even power transistors! Since we just heard the good news that Elrog is coming out with type 50 tube, now is a good time to look into this DHT tube!

Caution: Not any input transformers can be used in such circuit. Ordinary input transformers may not have enough core volume to sustain high voltage swing (usually <10Vrms). Ordinary input transformer primary winding may burn if driven by a power amplifier. Special input transformer is required for such purpose.

Some previous reading:
Supercharger Amplifier
Step-up input transformer

Type 50 tube amplifier


Take a look at the schematic above for type 50 tube. It is as simple as can be. Of course, you can complicate it a bit by making it fixed bias, add more bypass capacitors, LED bias, regulator tube bias, and etc. The power supplies for B+ and filament are kept out for the moment. Let's just keep it as is for now for simplicity sake.

There are 2 resistors that MAY be redundant too - the grid leak and the grid stopper. Grid stopper - prevent tube oscillations. Grid leak - as described in type 50 tube datasheet, needs to be <= 10K to protect the type 50 tube. In this case, it may not be necessary since the input transformer secondary acts as the grid leak path. The transformer secondary will be the least resistance path for the type 50 tube grid to take even if you connect a 10K resistor. Also, if the resultant waveform is not having severe ringing (even if it rings), the grid leak resistor, which act as the load for the input transformer, will tame the ringing. For type 50 tube, with input transformer, it is better not to have the grid leak resistor if possible.

Let's take the operating point of type 50 tube as 425Vdc B+, -70Vdc grid, 55mA, which is quite commonly used by a lot of folks. This needs about 140Vpp to drive type 50 tube to full power. That produces about 4W of undistorted power output to the load (your definition of undistorted may be different, especially the SS folks).

Say, let's use a standard source, which is an ordinary CD player, or DAC, with 2.8Vpp output and 600 Ohm of output impedance. To get sufficient Vswing to drive type 50 tube to full power, one needs a gain of = 140Vpp/2.8Vpp = 50. Wow, that's a lot of gain required, and is not feasible at all here. Let's drop the standard source.

Let's go for a preamp instead, say a 5687 simple tube preamp with output transformer, having output impedance of say 150 Ohm. 5687 has a u of 18, and is usually loaded with 5K primary impedance. With that, the resultant gain would be root of 150/5000 * 18 = 3. Not so much eh, but is good enough perhaps? Let's check.

With 50 / 3 (gain of tube preamp), we get to gain of 16. Hooray! STU-001 here has a gain of 1:18! Just close enough, with a little bit more for headroom or circuit tolerance. 

Conclusion? As previously mentioned, a very high drive strength preamp is required if a supercharger is driven. If tube preamp is used, something with output transformer and higher gain is required. The above example of using a simple 5687 with output transformer looks like a bare minimum supercharger amplifier can tolerate. 

Enjoy tube tasting! 

J&K Audio Design
15/10/2017

Tuesday, October 10, 2017

Easy Parcel and Parcel Hero

Hi guys,

Great news! 

We are engaging Easy Parcel and Parcel Hero now to ship out transformers and products. In addition to that, local post office has included EMS in the delivery options recently. 

With this, we hope to offer faster, safer and cheaper options of delivery the transformers to our customers! 

Instead of 8-16 days of port-to-port standard delivery duration, the new vendors offer much faster service, of 4-8 days, sometime faster.

Cheers!

J&K Audio Design
10/10/2017

Thursday, October 5, 2017

NOS Tubes Sound

What is true sound of NOS tubes? (Rants warning!)

Most NOS tubes players like to ask among themselves, what tubes do you roll on your amplifier? Or what tubes you like to play? How do you like their sound? 

Often, answers would be the manufacturer of the tubes, such as Western Electric, RCA, GE, Sylvania, Tung-Sol, GEC, and etc; or the model of the tubes, such as 300B, 211, 845, KT88, 2A3, and etc. 

For those with more advanced tubes knowledge, they would go into the year of manufacture, factory location, getter type/quantity, filament suspension style, plate structure, base type, special tube structure support, and such. 

Rarely, do people asks, what transformers are you playing with? People rolls tubes. They do not roll transformers. That's how it is now. I wish, some day, people would start rolling transformers too! 

One of the most important thing, other than the amplifier design itself, is the quality of the transformers, especially the output transformers! Without high quality transformers, no matter how good the tube are, the true sound of NOS tubes, or NOS tubes sound, can never be fully achieved or heard. 

When we talk about transformers, we are referring to things such as power trans, chokes, input / output trans, interstage and driver transformers as the main categories. 

All of them, play very vital roles in a tube amplifier. Don't even talk about NOS tubes sound if your transformers aren't done right in the first place. The quality of transformers will determine the sound quality, voicing, noise floor, linearity, scale, power delivery, transparency, tonality and all the parameters of having HI-FI sound. 

When we talk about transformers, all these below matter, just like NOS tubes.

* capacity
* lamination type and quality
* magnet wire type and quality 
* transformer electrical and mechanical design
* bandwidth 
* safety and longevity 

Something as simple as a choke, also varies in performance and sound. The grade of materials (core, wire, potting method, potting compound, bobbin, insulation, and etc), the design, the DCR, the inductance variances across frequency and load, and etc, are all different, and will affect the sound and electrical performance substantially. If one things that all chokes are built the same, think again. 

Try ordering a choke made with NanoCrystalline core with ultra thin lamination thickness, extreme low DCR design (example 5H 10 Ohm, compared to ordinary 5H 50 Ohm), OCC magnet wire, high grade potting compound/bobbin/insulation, adequately but not extremely oversized core, proper mechanical design (perfect wire strain and alignment), and compare it with a standard choke, one will witness the vast improvements one small thing like that will bring to the sound. 

If this is done on an output transformer, the difference will be much more significant! When we go into more complex transformers, such as the audio signal transformers, the factors impacting the sound increased exponentially, so as the sound. People often thinks about primary inductance as the basis for good low frequency response. That is not all. The primary and secondary winding DCR is very important as well. 

A 3.5K:8 Ohm standard output transformer often carries the DCR of 150-200 Ohm for primary, and ~1 Ohm for secondary. Try ordering a pair made with DCR of 30-50 Ohm for primary, and 0.1-2 Ohm for secondary, and with everything else staying the same, such as the primary inductance and bandwidth (Not all can do so. There's a penalty in price and size.). The result differences will be ultra significant! Hints: increase in dynamics, better power delivery, improve control, increase transparency, lower distortion, and etc). 

What I bring up here is just the tip of the iceberg and to get you to start thinking deeper. There are more than meets the eyes. 

From today onward, start thinking about rolling transformers, on top of rolling tubes. You'd be rewarded handsomely (better ROI in a lot of cases), since rolling tubes can be significantly more expensive than rolling transformers! Don't waste the NOS tubes if you don't play high quality transformers. 

Enjoy! 

Hear the unheard! Sail the uncharted! 
Long live custom made audio! 

J&K Audio Design
6/10/2017

Thursday, September 21, 2017

Tamura STU-001 Input Transformer

Tamura STU-001 Input Transformer

Tamura Input Transformer - STU-001, 150,300: 100KCT (Push PULL). Tamura STU-001 is widely used in designs by Sakuma-san, in Sunaudio amplifiers, and designs in MJ Audio Technology magazine. 

Unfortunately, STU-001 input transformers are out-of-production now(at time of publication), and is quite rare to be found now. We've received quite a lot of inquiries on similar high step-up ratio input transformer such as the Tamura STU-001 and have decided to open it up for mass market instead of making them quietly in the background. 

Below are some applications designed and built by HIFI enthusiasts from the East. It can be used as single ended step-up, or phase splitting for push-pull use. You will also notice that directly after the Tamura STU-001 input transformer, is power tubes, such as 211, or 300B, meaning that it is some sort of a Supercharger amplifier, or power amplifier. 

We have blogged about supercharger amplifier in the past - you can refer to this post:
http://jandkaudiodesign.blogspot.my/2016/01/supercharger-amplifier.html






Level 2 Step-Up Transformer  STU-001 for Supercharger Amplifier use - U$345/pc. 
- 150,300: 100K-CT (standard)
- Permalloy cores only
- SE, or PP input/outputs, configurable, customization allowed
- potted with silver plated copper turrets 
- bandwidth, depends on source driving impedance, the lower, the wider the bandwidth  
- Larger STU with bigger core, bigger swing, is available

 Applications

- transformer is a ratio machines, with such high step-up ratio, the secondary load needs to be very high impedance, and the primary source needs to be very low impedance, to keep the bandwidth wide enough for audio applications
- 300:100,000 equals a step-up ratio of 1:18, or impedance ratio of 1:333. Load will be reflected accordingly to the primary and the source will need significant drive strength to ensure satisfactory performance
- volume pot is not recommended at the primary of such input transformers for higher fidelity

Let's take 250K and 500K (maximum grid resistance 300B and 211 can tolerate in self-bias circuit, fixed bias will be much lower) secondary load for STU-001 as example.

- primary reflected impedance = 500K / 333 = 1.5K Ohm 
- primary reflected impedance = 250K / 333 = 750 Ohm

You can see that it is not a really friendly load for weak (high output impedance) tube preamplifiers. Most common-cathode topology simple tube preamps will not apply since the output impedance will be high. We would need tube preamps with low output impedance, such as those with Cathode Follower output stage to drive such STU-001 input transformers satisfactorily. Or, tube preamps with output transformers, that has low secondary impedance, such as 50-100 Ohm, or maybe lower, will work nicely. That reminds us of tube headphone amplifiers!

On the other hand, high swing low output impedance solid state preamplifier will come in nicely here. Therefore, choices are plenty. 

In some cases, secondary load may not be required, if there are no oscillations / overshoot or undershoot at the output of STU-001, and therefore, the secondary of STU-001 acts as a grid-choke for the driven tubes! 

One may asks, so what's the benefit of doing so? You can set the power tube free from the coloration of the driving stage! You get to hear the real sound, real character, true flavor of the power tube with such high gain input transformers. Imagine if the power tubes are WE WE 300B, 242, WE 211, WE 212, GEC & Telefunken power tubes and various other exotic power tubes. Such input input transformers such as Tamura STU-001 and the likes will come in very handy.

Note: Standard STU-001 may not have that much swing for high power tubes. STU-001 with larger cores (diff price) is needed for big power tubes. 


Hear the unheard! Sail the uncharted! 
Long live custom made audio! 

J&K Audio Design
9/21/2017

Wednesday, September 20, 2017

Autoformer Volume Control

Autoformer Volume Control, or Transformer Volume Control

We think that AVC, or TVC are one of the many great things that happened in audio industry in the past 10 years. The sound signature brought forward by AVC, or TVC can be stated as - better fluidity, warmer, wider bandwidth, and more analogous.  

For those that are unaware (not following us on Facebook, it is a good time to do so now!), we've found a new casing to house our TVC (Transformer Volume Control), or AVC (Autoformer Volume Control). 

Here are some pictures of the casing. The matte version is still available if one still want those. 





Some past articles on TVC and AVC. We can do both, but TVC is preferred due to various reasons, but we can still do AVC if customer prefers AVC. There's no right or wrong in audio, just what one prefers. 

Our preference:

** brushed pot -> stepped attenuator -> digital volume control -> AVC -> TVC 

http://jandkaudiodesign.blogspot.my/2016/10/transformer-volume-control-tvc.html
http://jandkaudiodesign.blogspot.my/2016/12/transformer-volume-control-review.html
http://jandkaudiodesign.blogspot.my/2017/04/j-transformer-volume-control.html
http://jandkaudiodesign.blogspot.my/2014/06/autoformer-volume-control.html

Some tips on using TVC / AVC: 
* low output impedance source is preferred but not 
* use a very high quality switch - it make or breaks the AVC / TVC
* durability of the switch is very important - you will be switching them quite frequently
* encased / sealed switch is preferred over open casing type
* step down type of TVC will have lower output impedance and will be capable of driving heavier loads compared to AVC 
* invest on good low melting point solder and good soldering irons - very swift soldering, with low melting point solder is preferred - TVC / AVC are made with very thin wires and are very fragile 

Hear the unheard! Sail the uncharted! 
Long live custom made audio! 

J&K Audio Design
9/19/2017


Tuesday, September 19, 2017

Tannoy Autoformer

Tannoy Autoformer / Tannoy Crossover Transformer  

We had a high end version of the Tannoy Autoformer / Tannoy Crossover Transformer with very high grade materials and that caused the price to shoot over U$500/pair. Quality and sound are excellent and first grade but that was quite prohibitive to most.  

As we are Tannoy lovers (Ken has once owned Tannoy HPD 385, Tannoy Arundel DCC-3839, Tannoy System 800, and Tannoy SRM12B), as with a lot of the audiophiles out there, we have decided to make it more commonly available to all Tannoy lovers to restore their Tannoy Monitor Gold, Tannoy HPD and other similar Tannoy loudspeakers, to their original glory. 

Here are the new prices: 
- Simple clone, bare square frame - U$140 / pair 
- Potted version - U$200 / pair

We had written about this Tannoy autoformer / Tannoy Crossover Transformer quite some time ago. We will not repeat them here. 

http://jandkaudiodesign.blogspot.my/2014/09/tannoy-crossover-autoformer.html

Of, if you ave only a single crossover transformer (actually, ANY transformer at all), or would like to clone them to get a stereo pair, just drop us an email and we can discuss on how to do so. 

Hear the unheard! Sail the uncharted! 
Long live custom made audio! 

J&K Audio Design
9/19/2017



Friday, September 15, 2017

J&K Transformers Review

J&K Transformers Review


Nothing beats hearing from a happy customer using J&K transformers! In addition, a real paying user review is 100x better than a paid review in a magazine. There is no conflict of interest, and the content is genuine, albeit it is not professionally or beautifully crafted by a writer. So here goes nothing, a J&K output transformer review.

Frank is from Germany and he was looking for a pair of very high end single ended output transformers for his tube amplifier using 300B XLS. He'd like to upgrade the output transformer on his ASL 1005 to something significantly better. Frank knows what he wants from the start - he immediately pointed to our ALIS-5SE Paragon Nanocrystalline Double C core output transformer, which is a Level 3 transformer. 

For more details of this OPT, you can refer to link below:
ALIS-5SE Paragon NanoCrystalline Double C Core

No pictures, no truth - here you go, some pics taken by Frank on his ASL 1005 300B amplifier.



A print-screen of what Frank has written after he'd tried our Level 3 Output Transformer on his ASL amplifier - in short, blown away! We've gotten his permission to post this of course. Frank's last name has been removed to protect his privacy. 



// Quote:


Hi Jolin,
the transformers are installed now, they sound really great. Everything is like it should, sounds really natural, 3D audio in perfection. 
The ends are more expanded, in particular the heights, absolutely no compression the sound is freed in all directions. The pictures of my amp you find attached. 

My amp was a Antique Sound Lab AQ-1005 MKII, but I’ve changed nearly everything (mains transformer and choke of the power supply, preamp is now 
Aikido cascode with 6SN7, only the casing is the same but with an additional ground floor for the chokes. The weight of teh amp is about 15 kg more than before.

Thank you very much for this wonderful pieces of technology.

Best Regards

Frank

// End quote.

Many thanks to Frank for voluntarily sending us his review! We appreciate it very much. We'd like to encourage others to send it too, so that more people can get to read their comments, and discover new path to audio nirvana.

Hope you enjoy the short, sweet and simple review of J&K products. 

Thank you and see you again!


Hear the unheard! Sail the uncharted! 
Long live custom made audio!

J&K Audio Design
9/16/2017

Sunday, September 10, 2017

Orient Hi B C Core

Orient Hi B C Core (Cut Core) Output Transformers 

What? J&K has new stuff again? Nuh, not really. This Orient Hi B C Core (Cut Core) is what we called it as Super Hi B C core. For those that followed us since 2014, they would have known that we have this excellent laser strip Hi B C core that are used to make output transformers, chokes and transformers. 

Orient Hi B C core is just another name, used by mostly Japanese manufacturers, such as Tango and Hashimoto. That also proves that, Orient Hi B C core, or Super Hi B C core, is an excellent material to be used for audio transformers. You can re-collect our past posts here below on these high grade Orient Hi B C core transformers: 

http://jandkaudiodesign.blogspot.my/2015/04/super-hi-b-transformer-review.html
http://jandkaudiodesign.blogspot.my/2014/09/super-hi-b-c-core.html
http://jandkaudiodesign.blogspot.my/2016/06/j-super-hi-b-power-transformer-user.html
http://jandkaudiodesign.blogspot.my/2014/06/hi-b-c-core.html

Why are we bringing this up again here? We brought good, no, GREAT news! We are lowering down the prices of transformers made with Orient Hi B C core (Super Hi B C core)! It was previously ONLY used in our Level 2-3 transformers and were quite out of reach for some folks, but now we are making them at Level 1, which means that the pricing will be following Level 1 pricing! 


Level 1 Output Transformers - with Orient Hi B Cut Core (Super Hi B) 

Single Ended OPT
15W SE - U$490/pair
- Primary DC current: up to 80mA
- Primary / Secondary impedance: user defined
- Size ~90mm x 80mm x 80mm

30W SE - U$590/pair
- Primary DC current: up to 150mA
- Primary / Secondary impedance: user defined
- Size ~110mm x 100mm x 90mm

60W SE - U$790/pair
- Primary DC current: up to 250mA
- Primary / Secondary impedance: user defined
- Size ~120mm x 100mm x 100mm

75W SE - U$890/pair
- Primary DC current: up to 350mA
- Primary / Secondary impedance: user defined
- Size ~135mm x 100mm x 115mm

100W SE - U$990/pair
- Primary DC current: up to 500mA
- Primary / Secondary impedance: user defined
- Size ~135mm x 115mm x 115mm

Push Pull OPT
70W PP - U$590/pair
- Primary DC current: up to 150mA
- Primary / Secondary impedance: user defined
- Size ~110mm x 100mm x 90mm
- UL: optional, user defined 

140W PP - U$790/pair
- Primary DC current: up to 280mA
- Primary / Secondary impedance: user defined
- Size ~120mm x 110mm x 100mm

180W PP - U$990/pair
- Primary DC current: up to 480mA
- Primary / Secondary impedance: user defined
- Size ~135mm x 100mm x 115mm

Interstage Transformer

1:1, 2:1, or 1:2 - U$390/pair 
- (multiple taps, email us) 
- Primary DC current: up to 30mA (>30mA, email us) 
- Primary / Secondary impedance: up to 8K (>8K, email us)
- Size: depends on complexity 

* Above are transformers with bare square or L frame. Potting requires slight addition to the transformer prices, from U$30/pc++, depending on sizes. 
* Sizes may vary, depending on incoming C cores. 
* Level 1 transformers CAN be made with OCC (Ohno Continuous Cast Copper) wires. OCC copper wires are expensive, but is well worth the money! 
Power transformer and choke prices are not listed. Their prices depends on the complexity and design parameters. Email us. 

Why do we constantly push out new stuff? Here's out motto: 


Promote vibrant custom-made HIFI industry! 

Imagine, how much more you can do, how much better you can get, how different you can be, with more high quality, uniquely custom made transformers from J&K! 

Grab one now, join us and be apart of this movement! 

If you have any bright ideas on what should be improved, added, or modified from our line of products and services, let us know. All inputs are very welcomed! 

Hear the unheard!
Sail the uncharted! 

J&K Audio Design
11/9/2017

Internet references, taken from pictures from the internet - "Orient Hi B Cut Core" can be seen on the label of the transformers for Hashimoto and Tango / ISO Tango transformers.




By the way, does anyone know why there's such a stain near the top of the tube?



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
8/20/2017

Saturday, August 12, 2017

J&K Products Review

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:
http://jandkaudiodesign.blogspot.my/2016/06/isolation-transformer-bandwidth.html
http://jandkaudiodesign.blogspot.my/2017/05/ultra-isolation-power-transformer.html

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
8/13/2017


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!

Materials
- 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
24/7/2017
 

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
6/5/2017

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