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

 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

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

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$160 / 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

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

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?