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
13/1/2020 

Supercharger Amplifier

• Have you ever felt that you are lacking of power in your amplifier?
• Have you got stuck because your existing amplifier has nostalgic value?
• Have you thought of upgrading but still like the tone of your current amplifier? 
• Have you imagined that what would happen if you have a couple of Watts more? 
• Have you ever liked a speaker so much but it is too difficult to drive for your existing amplifier that you liked so much too? 
• Have you imagined what a supercharged 45, 2A3, 50, 300B, or any low power direct heated tube would sound like?

Now here lies the answer! 

We have heard of pre-amplifier, power amplifier, integrated amplifier, and various amplifiers. Supercharger amplifier is a rare term, isn't it? 

This is not something new but it is not that common in tube amplifier world. A supercharger amplifier is THE power amplifier for integrated and power amplifiers -> power power amplifier? LOL... That would be funny, right? Therefore, supercharger amplifier or turbo amplifier will be a better term to use.

What it does is to boost the power of the existing amplifier by manifolds! What one needs to do is to connect the speaker output of the current / existing amplifier (yes, the speaker output to the supercharger amplifier, and the outputs of the supercharger amplifier are connected to the speakers. The picture above shows how it is connected. Simple isn't it? 

Some might ask, why can't I take a high power amplifier in the market, and connect it in such a way? Well, unless it is designed to work this way (like Musical Fidelity 550K Supercharger), most amplifiers aren't destined to work this way. The powered output from the existing amplifier would have overloaded the input stage of the high power amplifier and fried the amplifier. Also, there would be redundancy in the amplifier since the high power amplifier would have their own pre/driver stage to properly drive the power stage into full power. We would miss all the goodies (tonality, character, and etc) that the existing power amplifier would bring too. 

What we need is a supercharger amplifier that does not have the pre/driver stage, that could make full use of the goodies brought over from the existing high quality amplifier - direct drive, with honest transfer of the characteristics from the source lower power amplifier to the supercharger amplifier! In order to do so, the best possible way would be to introduce a high inter-power-stage transformer with a high step up factor to produce the signal drive required by the supercharger amplifier with a direct power stage. 

One might ask, can I connect an ordinary output transformer in reverse to do so? Yes, you can! It will work, but not optimally! The gain might not be right. The design of the output transformer is not suited for power to voltage conversion too. Ordinary output transformer converts high impedance to low impedance as a means of power transfer. The inter-power-stage (IPS in short) transformer is for voltage amplification. 

The secondary reflected to primary distributed capacitance will affect/change the distributed capacitance and the inductive resonance of the transformer. As output transformer secondary is always low impedance, the resonance will be attenuated by the load (therefore output transformer secondary must always be connected to a load). 

For IPS, the secondary of the transformer is always appeared to be open or at high impedance due to being connected to tube grid and grid leak resistor. With that, the resonance is fully reflected to the primary. This will have negative impact on the operation of the amplifier and therefore is not recommended to use ordinary output transformer as IPS. Of course there is a way to design an output transformer that can work as an IPS but this is something of a compromise and is not recommended. 

Some others might ask, can I use an ordinary step-up transformer to do the job? Yes, you can, if the step-up transformer is designed for this task - if it is with sufficient core size to handle the high signal level, and with heavier gauge cables to handle the current.

Above is a famous direct coupled Loftin White 2A3 amplifier. Needless to say, it is a great sounding amplifier. The only drawback is the limited output power to drive common speakers. What we can do here is to use a supercharger amplifier to boost the output power to a decent 40W-50W level, such as using the famous 212 tubes, be it NOS, or from new manufacturers. The supercharger amplifier is designed with very minimum components, and therefore it posses the least character or coloration of its' own, and is much cheaper & simpler to manufacture too. Of course, other power tubes like 211, 845, 833 and such can be used too with great results.

Where can we get these IPT (inter-power-stage) transformers to build/design the Supercharger Amplifier? Good new is, J&K has it, and we are offering it as our Level 2 and Level 3 custom made models for IPT. Sorry, we cannot do it at Level 0 or Level 1 for now due to the complexity involved, and the effort we spent to develop these IPT. Here are the prices in matched pair, rated at 10W power handling.

Level 2 IPT - U$590 (for driving 211, 212 and less demanding tubes)
Level 2 IPT - U$790 (for driving 845, 833 and high demanding tubes)
Level 3 IPT (1:5 step-up) - U$1090 (for driving 211, 212 and less demanding tubes)
Level 3 IPT (1:10 step-up) - U$1490 (for driving 845, 833 and high demanding tubes)
Level 3 IPT (1:20 step-up) - U$2290 (for driving 845, 833 and high demanding tubes)

Now isn't this a GREAT news?  

For those that wants a fully built system, please email us for more details and quotation. 

One warning for the users though - remember this rule - garbage in, garbage out. All the shortcomings or all the greatness of the existing amplifier will be amplified manifolds with such design topology.

J&K Audio Design
1/12/2016

Product Lists  
Level 0

Level 1: link 1, link 2, link 3

Level 2: link 1, link 2, link 3, link 4, link 5, link 6 

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

Iso-trans: link 1, link 2

* 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.

EL156 Tube Amplifier

Storm-trooper EL156 SE Tube Amplifier  
Here's another lovely EL156 Single Ended Triode Connected tube amplifier that we've made for a local audio enthusiasts, named after the movie Star Wars - Storm-trooper for the black and white color combination!


As what we always do, our designs are always extraordinary and is not done elsewhere. It uses 12SN7 instead of 6SN7 to leverage the availability of inexpensive NOS 12SN7. 6SN7 variants are too expensive as it is being used commercially. 

Here are some highlights of Storm-trooper EL156 SE Tube Amplifier

• Level 1 entry level build
• High torque, critically damped, tube rectified pseudo choke input B+ power supply for excellent low frequency response and driver control
• Carefully selected high grade components - optimized tone and body
• Special tweaks at mains input for low noise operation - super dark clean background
• Z11 overspec power transformer and Z11 choke - super dark clean background
• ALIS-5SE MK2 output transformer for excellent low frequency response and decent highs 
• 3MM turret board for component mounting - absolute vibration control for components
• Full aluminum chassis - non-magnetic and rust proof, professionally powder coated
• J&K proprietary grounding scheme - zero hum and noise even if ear is placed near high sensitivity speakers (ex: Zu Audio Soul Superfly with 100dB/w/m sensitivity)
• J&K proprietary tuning for mid to low frequency resolution and extension
• Properly isolated and bypassed stage by stage filtration for each amplification stage

Stock EL156 is from Shu-guang. NOS Telefunken EL156 is rare but still can be found. Even Siemen EL156 is available too, and is actually made by Telefunken too!

Now for some pictures...

Storm-trooper EL156 Amplifier

12SN7 and EL156

EI Z11 transformers

Shortest path Point-to-Point wiring

Philips/BC capacitors, Russian PIO capacitors, film coupling capacitors

Connections

 J&K Audio Design
12/21/2015

Product Lists  
Level 0

Level 1: link 1, link 2, link 3

Level 2: link 1, link 2, link 3, link 4, link 5, link 6 

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

Iso-trans: link 1, link 2

* 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.

STC 4212 Amplifier

STC 4212 Amplifier - transformers kit!

We've been supplying quite a number of WE 212 (STC 4212) output transformers to DIY folks. This tube is really getting us curious as we have not got a chance to try it ourselves. We tested our 212 output transformers with 845 in parallel to mimic the 212 tube electrical parameters all this while and that alone, is already quite scary (845 paralleled).

212 SE is already quite massive and powerful, and now comes the extreme - 212 PSE (that is FOUR 212's in a single amp!!!!)! We have even got a 212 PPP (Parallel Push Pull, this is EIGHT 212's, how crazy (oops) is that???) quote in progress! In audio world, the sky is the limit!

The 212 replicas from PRC are getting less costly and it is getting easier to reach for most people now. We've seen more and more guys online making them and showing off to the DIY community! 

Unfortunately I'm a fan or NOS tubes, or else I would have considered making one for myself. The NOS 212, as I understood from one of my customers, is that I should forget about it due to the rarity and not being as rich as the collectors to bid for it.  

Below is a modified 212 PSE power amplifier (monoblock) for my customer. This original schematic was obtained from online / website, which I believe should be designed by Sakuma-san. This modified version is not a full blown design yet as it was just a simple conversion from 212 SE to 212 PSE, for transformer quotation use.

If I'm the one designing it, then the B+ won't be at 1KV but higher to fully utilize the power of the 212 tube, and some other J&K proprietary tweaks would be included. Since this version is not tested nor totally verified usable, use with care please. 

I did not include the minor details too since I presume users that would embark on making 212 amplifier would have enough knowledge to extrapolate from the schematic.

 

 The transformers associated with this design will be as follow:

• Input transformer - not done by J&K
• Interstage transformer for 845
• Level 3 Nanocrystalline Double C core, potted - U$1900/pair
• Level 3 EI Z11, U$1390/pair
• Level 2 Super Hi-B Double C core, U$990/pair
• Pri: 5K 80mA, Sec: 10K
• Output transformer for 212 PSE
• Level 3 Nanocrystalline Double C core, potted - U$1790/pair
• Level 2 Super Hi-B Double C core, U$1490/pair
• Level 2 EI Z11, U$1090/pair
• Primary: 5K, 300mA, Sec: 8/16
• B+ inductor
• Level 3 - not doable
• Level 2 Super Hi-B Double C core, potted - U$690/pc
• Level 1 EI Z11 - U$340/pc
• 2.5H 800mA for choke input, HV usage
• Driver stage inductor
• Level 3 Nanocrystalline Double C core, potted - U$440/pc
• Level 2 Super Hi-B Double C core, potted - U$340/pc
• Level 1 EI Z11 - U$190/pc
• 10H 150mA
• 845 filament inductor
• Level 1 EI Z11 - U$190/pc
• 0.1H 5A
• 212 filament inductor
• Level 1 EI Z11 - U$190/pc
• 0.01H 9A
• Power transformer
• Level 2 EI Z11 - U$490/pc
• Level 2 EI Z10 - U$690/pc

For those that are interested for a full blown design, please stay tuned. We might design one when we have more time on hand.

J&K Audio Design
9/13/2015


Product Lists  
Level 0

Level 1: link 1, link 2, link 3

Level 2: link 1, link 2, link 3, link 4, link 5, link 6 

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

Iso-trans: link 1, link 2

* 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.

EL84 Push Pull Tube Amplifier

This is an EL84 Push Pull Tube Amplifier that we had made many months ago (sorry, we were too busy to update our blog) for one of our local customers that will use it to power his center channel as well as main speakers, depending on this mood.

EL84 Push Pull Tube Amplifier
* Triode + Pentode mode - convertible
* Stereo and mono-modes
* Active auto-biased, with external pots for balancing tubes
* Level 2 Z11 Precision Wind Output Transformer
* Full Z11 power transformer and chokes
* High end - audiophile components used all over
* Tube rectified, pseudo-choke-input power supply 
* 5U4G / 5X4G rectifier, EL84 x 4 power tubes, E288CC x 1 driver tube
* High quality ceramic tube sockets with gold plated copper pins 
* Full aluminum chassis with 5mm thick top plate 

Enough with the chatter, here goes more pictures! 

J&K Audio Design

8/16/2015

Product Lists  
Level 0

Level 1: link 1, link 2, link 3

Level 2: link 1, link 2, link 3, link 4, link 5, link 6 

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

Iso-trans: link 1, link 2

* 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.

Telefunken Integrated Amplifier

This is a an amplifier that we did not even think of building! I've been keep a pair of EL152 power pentode from Telefunken for quite some time. It was more for collection rather than building use. I was waiting for a free time that has yet to come to put the Telefunken EL152 into good use.

Just so happened that I have a good friend that wanted to build a tube amplifier by himself. I've designed the amplifier for him with 6B4G tube in mind for a 3.5W Single Ended DHT integrated. It did not get materialized as he moved to Singapore halfway during the process and now migrated to Australia. 

The whole set of transformers, chassis and components were stored at my place for at least 3-4 years if my memory serves me right. I have been bugging him to bring it back to complete it but it just never moved since Australia is quite far away from my place. Things got dragged on until several months ago where we decided to put it into action by building it ourselves using all the materials that were meant for 6B4G. 

The Telefunken power tube can output more power but due to the VA and voltages made for the 6B4G, it was generating only ~3W output. Anyhow, we were still quite impressed at the sound it produces. One day, perhaps, we will make the right power transformer to be used with Telefunken EL152 to fully optimize the circuit and output power.

Time for some pictures!

For amplifier pervs, here are the internal pictures:

J&K Audio Design
6/7/2015

Product Lists  
Level 0

Level 1: link 1, link 2, link 3

Level 2: link 1, link 2, link 3, link 4, link 5, link 6 

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

Iso-trans: link 1, link 2

* 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.