J&K Audio Design: December 2015

Thursday, December 24, 2015

Transformer Casing

We have been looking for decent transformer casing for some time. After our previous supplier stopped their production for transformer casing, we have had troubles finding a nice casing for our Level 3 products.

The Level 3 - 300B PSE output transformer (300B 并联单端输出变压器) that we just made uses this very nice casing.

The search ends now! Below are the casings we will be using for our Level 3 transformers, provided if they fit. 4 sizes are available only:

140 x 140 x 150 (EI 133)
130 x 130 x 130 (EI 114, 105)
110 x 110 x 130 (EI 96)
80 x 80 x 80 (EI 76, 66)

Note: it is STRICTLY not for sale individually, and is not for level 0 - 2 transformer use.

The actual units are actually much nicer than what the pictures shown below.

J&K Audio Design
12/24/2015

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.

Discount Program

How to get a 5% discount from our products for your next purchase? Read further!

Please click on the blog post you want to post a comment for. There you will see a text box opened right below the blog post.
Please write your comments in opening text box, as detail as you could. Minimum word count is 30 words.
Each comment entitles to only 1 order. So, try to accumulate your orders before placing it.
Discount is applicable for returning customers only, or customers that have physically used our products previously from friends or family. We want only valid comments instead of bogus comments just to get discounts.
If you have a Gmail account, please login before you post, or leave down your identity details in the posts so that it can be tracked back to you.
Postings at other forums like diyaudio.com, audioasylum.com, audiocircle.com, your blogs or websites, and others are welcomed too, and discount applies!

Thank you very much and hope you enjoyed it as much as we did making it for you.

J&K Audio Design

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

* 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.

Tuesday, December 22, 2015

Output Transformer Design

Output transformer design （输出变压器设计和调音） is an art. There is no right or wrong when you have reached a certain level of competencies in the design world.

Below is an example of how we tune our Level 3 Nanocrystalline Output Transformer for 300B PSE use. Take a look at these 2 output transformers. Both are designed for primary 1.5K, air gapped to 160mA.

You can see that with different winding methods, the results are quite different. Which one is better, which one is worse? Take a guess!

300B PSE output transformer 1:

20 Hz (-0.25dB) – 1kHz (0dB) – 20kHz (-0.43dB) at 8 Ohm at 1W
Full spectrum: 10Hz (-0.6dB) – 1kHz (0dB) – 68kHz (-3dB)
Primary DCR: 49.5Ω (50Ω) (B-P，9℃)
Primary inductance: 12H (11.9H) (DC bias at 180mA，20Hz，5Vrms)

FFT results

300B PSE output transformer 2:

20Hz (-0.49dB) – 1 kHz (0dB) – 20kHz (-0.1dB) at 8 Oh, 1 W
Full spectrum: 10Hz (-1.2dB) – 1 kHz (0dB) – 100 kHz (-1dB)
Primary DCR: 22.7（22.3）Ω（B-P，12℃）
Primary inductance: 6.6H（6.5H）（DC bias at 180mA，20Hz，5Vrms）

FFT results

There is no winner here actually. Both are excellent. What matters are how it is used, and what it is used for - the application matters. I have highlighted in BOLD, the main differences. At a glance, output transformer 2 seems to be better, right? Well, there is more than meets the eye.

In layman terms, output transformer 1 is better for more difficult loads and will be better in controlling the speakers. Output transformer 2 has lower distortion and has wider bandwidth but is not as good as one on difficult loads.

For general loudspeakers, output transformer 1 will be a better choice. It has higher primary inductance and therefore will present a better load at low frequency for better low frequency response and control. For those with very efficient speakers like Lowthers, Fostex and horns, output transformer 2 will yield better results and lower distortions. These types of speakers do not need that much primary inductance and will benefit from the lower distortion and higher extensions.

Still, it is not a rigid rule. It's up to each individual's taste. If one wants more control, body and tonality, they can still go for output transformer 1. Output transformer 2 will sound livelier and airy but will not be as thick and authoritative compared to output transformer 1.

For those that asks us to design for them, we will choose the design for them if they do not specify clearly.

Wish our readers and customers a very merry Christmas and a wonderful New Year!

J&K Audio Design
12/23/2015

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

* 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.

Sunday, December 20, 2015

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...