Peerless Input Transformer Repair

We've repaired a lot of power transformers and OPTs in the past. Chances of repairing input transformers are not has high since the failure rate is less compared to others but we still do get them once in a while, especially those very sought after versions, such as input transformers from Western Electric or Altec Lansing, such as this one that we just received.

The data was quite hard to be found online for this Altec Lansing input transformers. The owner provided the specifications to us after checking with the new owner for Peerless transformers. 

Input impedance: 25K CT

Output: 600 CT / 150 Ohm

This is how it looks like before it was dismantled. It is sealed in some sort of rosin and requires heating before the transformer can be taken out. 

After the extraction, the core lamination (obsolete now) are then cleaned up before it can be reused. The winding and bobbin are discarded as they no longer can be used. Due to the non-standard size of the core lamination, a customer bobbin has to be made to get a perfect fit. Standard size bobbin will not fit properly and there shall be unwanted design deviation that will not get it back to the original condition and performance. 

The original bobbin / winding are slowly and carefully unwinded to record down the original turns and taps location for rewinding later. Luckily the damage was not that bad that prevents us from doing so. If not, another unit might be needed to complete the big picture, or smart guesstimate based on physical unit + theoretical data will be required if no references are available.

Another challenge was presented to us when it is time to rewind it - the wires used are of diameter of 0.05 with 3000 rounds of primary turns with a center-tap!!! It is quite difficult to rewind and had to be manually done slowly. If it is broken, what's done will have to be thrown away and new one redone. 

After a 3 day affair, finally it is done! It will be shipped back for testing before another 3 remaining units are repaired with the same methodology & processes. 

Refurbishing or repairing input transformers will be worth doing so if it is those vintage exotic ones such as those Western Electric types where a pair could be U$1K - U$2K nowadays, or for those looking to restore expensive vintage equipment to original condition that can fetch pretty good price in the market.

J&K
9/9/2016

HIFI Ground Box Review

We've received another stunning review from notanotherhifiblog.blogspot.com! Click the link below to get to know more about it!

http://notanotherhifiblog.blogspot.sg/2016/08/grounding-for-better-j-audio-design-3io.html

Link to the ground box - 3io's BlackBox!

http://jandkaudiodesign.blogspot.com/2015/03/3ios-blackbox.html

This unique ground box is ONLY available at J&K Audio Design and not anywhere else in the whole world. It is made with unique passive electronic circuit that works indefinitely. It is not the mineral based grounding box that is flooding the market now with lots of clones from Hong Kong and China, which may or may not work. 

Enjoy!

Hear the Unheard!
J&K Audio Design
8/25/2016

3io Blackbox Review

Another stunning REAL user review from our audio transformer customer, not some paid write up or review! 

Usages
* Connect to phono ground 
* Connect to mains socket
* Connect to power conditioner
* Connect to power strip
* Connect to grounding post of equipment



3io's Blackbox

*** Start of review *** 

Hi, Ken and Jolin.

I'm angry. I like audiophile "accessories" as much as the next person. But when a manufacturer claims to "control a quantifiable amount of free electrons", my eyes glaze over. It's just this type of audiophile hyperbole that gives us all a bad name. Enter J&K's 3io BlackBox.

Let me offer a bit of background. I'm an electronics engineer by day and a hard-core DIY'er by night. I designed and built virtually all of my audio equipment myself. I have nearly 30 years of experience doing so. My system is vinyl-based, and all of my electronics use vacuum tubes with the occasional solid-state augmentation. My loudspeakers use pro drivers and a high-frequency horn.

I know the sound of my system quite well. Others have described it as big- and clear-sounding. It has slowly evolved over time to where it stands today. It is stable with no audio "surprises" when the music comes out. And music does indeed "come out", at least to these aging ears.

I recently had the opportunity to install a new phono cartridge, and I've been listening to it quite a bit. I felt that I had zeroed in on the characteristic sound of this cartridge, and I was pleased. I then received an email from J&K asking if I would like to audition the afore-mentioned 3io BlackBox, which was in the US for review. I know J&K make good stuff; I use and have heard several of their output transformers, so I know they can hear as well. Why not, I reasoned, setting aside my engineering sensibilities.

I figured the best place to start would be in my phono stage. I ran a clip-lead from the 3io BlackBox to the ground post on my phono preamp and sat down to listen. My mental notes go something like this:

"Hmm. The cartridge must still be breaking in. Sounds quite a bit nicer than last night."
"Gee, the bass has really tightened up!"
"Wow, listen to the separation of the instruments in the background!"
"It's like the singer took a step forward and the instruments in back spread out."

With trepidation, I started to wonder if the BlackBox had anything to do with it, so I disconnected it. It's as if a gentle haze had now settled in over the sound field, slightly but audibly affecting the overall system definition. Bass became a little "warmer" and things just seemed to get a bit more congested. "This can't be", I said to myself. I re-connected the BlackBox to the phono preamp, and the previous sense of clarity was restored.

I have confirmed to my own satisfaction that this 3io BlackBox has obvious benefits. Admittedly, its effect is pretty subtle, but not so subtle that it isn't plainly audible after a short period of relaxed listening. Its presence did not immediately announce itself; if it had, I would have been skeptical. I've learned that changes that jump out at you rarely prove to be improvements over the long term. It's the kind of change you'd hear moving from a $2000 phono cartridge to a $4000 one, and there are a lot of $2000 cartridges that I could live with. This 3io BlackBox brings the kind of improvement that I think most audiophiles and music lovers will appreciate.

No, it's not a magic clock or a fancy rock. Maybe there is benefit to harvesting all those free electrons polluting the grounds of my systems. But I'm mostly angry that my rational side doesn't understand the underlying technology. But at this price, who's complaining? I'm keeping the review sample.

Nice work, guys!

*** End of review ***

Hear the Unheard!
8/18/2016
J&K Audio Design

Audiophile DC Blocker Review

Nothing makes us happier to receive REAL user reviews for our DC blocker. 

The DC riding on his mains are giving him some issues and he requested for a pure DC blocker, without any noise filters and other functions with the DC blocker. The money saved are used to upgrade to better components for the DC blocker, and therefore better sound quality is achieved.

http://jandkaudiodesign.blogspot.my/2014/11/mains-dc-blocker.html

Hear the unheard.
8/8/2016

输出变压器设计

输出变压器设计

It has been a while since we posted. Today, let's talk about output transformer design (输出变压器设计).

Output transformer is the heart of tube amplifiers (OTL - output transformer-less designs are exceptions of course). The quality of the output transformer determines the overall quality of the tube amplifier. It is much easier to get a power transformer made correctly than an output transformer with wide flat bandwidth.Good tube amp manufacturers often places a great deal of focus on their output transformer design, such as McIntosh, AN and ARC, which are famous for their high quality output transformers. For those 2nd or 3rd rate manufacturers with unknown transformers, or transformer designs, the transformer quality is something to be examined further and purchased with caution. 

So, let's think about what qualities should a high quality HIFI output transformer possesses? 

1. High primary inductance - yes, on a surface,for better low frequency response and loading, matching the driving tube and circuit, but to a certain limit so as not to create other problems.
2. Low leakage inductance, and capacitance, sometimes more accurately described as distributed inductance and inductance, because they are evenly distributed across all the winding of the transformer. 
3. No resonances across audio bandwidth.
4. No distortions.
5. 0 phase delay across audio bandwidth (usually happens at both ends of the frequency spectrum.

For those that knows a bit or read about magnetic properties, it is very obvious that the above are very hard to achieve, and the parameters actually work against each other. 

In output transformer design, you get some, you loose some, and you can never have all. If someone tells you he can, think twice.

Magnetic cores, such as SiFe, or any cores, will introduce its' own distortion due to different and imperfect BH characteristics (curve). The input and output will be different due to the transformer core BH behavior, and therefore some sort distortions have been introduced.

We are often asked about having unusually high primary inductance for Single Ended output transformers for their orders. Yes, high primary inductance is good, but over-design is never ideal in output transformer design. In order to have high primary inductance, we need much longer wires, thinner wires, and more turns. These have the side effects of higher primary DCR, higher copper loss, higher leakage (higher distributed inductance & capacitance), and higher phase shift. This will cause narrowing of the bandwidth, phase shift at both audio frequency extremes, and decrease of dynamic range. 

That's why, often, for those with high primary inductance requests, we will usually ask them to trust us in our judgement to select the best design for their applications. If one blindly follows the "high primary inductance" rule, they are free to suffer from their own decision. Some just focus so much on the primary inductance, that they do not really care about the high frequency response, making their tube amplifiers sounded very smooth, warm and mellow. At first, it may sound soothing and nice, but after a while, listeners with good ears will start to feel something amiss - the HIFI component, i.e., the high frequency components and dynamics will be missing. It may sound dull and lifeless, but some may like it, mistaking it as fake warmth or vocal (mid-range) superiority. Such kind of tube amplifiers may be good for speakers with high frequency focus loudspeakers, with a drift that goes upwards in the frequency response, compensating this design defect.

We strive to design a wide bandwidth (frequency response) output transformer that excel at both frequency end, with very flat response at the standard 20-20kHz region, at +/- 1dB flatness, or better.

The way to achieve this is to fulfill the highest primary inductance requirement according to the design at stake, and try to lower the distributed capacitance and leakage inductance to achieve the high frequency response for modern playback/recording devices usages. The application of high quality transformer core materials such as high grade SiFe, amorphous cores, Nanocrystalline cores, Permalloy cores, and with complex winding methodology, we try to get as close as we can to a perfect output transformer. 

As we have mentioned, the parameters are contradicting each other and therefore the bandwidth will not be as wide as an output transformer-less tube amplifier or Solid State amplifiers. Still, we love and we are addicted tube amplifiers with output transformers!  

Sometimes, bandwidth limitation can be a blessing! You have heard of deployment of high quality vintage input transformers from the golden age of tube amplifiers, such as input transformers from Western Electric (which have attained a cult following, with insane sky high prices) makes the sound better, smoother, despite their limited audio frequency bandwidth. Such bandwidth limitation acts as a filter for the high frequency noises, interference from surrounding or playback electronics, or even high frequency component of music signals. Therefore, making the sound smoother, and less harsher compared to direct connection or equipment without coupling transformers. McIntosh, for one, uses such output transformer technology on their solid state amplifiers. 

The leakage inductance, distributed capacitance, the primary inductance, the tube plate impedance, the primary current, the plate load impedance, the primary/secondary DCR, primary/secondary turns ratio and the desired flatness in audio frequency range, has a semi-fixed relationship, and there is a formula (cannot disclose here, J&K proprietary, but can be found and derived from various magnetic formulas and textbooks) to ensure the design meets a certain HIFI criteria or requirements. The primary/secondary DCR cannot be too high, or else the dynamic range, resolution and transient responses will suffer. These all actually sums up to be the primary impedance of the output transformer, i.e. the load for the tube in use. Varying components at difference frequencies within the audio frequency range will affect the flatness of the response curve, and also the phase shift over the frequency range. Deviation of the phase response and response curve flatness generates distortions, and power loss or variations across frequencies. 

Furthermore, these inductance and capacitance that exist in the transformer forms a LC (RLC) circuit and causes resonances at certain frequencies. At resonances, the impedance at such frequencies are either 0 or infinite, causing peaks and dips, abnormality/gradients on the frequency response curve. It may cause premature roll-off at both ends of the frequency spectrum if resonances fall at those 2 extremes. Therefore, one other factor to consider is to design the output transformer so as to reduce these artifacts, or make them fall FAR outside of the audible frequency spectrum. 

We often stress on the quality of transformer cores because of the effect is has on the dynamic ranges (of course there are other effects). The signal amplitude, or the responsiveness to response to minute or major signal changes, highly relies on the induction density and permeance rate of change, which varies according to the signal amplitude, and therefore affects the dynamic range, or how well it responds to small/big signal changes. 

Another factor that is related to signal amplitude is the transformer core saturation. If the signal is large, it may be working at the saturation region of the B-H curve and therefore further increase in signal amplifier will be saturated and output be distorted. That is why some magnetic cores are for small signal usages, and some are for power output usages due to their core magnetic flux density limitation. 

We have not talked about DC magnetization of the cores, such as in single ended tube amplifier application, where we need to add air-gap in the cores to prevent saturation. The control of the air-gap size will affect the magnetic properties of the core. Sometimes, some air-gap is used on push-pull output transformers too due to mismatch in both arms of the push-pull output transformer caused by mismatched tubes or unbalanced loading (difference in DC bias). 

We've discussed a lot in this session. Till then. 

Hear the unheard!
J&K Audio Design.
7/23/2016 

Father's day sale - counting down...

Guys - last reminder on date to secure your order is on 7/19/2016! 

*Tips: You can place a 50% deposit to secure the price 3 months too if you are still unsure on the final specifications. 

Father's day sale!

Apologies for no postings for some time. We are very busy preparing the orders from Father's day sale!

Hear the Unheard.
Hear the Difference.
Only at J&K Audio Design.