Value for money output transformers

Best bang of the buck output transformers! Value for money output transformers! Good sounding output transformers! Good things need to repeat 3 times!

Hope everyone is well in terms of the COVID-19 outbreak, as well as the current stock market correction period. In such treacherous period of time, what’s better than staying home and do some self-improvement reading, market research/analysis and new product design!?!?

Who’d like to have a best bang of the buck output transformer? Please raise your hand! We’ve surveyed the market of output transformer makers, list out some of the popular names such as Lundahl, Tango, Hammond and etc to analyse what’s good, and what’s to be had.

The picture shows our rating based on our own criteria – take it with a cup of salt.

What are the critical parameter for output transformer?

1. Primary impedance ~2.5K to 3.5K (common impedance for most tubes)
2. Primary DC 100mA at minimum (suitable for 2A3, 300B, KT88, KT100, KT120 till KT150)
3. Primary inductance of ~6H per 1K Ohm (for better low frequency loading/response)
4. Secondary 0 – 4 – 8 Ohm (suits most speakers out there)
5. Output power 30W (decent, but not too low)
6. Frequency response of at least <20Hz and > 20kHz (for full HIFI bandwidth)
7. Tolerance of +/-1dB (where human ears could hardy differentiate a 1dB difference)
8. Decent headroom/core volume >= 1KG per 10W SE
9. Decent price <$150/pc

With all the above criteria in consideration, we have come up with 2 output transformer designs to satisfy most users needs. We cannot do an All-In-One output transformer as the design trade-off is just too much.

Therefore, one (JK Fighter P-OPT) is designed more for Pentode (KT88, EL34, EL84, KT120, KT150, and etc).

• Higher primary inductance to cater for higher tube Rp (Pentodes in general)

The other (JK Fighter T-OPT) is designed more for Triode (50, 300B, 2A3, 45, 71, R120, 300BXLS, PX4, and etc).

• Lower primary inductance to cater for lower tube Rp (genuine Triodes in general)
• Additional 16 Ohm secondary for high efficiency speakers  

For those that wish for a warmer sound, they can use JK Fighter P-OPT with Triodes or even Pentodes. For those that want a more high fidelity sound, JK Fighter T-OPT is the one to go.

Expected availability ~June 2020. If you’ve feedback on the design for improvements, or you happen to be looking for one for your design(s) – let us know before we finalize the design. Email us! If they are valid and genuine, and doable within the budget, we will include them.

To keep the price low, they are all fixed design. If you need to customize, it will have to be on standard customize price. Custom made version will be more expensive, and will have better dynamic headroom too.

We have no plans to release Push-Pull versions since those have lower demand. If there are a lot of queries, or even OEM requests, we may consider doing so – let us know.  

Thank you for your support!

Take care everyone! 

J&K Audio Design

28/2/2020

Vacuum Tube Repair

Good health to all J&K readers, supporters, and most importantly customers! 

Just a little update on the COVID-19 outbreak - latest news is that some of our suppliers will resume work on 24th FEB 2020 - hope that situation improves that much to enable them to resume production. 

Now back to our agenda here - vacuum tube repairs, or vacuum tube revivals!

I believe, transformers repair is nothing new to our followers. We've repaired hundreds, if not thousands of them over the past many years. 

Another critical part of the solution chain would be on vacuum tube repair and revival, especially on those exotic NOS tubes that cost quite a considerable amount of money. We now offer vacuum tube repair or revival service to our customers through our long time partner (a tube maestro). 

Do note that not all vacuum tubes can be repaired or revived. Some are dead for good. For some that are still having some life in it, or failed prematurely, or even fail as DOA, maybe they could be repaired. In some cases, some even be buying those expensive exotic NOS tubes that are dead at a dirt cheap price, and sending them to us for repair! If by any chance those dead exotic NOS tubes can be repaired, they could save thousands of dollars comparing to buying good exotic NOS tubes. Those that are worth repairing are those Western Electric signal or power tubes, Genelax / Gold Lion signal or power tubes, or even any old big power tubes that worth fortunes. 

Since repairing or revival could a 50-50 or worse kind of odds, one may need to weight the pros and cons before sending for repair. Vacuum tube repairs or vacuum tube revival starts at U$100 per piece, and could be more depending on the type of tubes and illnesses. 

Loose base, no connection at tube pin due to broken wire or cracked solder, or broken pin can be easily repaired by base replacement or re-connection internally at the base. Broken filament, could possibly be repaired, on case by case basis. 

Here are some things to be considered before sending vacuum tubes for repairs or revivals: 

1. Are they worth the trouble or worth the price? Repair price could be more than buying them new or  or buying NOS. 
2. Mechanically broken vacuum tubes are not repairable - such as broken glass or vacuum loss (inside appears all white). 
3. Severely broken tube internally (massive internal structure failure, broken plates for example).

For other cases, please send us some pictures and descriptions and we shall see what we can do. 

Examples for some cases on vacuum tubes that could possibly be repaired:

1. Crackling noise
2. Keep blowing fuses 
3. Filament shorted 
4. Internal pins shorted 
5. Open connections 
6. Intermittent operation
7. Missing base / base repair / base replacements
8. Oxidized tube pins / internal wires
9. Weak tubes 
10. And etc... can't list all since there could be other illnesses 

Contact us, if unsure.

Now, go dig your storeroom and see if there are any vacuum tubes you'd like to be repaired. Better still, go ask all your tube audiophile friends for used tubes, broken tubes that they do no longer use, and see if they are worth repairing or reviving! They could save you a fortune, or make you some good money after being repaired! 

Tubes that are worth repair, for example, could be 212, 4212, 211, 4211, 4300B, 300B, 2A3 single plate, 2A3 double plate, 801A, PX4, AD1, 53KU, 52KU, U52, EL156, KT88, KT66, Telefunken, Western Electric, Genelax, and various other expensive exotic tubes. 

Vacuum tube dealers, sellers, shops owners - if you have tubes that you think are worth repairing, please contact us and we may be able to repair them for you for re-selling later. The same 3 rules above apply. 

Start digging! You may encounter a few gold mines! Don't let the exotic tubes go to waste - recycle them! 

J&K Audio Design
18/2/2020 

Corona Virus

Some states or regions in China, including places where some of our raw materials vendors are located, were mandated by the Chinese Government to remain close until 10^th February, 2020. This is to prevent wide spread of the Corona virus, and is one of the precautionary measures to avoid further spread of the disease and threat to the nations.

This has affect the continuous supply of raw materials needed to produce our products. This may have some impact to the production and may delay delivery of some shipments. We are could and are still in contact with the raw materials vendors for the latest update of the situation.

As of now, most of our raw materials vendors will resume production on 10^th February, 2020. Given the uncertainty of this matter, we’re still actively monitoring the situation.

Kindly contact us if you’ve any concerns. Thousand apologies for the inconveniences caused.