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