Surplus transformers for sale

Howdy everyone! Greetings from J&K Audio Design team. Hope everyone is safe and sound. 

We're clearing out stocks again! There are just too many old stocks lying around that are taking out our storage space. If you are flexible in terms of transformers, we have some surplus power transformers and audio (input/output) transformers to let go at discounted and very decent prices. Email us your needs and we will search around to see if we have something close. 

Below is a pair of the recent surplus pair of Level-1 0.35mm GOSS 400VA power transformers we have. 

Primary: 0-240-250, G (electrostatic shield).

Secondary: 3.15-0-3.15@14A; 270V-0@1.15A.

400VA each, sell in pair.

Good for high power amplifiers with 6.3V filament tubes. Copper shields. Teflon lead outs. 15KG packaged and ready to go anywhere. MY$1100/pair (U$260), as is.

Till then, take care everyone.

J&K Audio Design

23/4/2022

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

Tannoy Autoformer

Tannoy Autoformer / Tannoy Crossover Transformer  

We had a high end version of the Tannoy Autoformer / Tannoy Crossover Transformer with very high grade materials and that caused the price to shoot over U$500/pair. Quality and sound are excellent and first grade but that was quite prohibitive to most.  

As we are Tannoy lovers (Ken has once owned Tannoy HPD 385, Tannoy Arundel DCC-3839, Tannoy System 800, and Tannoy SRM12B), as with a lot of the audiophiles out there, we have decided to make it more commonly available to all Tannoy lovers to restore their Tannoy Monitor Gold, Tannoy HPD and other similar Tannoy loudspeakers, to their original glory. 

Here are the new prices: 
- Simple clone, bare square frame - U$160 / pair 
- Potted version - U$200 / pair

We had written about this Tannoy autoformer / Tannoy Crossover Transformer quite some time ago. We will not repeat them here. 

http://jandkaudiodesign.blogspot.my/2014/09/tannoy-crossover-autoformer.html

Of, if you ave only a single crossover transformer (actually, ANY transformer at all), or would like to clone them to get a stereo pair, just drop us an email and we can discuss on how to do so. 

Hear the unheard! Sail the uncharted! 
Long live custom made audio! 

J&K Audio Design
9/19/2017

Orient Hi B C Core

Orient Hi B C Core (Cut Core) Output Transformers 

What? J&K has new stuff again? Nuh, not really. This Orient Hi B C Core (Cut Core) is what we called it as Super Hi B C core. For those that followed us since 2014, they would have known that we have this excellent laser strip Hi B C core that are used to make output transformers, chokes and transformers. 

Orient Hi B C core is just another name, used by mostly Japanese manufacturers, such as Tango and Hashimoto. That also proves that, Orient Hi B C core, or Super Hi B C core, is an excellent material to be used for audio transformers. You can re-collect our past posts here below on these high grade Orient Hi B C core transformers: 

http://jandkaudiodesign.blogspot.my/2015/04/super-hi-b-transformer-review.html
http://jandkaudiodesign.blogspot.my/2014/09/super-hi-b-c-core.html
http://jandkaudiodesign.blogspot.my/2016/06/j-super-hi-b-power-transformer-user.html
http://jandkaudiodesign.blogspot.my/2014/06/hi-b-c-core.html

Why are we bringing this up again here? We brought good, no, GREAT news! We are lowering down the prices of transformers made with Orient Hi B C core (Super Hi B C core)! It was previously ONLY used in our Level 2-3 transformers and were quite out of reach for some folks, but now we are making them at Level 1, which means that the pricing will be following Level 1 pricing! 

Level 1 Output Transformers - with Orient Hi B Cut Core (Super Hi B) 

Single Ended OPT
15W SE - U$490/pair
- Primary DC current: up to 80mA
- Primary / Secondary impedance: user defined
- Size ~90mm x 80mm x 80mm

30W SE - U$590/pair
- Primary DC current: up to 150mA
- Primary / Secondary impedance: user defined
- Size ~110mm x 100mm x 90mm

60W SE - U$790/pair
- Primary DC current: up to 250mA
- Primary / Secondary impedance: user defined
- Size ~120mm x 100mm x 100mm

75W SE - U$890/pair

- Primary DC current: up to 350mA
- Primary / Secondary impedance: user defined
- Size ~135mm x 100mm x 115mm

100W SE - U$990/pair
- Primary DC current: up to 500mA
- Primary / Secondary impedance: user defined
- Size ~135mm x 115mm x 115mm

Push Pull OPT

70W PP - U$590/pair

- Primary DC current: up to 150mA
- Primary / Secondary impedance: user defined
- Size ~110mm x 100mm x 90mm

- UL: optional, user defined 

140W PP - U$790/pair

- Primary DC current: up to 280mA
- Primary / Secondary impedance: user defined
- Size ~120mm x 110mm x 100mm

180W PP - U$990/pair
- Primary DC current: up to 480mA
- Primary / Secondary impedance: user defined
- Size ~135mm x 100mm x 115mm

Interstage Transformer

1:1, 2:1, or 1:2 - U$390/pair 
- (multiple taps, email us) 
- Primary DC current: up to 30mA (>30mA, email us) 
- Primary / Secondary impedance: up to 8K (>8K, email us)
- Size: depends on complexity 

* Above are transformers with bare square or L frame. Potting requires slight addition to the transformer prices, from U$30/pc++, depending on sizes. 

* Sizes may vary, depending on incoming C cores. 

* Level 1 transformers CAN be made with OCC (Ohno Continuous Cast Copper) wires. OCC copper wires are expensive, but is well worth the money! 

* Power transformer and choke prices are not listed. Their prices depends on the complexity and design parameters. Email us. 

Why do we constantly push out new stuff? Here's out motto: 

Promote vibrant custom-made HIFI industry! 

Imagine, how much more you can do, how much better you can get, how different you can be, with more high quality, uniquely custom made transformers from J&K! 

Grab one now, join us and be apart of this movement! 

If you have any bright ideas on what should be improved, added, or modified from our line of products and services, let us know. All inputs are very welcomed! 

Hear the unheard!
Sail the uncharted! 

J&K Audio Design
11/9/2017

Internet references, taken from pictures from the internet - "Orient Hi B Cut Core" can be seen on the label of the transformers for Hashimoto and Tango / ISO Tango transformers.

By the way, does anyone know why there's such a stain near the top of the tube?

DAC output transformer

We have got a few requests to custom make DAC for a few customers locally, and have been researching on how to make a better output stage for I/V conversion for DAC chips with current output, especially differential types. 

We've tried many types, such as Op-amp, discrete, passive resistor, and transformer based. So far passive resistor and transformer based are our favorite. Both these give the most natural and organic sound. 

We've done some Googling, and we found that we're not alone! A few very famous modders (Lampizator) and custom builders (Andrea, and etc) have been promoting DAC output stage with resistors and transformers! 

It just so happen that we do have some ready made input transformers made previously for preamp input coupling / isolation use. It can be used perfectly as DAC output stage.

DAC input transformer

  600 Ohm : 600 Ohm DAC output transformer

• Permalloy EI core, with a small % of Z11 for voicing / sound tuning
• Core size: EI 35 
• Size: 66mm x 3mm x 33mm H 
• Signal level: 3 Vrms @ 20Hz 
• 20Hz -0.1dB to 100kHz -1dB
• Usages
•  DAC output, CD output, Op-amp preamp output, signal coupling (input transformer, output transformer), output inversion use
• Price: U$150 / pair 
• Limited quantity only, left over from mass production for a high volume manufacturer
• 5：1， 10：1 versions may be available, please email 

The simplicity of having transformer as DAC output stage is also something we liked!

 

This is as simple as it gets, and results are extraordinary!

J&K Audio Design

5/7/2017

Parafeed Output Transformer

Busy is the only word left on our dictionary for quite some time! Time to update our blog or else people might think that we are MIA.

Since a customer from down South in Australia asked for a pair of parafeed output transformer (parallel-feed), we might as well do an introduction here. Parafeed output transformer is not something new. 

Below is a sample schematic from diy-audio-guide. It is a parafeed tube amplifier designed to operate with 2A3 / 6B4G / 6A3 vacuum tube.

How it works is that the tube load, which is originally a single output transformer, is now split into 3 parts - the load inductor (can be resistor, or CCS too), the parafeed coupling capacitor, and the parafeed output transformer. The parafeed capacitor can be placed on the receiving arm of the parafeed output transformer, or the grounding arm. Both way works but if the parafeed output transformer do not have high insulation strength, it is better to place it at the receiving arm to isolate DC from the parafeed output transformer.

The parafeed coupling capacitance for flat frequency response can be calculated (estimation) as follow:

C = 2*L/(R*R)

C is in Farad
L is in Henry
R is load impedance (transformer primary impedance) in Ohm 

John Broskie from Tube Cad Journal has the formula as follow: 

C  = 159155/(rp + Rload)/Frequency,

C is in µF 
rp is the tube plate resistance. 
Frequency is the cut-off 
Rload is the primary impedance of parafeed output transformer

The most frequently faced problem with single ended tube amplifier is always the output transformer capability (bandwidth). As we have always mentioned, the design constraints of output transformer are always contradicting each other. In this case, the air-gap required for SE operation will work against the primary impedance that is required for better low frequency extension/responses. With parafeed configuration, this is eliminated where we do not need to have air-gap for the output transformer due to only having AC going to the parafeed output transformer, which in turn, make it smaller and better optimized for lower capacitance and leakage inductance. Benefits to output transformer design one of the most important benefit for parafeed configuration.

Of course, there are other benefits as well such as better PSRR due to having a choke as load (hum reduction), having the opportunity to use exotic core (nickel/permalloy, cobalt, nanocrystalline, amorphous and etc) for the output transformer since DC saturation is no longer an issue.

Parafeed is all pros but no cons? Nuh... don't be happy so soon. There are drawbacks of course:

• High quality high value load inductor will be needed since it will experience full audio frequency spectrum instead of 120Hz or 60Hz mains frequency, and provides high impedance at all audio frequencies
• Additional parafeed capacitor is in the signal path
• Tuning may be needed to optimize the inductor / capacitor 
• More tube amp real estate is required
• Etc

Although there are so many drawbacks, they can be individually tackled/resolved (with money), that's the beauty of parafeed configuration! You can have a high quality plate load choke, high quality teflon / oil / film coupling capacitor, and you are half way to heaven!

We had tried parafeed amplifier and they do have excellent low frequency response, coupled with sound that feels louder than the Watt rating. Of course, the sound quality will be dominated by the 3 parts now (parafeed load choke, parafeed capacitor and parafeed output transformer) instead of 1 single output transformer.

For those that are interested to build a parafeed 300B / 2A3 amplifier, you can consider the following output transformer options: 

• Level 1 - 10W Parafeed Output Transformer
• EI Z11 - U$190/pair
• EI Z9 - U$240/pair
• Level 2  - 10W Parafeed Output Transformer
• Permalloy OPT - U$640/pair, potted
• Level 3 - 10W Parafeed Output Transformer
• U$890 for EI Core potted
• U$1090 for Nanocrystalline Double C potted

Hear the Unheard! 
J&K Audio Design
9/15/2016

R-core transformers

Introducing low cost R-core transformers! 

Textbook says (not us), the benefits of R-core transformers are, but not limited to:

• Stray magnetic flux is low, x10 lower that EI transformer
• R-core transformer is smaller than EI by 30%, slimmer by 40%, and lighter by 40% 
• R-core transformer generates 50% lesser heat than EI transformer
• R-core transformer generates lesser noise compared to EI or gapped core transformers
• R-core is more reliable, easier to install and better stability than toroid transformer
• Etc...

Well, a lot of the statements above are questionable since the properties depend on a lot of other factors too, but one thing for sure is that R-core does have its benefits and sound signature.

R-core transformer employes a circularly wound steel core. The primary and secondary coils are wound on it. Due to the minimal gap between the coils and core, the loss is very low. Also, annealing treatment can be applied directly to the core to condition it at its best magnetic state to reduce distortion.

Our R-core ranges from 10VA (~U$25) to 1250VA (~U$340) per unit, depending on customization. If higher capacity is needed, customers can go for toroid transformers or parallel R-core transformers to go to as high as 2500W. Such parallel usage would be for balanced isolation transformer where the +ve is by a 1250VA unit and the -ve is by another 1250VA unit to make 2500VA in total.

One good example would be to make isolation transformers with R-core transformers! Due to the low profile nature of the core and windings, it can be made very compact with very good electrical properties! 

On the other hand, those who does not prefer R-core or still do not believe in R-core can still go for single C core transformers. We are introducing the economical C core power transformers as well ranging from 5VA (~U$28) to 1600VA (U$460), depending on customization. Parallelism can be done to get 3200VA unit too if needed. 

Single C core transformer - horizontal version

Single C core transformer - upright version

 Email us for a quotation with your customization needs. 

J&K Audio Design
23/5/2015

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.

Toroid Transformer

We have received considerable requests from customers on providing high quality toroid transformers. We are not really a supporter of toroid transformer but there are just cases where EI or C core transformers cannot fit. Therefore, J&K toroid transformer is born, just before April Fool's day! 

Toroid transformer winding method is totally different compared to EI or C core transformers as it does not need bobbins and requires machine to do the work right. Investment alone on the automatic winding machine is hefty! 

As usual, we only offer high quality cores, and our toroid cores are high quality customized cores from Nippon Steel. Due to the nature of how toroid cores are wind, we highly recommend the toroid transformer to be potted and filled with potting compound to keep it mechanically stable, for sound quality and longer life.

Normal grade toroid transformers rattles and have very obvious noise, especially when it is loaded. This really gives audiophiles a big headache. If you are sensitive to this and want a truly quiet fully rated toroid transformer, this is the one to get.

• <500W toroid transformer is about 130-150mm D x 75-97mm H with cover 
• 1200W toroid transformer is about 159mm D x 110mm H with cover.
• 1500W toroid transformer is about 180mm D x 120mm H with cover.
• 2500W toroid transformer is about 210mm D x 120mm H with cover.

When you order, please specify the voltage needed on what conditions - no load, half load or full load. They are built with 24x7 operation in mind - industrial + audiophile grade! All transformers are meticulously tested, with primary being flashed with 4KV for 1 minute.

Nippon Steel cores are quiet on empty or full load. Our design guarantees that it will not make noise at full rated load! We have two types of toroid cores too - flat 90deg and doughnut (smooth O, better) ring (600W, 800W and 1000W only).

Applications:

• Single ended or balanced isolation transformer
• Power transformers (single ended or balanced) for solid state amplifiers or tube amplifiers (1Vac to 1000Vac)

Indicative price is as follow. Please contact us for actual price with your specific requirements and specifications.

• 500W - U$200
• 1000W - U$300
• 1500W - U$400
• 2000W - U$500

These are high grade toroid cores, winded with high grade copper magnet wires, customized per customer needs and therefore will be pricier than standard toroid transformers. As far as I know, even the small time manufacturers will only do so for customers with MOQ (minimum order quantity) of 10 units. We accept even 1 unit! 

For those that requires low power applications (<500W), we usually recommend EI or C core transformers. For high power applications (>500W), toroid transformer becomes more economical option to consider. Coupled with the lower stray magnetic field compared to EI or C core, it is something audiophiles should not forget. With the potting and shielding from the case, making a low noise high power solid state amplifier becomes a reality.

If you have been considering to make isolation transformers for your beloved HIFI gears, this is the time to do so! You can use toroid isolation transformers (balanced output if possible - better!) for your power amplifiers, and EI / C core isolation transformers for your low power gadgets like preamplifiers, CD Player or DAC. Each equipment should have their own isolation as the equipment themselves are noise generators too. Having individual isolation transformers serving individual gears will give you much better isolation and much lower noise (darker background) comparing to sharing a same huge isolation transformer.

Now, send us your wish list and we will do it for you! If you have wanted your own isolation transformers similar like those used in BPT, Equitech, Isotek and such, now is the time. You can DIY it yourself, or have us custom make one in a proper chassis for you. An example below is posted for your reference.

P/S:

• We only supply high quality products and that comes with a price. If you want to search for low cost or negotiate for very low price, please look elsewhere. We cannot satisfy this type of requests. 
• High quality products take time to be built. If you want fast delivery, please consider twice before ordering from us. We will provide a lead time estimate upon ordering and we shall try our best to meet it but it is not guaranteed.

J&K Audio Design
3/31/2015

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.

Transformer Case

*** 12/2015 - no longer available, manufacturer stopped production ***

These are the transformer cases that we are using for some of our potted transformers. Since a lot of people asked about what we use, we might as well publish it here to save all the attaching work. :)

3 sizes:

1. 80 x 80 x 90 (H) mm, mounting hole 60 x 60 mm, 4m thread, window 46 x 46mm, 1mm thickness top, 1.8mm bottom plate, for EI76, for single C cores - U$33/pc
2. 105 x 105 x 105 (H) mm, mounting hole 83 x 83 mm, 4mm thread, window 67 x 67mm, 1mm thickness, 1.8mm bottom plate, for EI96, for single and double C cores - U$35/pc
3. 122 x 122 x 130 (H) mm, mounting hole 96 x 9 mm, 4mm thread, window 73 x 73mm, 1.2mm thickness, 1.8mm bottom plate, for EI114, for double C cores - U$D38/pc

Notes:

• Internal dimension is external - ~3mm.
• Special prices if is used with our transformers. 

J&K Audio Design
27 Aug 2014

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.

Double C Core Power Transformers

Check out our double C core power transformer. This is a premium (level 1) grade power transformer made for a fellow local tube enthusiasts. It is about 300VA in size. Level 2 will use the Super Hi-B C cores.

It does not have any matching enclosure and therefore it will be bare naked. Afraid not, the stand and frame are very sturdy.

13 August 2014
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

* 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.

Audiophile Z11 Power Transformers

These are special custom made audiophile Z11 power transformer for tube amplifier (filament supply). It is not cheap but definitely is worth the investment. The wires used are UK made silver plated OFC with Teflon insulation.

The secondaries are drawn out directly using the same wire materials instead of via solder-tags then with other types of wires. For those that might not be aware, there is a reason for such designs. Different wires have different characteristics impedance. Once you go though a change of materials, that equals to change of characteristics impedance - see below:

On DC world, it looks like this:





* Wires A - connector - wire B

On AC world, especially on high frequency operation, it looks like this:
* Wire A (impedance A) - connector (impedance C) - wire B (impedance B)

What happens when the impedance change? Reflections, attenuation, boosts, and all sorts of artifacts of impedance mismatch. This will indirectly affect the signal integrity of the music signal. At audio signal range, it should be negligible but every little things matter.

It's better to take every precaution possible, and therefore the birth of this special made audiophile Z11 power transformer.

Of course, we will not forget to share some pictures! Enjoy!

Z11 audiophile tube filament transformers

Teflon insulated silver plated OFC

Audiophile Power Transformers

Till then.

J&K Audio Design
13th July 2014

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.