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Tuesday, June 21, 2016


This is the Q&A database that we have collected over the years, that will be useful for interested parties. We will constantly update it whenever we have time. 

Q: Can you make OPT with multiple primary and secondary taps? Will having multiple taps at primary and secondary affect the performance?
A: Yes. We can make multiple primary and multiple secondary if you still insist. Please specify which is the mostly used primary secondary tap and we will optimize those taps for the best performance. Other taps may have slightly inferior specifications. Others may have not told you the side effects but that is what happens. 

Q: I would like to specify the primary inductance to obtain the best low frequency response. Is this doable?
A: Our OPTs are usually tuned as with overall balanced sound. If you have preference of low frequency linearity versus overall bandwidth, please let us know and we will try to optimize for you – not for fixed specifications models. We cannot guarantee a certain primary inductance value but as best effort basis.

Q: Is transformer size important? I play to make an EL84 SE tube amplifier. Can I choose higher Watt OPT?
A: EL84 SE is 3W – 5W. You can choose a 5W or 10W OPT for better dynamics. Anything 4x over the intended OPT will not bring much benefits and maybe have shortcomings.

Q: Do you have standard power transformers?
A: We do not. We believe in custom made power transformers, tailored exactly to the right usage with the exact voltages needed for optimal results. Standard voltages means you need to use R/L/C to tune the voltage and that will involve compromises. If you do not know what you need, we can help you with the design.

Q: How high is the operating voltage?  
A: It depends on the transformers. We will do voltage stress testing before release – primary to secondary, and primary to core for 1 minute, according to the voltage level required for the specific transformer applications.

Q: Is potting available for all transformers?
A: It depends on the size and availability of the transformer cases.

Q: Can you make the transformers to a specific size to fit my existing chassis?
A: On case by case basis. If the application calls for core bigger than available size, then no. If it is smaller, usually it is doable. We have made adaptor plates or casing according to customer casing before. It takes longer time as we involve 3rd party to fabricate the casing.

Q: Can I customize the color of the casing?
A: It depends. Please email us and we shall try. In addition, it cannot be matched 100% too as it is controlled by 3rd party vendor. We do not make the case. We commission 3rd party vendor to make the case.

Q: Where are the transformer cores made?
A: it is made in Japan and USA.

Q: Can you use smaller transformer case?
A: We need to keep a distance between the core and the case. The case is made of ferrous materials and will generate Eddy Current (loss). If it is made of non-ferrous materials, there is not much shielding effects. That defeats the purpose of the shielding.

Q: Can I specify – primary DCR, primary inductance, feedback winding, secondary DCR, THD, noise, frequency response, withstanding voltage, specific magnet wires, Faraday shield / electrostatic shield, special cores and etc?
A: Yes, you can. We will try to accommodate all your requirements. There might or might not be price increment, depending on the customizations. Email us.

Q: Do you have combo price?
A: Yes, we do, when you order power transformer, choke and output transformers in one shot.

Q: Do you vacuum impregnate your transformers?
A: Yes, vacuum impregnation is standard process, including baking it to dry afterwards.  

Q: Will your price go up or go down in long term?
A: It will go up due to inflation, rise of materials cost, rise of labor cost, rise of everything! Order early to lock down the current price.
Q: What is the benefits of vacuum and oil immersed transformers?
A: Better protection from oxidation, better operating conditions, better sound!

Q: Your Hybrid Permalloy comes in EI core format only?
A: We have pure Permalloy C core too. Please email us if you want to have it in C core format. Do note that not all interstage / output transformers can use the Permalloy C core as we cannot interleave it with other cores to increase the power handling capacity.

Q: Can Hybrid Permalloy interstage / driver / input transformers come in bare format?
A: Interstage / driver / input transformers need shielding to isolate them from noise. They must be potted.

Q: Do you have discounts?
A: We have promotions on and off. Please check our blog regularly for latest updates.

Q: What is your lead time?
A: ~3 weeks. If there are holidays during the ordering period, or peak production time, lead time will be longer.

Q: Can you shorten your lead time?
A: Unfortunately, no.

Q: Can you customize the parameters for me?
A: Yes, we can. Please email us with details.

Q: Will your transformers specifications change in future?
A: Yes, we always try to improve our transformer designs to produce better and better design over time.

Q: Do you offer high voltage power transformers for high B+ use?
A: Yes. We can build it to withstand 1.5KV – 2KV B+. Our testing goes up as high as 4KV-5KV, depending on models.

Q: Can I have specific lead out length or solder turrets?
A: Yes. Solder turrets are only for potted transformers.

Q: Should I fully utilize the available VA for the power transformer order?
A: No, you should not. Our transformers can work at full load no doubt, but still please leave at least 25% as spares to keep the operating temperature low and for longevity purpose, not mentioning better sound! If there are too many taps, and mixture of high and low voltages, the efficiency will be lower.

Q: Where does your transformer cores come from?
A: We order from Japan and USA.

Q: Can you make vacuum and oil immersed power transformers and chokes?
A: Yes, for up to a certain size only. Please email for details.

Q: What core do you usually use for your power transformers and chokes?
A: Z10 and Z11.

Q: Will bare transformers rust?
A: Yes, they will, especially when operated near sea (on island), or near damp area. Transformer cores are made of iron and it will rust after long use even if it is painted. If you are worried of rusting, please order potted version, or add additional lacquering/painting yourself for additional protection for even longer rust protection.

Q: Can you do bifilar winding?
A: Yes, we can.

Q: Can you do solid state output transformer?
A: Yes, we can.

Q: Can you repair transformers?
A: Yes, we can. Please provide the size, pictures and weight for quotation.  

Q: How many set of windings can I have on power transformers?
A: It depends on the size of the power transformers. There are limited winding space and we usually limit it to 6 sets. Please email us if you need more than 6 so that we can evaluate if it can be fitted to that particular core size.

Q: Can you design plate choke / anode load choke?
A:  Yes, we can. Please email us the specifications and we will quote. 

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Hear the Difference.
Only with J&K Audio Design. 

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