Importance of power transformer

Importance of power transformer, or importance of transformer to match your usage requirements!

(Editor: wow, it has been a while since we posted. We must make it a point (or a new year resolution), to post more frequently. Let's start with the target of at least 2 - 4 post a month, on any topics at all, related to audio, of course.)

We have stressed many times, the quality of the power transformer is directly proportionate to the quality of your audio amplifier. Taking the quality factor aside, there's another factor that is equally as important - the matching of the transformer primary and secondary voltages towards your incoming mains, and the amplifier voltage requirements. 

Why? Let's look further (with some remedies later): 


Primary voltage
Transformer is a fix ratio voltage converter. The step-up, or step-down ratio is fixed. What is present at the input, will be converted according to the designed ratio. If the input is higher, the output will be higher too, and vice versa. And that my friend, will be an issue where the voltage can be too high or too low for your design, be it regulated, or unregulated power supplies. 

Take mainland China equipment to be used in Bolehland for example. Often, mainland China equipment is built for 220Vac, where as Bolehland mains is 240Vac. The ~10% extra at input of the equipment will produce ~10% output at the secondary, and that will be very damaging, especially for tube amplifiers. 

Take the B+ as an example: 350Vac gets you about 470Vdc after rectification. 470Vdc is a very common voltage used by cathode biased 300B amplifiers, where Vplate is 400Vdc, and Vcathode is 70Vdc, adding them up to get B+ of 470Vdc. B+ PSU caps are usually rated 500Vdc, which is a very common values and economically available to be used in tube amplifiers. 

Simple B+ PSU, just for demo purposes:





Now say 220Vac mainland China amplifier is connected to 240Vac mains in Bolehland. (By the way, in my area, the usual voltage is 250Vac, mind you!) 



Look at what happened to the B+? It is whopping 520Vdc! What are the consequences to this? Or to say, what are the consequences of operating 220Vac input 300B amplifier in 240Vac Bolehland?

1. 300B B+ may potentially exceeded max voltage, or very close to max value
• Consequence: shorter 300B lifespan, or burnt 300B. 
• 450Vdc is max. With above example, Vplate is at 450Vdc after minus the Vcathode.
2. 300B max plate dissipation may potentially be exceeded
• Consequence: shorter 300B lifespan, or burnt 300B, red plating.
• Max plate dissipation is only 40W max for 300B. Some designer may run it close to max to produce max power. If it is biased conservatively, following old school design (~75-80%), then it may still be OK.
3. 300B filament is 10% higher
• Consequence: filament will burn out faster with 10% higher filament voltage, or worse, burn out  immediately (open circuit), causing tube to fail. 
• Emission may be higher with hotter cathode, causing higher current, and issue #2 above may occur.
4. PSU capacitors max Vdc rating exceeded
• Consequence: shorter PSU capacitor lifespan, or even fireworks immediately, kaboom!!! 
• Electrolytic capacitors of 500Vdc working at 520Vdc... go figure. Needs no further explanation. 
• Some cheaper ones may even use 450Vdc caps and overwork that all the time (we've seen some)!
5. Overworked power transformer
• The transformer core and wire gauge may be rated for a certain values only. If it is higher than rated, it may be hotter, melted, degrade, rattle, and such. Of course, properly designed and overspec'ed transformer may not have such issues, which is rarely the case for low end on-the-shelf products. 

There may be more issues, but let's just stop here. 

Some references for your reading pleasure:

300B datasheet states that max Vp is 450Vdc. Do not exceed that!
 

Filament rating caution - need to be operated as near rated voltage as possible! 

Remedies - Alright, you may say that "I'm scared! How do I rectify this problem?" 

Here are some methods that you can consider:

1. Use a step down transformer (240Vac -> 220Vac)
2. Use an isolation transformer, or ultra isolation transformer with step down (even better, kill 2 birds with one stone!)
3. Use a mains regulator that can regulate down (duh, some may not like regulation in amplifiers, me too!)
4. Replace the power transformer (complicated, but may be worthwhile if space is a constraint to add additional gears)
5. Connect a small transformer in reverse to drop the mains voltage slightly (not recommended due to several reasons) 
6. Don't buy equipment with mismatch mains voltage (Just kidding!)

Secondary voltage - Now, what about the impact on the secondary voltages, after we discussed about primary?

Let's leave this for another follow up article. There's a lot more to cover here than the primary, trust me! After reading that, standard on-the-shelf power transformers will not be your cuppa anymore!

Till then, we've written too many words for this page, and have to stop!


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J&K Audio Design
3/3/2018

811 Output Transformer Review

Another user review of J&K Output Transformer - this time is for 811 tube. 

Advertisement time! 

1. We customize low to very high end, low to very high power transformers.
2. We accept individual retail and corporate orders.
3. We customize amplifiers, DACs, power conditioners and various audio gadgets (depending on our free time and available slot).
4. Email to order! Lead time is 4-6 weeks. To avoid the long wait, order early! 

Just a side note - is HIFI enthusiasts so into spending for HIFI that they cannot get a phone with better camera? (Just kidding!).

Here goes another user feedback in USA:

The sound is awesome, I have monblocks, so I can do A/A testing. I changed on one amp, and my wife me tested some mono recordings..

with J&K it was like a thick veil got lifted, the musical details increased on all spectrum of frequencies, it was just amazing..

Now to change my next amp in 2 weeks when I am back from my travels..

Attached is a picture of the new output transformer in a separate chassis on the 2nd shelf

cheers

Schematic shown is not for commercial purposes.

We will try to put in more post this year... we hope. 

J&K Audio Design
31/1/2018 

Transformer upgrades with J&K ultra isolation transformer

Another great testimonial from our customer using our J&K Ultra Isolation Transformer - a real paying user feedback, rather than bogus paid reviews on blogs or magazines. 

Rich has been replacing all his transformers on his existing HIFI equipment with our Ultra Isolation Transformers. 

* Replace existing transformer with ultra isolation transformer
* Separating critical power rails to separate ultra isolation transformer
* Upgrading super critical power rails with OCC made ultra isolation transformers
* and many more... 

Without further ado, here goes the feedback from Rich. This is just the tip of the iceberg on the upgrades he had done to his HIFI and Home Theater gears. 

Auralic Vega DAC upgraded power supply with J& K Discrete Ultra ISO transformers replacing original toroid. Now front-ended by two stages of balanced Ultra ISO transformers for each of the three  secondaries in the Vega. Since upgrading the Crystek clock to the Pulsar, the lowered noise can really show what the clock can do for cleaning up transients, illuminating blur, spaciality/imaging and a very natural listening experience. J&K Ultra Transformers mounted in the silver enclosures on top of the Vega.
Also using two Ultra ISO stages for both the Uptone Audio USB Repeater and Antipodes Music Server.

Fantastic!

Rich

Main 240VAC Distribution Hub for front-end components

- Preamp
- DAC
- Music Server
- USB Regenerator
- Home Theater Processor

Fused 240VAC mains input into overbuilt J&K Audio-inspired DC blocker with fused 240VAC feeds to six external Ultra ISO balanced secondary Transformers for source components. Voltage (240V) display on front panel.
500W OCC wound 120VAC balanced secondary Ultra to three feeds for separate OCC wound Ultras for front-end analog circuits.
All power feeds to the system are now balanced.

Apologies for not posting that often. We are super busy with orders. 

J&K Audio Design

31/1/2018

OCC Transformers

Greetings J&K followers! 

Apologies for not posting for some time. Busy, busy, and busy... that's what's left in our life! 

We didn't intend to post but we can't resist to do so since we have to take some pictures for one of our customers locally. He had ordered a set of unique transformers for his preamp - OCC copper power transformers, OCC copper filament transformers, and OCC copper chokes! 

We have always been a producer of high quality transformers. We can't resist the opportunity to promote OCC based transformers! Most of the time, OCC are used only in speaker cables, interconnects and power cords, but why not transformers? 

For us, OCC output transformers are quite common. OCC power transformers and chokes are rare, although not uncommon actually. We've made quite a lot of OCC ultra isolation transformers and output transformers for a few customers based in U.S.A. 

What are the benefits of OCC based transformers? From electrical properties perspective, they have lower DCR compared to standard magnet wires - lower impedance. The insulation paint is a few magnitude better than the standard ones too - longer life! 

Based on our listening tests, and feedback from customers, are that OCC copper transformers have smoother highs, more extended in mid-low bass and more refined in mids + highs. In overall, they are well worth the money spent compared to spending them on power cords, interconnects or speaker cables IMHO. The length used in transformers alone would explain why the differences are more significant compared to exterior cables. If you are already using OCC cables, investing in OCC transformers are a must in order to fully exploit the goodness of OCC wires.

Post-script: We are starting to explore OCC silver cables. We have limited stock of OCC silver wires ordered for a customer. There should be some leftover that can be used for a limited range of transformers. For those that could not fit what we have, we are very sorry that we still need some time to stock up more OCC silver wires (raw OCC silver wires are ultra expensive. The finished OCC silver transformers will be pricey.). If you are interested in OCC silver wires made transformers, drop us a mail and we shall see if something can be made just for you. 

Till then!

We wish you a very Merry Christmas, and a Happy New Year! 

J&K Audio Design
12/20/2017

GM70 Amplifier Review

GM70 tube amplifier review (a short one).

Domnic uses full set of transformers from J&K Audio Design - the GM70 output transformer, separate power transformer for B+ and filament transformers. 

Enjoy the pictures - very nicely done!

Short and sweet comments from Domnic!

The hum & hissing are not related to the transformers but the design of the amplifier. After several emails between Domnic and us, this issue is fixed by adding some additional circuit to the amplifier. The amplifier is as quiet as the deep wide universe now, and he's a very happy camper!

Some GM70 amplifier internal picture for those more technical minded. A lot of audiophile components are used, such as Mundorf electrolytic capacitors, Jensen PIO coupling capacitors, Kiwame carbon composition resistors and of course, full set of J&K transformers.

Again, this is as honest as it can be - review from real user! No alteration of the customer posts have been made.

J&K Audio Design
11/3/2017