Western Electric transformers

Hi guys,

Merry Christmas and Happy New Year! 

We've an important announcement to make.

Western Electric cores are running low on the market. We're working on a customer order and got a shock. A lot of these cores are swooped by some vendors and make them to sub-par transformers - what a waste. As a result, these Western Electric cores are no longer abundant and choices are very limited. 

If you intend to use Western Electric cores to make transformers, please be quick and order soon. In future, we may need to buy those sub-par ready made transformers to obtain those nice Western Electric cores for rewinding to something much better.

We've made some in the past, as you can see below: 

http://jandkaudiodesign.blogspot.com/2016/01/western-electric-output-transformer.html
http://jandkaudiodesign.blogspot.com/2016/12/western-electric-we-618b.html
http://jandkaudiodesign.blogspot.com/2016/01/western-electric-transformers.html

There are still some original WE cores, untouched at decent price. Make a move quick before it is gone. The WE1048 that used previously are no longer available at our previous source. What a sad news! 

Apologies to break such a news at such time, but I think it is a good news that we discover it early. Else, it will be as rare as the 1950's - 1960's WE 300B tube. 

25/12/2018
J&K Audio Design

Transformers repair

Repair transformers? Call us trans repair king! I think hundreds, if not thousands of transformers have gone through our hands over the years. 

We are very happy to hear that our customer's McIntosh amp are repaired. Well, this is just one of the message we get, there are many more that we're just too busy to post. 

We can learn the transformer winding method from others, and we help to restore the damage equipment - saving mother Earth from being overwhelmed with more electronics junk! 

Nobody (or very less, LOL) repairs transformers like us. We'll unwind EVERY unit received and record down all the data about the transformers so that we can rewind it back exactly, according to the original materials, if can be found. 

Your transformers will get a new lease of life for another few centuries as long as it is working in the original designed conditions. 

Repaired transformers get a 1 year warranty. Conditions apply, such as, as long as is not abused, or placed in a faulty amplifiers (well, that could be what caused it to burn initially, right?). 

Tips: it is very important to keep the original core of the transformers. Once it's gone, it's gone. That's the most important component in repairing transformers. We recommend to reuse the original core to get back the original sound signature of the transformer. 

Now, get your damaged transformers here! McIntosh, Marantz, Scott, Dynaco, AudioNote, any transformers, as long as they are not burnt to ashes, we can repair it. Satisfaction guaranteed! 

J&K Audio Design
22/12/2018 

Alternative payment option

Dear all,

We've found a way to save customers expensive PP transaction fees of 4.5%-5%. 

Contact us and we shall inform you how to do so during purchase!

2/11/2018
J&K Audio Design

50 Tube

Type 50 Tube

For those that plays with DHT (direct heated triode), type 50 tube tube should not be a stranger to them - either a love or hate situation. They love it for the tone and character, but hate it for the scarcity of getting NOS (new old stock) tubes. They are getting rarer everyday, and price is quite hefty for such a low power tube - definitely a collector's item. 

No doubt, it is an interesting tube though, with many variations of the type 50 tubes, that I can't even comprehend all. These are the main old types and there may be more: 450 globe, 350 globe, 250 globe, 50 ST19, and 50 ST16. It is said to have a type 50 globe with mesh plate that I have not seen of myself, with heavenly sound some claimed.  

There are some new type 50 being manufactured due to the popularity of such tubes, such as Shuguang SG-50, Shuguang SG-60, EML 50, ER 50, Psvane globe mesh 50, Psvanwe WR50 and some that I may not even be aware of. 

I would suggest new users to just go with new tubes. Old tubes are quite hard to match and those that comes within the same date code, matching Gm, matching gain, matching internal structure, are almost impossible to come by, unless one is willing to pay an arm + a leg for them. 

The Shuguang SG-50 will be cheap as a test rig and casual listening tube to own. The EML 50 is ~$750/pair, oops. The EML 50 does have higher plate dissipation at 28W and can be pumped up to 6W output with a 4.1K OPT. 

Below are some pictures of the type 50 tubes. 

Shuguang type 50 with mesh plate

Type 50 ST19 - old stock

If you look at the picture of the type 50 ST19 above, you will see that there is some darkened patch on top of the tube, quite near the vent to the filament/plate cavity. I've seen quite some type 50 tubes having the same black patches. Some say that it is some sign of use and/or abuse but I cannot confirm that yet. Maybe someone with more knowledge can enlighten all of us via comments tab below.  

Type 50 Globe - old stock

Tips: If you have (lucky you) and use a type 50 globe on your amp - consider lowering the actual operating voltage as compared to the datasheet to prolong the tube life. 

Below is the snippet of the type 50 operating conditions and characteristics. It's somewhere in between type 2A3 and 300B, with a maximum power of 4.6W when driven to the max. I wouldn't mind if I'm using some cheap type 50 clones, but definitely not for the NOS tubes. 

Somewhere at 400Vp with 55mA plate current would be something I'm more comfortable with or maybe even slightly lower at 400Vp and 50mA to get 20W plate dissipation, for longevity of the type 50 tubes. Hey, they are very rare, mind you! 

Type 50 tube datasheet

One of the very important application note of this type 50 tube is the grid leak resistance value. It must not exceed 10K Ohm. That leads to either grid choke, or interstage coupling, where latter is what would prefer for the uncompressed sound. A 10K grid leak resistor is possible too but that is rather a waste considering the price and rarity of the tube, blasphemy! 

Filament voltage is 7.5A 1.25A - for those that like AC heating, please stay away. For acceptable hum level, DC filament heating is a must to get it to acceptable level low enough for enjoyment. Exotic high frequency AC heating might work, but I've not tried that personally. 

I did not personally built a full set yet for this type 50 tube, but just a test rig, built on a piece of wood (LOL!) with a level 1 5K output transformer, powered with some parts that I dug out from my stash of components. The pre/driver tube was a 5687 RC coupled 5687, with some cheapo diode bridge rectification and some FT caps. B+ is 470Vdc with cathode bias and -70V of grid voltage. With the few variations of type 50 tubes I have on hand, all seem to fall to the bias quite closely on the very same circuit. 

Even with that, the body, harmonics and tonality stands out from all the other tubes I've built with. 

A fully built version will come soon, when I have more time on hand, or when there is a order for it being placed. Well, in actual fact, there is one set to be built for a local audiophile, but the build date has yet to be confirmed due to busy schedule.

Meanwhile, enjoy life, and then get back to work again! 
17/10/2018
J&K Audio Design

General transformer problems

General transformer problems?

Temperature is too high

- Short circuit in the winding, at primary or secondary. Once shorted, the current will be high and cause rise in temperature. If this continues, not only the insulation layers will be burnt, and the adjacent winding will be burnt due to high temperature, and the vicious circles continues, until the whole transformer is burnt. This high temperature happens whether it is loaded or unloaded. The only fix is to remove the bobbin and remove and replace the burnt winding(s), or all altogether.

- High temperature may happen at small transformers and goes un-noticed, where there are a lot of turns in a single winding. If the adjacent magnet wire got short-circuited, since the voltage is low, wires are long and thin, the temperature may not reach the exterior, but it will not work for long. 

Note: When there are shorts in the transformer, the no-load current will be higher than normal.

- Magnetic flux density (B) set too high - especially when using unknown transformer core/lamination. If B is set too high, causing the turns to be lesser than ideal. With reduced primary turns, the no load current will be too high, causing increase of transformer temperature. Even if secondary are unloaded, the transformer temperature will rise high. If you reduce the primary voltage up to a certain point, the temperature will be at normal temp, for such kind of transformers.

- Overloaded transformer - self explanatory

- Magnet wire is too thin - high DCR causing more power dissipated at the wires.


Electrocute feeling when touching the core

- If one touches the core and feels a slight tingle or eletrocute feeling, this is due to parasitic capacitance between the winding and core. You can measure a certain Vac value on the core with respect to ground. This may be resolved by adding grounding to the core or mount it at a grounded plate.

Magnetic flux leakage is high - causing noise

-When powered on, the field generated by the winding should follow the path formed by the core, and should have low magnetic path resistance, to enable a high efficiency transformer. Due to various reasons, if the path is not smooth, leakage form where magnetic flux to goes through the air instead (magnetic flux leakage). That could happen to uneven surface between the cores (gap), or cores not tighten enough with the E/I lamination, or the air-gap laminate is too thick, and various other reasons.

- If the transformer works alone, the impact is not much and may not be noticeable. If it is mounted in jam-packed equipment with lots of sensitive electronics, the magnet flux leakage will be detrimental, causing AC hum to the adjacent components (therefore, giving EI transformer a bad name). 

- To check for magnetic flux leakage, one can wind a 200-300 turns of wire on an iron nail, connecting it to a high impedance sensitive headphone, and move this to a powered transformer with magnetic flux leakage, and see if there are audible hum generated in the headphone. 

- To avoid this, the lamination must be even so that the interface is as close as possible. This is even more important when using refurbished cores. It has to be clean enough and polished to ensure the closest interface. OTOH, transformer designer should not design it close to the maximum magnetic flux density. Also, the copper band will come in handy to prevent such leakage from affecting the environment. Distance may help too since the density drops as it moves further away from the transformer. 

Noise when powered

- Ringing / hum when powered - this could be due to loose lamination. Lamination could get loose in many ways - abuse, drops, not tightened enough, and etc. Low grade core with un-eveness in the cores (not flat enough).

- Short circuit in the transformer, where there is high current flowing., causing the lamination to rattle, and heate up. 

- Misaligned lamination - you can see the un-eveness alignment of the lamination when the whole transformer is constructed. Such zig-zag lamination will cause noise. This should be easy to see externally. 

So, you have been empowered now with the knowledge to know the general transformer problems. Choose wisely. 

8/5/2018
J&K Audio Design

Transformer selections for isolation transformer

We've seen some fully built isolation transformers appearing on the net that is quite close to what we're offering. I guess, imitation is a kind of artless! We'd like to emphasize: get only the originals, for peace of mind, for quality, and most importantly for excellent sound (pun intended)!

What's the recommended isolation transformer for my application? We've replied this question for countless times. Therefore, it is time for a post! 

Q&As:

High power SS amplifiers, home theater amplifiers (>200W class AB, or >40W class A)
* Do not use isolation transformers unless necessary, where you are having noise, sibilance and over-voltage issue that requires some step-down.
* Isolation transformers that you can consider using are toroid (for the size / efficiency 

Lower power SS amplifiers, all tube amplifiers
* EI isolation transformers, or Ultra isolation transformers (quieter, cleaner, better!)

Sources, such as CDP, DAC, preamp
* EI Ultra isolation transformers (highly recommended), standard isolation transformers 

Toroid vs EI
* Toroid has better efficiency and therefore is more suitable for high power applications. But, toroid has higher bandwidth and therefore is not a good filter / isolation device. Toroid has more noise that leaks through primary / secondary compared to EI.
* Most importantly, EI sounds warmer, cleaner, better bass definition, less sibilance, and better body when compared to toroid. EI is the one to use if the power required is not extremely high. 
* Toroid has lesser radiated magnetic field compared to EI and may be acceptable to use un-potted but once EI is potted in metal case or have comprehensive copper bands , it will have similar behavior on radiated noise.

Grades of cores
* For toroid, we only use the highest grade silicon steel toroid core from Japan, that is only available up to 3.5KVA for now. 
* There are lower grades toroid cores with higher VA out in the market that are less efficient and have high mechanical hum. We don't use them. 
* For EI, there are several types available too. We only use Z9 for higher end units (lesser loss, runs cooler, sounds better), and Z11 for standard units (still pretty high end compared to others out there).
* The H-grade EI cores are much lower end and we try not to use them unless budget is really a concern. 

Potted vs un-potted
* Definitely potted if possible 
* Potting dissipates heat better, is mechanically damped, protects the transformer from moist/rust, avoids misalignment of the cores (EI) from abuse, and etc

Input and output taps
* If step-up or step-down is required, multiple input/primaries can be made and users can select them based on incoming mains condition
* Secondary can be multi-tapped too but is not recommended. Try with only multi-tap primaries first, such as 250-240-230-0 or 120-110-100-0 (and etc combos) to tailor to various input mains levels. 
* Secondary is recommended to be configured as balanced, aka balanced-power, such as 120-0-120 for 240Vac, or 65-0-65 for 110Vac, and so forth.

Multiple isolated outputs
* Instead of all equipment sharing the secondary and cross-pollute one another, we can build isolated secondaries in a single isolation transformer so that one can still enjoy the benefits without paying too much for dedicated isolation transformer per equipment
* Secondaries can be of multiple similar or different voltages, similar VA or different VA, balance or un-balance power (there is a limit of how many secondaries are available, try to keep to 20 taps total). 
* Extreme example is as follow
-- Primary: 250-240-230-0, 2KVA total
-- Sec1: 120-0-120, 500VA (for 240Vac for British gears)
-- Sec2: 65-0-65, 500VA (for 110Vac USA gears)
-- Sec3: 110-0-110, 500VA (for 220Vac China gears)
-- Sec4: 50-0-50, 500VA (for 100Vac Japan gears)

Standard isolation versus Ultra isolation
* Ultra isolation transformers have multitudes better noise isolation properties than standard isolation transformers 
* Ultra isolation transformers size is ~2x of standard isolation transformer to fit all the additional secret sauce and is 50-80% more expensive


Magnet wire options
* OFC (standard)
* OCC Copper (recommended for high end gears and golden ears)
* OCC Silver (for millionaires and billionaires)

Outputs
* Wire/lead out with OFC
* Wire/lead out with OCC copper or OCC silver
* Wire/lead out with original magnet wire (not for small transformers with thin wires)
* Solder tags (be warned to not over-solder, or use too high power soldering irons)
* Binding posts 

Sizing or over-sizing isolation transformers (important)
* We are already oversizing the core for cooler operation and better sound, if you want further oversizing, please inform us.
* If is oversized, output voltage may be much higher when lightly or un-loaded 
* Inform us the estimated usage so that we can custom to reduce the output voltage (ex: rated voltage at 50% load or 25% load) - VERY IMPORTANT
* Over-voltage due to light load will burn your equipment, be warned! 
* We have often seen buyers of on-the-shelf isolation transformers to suffer from over-voltage issues since the on-the-shelf isolation transformers VA are higher than needed/used.
* Multi-tap primary may help to reduce the output voltage too, such as connecting the incoming mains of 240Vac to 260Vac input tap of the transformer will effectively lowers the output voltage. 

DC Blockers
* Highly recommended for toroid isolation transformers, and recommended for EI isolation transformers
* Removes DC from the mains, transformers run cooler and have less noise electrically and mechanically
* Price varies depending on the components used, long life electrolytic capacitors are recommended since these caps pass current constantly when equipment is switched on - do not skimp here 


Soft-start
* Not required for EI isolation transformers or toroid isolation transformers with <500VA capacity.
* Recommended for toroid isolation transformers >500VA 

EMI/RFI filter modules
* Optional, may be good or bad, very system dependent, add at your own risk
* Can be placed at input or output of isolation transformers
* Results will be 50-50 (option, have dual secondaries, one with and one without) 


Due to the higher grades of core being used, prices to produce these isolation transformers are higher compared to those out there. Don't use industrial grade core products to compare to ours! Low-ballers, please save your energy.

8/5/2018
J&K Audio Design

J&K OCC Silver Input Transformer Review

Nothing is more satisfying than receiving good feedback from our customer(s)! Thank you Kris for your post!

The product in the post is a pair of Level 3 OCC Silver Input transformer, specially made for un-balance to balance conversion.  

Actual paying user review is always more realistic than "paid" reviews on magazines.

Till then, continue to enjoy music!

8/5/2018

J&K Audio Design

Super Hi-B EI Output Transformers

Good day folks! We have been quite quiet these days on the blog, but we aren’t dead!

Things are moving at a very fast pace at the background to fulfil all the orders. Apologies if your orders take such a long time. Lead time is long to maintain the quality of the products. If you are in a rush, please submit your orders early, or go somewhere else please if you’d like to rush things. I’m sorry we cannot take rushed orders. Thank you for your patience in advance, and your support all these years. We cannot make it that far without all your love and blessings on our products!

For those that prefers more frequent updates, they can visit our Facebook page where we frequently post about our product news, and interesting HIFI related topics. We welcome your emails to discuss about anything related to HIFI or audio transformers with us. We are open to partnerships or ODM for your equipment needs. Just drop us a mail.

For this round, we would like to introduce you guys to our Super Hi-B EI core. I believe all would be familiar with the EI Z11 core used all over our standard offerings, which is considered quite high quality compared to the lower H cores used elsewhere. The Super Hi-B EI core is even better.

The Super Hi-B EI core have higher permeability and lower core loss (~35% lower than EI Z11). Super Hi-B EI core loss is only ~0.92W/KG (versus ~1.25W/KG for EI Z11)! We have been experimenting on using this core on the most commonly used 300B output transformer and got excellent results. Based on all similar design parameters, with just the difference on the core material, Super Hi-B EI versus EI Z11, the Super Hi-B EI core boasts 20% higher primary inductance compared to EI Z11. This has opened a door for a better output transformer design!

With the lower core loss and higher inductance generated with the Super Hi-B EI core, we can notice obvious improvement on the output transformers. The low frequency, in terms of linearity, extension and quantity, are so much better with the Super Hi-B EI core compared to EI Z11 version. The control and grip on the speakers are much stronger, and therefore you can “feel” that the power is higher. There are some improvement on clarity and transparency too, possibly due to the lower loss of the core, and the different design approach we take for this core since consideration or compensation for higher primary inductance is lesser in some degree.

A lot of tube amplifier users feel that the low frequency fidelity for tubes are not good and deep enough. They should try to listen to this version with Super Hi-B EI core. We can easily get low frequency response of 10Hz @-1dB, and more if the users have special request.

The EI core size profile is quite complete for this Super Hi-B EI core compared to the C core version that is limited in sizes, and therefore there are more flexibility in terms of the VA or capacity, and the ease of more deeper customizations. Super Hi-B EI core has size of EI 66, 76, 86, 96, 105, 114 and 133.

And yes, to answer some extreme customers, that these cores can be used as power transformers or chokes too. And yes again too, for even more exotic users, we can pair this with OCC Copper or OCC Silver wires, to make the ultimate output transformer for your project.

Send in your orders now, and be amazed with the renewed life of your tube amplifiers! Apologies on all words article – the EI core all looks the same. There is nothing much to see, but it is much to hear!

J&K Audio Design

27/7/2018

SIT Amplifier with 2SK180

Below is an interesting amplifier design from M. Rothacher.

It uses SIT (Static Induction Transistor). SIT characteristics is quite close to vacuum tube Triode. Based on many user's feedback online is that SIT sounds quite close to Triodes! 

SIT, THF-51S, 2SK180, 2SK180ES and such are very high power devices with PD of ~400-1KW. Say we take 15% as efficiency of class A amplification, we can easily get 60W - 150W out of SIT! This is definitely more economical and simpler than to draw 50W out of a 212 tube. 

A level 1 OPT, tailored for this above application
- Z11 - U$490/pair, Z9 - U$590/pair.
- Pri: 250 Ohm (configurable), inductance ~1H 
- Pri DC: 1A (others are available) 
- Second: 0-4-8-16R (any)
- Output power: 70W

Some samples bias settings (not tested):

A sample circuit from Nelson Pass, in his SIT Nemesis article: 

This looks alike to a normal SPUD circuit and is simple enough for DIYers with experience on building tube amplifiers. 

It would be quite interesting and ear opening to try out such designs.

J&K Audio Design
21/6/2018 

Miller Effect on Resistive Attenuator

Have you ever wondered, why TVC, or AVC are much better sounding that resistive attenuator, or resistive volume pot? 

The answer(s) to why transformer / autoformer based volume control is better than resistive volume pots, is quite complex, as there are many factors to it. But, one that stands out, that many may not be aware of, is the Miller capacitance + volume pot effect, that caused the amplifier bandwidth to be reduced significantly when used with a resistive attenuator, or resistive volume pot. This is especially significant if a high value volume pot is used, such as 100K-250K pot.

Everyone knows about Miller capacitance, and why grid stoppers are required, right? But, is he aware that volume pot is part of grid stopper too?

The resistance from the pot has the same effect as a grid stopper (The resistance, starting from input of source, to the volume pot viper section,  is part of the grid stopper!), creating a RC low pass filter with the input capacitance of the tube connecting to the volume pot. This RC low pass filter will attenuate any content above the cut-off frequency. 

The cut-off will be worsen by higher gain tube as the Miller capacitance is multiplied by the gain, in simple calculation sense, a good example, will be 12AX7. (Could it be the same reason where some prefers lower gain tubes in their amplifier instead of a high gain ones?)

Take 12AX7 as an example, the Cin (Miller capacitance) will be ~200pf, give a  take a few or tens of pf. 

Say, with 100K Ohm resistive volume pot, the setting now is at mid point of 50K, indicating that there's a 50K+ "effective grid stopper" connected to 12AX7. Ignore the actual grid-stopper connected for the moment. With that, the resultant cut-off shall be:

f cut-off = 1 / (2 * pi * Rg * C) = 1 / (2*3.142*50,000*200pf) = 16kHz (!!!) 

That's a freaking 16kHz low pass RC filter in the amplifier without one even realizing it. That is sad...

That's why a lot of folks prefer TVC or AVC versus resistive volume pot. That's why most people will say that the realism is better, the highs are airier and with more body once they migrated to TVC or AVC. Once they tried TVC or AVC, they will never go back to resistive volume pot.

Till then. Go figure.

J&K Audio Design
6/11/2018

J&K Audio Design Facebook Page

For those that wonder why there isn't much activities in the blog, we apologies for not having to much time to write now. We will, but just not as frequent.

Still, we will find some short intervals between here and there to publish a few pictures or posts on our Facebook page. For those that have not followed us there, or liked our Facebook page, it is time to do so now to keep yourself updated on the latest development, and have some real time interactions there. 

It will be fun. See you there!

https://www.facebook.com/groups/jnkaudiodesign/

J&K Audio Design
6/11/2018

Fully Built Transformer Volume Control

Fully Built Transformer Volume Control - would anyone be interested?

We REALLY hesitated on introducing a fully built transformer volume control due to the amount of manual labor required to solder the TVC to the step-switch. One unit of fully built stereo Transformer Volume Control takes 5-8 hours to solder!

Due to the overwhelming response from readers asking for a fully built TVC as not many are trained on soldering and building audio kits, we are introducing this, for a limited time, for a limited quantity, for batches order only so that we can keep the quality in control. 

Also, we think that Transformer Volume Control is something that an audiophile must own as the improvement in sound is just substantial over the price paid (very high cost / performance ratio), we are doing a limited time promotion on standard configuration standard TVC to keep the cost of making them down. 

Standard standalone 24-step TVC - U$590/pair (RM-2350) (special batch order price only)
* 24-step, potted with turrets
* Hi-B core only (others - will be normal price) 
* Primary 600 Ohm, secondary: 600 Ohm

Note: It will be built in a batch of >=5 sets. You can order 5 sets or more, or wait for 5 sets to be accumulated before build starts. If you order >=5 sets, you can customize it slightly, please email for details.

Fully built stereo unit - U$990/unit (RM-3950) (special batch order price only) 
* built with standard 24-step TVC above
* full aluminum chassis
* 24 step attenuator switch 
* double-screw chassis 
* input grounded, or output grounded, or floating (need to ground at chassis)
* single set of stereo input and stereo output

Note: It will be built in a batch of >=5 sets. You can order 5 sets or more, or wait for 5 sets to be accumulated before build starts. If you order >=5 sets, you can customize the parts used (some at extra cost), please email for details.

Sample fully built TVC is as follow: 
* outlook and materials may change depending on parts availability

TVC - fully built

23 step TVC only (shown is 33-step as sample only)

Silver Plated OFC wiring

33-step version shown as sample only

Made in Taiwan 24-step switch

What's the difference between this and the custom made version? Custom made (more expensive) version offers superior cores - NanoCrystalline (aka Finemet), Permalloy and Amorphous, and is customisable (different primary/secondary impedance, different step-up/down ratios, configurable and etc), different grade of wires, solder, and etc. Sound quality wise, custom made version is a grade higher too (that justifies the price!). 

Still, this standard version is excellent sounding - with extended frequency range, solid vocals/body and clarity! The difference between TVC and resistive stepped attenuator is easily differentiated even by non-audiophiles! You owe yourself to own it, trust us!

Till then, grab hold of this opportunity to get yourself a fully built TVC, or a raw Transformer Volume Control, for your long awaited birthday present, Christmas present, 1st draw pay gift to yourself, wedding anniversary present, and(or whatever reasons you can cook up)!  

While it lasts... don't regret after promotion is over, or before we regret it.

J&K Audio Design
4/21/2018

J&K DAC Review

J&K Audio Design DAC Review - submitted by customer. 

OCTOdac: Fidelity and Musicality Beyond Sound.

Two years in the making, from design to sourcing and subsequently the final built, the entire journey was a huge learning curve and also one filled with utmost satisfaction. Credits to J&K for bearing and taking the journey with me.

Listening: Round One - First Impression

It was flat and dull!... Seriously! With all the additional caps in the DAC unit, it does sound like a punctured tyre trying hard to complete the journey while waiting to be inflated back in shape. Not forgetting the tubes were NOS dating back to the 30s and 40s.  Well, that was the first impression. It did not take long for the DAC to gradually open up and reveal herself. After warming up probably for about 2 hours, the character of design became more apparent. Clean, dark, transient, deep, wide and warm. If I were to put them into simple words, that would be it.  Sonically,  if there’s such words it would be musical neutral yet analoguely warm. Why I didn’t mention accuracy? That in my humble opinion is subjective to the overall setup, room acoustic and head knowledge of the audiophile. One man’s meat, may be another’s poison. A Concert Grand Piano will definitely sound different from a Full Upright Piano… let’s not go down that dark dark alley of audio apocalypse. For mention’s sake…. The design and backbone of this DAC is capable of processing the difference. Everything falls back on the listener.

Listening: Round Two – Width and Depth

Fast forward one week later, after daily non-stop playback of 10 – 12 hours, the full blossom of the DAC is at full bloom. Sonic control was just enough, not like the army general howling battle cries, but enough to keep the darling at arm’s length. Stage depth and width was and still is, beyond walls. Keeping things in perspective, the speaker fades and the band / orchestra / ensemble takes center stage. Dynamics were fast and attacks were strong yet gentle to the ear. Guitar rifts up and down the frets keeps the listener on the edge of our toes, anticipating the next bar or expressive fingerpicking. Attacks of the Flamenco accompanied by the shoe taps of the tap dancer reverbs across the room.

Listening: Round Three – Instrumentals

Electronic sounds like techno and new age were less defined as this DAC was designed with NOS in mind. Old School sound with a touch of new component technology. The thumb of the techno bass and electronic drum were less engaging. Head bangers will find this very upsetting. Though it raises some hair, it doesn’t thump the heart to a point of cardiac arrest. Moving down the spectrum, Rock, Soul, R&B audiophiles will not find any lacking in this. The depth of the bass, tightness of the drum skin and mood of the R&B and Soul are felt across the spectrum. Nothing is short changed during playback. Going further down the stream to acoustic instruments is where this DAC shines! Though only decoding at 20-bits, no details are spared. Starting with the Quattro bass, each slap, slide, pop, bend and vibrato is clearly audible. Brass instruments are bright and zingy. Woodwind blows mellow and sweet. Strings are majestic and swift, each pull of the bow is well defined and expressive. It truly takes a lot out from a DAC to realistically reproduce the sound of a live quartet or orchestra performing in front of the listener. I would say OCTOdac holds up pretty well. Of course system matching and room acoustic also comes into play and both are equally important.

Listening – Round Four (Vocals)

The separation job done by the DAC was superb! Be it in a choir, solo or acapella, the vocals are spot on. Emotions are positively passed on to the listener. Vocal expressions are represented in a way that will keep you anticipating on what will come next. Layers of sound are clearly defined. Vocals lean toward the neutral side. Not excessively warm, neither is it freezing cold. Dim the lights, sit back and crank up the volume. Indeed a hair-raising experience, bordering the fine line of being horrifically silent. Probably Chucky lurking round the corner of the room.

Design

The OCTOdac was fully custom designed with flexibility and future upgrades in mind. The Processing (DAC) Module is truly modular and hot swappable. In the event I would like to have a more vocal centric sound, I can simply build another DAC and swap with my current PCM1702. Satisfying my incurable itch for symmetry, the GainStage was build and design to match my current monobloc amplifier.

DAC configuration & description

Processing (DAC) Stage

Inputs: Fully dedicated S/PDIF and Digital Coaxial.

Output: Single-ended (RCA) analogue outputs.

Convertor: Dual Mono BurrBrown PCM1702 20-bit

Digital Power Trans:  EI - Z11 (Level 2)

Analogue Power Trans: Super Hi-B Dual Core (Level 3)

Gain Stage (monobloc units)

Tube Compliments: 6J5 (driver) , RGN1064 / #1805 (rectifier).

Super Hi-B Dual Core Tube B+ Power Supply

Tube Output Trans: Western Electric Core 15K – 600

Tube B+ Choke: Western Electric Core

Conclusion

The OCTOdac filled the missing piece in my audiophile quest. Truly a bang for buck, value for money and fully customized piece of gem. It doesn’t just bring you music, it carries along with it the joy and emotions of sound. Adequately defining the true meaning of Fidelity and Musicality Beyond Sound.

ED8000 tube amplifier schematic

When I'm talking about NOS Telefunken tube amplifier, it gets me excited and makes me sleepless! 

For those that are unaware of the previous article, please visit:  
http://jandkaudiodesign.blogspot.my/2018/03/ed8000-tube-amplifier.html

Here goes revision 1 of our proposed ED8000 tube amplifier design. There are tonnes of methods to build ED8000 tube amplifier. Below ED8000 tube amplifier schematic is just one of them, a simple one in fact. It needs only 1pc of 5687 to drive both Left and Right channels, with the use of 1:2 step-up input transformer to provide sufficient gain to drive ED8000 tube to full power.

P/S: circuit has not been tested yet, further fine tuning may be required.

Other than the usage of 1:2 input transformer, there is the innovative use of a 200H plate choke for 5687 as load to keep the B+ low to match the B+ of ED8000, where B+ is quite low compare to other tube amplifiers such as 2A3 or 300B. If resistive load is used for 5687, then the Vplate of 5687 needs to be lower so that the B+ needed does not exceed 177V. 

Or, use interstage transformer! With interstage transformer, ED8000 grid leak resistor can be removed, together with the coupling capacitor, which is an even more elegant and better sounding design. Of course, interstage transformer comes with a slightly heftier price tag.

All the components for the ED8000 single ended tube amplifier schematic are carefully calculated for the best effects and are not simply plugged from the sky. If you copy the design, please do not change the values of the components used. If you change it, and it does not sound good, blame yourself! LOL. 

The B+ can be slightly tuned by adding a small capacitor of 0.1U - 0.68U after 5U4 rectifier tube rectifier. This converts the choke-input rectification to pseudo capacitor-input, and raise the B+ slightly.

If you build it and like it, let us know! If you need the irons, let us know too! If you see errors in the design, let us know. It was designed in a matter of minutes.

Enjoy!

J&K Audio Design
11/3/2018

ED8000 Tube Amplifier

Let's talk about a slightly different topic today, ED8000 tube and how to use ED8000 in Single Ended Amplifier! 



Little has been said about this tube in the internet. We've Google and didn't find much articles on ED8000 in tube amplifiers. This tube often appears in eBay at very decent price still, considering it is a Telefunken tube (perhaps audiophiles do not like it since it is supposed to be a series/pass regulator tube). Most are German made (Valvo, Telefunken and Siemens) and price are quite decent too, around U$10 - 50/pc, depend on whether it is NOS or used. We suspect all of them are from Telefunken factory (anyone can confirm?).


Datasheet:
http://tdsl.duncanamps.com/pdf/ed8000.pdf

Why do we like this ED8000 tube? There are a few reasons! 

1. We love Telefunken tubes. Most sound good, and very reliable.
2. It is a long life tube, guaranteed for 10,000 hours operation.
3. Tight tolerances grade (Telefunken tubes are known to have tight tolerances even for the general type).
4. Special grade vibration and shock proof tubes.
5. High transconductance and low Rp (easy to make the output transformers). 
6. It is a TRIODE! 



If the circuit is made right, we can actually make an ED8000 tube amplifier that is compatible with 6AS7 / 6080 tube! 6AS7 / 6080 SET, to some, are poor man's 300B amplifier. Their Rp, operating point, output transformers and other electrical parameters are close enough to be made compatible. Do no try this at home! Only special made amplifiers can do this.

Looking at the ED8000 tube Ia/Ua curve, with Pa =17W, the tube can be biased at 140V plate, 100mA Iplate, and -26V Vgrid. That gives Pd = 82%, which is near the 75% ball park, which is the usual values that one would bias their tubes for class A operation. Since this is a special quality tube, I do not mind biasing it hotter to get more power out of this. 



With such bias, ED8000 needs only 52Vpp to bring it to full power. A simple 2 stage driver will be sufficient, such as 6SN7-6SN7, or 5687-5687. If one employs a step-up interstage transformer of 1:2 (recommended), single driver tube will be enough. Or, go for a higher gain driver tubes, for example: 5842 / 417A, EC8010, E55L / 8233, 6SL7, 12AX7 and similar tubes. Low Rp tube are recommended though to have better bandwidth.

Output power of ED8000 single ended amplifier will be around 3W-4W, depending on what distortion figure you are looking at. It is a poor man's 2A3 SET. ED8000 is priced like a Chinese 2A3 replicas, and you get old school Telefunken quality (sound!)! This is definitely worth considering.

With high quality OPT (from us of course, LOL!) to go with (not difficult to make since primary impedance is only ~1K Ohm, no complex winding scheme is required), it should be awesome. Did I mention that it can be a good headphone driver too?

Important note: with high transconductance tubes such as ED8000, cathode bias is recommended to prevent runaway. I would use a CCS at the cathode to keep it locked in place. 

Now, go build it and let us know how it goes! Let us know if you need the transformers to go with this wonderful ED8000 tube. We can supply a whole kit to you.

J&K Audio Design
10/3/2018