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Thursday, March 29, 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.

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

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.

Saturday, March 10, 2018

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:

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.


J&K Audio Design

ED8000 Tube Amplifier

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