Nightshade Amplifier

Nightshade went for some matching test at a fellow audiophile place - with pretty high end gears before actual delivery happens.

Nightshade on Symposium clone - recommended.

Nightshade matched with Focus Audio

 Not a good match in terms of power but the sonic character is a good fit. If it can be made to produce higher power...

Nightshade is hidden behind the AudioNote Preamp

Now you see it, a temporary station for Nightshade.

Another view of the setup.

Nightshade mated with GEC U52 (original rectifier is German made Lorenze GZ32)

Nice glow from the GEC U52

Conclusion:
Do not expect Nightshade to do wonders by being able to drive the Focus floorstander fully but the sonic signature is really transparent, forward, detailed and revealing. At low volume, everything falls nicely into place, as what the Nightshade is meant for, night listening.

Nightshade can fully drive the Zu Soul Superfly but the highs come in too hot. Both components are more forward sounding and therefore the mid-highs are emphasized too much. Although so, the bass is impactful, taut and low. We can feel the sofa vibrating when there are low bass involved.

For those that like warmer character, it can be tamed further by selective parts for mellower sound. With the right partner, Nightshade should perform, and perform extremely well.

J&K Audio Design
12 May 2014

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* 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.

300B Amplifier Modifications

300B amplifier modifications turned 300B repair!

We've received a case from customer on upgrading his 300B SET - changing Alps Blue Velvet to stepped attenuator, change stock output transformer to Precision Wind Z11 OPT, and upgrade some of the components.

Upon opening the chassis, it turned out to be a nightmare! At the end, as the design was too bad, owner preferred to just repair the amplifier and sell it. Original funds will be used to build a brand new J&K 300B SET instead (Like!).

300B SET

Vintage GEC U52 Rectifier

Looks fine from far but is a nightmare!

This design is flawed. Putting the tuning factor, there are several design rules violated.

It uses capacitor input rectification but the 1st capacitor connected to the rectifier is at least 470uf x 2 in series, resulting a whopping 235uf for the GEC U52! Maximum value for capacitor input is 47uf - 60uf. Please say hello to the GEC U52 tube before it says bye bye.

DC is used for indirectly heated tubes - unnecessary. AC is fine and is dead quiet. AC sounds better too. Do not hide the design flaws by using DC filament supply. 300B filament supply is just using a bridge + 10,000uf capacitor - high ripple and bad for 300B filament longevity. Such DC supply does not sound good too.

Cheap source selector is used. Period.

Wrong design of how the 5692/6SN7 is connected. It uses only 1 triode from the double-triode but it is wired the same for both sockets. It should be alternated so that the tubes can be swapped to utilize the unused side of the double triode.

I better stop here before everybody stops buying this amplifier.

Trios that need to be changed as they leak and bloated - going to explode soon.

Change Blue Velvet to J&K precision matched stepped attenuator with SMT resistors for shortest signal path.

One of the cold solder joints (tonnes of them!) - touched and it just snapped off.

Original condition - coupling cap is mounted with double sided tape!

What kind of job is that - sticking the capacitor onto the chassis with a normal strength double sided tape? Crappy job!

Good parts are used but 1st modder workmanship is pure rubbish!

Original: wires are "glued" using solder onto the IEC socket. What sort of rubbish this is...

Parallel rectifier - bad design.

Bad design turned savior? 1 of the GEC U52 has already got 1 of its' filament burnt. It could still work since the rectifier is wired in parallel.

Bloated trios.

Left and right capacitors are leaky and bloated. Right capacitor still looks fine but it was changed too as it might have aged. Fresh capacitors are installed.

10th May 2014
J&K Audio Design

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* 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.

Order Delivery

It is going to be a busy Sunday...

Z11 filament choke x 2, Z11 power transformers x 2

Mini amorphous EI output transformers, 1:5 input transformers, Z11 ESS DAC power transformers

Z11 10H 400mA choke x 2, 300B QCAMOPT-L01 OPT, Z11 filament power transformer

Z11 Precision Wind A2 60mA 5K:1+1 output transformer, Z11 Precision Wind 300B output trans

J&K Audio Design
4th MAY 2014

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* 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.

Amorphous Choke

Special introduction - we have been shipping lots of amorphous C core chokes and got really good feedback on how much improvement they bring to our customers!

Prequel: 
What are the ways of upgrading your existing amplifier, other than playing with interconnects, speaker cables, platform isolation, and various other tweaks?

For DIY-ers, they would say - just change the components! That, to them, would bring more significant changes than playing with external factors. With the same amount of $$$ used on cables or other tweaks, DIY-ers can upgrade their amplifiers substantially, really substantially!

Nowadays, interconnects and power cords cost over USD$1K-5K easily. Imagine what can be done with the same amount of money! One can use all silver internal wiring, all Mundorf Silver/Gold capacitors, branded resistors, BlackGate capacitors, and any audiophile components one can possibly imagine. USD$5K can almost (very close) buy a pure silver output transformer already!

Changing capacitors, resistors, internal wiring, mechanical components and such are pretty common nowadays. Today, I'm going to introduce you another modifications that will bring substantial ROI to your amplifier:

AMORPHOUS CHOKE!

1. For amplifiers with only RC filter, add an amorphous choke!
• Produces lower voltage + current ripple, lesser heat (more efficient), lower partnering capacitance needed.
2. For amplifiers with normal choke, add an amorphous choke! 
• Better micro-dynamics, micro-details, better filtration, lower noise.
3. For amplifiers with DC filament supply, add an amorphous choke!
• Natural slow start, protect your tube filament for longer life.
• Others are same as above points #1 and #2.
4. For amplifiers with resistive load, add an amorphous plate/anode choke! 
• Higher efficiency - lower voltage drop.
• Better AC reactance (higher load, better linearity!
5. And many more! 

We have published only 1 size of DCAMC-M01 amorphous double C core choke but we can custom make other sizes too. Do let us know if you need other value chokes.

For USD$109 for an amorphous double C core choke, high ROI tweaks never come cheaper than this. Nowadays, even exotic capacitors can cost many times of such price. Now, start using more chokes in your amplifier design!

Some people talking about of amorphous chokes:

• DHTRob
• Jimmy Auw
• VT52 
• Tamura A-4006 

Amorphous Double C Core Choke (nickel steel alloy) – DCAMC-M01

This is made using 4 pieces of C-core per transformer, having 8 pieces altogether for a pair of high end amorphous double C core nickel steel alloy choke. The amorphous C core is very thin and extremely brittle. Please do not drop the transformer to prevent damage. Take precaution when installing the transformer.

• Available types: air-gapped choke (various sizes within core permit able values)
• Primary inductance: 8H
• Primary current: 300mA maximum
• Primary DCR: 70 Ohm
• Weight: 1.2KG per piece
• Size: 60mm x 75mm x 90mm

J&K Audio Design
3 MAY 2014

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* 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.

Nightshade Miniamp - 5687 GZ32

Nightshade Miniamp

5687 + GZ32

750~1000mW

RRP: RM4,500

Front View

Side view

Night view - 5687 is pretty bright!

Dim light view - still very nice!

High quality components!

Layout for shortest signal path and least interconnects!

• Certified made in Japan Z11 low noise power transformer
• Certified made in Japan Z11 power chokes x 2
• Certified made in Japan Z6 output transformer
• Tube rectified - GZ32
• Made in UK internal wiring - OFC
• Audiophile capacitors + resistors
• Kiwame, Holco, Dale, PRP, hand matched
• Elna, FT (Germany) capacitors
• No capacitors in signal path - direct coupled
• Simples topology - using 5687 as single/output tubes
• High quality gold plated ceramic tube sockets
• High quality 3mm turret boards 
• Solid, full Aluminum chassis, 3-5mm thickness overall
• Extended chassis support for absolute stability

J&K Audio Design
26 APR 2014

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* 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.

Nickel Ferrite Amorphous Output Transformer

Since I have more time this week, let me share some pictures of the 2 sets of poison that had gone to their new homes. :)

• 1st pair - 2.5K:8R/16R for 2A3, using L01 (oversided) quad C core, luxury stuff! 
• 2nd pair - 3.0/3.5K: 8R/16R for 300B, using L01 quad C core, tasteful!
• Both nickel ferrite amorphous cores!

Depending on the packaging material, a layer of foam added to the binding posts to protect the pins.

Wrapped in foam, protected by another layer of foam before going into the 1st box.

1st box goes into the 2nd box, with lots of foam protection.

Output transformer - pair 1 - Singapore

Output transformer - pair 2 - Singapore again!

J&K Audio Design
26 APR 2014

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* 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.