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Friday, July 24, 2015

212 Output Transformer Review

We just love feedback, especially from real users, especially the good ones. LOL. Below is the link to our 212 output transformer introduction and measurements.

212 Output Transformer

These below are comments and pictures from the initial testing of our customer from Thailand. They are really dedicated to this hobby and we respect such passion for audio! 

More to come when he finally installs it into a proper 212 machine. This is just the preview! Some really, really high end stuff are in the room - it is a multi-million dollar setup, no kidding.

J&K replacing the stock Tango S2108 OPT

J&K Audio Design OPT in action

Initial user comments

J&K Audio Design

Friday, July 10, 2015

212 Output Transformer

Output transformer for 212 tube. If you are a fan of high power class A single ended direct heated Triode, then you should take a look at this tube - 212. It has a plate dissipation of 275 Watts! Say if we go with 20% efficiency of class A Triode designs, we are looking at a staggering 50W output power!

Western Electric 212E

If you cannot find Western Electric or STC 212 tubes, worry not! Psvane has come up with a replica and is rumored to be as good as it gets! 

Psvane 212

This tube has been featured in a HK magazine - read about it here.

We have received an order for Level 3 Nanocrystalline double C core output transformer for this tube and therefore we'd like to share the results with our followers as well. It is a 22KG pair of state of the art output transformers! For those that knows output transformer design, they would have understand how difficult it is to design a big size wide bandwidth output transformer as the parameters actually work against the results.


·         Nanocrystalline double C core
·         Output power: 70W (20Hz)
·         Measured frequency response
o    20Hz (-0.23dB) – 1kHz (0dB) – 20kHz (-0.41dB), 8 Ohm, 1W
o    Full bandwidth: 5Hz – 70kHz -3dB
·         Primary impedance: 5KΩsecondary: 0-6-8Ω
·         Primary DCR: 130.1Ω 130.2Ω)(B-P26℃)
·         Secondary DCR: 0-6Ω tap - 0.27Ω,0-8Ω tap - 0.31Ω
·         Primary inductance 28.9H28.1)(measured at primary current 150mA20Hz5Vrms
·         Primary current: 280mA (maximum), recommended optimal at 150mA
·         Efficiency0-6>93%),0-8>93%

Measurement condition: Shuguang 845 x2 (parallel), plate voltage 1000V, plate current 150mAfixed bias, and secondary 0-8Ωtap connected 8Ω, power at 1W.

Matching results:  
·        Primary DCR <2%0.2Ω)
·        Primary inductance <5%0.9H

212 Output Transformer Frequency Response
This pair is a very decent price of U$1300.

J&K Audio Design

Saturday, June 6, 2015

Wavac PRT1 Tube Roll

We're helping a friend with a set of very high end audio gears to fine tune is system for better performance. His system consist of full set of Wavac amplification gears and Acapella Campanile speakers (huge)! 

The sound was rather noisy and the imaging was messy and rather veiled. Bass was bloated and could not dive as long as it could. A lot of steps had been taken and it brought significant improvements. Still, there were something wrong with the setup. It did not sound that "high end" considering the price paid for the system (>U$200K we think).

Since the Wavac PRT1 never had its' tubes changed, we decided to give it a try. The stock unit were unknown until we opened up the unit. It was JJ. We ordered a batch of Siemes E82CC, long plate, triple mica NOS, matched quads and gave it a go. 

The changes in sound is just substantial - deeper and more natural bass, veil is removed, soundstage deepens, tonnes of details revealed, vocals are warmer, clarity improved significantly. Now it sounds like a U$200K system.

After this change, the improvement was so significant that owner asked if we can upgrade the tubes and components inside Wavac PRT1 as well as his Wavac 300B and 805 power amplifiers! Well, that's for another time. We still have his EL84 push-pull power amplifier to complete and other customers' projects to finish before we can come back to his amplifiers again.

Here are some pictures for your enjoyment: 

Chassis milled from a solid block of aluminum

Some red wine to add flavors to the sound

Internal of Wavac PRT1

Tango Output Transformers (we think) is used at output stage

A bunch of JJ ECC82 are retired.

JJ ECC82 tube

Tube covers

Tubes rolling.

Siemens E82CC inserted

Observing the components used in Wavac PRT1

Capacitors used in Wavac PRT1 - certainly we have lots of room for improvements!

Input transformers (we guess, cannot see inside) for Wavac PRT1 (botom left)

On top of the tube roll, we've brought a secret weapon along too - a pair of J&K super-interconnects (RM1.2K a pair).

  • improved signal-to-noise ratio and interference rejection
  • high frequency shielding
  • shielding at bents (soft shield)
  • optimized cable capacitance and inductance, matched pair
  • meant for high speed transmission
  • extreme flexible body
  • multi-core cabling technology

This cable performed so well that 2nd pair were ordered to connect from Wavac PRT1 to Wavac EC300B and Wavac MD-805MK-II power amplifier to biamp his Acapella Campanile speakers, in replacement of his super expensive interconnects that cost many times over this J&K interconnect.

J&K Audio Design