We can make anything that you can dream of. Just shoot us an email at jnkaudiodesign@gmail.com or fill in the form below. Greetings from Penang, Malaysia!

Monday, September 14, 2015

Linestage Output Transformer

Can you do linestage output transformer? I've seen a lot of publications about output transformers but I've not seen you said something about linestage output transformer, or preamp output transformers, one customer asked.

Of course we do! And here's the reward for asking that question! This customer requested a 8K:600 linestage output transformer for his 5842 simple preamp, running at ~25mA at 130V B+. 

Level 3 Nanocrystalline Double C Core Linestage Output Transformer
  • In circuit measurement
    • 600 Ohm load: 20Hz (-0.38dB) - 1kHz (0dB/ref) - 20kHz (-0.16dB)
    • 100K Ohm load: 20Hz (-0.54dB) - 1kHz (0dB/ref) - 20kHz (-0.09dB)
  • Primary DCR: 390.4 Ohm, 391.1 Ohm (B-P, at 22 degC)
  • Secondary DCR: 30.4 Ohm, 30.4 Ohm (600-common)
  • Primary inductance: 48.5H, 49H (DC bias at 25mA, 20Hz, 5Vrms)
    • Lower bias current will yield higher primary inductance (68H at 0 DC). 
  • Max. primary current: 30mA (recommended <=25mA)
 5Hz - 85kHz +/-3dB
FFT with difficult load (SS amp)
5Hz - 100kHz +/- 3dB

FFT with easy load (tube amp)

J&K Audio Design

Sunday, September 13, 2015

212 Output Transformer Specifications

212 Output Transformer Specifications (refresh)

  • Nanocrystalline double C core, Level 3 (U$1390 per matched pair)
  • Single Ended Output Transformer, single tube use (PSE option available)
  • Output power: 70W @ 20Hz (higher power available per request)
  • Measured frequency response
    • 20Hz (-0.2dB) – 1kHz (0dB) – 20kHz (-0.4dB), 8 Ohm, 1W
    • Full bandwidth: 5Hz – 70kHz -3dB
  • Primary impedance: 5KΩsecondary: 0-6-8Ω (or 0/4/8, or 0/8/16, or user defined)
  • 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 (absolute maximum), recommended (optimal) at 150mA
    • For 212 PSE, will be 300mA (or user defined)
  • 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.

Note: for customers ordering from us, please specify the ACTUAL running idle current to us. Please do not buffer the idle current since our transformers are designed to work at +20% over specifications. Buffering will cause the bandwidth to be less that ideal, especially for single ended output transformers with core air-gap.

Matching results:
  • Primary DCR <2%0.2Ω) 
  • Primary inductance <5%0.9H
 FFT results (combination of 2 curves since the spectrum analyzer we used are limited in bandwidth:

5Hz – 70kHz +/- 3dB (ruler flat from 20Hz to 20kHz)

Note: 212 output transformer bandwidth can be tailored according to customer preference (with a price). If customer has no preference, we will optimize it to the best possible specifications.

J&K Audio Design