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Audio Note Kit1 2014 Edition

8W Class A single-ended 300B valve integrated amplifier. More details on ANK Audio Kits website.

INITIAL TUBES

  • Electro-Harmonix 5U4GB

  • Sovtek 6SN7GT

  • 2 x General Electric JAN 5687 WB

  • 2 x Shuguang 300B-98

LAYOUT

MEASURES

  • Idle current (measured at pin 8 of 5U4GB): 200mA

  • Gain (at 1 kHz): 37.2dB (left), 36.7dB (right)

  • THD+N (at 1 Watt into 8 Ohms at 1 kHz, source impedance 600 Ohm): 0.55% (left), 0.51% (right)

  • THD (at 1 Watt into 8 Ohms at 1 kHz, source impedance 600 Ohm): 0.54% (left), 0.50% (right)

TUBE ROLLING 1 - Sovtek 6SN7GT replaced by RCA JAN V-231 "Grey Glass" NOS:

  • Slightly lower gain (at 1 kHz): 36.6dB (left), 36.1dB (right)

  • THD+N (at 1 Watt into 8 Ohms at 1 kHz, source impedance 600 Ohm): 0.55% (left), 0.52% (right)

  • THD (at 1 Watt into 8 Ohms at 1 kHz, source impedance 600 Ohm): 0.52% (left), 0.51% (right)

  • Significant improvement comparing to Sovtek tubes - deeper, more 3 dimensional sound stage, a bit more delicate high frequencies, overall sounds lighter, but also much more realistic, musical.

TUBE ROLLING 2 - Electro-Harmonix 5U4GB replaced by Sylvania 5U4GB/5931 NOS:

  • Slightly stronger, better defined bass comparing to EH tube.

TUBE ROLLING 3 - General Electric JAN 5687 WB replaced by Tung-Sol JTL-5687 early 1950s matched pair:

  • Left tube: 9.8mA/4800, 10.2mA/4800

  • Right tube: 10.8mA/4800, 10.8mA/5000

  • Gain (at 1 kHz): 36.1dB (left), 36.2dB (right)

  • THD+N (at 1 Watt into 8 Ohms at 1 kHz, source impedance 600 Ohm): 0.56% (left), 0.77% (right)

  • Excellent sounding tubes, huge improvement comparing to the stock GE tubes.

TUBE ROLLING 4 - Shuguang 300B-98 replaced by Genalex Gold Lion PX300B matched pair:

  • Both tubes: 64mA / 5.8mA/V

  • Gain (at 1 kHz): 35.9dB (left), 36.1dB (right)

  • THD+N (at 1 Watt into 8 Ohms at 1 kHz, source impedance 600 Ohm): 0.39% (left), 0.49% (right)

TUBE ROLLING 5 - RCA JAN V-231 "Grey Glass" NOS replaced by Sylvania 6SN7GTA "chrome dome" (made in USA, 1953):

  • Unfortunately RCA tube started buzzing after about 8 months of use and I decided to try Sylvania.

  • iP / Gm: 8.9mA / 2600 and 8.7mA / 2600

  • Gain (at 1 kHz): 36.3dB (left), 36.4dB (right)

  • THD+N (at 1 Watt into 8 Ohms at 1 kHz, source impedance 600 Ohm): 0.46% (left), 0.33% (right)

  • First impressions: good, strong bass, great dynamics, a bit dry in the midrange, a little agressive upper frequencies, slightly sibilant

TUBE ROLLING 6 - Sylvania 6SN7GTA "chrome dome" replaced by RCA 6SN7GTB "black plate" (1960's):

  • I didn't like the upper range with Sylvania, which sometimes could be quite harsh and sibilant, so I replaced it with this RCA tube.

  • Balanced triode sections, low noise and microphonics

  • Gain (at 1 kHz): TBC (left), TBC (right)

  • THD+N (at 1 Watt into 8 Ohms at 1 kHz, source impedance 600 Ohm): TBC (left), TBC (right)

  • Comparing to Sylvania it sounds somewhat slower, bass is less controlled, but with smooth, rich midrange, harshness is gone completely

LINKS

Last update: 22.06.2018.

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