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EML 20B Single Tube Directly Heated Single Ended Triode

One Tube Amp (OTA)

Built for Dixon Chen of Malaysia

Completed on 11/02/11


This is my third EML 20B amp, this one being the second of the fixed bias version. Dixon supplied about 70% of the parts for the amp, including the 10K Hashimoto OPTs, the Lundahl choke, the Tango chokes, the heater regulators, the caps, the teflon tube sockets, etc. I supplied the EML 20Bs and the Hashimoto power transformers. I built the chassis and the rest. See below for my comments on the build.




This amp is back-heavy, thanks to the split rail power supply with nothing but chokes and filter caps. Those Hashimoto OPTS and power trans are pretty hefty too. Notice those Cardas binding posts.


Lots of high quality parts found in this picture, including the Jupiter Beeswax coupling caps, the Lundahl input irons, the Jensen filter caps, and the heater regulator moudules for the 300Bs.
This amp really comes alive in the bass department compared to my previous builds using the same tube. I think there is something to be said about having a robust power supply for this. The 20B is biased at around 370 VDC on the plate with - 7.5 vdc on the grid for 37 mA. This, to me, seem to hit the sweetspot. Click below for operating ranges of the EML 20B: 

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