双色球模拟选号器

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815 Class AB2 amp

mr. and mrs. potatohead live!

i have the stereo pair of 815 amps assembled.  testing is ongoing... on the 8 ohm taps, i get over 50 watts out, and still low thd at 1 watt (~0.02-0.04%).

双色球模拟选号器i have not yet listened to them.

双色球模拟选号器here's what it looked like on the breadboard:

双色球模拟选号器the is a bit of an ugly duckling.  it is a pair of beam tubes in one glass envelope, designed for rf transmitting use.

the 815 and 2e26 have never been very popular as audio amps.  they have a low plate dissipation rating, a low maximum screen grid voltage rating, and are not very linear when operated in class a or ab1 (mostly due to those restrictions).

however, if you operate them close to the published ratings in class ab2 (where you drive the grids positive), the performance is pretty impressive.

双色球模拟选号器 i get 50w out from a b+ voltage of 475v, and 0.02% thd at 1 watt.  using a output transformer, the frequency response is within +/-0.3db 20hz-20khz, with -3db at 75khz or so.   more measurements, fft, imd, etc. coming soon.

The driver PCB uses a 6AC10 triple triode compactron, so the whole amp uses only two tubes (granted, multi-section tubes).  It uses MOSFET source followers to drive the grids of the 815 positive (that's the black heatsink at lower right), and a "Maida" regulator to generate a 125V screen voltage (black heatsink at the left).  A power supply at the left rear generates 475V, 235V, and -95V from a ClassicTone Marshall amp power transformer (40-18053).

Plate current for each plate is measured using an isolated current sensor双色球模拟选号器 and a PanelPilot programmable LCB panel meter.  Since the cathodes are internally connected, you cannot sense the current there, and I wanted to be able to separately adjust the bias on each half of the 815.

All these PCBs are available on eBay.

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