Heathkit HA 10 Warrior Amplifier.

A friend sent in a photocopy of the Heathkit HA 10 Amplifier. I've scanned the circuit diagram and saved it in the gif file format. This amplifier circuit uses four 811a tubes in grounded grid operation. There are many different methods to provide the bias in grounded grid operation. Amplifiers built in the previous decades tend to use a DC lifted grid method. This amplifier is one such design along with a neutralization capacitor.

In my opinion, a major advantage of zero-bias and grounded-grid tube operation should include the elimination of bulky bias supplies and rf feedback circuits. This original circuit layout built up in the shack as a homebrew amplifier should have the bias (control) applied through the filament transformer center-tap and the neutralizing capacitor circuit left out (if appropriate current amplifier construction techniques are used).

As time allows, I hope to scan in a redraw of a more conventional 811a amplifier circuit layout to add in this package. The addition of a tuned input would also be great. I have an 811a amplifier I built in the 80's using a similar circuit circuit, which as built has never failed or shown instability in operation. More to come, please enjoy the diagram as presented and feel free to Email me your comments or things you have to make available.


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