SInce you'll probably need to keep the filaments above at least 2v, from their constant load graphs it look s like you'll get maybe 30hours off a pair of D cells. If you use Duracell brand alkaline "D" cells, they rate their batteries at 15 Ah load) to 0.8v per cell. The filament current is about 50mA per tube so 100mA per pair. The current draw is only about 1mA per channel so the nine volt batteries should last a good long time. it is just a simple preamp but the distortion numbers look good. Only Registered Members may view attached files. Don't get me wrong, it would make a great conversation piece. After doing this much design, I'm not sure I'm sold. So here we have a battery powered 3S4 basic stage design which is NOT the "Quickie" but is based on the same principle. Rechargeables may be a good idea here but their voltages are different, so design accordingly.
Now the gain is low, only about 3, so it is just a simple preamp but the distortion numbers look good.
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