Posted by Tnuctip [ 64.12.116.14 ] on December 21, 2004 at 16:37:08:
In Reply to: Re: what in the hell is a 5861? posted by colinhester on December 21, 2004 at 16:11:36:
hey-Hey!!!,
Anyway, it is a simple thing. Output Z, as dominated by that itsy-bitsy cap is going to be steep. 5 uF is a good place to start. Then we're still looking at ~3k from the 5687. So, is this good enough?
It is my opinion that if you're going to the bother of cutting holes in a chassis, it should be better.
A 300-0-300 plate winding and two 12AX4 damper diodes is a good place to start. Feed a choke, like Hammond's 30 Hy/40 mA and 100 uF of motor run cap and if you're past critical current( 20 or so mA ), you'll have less than a volt of ripple peak-to-peak.
Also, what about gain? be sure of the requirement, so as to avoid padding the volume control as a lot of folks have had to do when building with 12AU7's.
A single 12B4 is one of my fav's. or get nuts, and pick the 26, or 45, or 10...
And then, there is the question of plate loads. Resistive, CCS, or inductive? There are advantages to each to be sure. A single DN2540N5, a gate stoper resistor and a 1k/10 turn pot is one of the simpler ways of doing a CCS. Cost ~$5 depending on sourcing and shipping costs. Cascoding the 2540 is better but a bit more complex as well.
regards,
Douglas
....damned Thrintun!
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