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In Reply to: RE: Q About Edcor Transformer Performance posted by Triode_Kingdom on October 26, 2014 at 13:59:11
If the CCS is to be the load, you'll want more B+ than for using the choke as a load.
A cheap 10H choke is likely to have frequency response issues both up top and down low.
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That's a good point, something I've been looking at in SPICE. Remember I said this won't be a conventional design? Well, just to provide a few more details, the output stage will be a funny-looking single triode with an anode cap. It will be configured as a cathode follower, with the anode connected to chassis ground. Negative voltage will be applied to power the tube from under the CCS (or choke/transformer). This design will allow me to leave the tubes exposed, so their unique physical characteristics will show, without the need to build a glass cage to prevent a shock hazard.
Speaking of all this, I noticed last night that LTSPICE didn't like it when I reversed the voltages in this way. When I grounded the anode and applied B- to the previously grounded points, the CCS stopped working. I need to look at this again, just to see if it's a simulator bug.
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A cathode follower driving an output transformer is somewhat strange. Grounding the anode and providing negative voltage to the cathode can be a fun trick to directly couple and provide negative fixed bias in a power amp.
In your case, I would wonder what benefit you'll find, as you'll need to get some voltage gain up front to drive all of this.
This topology has been used going back many years. The advantages for my project are twofold. First is the ability to leave the tubes and anode wiring exposed. Second, the CF configuration will "linearize" the output stage.
As you say, all the voltage swing must be developed by the driver. That means this configuration is only practical in low power designs. Even at less than one watt, I'll need to swing the grid about 175 V p_p due to the 5K load.
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