Tube DIY Asylum: Re: Input/driver for 2A3 parafeed by Sector-7G Do It Yourself (DIY) paradise for tube and SET project builders.

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Posted by Sector-7G (A ) on November 19, 2003 at 14:07:03

In Reply to: Input/driver for 2A3 parafeed posted by Tubefever on November 17, 2003 at 09:05:39:

Hey-Hey!!!,
Go with a 5687. Cascade the two sections. Resistive load will give yo an output z in neighborhood of 3k Ohms. If you have a stereo amp on the same chassis, use a 5687 as input, shared the sections to each side and drive a 12B4A or 7233. Low mu, low plate z tubes will give you maximum voltage swing for a given B+. I think the 12B4 is plenty of drive for a 2A3, and its output z can be reduced with the mu-follower CCS connection pioneered, and written up by Gary Pimm( thank you, thank you, thank you, thank you). Gain will be about 100 and output z will be adequate to get ultra-sonic.
regards,
Douglas
ECC99 can be subbed, along with 6H6Pi, 6SN7, or try cascading the sections of a 6DN7( oh yes, this might be best yet). I think Bottlehead did this on one of their early amps.

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