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Old 18th November 2008, 05:37 AM   #1
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I have plenty of 6N1Ps and was considering using two pair for an Aikido build. Yet I can't find a single example of anyone using a "quad set" rather than differing pairs for the two stages.

I do understand the necessity of using matching tubes within a stage but I can't envision a reason for using dissimilar types between the two stages nor can I find guidance in Broski's writings. Is there a reason?
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Old 18th November 2008, 11:48 AM   #2
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No reason not to. Often, the input stage and follower have different tubes because the stage requirements are different. For example, a 6SN7 is a terrific voltage amplifier, very linear and appropriate gain (20dB in Aikido) for a line amp. But 6SN7s don't have a very high transconductance, so they're mediocre followers.
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Old 18th November 2008, 05:00 PM   #3
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OK, that makes sense.

The 6N1P has a transconductance value of 7500 micro mhos. I think of that as a good value for a follower, but is it? What range should I be looking for in a follower?

Thanks
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Old 18th November 2008, 05:16 PM   #4
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While we're on the subject, I'm trying sizing the power transformer. In doing so I'm using the plate resistance summed together with the cathode and plate resistor values to calculate how much B+ current I will need to supply. Is that the correct method? Perhaps the plate resistance is not the parameter I should be looking at.

For instance current should be let's say 300 volts divided by resistance of two times 4400 for plate resistance in the two tubes plus a pair of resistors at 642 ohms each. That's about 30 ma for the first stage, a little more (32 ma) for the second, and another 7ma for grid current gets me in for under 70 ma. I suppose that is quite believable; but is it correct?

Thanks in advance. This IS my first rodeo.
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