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Tube DIY Asylum Do It Yourself (DIY) paradise for tube and SET project builders. |
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Tube DIY Asylum Do It Yourself (DIY) paradise for tube and SET project builders. |
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In Reply to: Driving 6Y6GTs with El Cheapo 12AT7 front end? posted by jyourison on April 25, 2013 at 10:47:34:
Pentodes in pentode mode don't have Miller capacitance, so their input capacitance is small and it does not take much current in the driver to drive them to clipping. This is not the case in ultralinear or in triode mode.
However, if you need to drive them into grid current on transient peaks (WAY more common than you'd think!) the above kind of goes out the window and the analysis gets all messy and nonlinear - very difficult to generalize.
Triode drivers with high gain need high plate voltage in order to avoid drawing grid current in the driver stage. Usually grid current becomes enough to introduce distortion when the bias minus peak signal is less than 1 volt. Bias is normally 50% to 70% of (plate voltage divided by mu), so you can see why high mu needs high voltage.
A final note - the 6DJ8 is specified for 130v maximum quiescent plate voltage. In practice it has a reputation for early failures if that voltage exceeds 80 or 90 volts. That's pretty low - something like a 5670 with similar gain but higher voltage tolerance is probably a better choice.
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Follow Ups
- RE: Driving 6Y6GTs with El Cheapo 12AT7 front end? - Paul Joppa 04/25/1320:48:01 04/25/13 (2)
- Grid current - Triode_Kingdom 22:42:04 04/26/13 (0)
- RE: Driving 6Y6GTs with El Cheapo 12AT7 front end? - jyourison 21:11:03 04/25/13 (0)
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