| The HF Range “F” channel: The 6E6P-DR at 30mA connected at tetrode. The filter is second order with Sowter 9858 Pultec MEQ-5 EQ Inductor 420/277/145/108/61/34 mH) and variable air cap. The variable inductance and capacitance allow me to write any prefer Bessel curve against any frequency I wish and I have now much more gain on in tweeter then I need. The driver is tetrode strapped to defeat the insertion loss of the 175:1 transformer and to have more then necessary gain to run the “Water Drop” Tweeter on transition slope, crossed at 30kHz-40kHz with second order. The shortcomings of the tetrodes (loosing of damping, increase of output impedance and so on…) are absolutely not applicable in my case as the ribbon tweeter care less about the damping. In fact if I have a tube with more transconductance then 6E5P-6E6P (30-35ma/V or 30.000mS in Western scale) that has >3-4W on plate and more then 2-3V of bias I would stick it in. I might use something like 7788 pentode only with more power and more bias. If you know any of them then please pitch it to me as to have too much gain on tweeter do not hurt. Do not forget that the chennal will not do “sound” but rather the “space noise”. Still, even what I have now is ~ 12dB more then I needed and it is already is very good. |
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