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26 preamp

Posted by sser2 on March 31, 2017 at 13:27:23:
The first one is active crossover. 2C51 amplifies high frequencies, with 22 nF capacitor acting as a high pass filter. The 26 section amplifies low frequencies, with output transformer acting as low pass filter. In this implementation, a cheap output transformer is needed with relatively high leakage inductance.

The choice of 2C51 is strange. Its amplification factor of 35 is grossly mismatched with that of 26 (mu=8). Otherwise, it is a nice linear triode with low Miller capacitance and low Rp, if sections are paralleled.