All tube operating points below are by no means definitive good sound recipe for your particulate tube project. Lowest THD point is not necessary best sounding one and there is always some variance even in a NOS tube batch from the same manufacturer!  Below information is only useful as a general starting point and is ment to get you in a ballpark when no measurement equipment is available.

Lowest THD and recommended operating point spectrum

40mA, -1.7V BIAS

Other operating points

20mA, -3.4V BIAS

Traced plate curves


EL83 version with 15V heater. Little microphonic and has higher harmonic content, but it’s always monotonic and low, so shouldn’t be a problem sonically. Very linear in triode mode, but μ is only 15. Available for sale.

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