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wd40addict · 15th Sep 2021, 1:15 pm

I'd have to disagree with Andy on this. Twice I've designed Baxendall tone circuitry for PA amps. One was active based around an EF86, the other passive. The important thing was that I simulated both circuits in Spice in context, with source and load impedances, and they both performed as expected once built.

Cutting and pasting a tone design into a different amplifier is not likely to be that successful.

Re the raw performance of the EF86 in pentode mode I once measured a gain of 200 with 0.1% THD. I didn't try triode strapped, but the idea (myth?) it has good performance in this mode dates back a long way. I remember a colleague who was an enthusiast back in the 50s telling me this.

15th Sep 2021, 1:15 pm	#34
wd40addict Octode Join Date: May 2009 Location: Stevenage, Herts. UK. Posts: 1,518	Re: Advice on this linestage build I'd have to disagree with Andy on this. Twice I've designed Baxendall tone circuitry for PA amps. One was active based around an EF86, the other passive. The important thing was that I simulated both circuits in Spice in context, with source and load impedances, and they both performed as expected once built. Cutting and pasting a tone design into a different amplifier is not likely to be that successful. Re the raw performance of the EF86 in pentode mode I once measured a gain of 200 with 0.1% THD. I didn't try triode strapped, but the idea (myth?) it has good performance in this mode dates back a long way. I remember a colleague who was an enthusiast back in the 50s telling me this.