I've never understood why you wanna use, such a high gain signal pentode tube, as the EF86, and then connect it as a triode, seems like a waste.... why not use a triode insead? If the EF86 is to sensitive, and picks up hum and microphony(I wonder if I spelled that right...), then us a triode. Sure the curves and 'ra' etcetera becomes different with a triode connected pentode, and I prefere the 'triode-sound' from the output-tubes, rather then UL or pentode coupled, like EL34, 6885 or beamtretode 6L6, KT88 in triode mode, I usallaly design the amp so you can change from pentode to triode mode, the sound is a bit varmer and the amp is more liklely to distort, but in a natural-way.
I've build a p-p amp w/ 2x6885(KT88)/ch., and in pentode mode I get about 30W rms, in triode mode, barely 8 W rms! With resonable THD, less than .1%, I could increas both voltage and plate current, but I like my tubes to keep their characteristics over a longer periode.... I trimmed my brothers PA-top(A Fender 80W), it has two 6L6 in it, and to get the right bais and plate dsip. the voltage was above 450V, but he needs to switch tubes once per month almost - depending on how loud and often he practice w/ his band, "BYOK"(Bring your own knife)...
As giutar pick-up preamp, the EF86 is great, by the way....
I've build a p-p amp w/ 2x6885(KT88)/ch., and in pentode mode I get about 30W rms, in triode mode, barely 8 W rms! With resonable THD, less than .1%, I could increas both voltage and plate current, but I like my tubes to keep their characteristics over a longer periode.... I trimmed my brothers PA-top(A Fender 80W), it has two 6L6 in it, and to get the right bais and plate dsip. the voltage was above 450V, but he needs to switch tubes once per month almost - depending on how loud and often he practice w/ his band, "BYOK"(Bring your own knife)...
As giutar pick-up preamp, the EF86 is great, by the way....
This is a good question. Triode tubes like 12AU7, 12AT7, 5670 as input stage sound smooth and warm. Many people like triode sound. EF95, EF86, 6J7 are high-mu penotde tubes sound different with triode tubes. They are powerful enough to drive many power tubes. For the EF95-EL84 amplifier, it is very easy for EF95 to drive EL84. If we use EF95 in pentode connection to drive EL84, the gain will be very high, and easy to have distortion. Therefore, we prefer EF95 in triode connection to control gain and distortion in proper level. On listening, EF95 in triode connection to drive EL84 single end is powerful and refined without lack of warmth.
Thanks for your sharing.
Tony.
Hi dave,
I like the sound of EF86-EL84 SE also. This is a classic circuit. Mullard made it in the past.
Thanks.
Tony.
This is Mullard EL84 amplifier.
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This is our EF86-EL84 single end amplifier.
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These are not vintage English Partridge transformers. They are hand made transformers by using vintage English EI steel cores and enamelled wires. The workmanship is excellent.
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Alejandro,
Yes, higher quality parts and components were used into this amp. It is our reference amp.
Thanks,
Tony.
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