Hi folks,
i'm working at a PP amp with EL84 as outout and a triode -pentode as front end - phase inverter.
I posted time ago about using ECF80 :
http://www.diyaudio.com/forums/tubes-valves/238547-ecf80-driving-el84-pp.html
After some mods mostly on resistors values around the pentode input i have a good sounding amp, despite the output irons are from an old juke box, i have a good flat response down to 30Hz estimating the -3dB point at 22Hz with only 6dB of GNFB plus the UL feedback.
Yesterday i bought 4 6AN8 2 from GE others from Sylvania , for about 4€ each and they're NIB! Tested ok
Now i'm wonderin' if would be better use 6AN8 (Dynaco used them) or stay with the ECF80 (Siemens)
I suppose some resistors valuer must be replaced to use 6AN8, maybe just looking at the Dynaco Mk2 circuit and of course (the boring part) i've to change the pin connections.
Any advices?
i'm working at a PP amp with EL84 as outout and a triode -pentode as front end - phase inverter.
I posted time ago about using ECF80 :
http://www.diyaudio.com/forums/tubes-valves/238547-ecf80-driving-el84-pp.html
After some mods mostly on resistors values around the pentode input i have a good sounding amp, despite the output irons are from an old juke box, i have a good flat response down to 30Hz estimating the -3dB point at 22Hz with only 6dB of GNFB plus the UL feedback.
Yesterday i bought 4 6AN8 2 from GE others from Sylvania , for about 4€ each and they're NIB! Tested ok
Now i'm wonderin' if would be better use 6AN8 (Dynaco used them) or stay with the ECF80 (Siemens)
I suppose some resistors valuer must be replaced to use 6AN8, maybe just looking at the Dynaco Mk2 circuit and of course (the boring part) i've to change the pin connections.
Any advices?
Tesla,
On paper there is very little difference, and what difference there is is easily 'absorbed' by the operating point you choose. The 6AN8 has somewhat higher anode dissipation ratings if that should enter the situation. Price might easily determine the choice. (Pin-out is different, so no direct comparison possible.)
What I did find interesting has little to do with sound. That is that the 6AN8 has a controlled heater current, thus they can be used in series, and that makes the application of a d.c. heater supply easier (12,6V at 450mA for two). I found that the heater current draw of ECF80s differ enough that different voltages will exist across series connected heaters. But that is conditional - the sample is no more than 6 tubes, all Mullard. Still.
On paper there is very little difference, and what difference there is is easily 'absorbed' by the operating point you choose. The 6AN8 has somewhat higher anode dissipation ratings if that should enter the situation. Price might easily determine the choice. (Pin-out is different, so no direct comparison possible.)
What I did find interesting has little to do with sound. That is that the 6AN8 has a controlled heater current, thus they can be used in series, and that makes the application of a d.c. heater supply easier (12,6V at 450mA for two). I found that the heater current draw of ECF80s differ enough that different voltages will exist across series connected heaters. But that is conditional - the sample is no more than 6 tubes, all Mullard. Still.
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