6SN7 for Firefly ?

[petemoore]

http://www.ax84.com/index.php/oldpro...ect_id=firefly
Anyone tried this using a 6SN7 ?
Seems like it should work, any suggestions as to what I would need to mod [beyond the pinout/assignents and heater] are welcome.
The other bit of info I can muster about the 6SN7 is shown in the negative grid bias setup of the October, I wonder if that is 'necessary' or for what reason it is used for the Oct.
http://www.ax84.com/october.html

[zhyla]

A quick google turned this up on the AX84 forum:

http://www.ax84.com/bbs/index.php?id=174301

There's a few bits and pieces there. Are you trying to get more volume out of your Firefly?

[petemoore]

Actually I'm either trying to get less volume from my 5e3 or 18watt, or simply make use of the 6SN7's and 6SL7's and a PP output transformer came out of an AC15 RI amp.
I have a SS Recto PS built up that puts out 228VDC, I might try it like that for a while then maybe put transformer for a higher voltage B+ in at some point.
If I crank these >10w amps to the point where they sound right in the living room...other forms of communication are severely impaired, TV / Phone calls must then be done / made outside, basically.
Moonlight looks about right I think, that or...probably the Moonlight amp.

[tedmich]

A 6N1P in a Ax84 High Octane, with a purposely inefficient speaker sounds very nice at ~1/2 watt, or include the Firezog headphone in the FF?

[GibsonLover]

The negative bias on the October is fixed bias, and the small cathode resistor is for current sensing so you can easily probe the output. The fixed bias will be a more efficient P-P (therefore slightly louder, all things considered) because you don't loose power dropped across a larger cathode resistor found with cathode bias.
Why not try a SE circuit with an EL84 and a master volume? Master volumes don't give you identical 'cranked' tone, but then using a 6SN7 as an output is a different animal too. Even 1W is surprisingly loud. The EL84 might work pretty well with your supply. For example: 264V with 200 ohm cathode resistor idles you at ~40mA = 74% of plate dissipation. It would also only take 7 or 8Vpk to drive it before clipping.

[GibsonLover]

.... (I see your supply is different) at 228V and cathode reisitor of 120 will idle at 46mA @ 72% and take 5 to 6Vpk to clip. Any OT with 2.5K to 5K primary would be fine.