|Tubes / Valves All about our sweet vacuum tubes :) Threads about Musical Instrument Amps of all kinds should be in the Instruments & Amps forum|
Please consider donating to help us continue to serve you.
Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
||Thread Tools||Search this Thread|
|25th October 2007, 05:21 PM||#1|
Join Date: Oct 2006
6SN7 plate voltage, current and lifespan
My PSU tweaking on my Aikido is reaping tangible results with regard to hum.
I added 30K across the final cap to bring current draw up to around 32mA, then added an extra 0.1uF to my PSU input cap (to give a total of 0.78uF on the tuning cap). Today, I will look for a 1uF motor-run cap as well as 80-100uF Motor-run caps for my filtering caps.
All of this brings me to questions of voltage, current, wattage and lifespan of my 6SN7GTA's.
I currently run the inputs at 4.5mA and the outputs at 7.2mA (or thereabouts). At it's present config, B+ is around 278VDC. When I do further tweaking with the "tuning" cap and maybe remove the 30K current sink, I expect that B+ will rise to somewhere in the region of 360VDC. Anyway, this would mean that each plate of my 6SN7's will be seeing 360/2 = 180VDC.
The tube specs give maximum ratings as: 450VDC per plate at 20mA cathode current with power dissipation of 5W for a single plate, 7.5W if both plates are used.
By my reckoning, if each plate does end-up seeing 180VDC, even at 10mA current, each plate would be required to dissipate around 1.8W. This is well within the tubes specs.
OK, I noticed when I added current-draw, that sonically, the amp, with 278VDC (as opposed to 317VDC) sounded a tad more sluggish - still amazing, but somehow the polish was dulled slightly. Sorry for the poor adjectives.
Now my QUESTION: with the high cost of NOS 6SN7s, to what degree does would running the tubes hotter (ie. higher wattage) effect lifespan? Of course, I am in no way going to get close to their max. I had read that many tubes were rated for 10,000 hours, is that running at max wattage?
|Thread Tools||Search this Thread|
|Thread||Thread Starter||Forum||Replies||Last Post|
|Plate Current VS Plate Voltage Graphs||Captn Dave||Tubes / Valves||2||13th February 2009 09:57 PM|
|CCs plate load for mu follower 6sn7||duderduderini||Tubes / Valves||4||8th November 2007 01:40 PM|
|does plate current/voltage effect tube sound????||benny||Tubes / Valves||10||7th July 2004 02:18 PM|
|Plate load for 6SN7 gain stage?||G||Tubes / Valves||53||16th July 2003 11:07 AM|
|New To Site?||Need Help?|