Low emissions

MrCurwen · 20th May 2011, 09:46 AM

I'm wondering what effects does low emission capability have on tubes. It's obvious that with lower emissions the maximum cathode current is reduced. What else changes? Mainly my concern is plate resistance and thus the curves.

Is there any difference with low emissions from age and wear, or low emissions on account of sub spec heater voltage?

Are curves measured in a low emission situation reliable (at least at lower cathode currents)?

DF96 · 20th May 2011, 10:34 AM

Low emission is likely to mean that current and gm go down. As mu will remain largely unchanged, the anode impedance will rise. This means that, on average, a triode circuit will survive valve ageing better than a pentode circuit - triode amplification is largely set by mu, but pentode amplification largely by gm.

20th May 2011, 09:46 AM	#1
MrCurwen diyAudio Member Join Date: Feb 2010	Low emissions I'm wondering what effects does low emission capability have on tubes. It's obvious that with lower emissions the maximum cathode current is reduced. What else changes? Mainly my concern is plate resistance and thus the curves. Is there any difference with low emissions from age and wear, or low emissions on account of sub spec heater voltage? Are curves measured in a low emission situation reliable (at least at lower cathode currents)?

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Low noise, low microphony, low hum valves	MarcelvdG	Tubes / Valves	28	31st December 2010 09:41 AM
preamp supply LOW power LOW noise LOW cost	drdagor	Power Supplies	1	13th September 2010 11:39 PM
Extremely low power and low loss transformers	percy	Tubes / Valves	12	23rd February 2005 10:30 AM
how low is 'low DC' on SOZ outputs?	psarin	Pass Labs	8	8th March 2002 01:39 PM

New To Site?	Need Help?
Register to Participate Search Privacy Statement Contact Us	Frequently Asked Questions Did you forget your password? Mark Forums Read

20th May 2011, 10:34 AM	#2
DF96 diyAudio Member Join Date: May 2007	Low emission is likely to mean that current and gm go down. As mu will remain largely unchanged, the anode impedance will rise. This means that, on average, a triode circuit will survive valve ageing better than a pentode circuit - triode amplification is largely set by mu, but pentode amplification largely by gm.

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)