ampage
Tube Amps / Music Electronics
For current discussions, please visit Music Electronics Forum.

ampage archive

Vintage threads from the first ten years

Search for:  Mode:  

EL84 current draw


 :
11/7/2003 6:40 PM
Tesno8 EL84 current draw
Tube charts always seem to confusing me. I'm going to use two EL84's with about 300V on the plates in push pull; What do you think the current draw will be? I wan't to make sure I don't over load the 269jx power tranny? Its rated at only 60Ma.
 
Today
ampage
archive
And now, a word from our sponsors:


 
11/7/2003 8:44 PM
Chris ( CMW amps )

Hi Tesno  
 
Most of the time you'll use them in a so called class AB1 circuit . The biasing ( plate-current at idle ) should be between 50% - 70% .  
P=U.I  
P=12 Watts ( max. plate power )  
U= voltage you measure between plate and cathode  
I= ( then needed ) current  
 
I hope this does help a LITTLE , hope some fellow Ampagers can explain this more shortly and clear for you , my english sucks :)  
 
Chris  
 
Ps most of the time EL84s with that voltage are used in cathode biased amp , the plate and screenfrid-current go through the cathode-resistor . Measuring the voltage across that R and deviding it by the resistor-value will give you the ( shared ) plate- and g2-current from both tubes .
 
11/7/2003 11:01 PM
Tesno8
Hi Chris:  
 
I tried searching for CMW amps, do you have a link? Thanks for your info. Let me ask you this 12ax7 pre amp tubes draw about 3Ma each to the best of my knowlage what do you think the average Milli amps would be with an EF86?  
 
Thanks
 
11/8/2003 11:02 AM
Chris ( CMW amps )

Hi  
 
Here's the link : http://www.cmwamps.com  
Still in dutch only , a new & updated website in english , german & dutch will be made before the end of this year ......  
 
The current depends on the circuit and the used cathodeR values ( 12AX7s and all other tubes too ) .  
Here are some specs from an EF86 ( 220k plate , U+ 250V ) :  
Rg2 1M  
Rc 2k2  
Rg1' 680k ( load from volume-pot/next stage/etc. )  
cathode-current 0.95 mA  
gain 180x  
 
Hope this does help ,  
 
Chris
 
11/8/2003 12:31 PM
Tesno8
Yes that does help! Thanks for the link.
 
11/9/2003 6:07 AM
scott c
my spitfire homee has 352 volts on the plates with about 16 watts dissipation. the tubes dont seem to mind, neither do i since the tone is awsome.
 
1/5/2004 1:50 AM
Mark Abbott

I have been building a Liverpool clone, currently I'm using a transformer that puts out 322VDC at 55mA's. The amp is quite loud with this transformer, but what ends up happening is the the rail voltage drops to 291VDC, and the maximum current is 145mA's.  
 
I have heard that Heybour sell a transformer that is 250-0-250vac and rated at 200mA's. This sounds like it would be a better transformer for your amp.  
 
Yours Sincerely  
 
Mark Abbott.
 

  Page 1 of 2 Next> Last Page>>