Tube Amps / Music Electronics
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|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.
|11/7/2003 8:44 PM|
|Chris ( CMW amps )
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=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
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|
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?
|11/8/2003 11:02 AM|
|Chris ( CMW amps )
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 ) :
Rg1' 680k ( load from volume-pot/next stage/etc. )
cathode-current 0.95 mA
Hope this does help ,
|11/8/2003 12:31 PM|
Yes that does help! Thanks for the link.
|11/9/2003 6:07 AM|
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|
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.
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