Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Tone Junkie on March 31, 2012, 08:08:51 pm
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Im shure this has been asked many times before why is a 2 power tube marshall PT rated at 150 MA and fenders seem to be rated at 200 MA I thought EL34 put out more power than 6l6 tubes.
Is a marshall type transformer ok to use in a 2 6l6 build, Ive been to the tube data sheets trying to figure this out for myself, but there are still some things I dont get yet.
Thanks Bill
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fenders seem to be rated at 200 MA
Take a look at Hoffman's PT for a Super Reverb #022798:
http://www.el34world.com/Transformers/fentrans.htm (http://www.el34world.com/Transformers/fentrans.htm)
rating is 140ma (compared to Hoffman's 50w Marshall which is 150ma)
I have a PT that is rated 150ma and I've been using it with 6L6's & 5881's for over a yr. It doesn't even get warm & no drop in heater voltages.
With respect, Tubenit
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Im shure this has been asked many times before why is a 2 power tube marshall PT rated at 150 MA and fenders seem to be rated at 200 MA I thought EL34 put out more power than 6l6 tubes.
I'd estimate that most guitar amps claim a similar amount of power when using a pair of either type.
You might be thinking of how 2-ouput tube Marshall's are generally called "50w" while 2-output tube Fender's are called "40w". I doubt most folks have actually measured the power output of each for comparison; regardless, the difference between 40w and 50w is quite small compare to the difference between 5w and 15w.
Last, 6L6GC's are rated for 30w plate dissipation (which can provide an indication of possible power output), where EL34's are rated for 25w plate dissipation. So the 6L6GC should be capable of more power than the EL34. For a 60's and earlier tube, other non-GC 6L6 variants are rated for the same, or less, output power than the EL34, depending on the specific tube in question.
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Is a marshall type transformer ok to use in a 2 6l6 build,... (?)
If you have 2 x 6L6s in PP (for most amps with 3 pre-amp tubes), 150mA on the High Tension winding will suffice. More power handling will mean the PT runs cooler (but this more more noticeable in respect to high current windings i.e.: the heaters)
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I guess that answers it thanks guys i have a chassis non of the fender stuff fit in the laydown area except 100 watt iron and that didnt have the heater rating I needed . but the laydown marshall transformer fit perfect and had more than enough heater current . i just wanted to be sure it had enough B+ amperage for the tubes.
Thanks Bill
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Not exactly sure of the import of your question, but here's another take. There can be large wiggle room in how manufacturers rate a tranny, and not necessarily commonly accepted industry standards. Also, back in the day, like the 1950's, manufacturers of consumer electronics often skimped on PT's which ran quite hot. Other than consumer grade, there's also commercial and then military grades. Military grade is expected to run 24/7 for years and without failure. So a 150mA military grade tranny will be quite robust and run cool; while a consumer grade 150mA tranny might be puny and run hot. But it will only be used a few hours per day or per week. So it is not expected to overheat in normal use and will last for years anyway.
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Thanks jjasilli that ads another layer of complexity, I have both magnetic components transformers and weber transformers.
With one I build to last with the other Im just trying new things amazingly I have built a couple of things with weber and they ran quite cool even turned up real loud for long periods.
Bill