Really stupid question

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jestaudio
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Really stupid question

Post by jestaudio »

Noticed on alot of TW layouts the Trannies are rated at 120ma plus yet the tube rec onlt supplies 120ma max(gz30), is there any particular reason for the amount of spare juice on tap or is it a case of a bit of overkill
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cbass
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Re: Really stupid question

Post by cbass »

Um the GZ34 rectifier is rated for 250mA.Depending on the voltage.Thats about what you need for 2 el34's or 4 el84's.

Trainwreck PT's are rated at 300mA a little overkill but I think the reasoning was to supply a stiff power supply that doesn't sag.

Maybe someone can shed a little more light on the subject.
jestaudio
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Re: Really stupid question

Post by jestaudio »

cbass wrote:Um the GZ34 rectifier is rated for 250mA.Depending on the voltage.Thats about what you need for 2 el34's or 4 el84's.

Trainwreck PT's are rated at 300mA a little overkill but I think the reasoning was to supply a stiff power supply that doesn't sag.

Maybe someone can shed a little more light on the subject.
sorry my bad :oops: looking at the wrong spec :P however i,m using a 5y3 in my wreck which appears to be rated for 125ma with some Bad cat spec trannies(talk about overkill) without any appaarant problems, in fairness i havent pushed it to full power but i suspect that i would have more sag than usual nin comparison th the GZ34 or th 5ar
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cbass
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Re: Really stupid question

Post by cbass »

A 5y3 isn't robust enough for a 2xEL34 or 4xEL84 amp.
jestaudio
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Re: Really stupid question

Post by jestaudio »

cbass wrote:A 5y3 isn't robust enough for a 2xEL34 or 4xEL84 amp.
Not el84s, 2 x 6l6, which in PP draw 116ma + 3x12ax7 at around 1.2 ma each, very close i must admit but as i never run at full steam it should be ok
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cbass
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Re: Really stupid question

Post by cbass »

Is that 116mA at idle because they will draw a lot more when you are playing.
jestaudio
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Re: Really stupid question

Post by jestaudio »

cbass wrote:Is that 116mA at idle because they will draw a lot more when you are playing.
116ma max, the idle should be around 30-40 ma
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cbass
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Re: Really stupid question

Post by cbass »

What is your plate voltage because a pair of 6l6gc at 400VDC Biased to 70% Max disapation, should idle around 110mA
jestaudio
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Re: Really stupid question

Post by jestaudio »

cbass wrote:What is your plate voltage because a pair of 6l6gc at 400VDC Biased to 70% Max disapation, should idle around 110mA
Cathode biased mate
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cbass
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Re: Really stupid question

Post by cbass »

ok then what value cathode resistor are you using? what is your plate voltage?What is your voltage on pin 8?

You can determine the current flowing through each tube by Measuring resistance of each primary of the Output transformer with the amp off.Then turn on the amp and measure the voltage drop between each side of the OT.(from your B+ A to pin 3)Divide the voltage by the resistance and this will tell you in mA the current flowing through each plate.
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