Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: worth on October 29, 2010, 02:01:20 pm

Title: transformer ratings question
Post by: worth on October 29, 2010, 02:01:20 pm

If I use a Fender PT for 325-0-325@200ma. for a single channel fender build with tube recto and reverb , ( 4 preamp tubes instead of the usual six ) how much should I expect the voltage to rise with two less tubes ?

Title: Re: transformer ratings question
Post by: jojokeo on October 29, 2010, 02:12:03 pm

For B+ - very little if any since preamp tubes use so little current. Budget 3mA for a 12ax or ay, and more like 10mA for a 12au. Practical or actual use is less. Same for 6.3 heaters, you're only talking .6amp on a tranny like that won't any noticeable difference.

Title: Re: transformer ratings question
Post by: HotBluePlates on October 29, 2010, 07:07:36 pm

Will you use a similar number and size of output tube? That would alter the B+ much more than the preamp tube current draw.