|
Audio Asylum Thread Printer Get a view of an entire thread on one page |
For Sale Ads |
173.189.218.254
I think the nice mil spec potted power transformer that is currently on my old preamp psu has enough ommph for the deuce26/45 amp, but I am trying to make sure.
I own three books on diy tube amp buiding, including Rozenbilt and Jones, and I can not find a nice, simple explanation of how to size a power transformer for your project in any of them. Bah, hum bug.
This is what I think is needed, but I would appreciate any input anyone might have.The 45's need 36mA of plate current, so 2 x 36 is 72mA. The 26's need 6.2mA, so 4 x 6.2 is about 25mA for the 26's. That's a total of 97mA of current needed from the B+. Allow roughly 25% for losses, etc., and you get say 125mA.
All the filament needs are covered with separate trannys or are on separate windings on the big tranny.
The power tranny in question has a rating of 880vct and 165mA for the B+ winding. It seems to me that is a pretty good match. Am I missing anything?
Edits: 01/20/16 01/20/16 01/20/16 01/20/16Follow Ups:
Yes, you are missing something. When you cap. I/P filter, only approx. 1/2 of the RMS current produced by the rectified winding is available as DC. The power trafo you mentioned is not up to the job at hand.
Eli D.
I don't think that is always the case.Hammond's current ratings assume cap input.
On page 11 of the Hammond cat. linked below it shows a full wave capacitor input load as IDC = 1.0 X Sec IAC
And a full wave choke input load as 1.54 X rated.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Edits: 01/20/16
Guess i will just have to give it a try and see if it turns into a hot plate. : )
Tre',
I have often worked from this page by Hammond. Some of my setups end up with pretty warm PTs after an hour or so. I wonder why. I'm careful to distinguish AC and DC current, and try to find the manufacturers DC ratings and leave plenty of room (50 - 100%). I've had great (cool temp) results with Edcor, but some of my Triads and Hammonds get hot.
Maybe I need to leave even more overhead room in the ratings?
--Jeff
Post a Followup:
FAQ |
Post a Message! |
Forgot Password? |
|
||||||||||||||
|
This post is made possible by the generous support of people like you and our sponsors: