|
Audio Asylum Thread Printer Get a view of an entire thread on one page |
For Sale Ads |
82.39.104.89
In Reply to: RE: Does overspecing transformers use extra energy? posted by amnesiac on August 07, 2014 at 09:54:51
I usually spec everything with about the same headroom you mention . You don't want to run power transformers flat-out . Hotter windings increases DCR , heat increases cause copper loss . The only caveat I think of using a monster transformer apart from size and weight is if it's old . Old iron sometimes degrades and typically 'throbs' at power on
Al
Follow Ups:
+1
If you are using PSUDII to calculate your values you should be sure to accurately measure the resistance of the primary and secondary, and calculate your load accurately too. Plug these numbers into PSUDII and you will get fairly accurate results. Otherwise your B+ may be way off what you are shooting for.
Over spec'd transformers can contribute a lot to good PS regulation, which (IMHO) is very desirable. I think they are a little harder on the rectifier and caps, and I think it is a littler more difficult to get the ripple under control (compared with a higher resistance transformer), but I think you end up with a better sounding amp.
Note that if the B+ is over spec'd then the filaments (if it has them) will probably run high also, so you may have to employ some resistance or bucking to get them right.
Yes and Yes I like PSud11 I always use it and learn gradually how to understand it I little more. I usually try what trans I have and select for amps that fit. Often with my scrounging it's more build an amp to suit the parts then the other way around. Always pays to have many amps on the go at once.
The trans I have in mind is 500volts single winding old army transmitter with bolts for taps. That will give you an idea of how big it really is. I understand that the low dcr will cause headaches but didn't consider the start up pulses and vibration's only time and some new soft start modules I bought will tell if it is useable. I used it's matching choke in a supply that worked well. Just polished those threaded taps shiny and bolted solder tabs on.
I find that in all well-designed supply iron, power transformers and chokes, "20 Ohms or less" is sounding best to me. That would be from either end of the HV winding, to the center tap, or, across a choke winding. If its a non center tapped power transformer, it would be 20 Ohms end to end. For the last eight years however, I use ten Ohms or less in all my iron, and I like that a lot. You want minimal series resistances in the supply / filter to the finals.Do you know to measure the primary's DCR and apply that to the secondary in PSUD2 ?? ( I ususally like to listen to a primary that is under one ohm. ) Here we go :
When you work with Duncan amps PSU Designer II, please use the formula for Rtransformer:
Rtr. = Rsec. + (n x n x Rprim.)
Rsec. = DC Resistance secondary [Ohm], measured between (0V - high volt) of one 'leg'.
n = step-up ratio (= voltage secundary / voltage primary)
Rprim. = DC Resistance primary [Ohm]
This is the transformer resistance as it's 'seen' by the rectifier
tube.
Jeff Medwin
Edits: 08/08/14 08/08/14 08/08/14
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: