Will a cheaper PT cause more sag??

[Ringwraith]

I think I'm experiencing an excessive amount of sag in my 5E3.
I'm not sure if it's just the circuit or maybe my Weber PT is adding to it.
Would there be any difference between say a Heyboar PT & a cheap Asian in the sag department? I know the Heyboars are better made but I was thinking the PT wouldn't really affect the sound. I bought a HB & Weber OT & found not much difference in sound but the Weber's thin shell vibrated like crazy so out it came!

Thanks
Sean

[macdillard]

I don't know for sure but I thought that "sag" had more to do with the rectifier than the PT. ie: voltage drop resulting from the internal resistance of the rectifier and the current flow.

[Enzo]

The resistance of the transformer wire can also contribute to sag.

The voltage coming out of a power transformer ideally is determined by the primary voltage and the turns ratio. But the winding wire has resistance, so the heavier the wire, the lowr the resistance. SO two transformers with the same secondary voltage can perform differently when one is would with thinner wire. That one will have higher winding resistance and hence more sag.

[Ringwraith]

Interesting Enzo.

I believe the PT does contribute to sag but I guess I'm just wondering if a lesser quality PT would contribute more as it may be less able to handle the voltage demand?
Here's an interesting article on sag.
http://www.aikenamps.com/Sag.html

Cheers
Sean

[Enzo]

Aiken has many interesting things to say, read all of them.

First, it is current demand, not voltage demand. The voltage sags under the current demand. The transformer supplies voltage, the load demands current. Ohm's Law will tell you the voltage that will be lost to the wire resistance when a current flows.


As to cheapness, someone would have to do side by side comparisons with the particular transformers. There are a lot of ways to make things cheaply. You could make the exact same transformer in the USA and in CHina on exact same machines with exact same materials and it would be cheaper from China because the Chinese won;t expect US factory wages.

Another way to make things cheaper is to use lighter wire - less copper means cheaper. SO we get into ratings. Is that 100ma winding just barely capable of 100ma or is it easily capable with capacity to spare?

The construction and materials matter too. What iron is used in the laminations? How many laminations? What dimensions for the laminations? And the windings - how tight and what format are the windings. All these things affect efficiency and regulation.

And there are non-performance ways to make things cheaper. Thinner and cruder end bells, flimsier mounting brackets, shielding or no shielding.

SO when you specifically want to ask if the cheaper part will sag more, it all depends. COuld be a transformer is really cheap but doesn;t sag much because it used relatively heavy wire. Maybe they found it cheaper to wind both 50 and 100 watt transformers from the same size wire than to stock two sizes of wire. The 50 watter then gets heavier wire than it might have. That is of course all hypothetical.