On a PT Ht secondary mA question

[catnine]

 If the same amp has a 325-0-325 @70mA or one with 325-0-325 @180mA and they have all the componants of the same value and the same tubes and the same mA draw will the higher mA rated PT not drop the voltage as much as one with a smaller mA rating?

 The reason I ask this is my build uses the same tubes and every thing else as  6G2 princeton without the tremlo circuit yet the 6G2 has a 1k and 10k dropping resisters and mine has a 5K and 22K yet my B+ is much higher so it can't be the tube mA draw combined.

 I recall when I made my first build from some kit and it used Hammond PT and was a 5F2A then when I changed it to a 5F2A with 2 6V6's in parallel if I recall the PT HT voltage was the same but I had to get one with a higher mA rating. Of course I also had to change the OT .

 All I know reguarding the reason the princton PT I got could use 6V6's or 6L6's and to use the 6L6's I changed the 5K dropper to a 2.5K since the 6L6's needed more voltage with the 6L6's it was basically like a 5E5 Pro only adj/fixed bias. I also used a much larger PT for a BF deluxe but larger that could handle 6L6's on a 2 or 4 ohm load and 4 or 8 ohm load with 6V6's . The OT has a 7000 ohm primary . They are Allen AMps tranny's yet he changed the PT to 310-0-310 @ 150mA and the OT to use 6V6's with 8 or 16 ohm or 6L6 with 4 or 8 ohm to make the OT work with the more common 8 ohm speakers. I can't find my OT sheet but I think it was still 7000 ohm primary. It could have been an 8000 primary I am not certain.

[stratele52]

If the same amp has a 325-0-325 @70mA or one with 325-0-325 @180mA and they have all the componants of the same value and the same tubes and the same mA draw will the higher mA rated PT not drop the voltage as much as one with a smaller mA rating?
 

My experience said yes . Because Power Transformer have not a regulated output. It work with the load as you explain.

[HotBluePlates]

HBP has left the building.

[stratele52]

Very good explanation HotBluePlate

[catnine]

If the same amp has a 325-0-325 @70mA or one with 325-0-325 @180mA ...

The 325-0-325v @ 180mA should be interpreted as, "325-0-325v when drawing 180mA."

Transformers have coils with many turns of wire, which itself has resistance. If you pull less current through that resistance, the voltage drop across that resistance is reduced and output voltage is higher than the spec.

Throw into the mix that wall voltage could be slightly higher than the 110v or 115v or 120v specified, and that difference will be multipled by the turns ratio of the transformer.

 Makes perfect sense to me. This is why my P-P build with high 180 mA ratings and a pair of 6V6's and one 12ax7 and a 12ay7 ( using on triode ) has 415 VDC B+ and my SF champ build with 100mA  with just one 6V6 and one 12ax7 has a B+ of 384 VDC and that's with 118.2 VAC line. If I used the stack champ PT with 70mA then the VDC B+ would be lower.

[stratele52]

You are right Catnine