OK I moved here to brazil and the mains is 125V.This means that for my 300b(actually eml 520) amp on the 115v windings the B+ and of course the heater voltages are way over the top.The draw I calculate is about 200/ 220 VA.
What is the best way to get back to specs?
1.Put a huge bunch of about 5ohm total power resistors or ideally one 5ohm 50w power resistor just after the mains socket -drawback = lots of heat
2.Put the calculated resistors on B+ plus heaters - lots of work and calculation .That´s eight different resistors.
3.Use diodes or zeners.I haven´t really thought about it thru yet.Obviously the diodes will have to be after the rectifiers for the B+ and will have to drop around 90v.But you can´t use them for the ac heaters.
Up to now I was using a step down autoformer that gave about 220v on the 230v windings of the amp.However I generally don´t like the idea of using autoformers before the power amp.Experience has shown that they muddle the bass.
What is the best way to get back to specs?
1.Put a huge bunch of about 5ohm total power resistors or ideally one 5ohm 50w power resistor just after the mains socket -drawback = lots of heat
2.Put the calculated resistors on B+ plus heaters - lots of work and calculation .That´s eight different resistors.
3.Use diodes or zeners.I haven´t really thought about it thru yet.Obviously the diodes will have to be after the rectifiers for the B+ and will have to drop around 90v.But you can´t use them for the ac heaters.
Up to now I was using a step down autoformer that gave about 220v on the 230v windings of the amp.However I generally don´t like the idea of using autoformers before the power amp.Experience has shown that they muddle the bass.
What bass?😀
Seriously, the transformer option sounds the best. Proprly implemented - with an adequately rated transformer, and neutral continuity, I cannot envisage any sound deterioration.
The transformer could be one with 115v and 125v taps, or a 10v transformer with the secondary used in anti-phase to subtract 10v. The transformer size using this arrangement will be very small.
I certainly wouldn't get involved with nasty zeners 😉
John
Seriously, the transformer option sounds the best. Proprly implemented - with an adequately rated transformer, and neutral continuity, I cannot envisage any sound deterioration.
The transformer could be one with 115v and 125v taps, or a 10v transformer with the secondary used in anti-phase to subtract 10v. The transformer size using this arrangement will be very small.
I certainly wouldn't get involved with nasty zeners 😉
John
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