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It is currently 30 May 2020, 13:23

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PostPosted: 21 May 2020, 21:21 
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Joined: 04 Jun 2008, 20:59
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Location: Arizona, USA
Hi, A number of folks are using the 240 volt transformers on 220. The loss of B+ voltage is not significant and the output power will be essentially the same. In cases where the ac mains drops much more that can be an issue. At the 200 volt level it might matter and I would find a different transformer. Changing the resistors will not make much difference and a choke would would be expected to drop the B+ significantly more as the internal resistance is likely much higher than the 50 ohm resistor. The driver stage can actually work quite well down to about 150 volts.

Good listening
Bruce

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PostPosted: 22 May 2020, 01:22 
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I'm more concerned on the heater voltages, usually theres not much head room especially 5 or 6.3v so a 240v on 220v will nearly likey mean you may have less than recomended heater voltage


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PostPosted: 27 May 2020, 02:02 
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Joined: 14 Sep 2015, 09:36
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This is a good point. I may have to do convert the heater AC to DC to maintain the voltage.


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PostPosted: 27 May 2020, 03:59 
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You can always use a buck boost converter, one cheap from aliexpress, pay expensive shipping if you don't wanna wait 1-3months.
Which converts higher or lower input voltages to a fixed one


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PostPosted: 27 May 2020, 10:35 
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The drop in heater voltage is unlikley to cause any issues. The EL84s run fine from as low as 5.7 volts to about 6.5. So a 10% drop from the nominal 6.3 from the transfromers is still going to be fine. If you are using a variation with DC heaters that is regulated there should be no issue. and if DC unregulated changing a series resistor if present ought to work. A Boost converter will also work..just watch for the power load and check to see if you get switching noise that will need to be cleaned up.

Good listening
Bruce

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PostPosted: 27 May 2020, 19:18 
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My main concern is that below 6V heaters the drop in sound quality, also with arround 5-6V AC after regulated, there isn't enough voltage to either buck or boost the voltage, normally requirer diffrencee voltage of 2-3V to work well, so I recomend the buck boost.


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