| arnoldc |
hi guys,
what will it take to add headphone capability to a 2A3 SET amp? Is it going to be another transformer?
any information on how to do so will be much appreciated as usual.
cheers! |
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| MIKET |
| You can just place a series resistor across the output of the amp to each earpiece.If you start at 470 ohms for the series resistor you can get the general idea. I am asuming these are the 200-600 ohm variety. If you are using the amplifier on low impeadance headphones then the resistor is even more important as you don't want to drive 2-4 watts directly into your ears. |
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| Sch3mat1c |
Duh, or just don't run the thing at 2W. (Like it has the voltage output to do that into >50 ohms anyway.) They make these wonderful devices known as volume controls...
Tim |
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| arnoldc |
ok, guys so i'll start with the resistor values recommended.
probably a switch too for amp/headamp operation.
cheers! |
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| arnoldc |
follow up question -
shouldn't i be concerned about the "load" the OPT will see? that will be the series resistor + the headphone impedance, right?
that's far off from the 8 ohm load it normally sees as the speaker. |
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| Frank Berry |
"shouldn't i be concerned about the "load" the OPT will see?"
Right you are. I'd put an 8 ohm resistor across the output of each amp. |
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| Sch3mat1c |
Not necessary unless it has NFB and is prone to instability. A higher load will produce greater linearity in the triode, not like you'll notice a darned bit of distortion at .01% of maximum power output. :eek:
Tim |
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| arnoldc |
no NFB guys
it's a JE Labs 2A3 using MagneQuest DS-025 OPT
so, as a safety precaution, shall i put the 8 ohm resistor across? |
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| fdegrove |
Hi,
| quote: | | so, as a safety precaution, shall i put the 8 ohm resistor across? |
There really is no need for it but you can try it for yourself.
Cheers,;) |
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