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Old 3rd October 2012, 04:35 AM   #11
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I'm just using some double A batteries in series to get 12volts.
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Old 3rd October 2012, 04:38 AM   #12
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If the amp is biased to 1/2 of the supply voltage (biased to 6v), you have to use a capacitor. The problem could be that the cap has insufficient capacitance. It could also be that the amplifier's output impedance is too high. If the output is distorted, it could be that the AA batteries simply don't have sufficient current to drive the amplifier and speaker.
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Old 3rd October 2012, 04:57 AM   #13
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my power supply is not biased because I don't know how to do that part. i'm using a single transistor. and the sound quality is obscenely good (darn good quality) and has a really natural sound to it. it is mono only though.
a considerable amount of DC still flows to my subwoofer.. I want to eliminate the DC so only the sound goes through my speaker and no DC flows through my speaker.
there is no distortion whatsoever at all levels.
the only thing that has a problem is the DC flowing to my speaker. if I place a capacitor in series to my speaker to get rid of the DC there is no advantage because then no sound at all gets to my speaker for some reason.. and I checked.. the capacitor is around 4,000uf's biggest one I could find.
I'm clueless on how to bias the power supply voltage...
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Old 3rd October 2012, 05:13 AM   #14
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There is no way to build a single transistor amplifier without significant distortion.

A single transistor would be a class A amp. It would have to be biased to 1/2 of the supply voltage. This is done in the design process. The selection of components (resistors) is critical. The amp won't be stable because the bias will change with temperature.

You will have to use a more complex design.
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Old 3rd October 2012, 05:18 AM   #15
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well then I guess I've done the impossible just now? All I've got is one single resistor to bias the input and that's it...
and a quite large heatsink (its almost bigger than my hand)
it also sounds perfectly acceptable at lower voltages
(3 volts is the bare minimum that it sounds okay with)
but it works flawlessly at 12volts except for the DC flowing to the speaker which I can't seem to fix whatsoever.. I'll take some pictures soon to show you what i'm doing.
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Old 3rd October 2012, 06:40 AM   #16
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get yourself a little 4:1 transformer. you should be able to run 2, 3, or 4 transistors from the 12v and drive them through another driver transistor. build it for 1ohm stable. then run the output through the transformer, and you can get close to 100w, for plenty of headroom. what transistors are you using?
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Old 3rd October 2012, 03:59 PM   #17
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I'm not sure and I don't know anything about transformers.
I'm just using some transistors that I've scavanged from an old TV motherboard that are quite large
but they still work great
how would I find a transformer that takes DC? I thought they only work with AC?
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Old 3rd October 2012, 06:59 PM   #18
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That is the point. If you use a reansformer, it can still pass some dc, but will only transfer ac to the speaker. Using a 4:1 will let you get to 50w with plenty of headroom
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Old 3rd October 2012, 07:08 PM   #19
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so if I put a transformer on the output it will make my speakers louder? :?
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