| Electronics > Beginners |
| Audio amp help |
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| Zero999:
--- Quote from: jeffheath on February 13, 2019, 11:38:39 pm --- --- Quote from: Richard Crowley on February 13, 2019, 10:32:38 pm ---You have left out a couple of important components: Rin1 and Rin2 are critical to the proper operation of the op-amp circuit. For unity gain they should be the same value as Rfeed1 and Rfeed2 If you provide Rin1 and Rin2 properly, then there will be no significant interaction between the value of the pot and the rest of the circuit. --- End quote --- I'm not sure whether or not I should have the capacitors before or after the pots, but I can change that pretty quickly, so I'll go ahead and get everything and put it together. --- End quote --- The capacitors should be after the potentiometers, otherwise the bias point of the circuit will shift, as the volume is adjusted. A capacitor is needed to block the DC voltage to the potentiometer. |
| paulca:
I recently built an audio/headphone amp with help from folks on here. https://www.eevblog.com/forum/beginners/decoupling-dilema/msg1508254/#msg1508254 If you want I can send you a bill of materials, KiCAD files, gerbers and a few already made PCB boards (for postage only). It does require some surface mount soldering though. Works perfectly, very high quality and very loud. Designed to fit into a box available online which I can dig out the part code for too. |
| jeffheath:
--- Quote from: paulca on February 15, 2019, 05:08:11 pm ---I recently built an audio/headphone amp with help from folks on here. https://www.eevblog.com/forum/beginners/decoupling-dilema/msg1508254/#msg1508254 If you want I can send you a bill of materials, KiCAD files, gerbers and a few already made PCB boards (for postage only). It does require some surface mount soldering though. Works perfectly, very high quality and very loud. Designed to fit into a box available online which I can dig out the part code for too. --- End quote --- I appreciate that; but this really just stemmed from a project I was doing and made me think; hmmm... what IS the simplest way for me to hook my headphones up to say, a dvd player, or game console or something, (and have volume control) so I want to see how this "one chip operation" does. So.... thanks but no thanks; but that is a very nice amp. Have you thought about posting the project on github? |
| jeffheath:
So I got the parts in from Mouser. I put it together, and it works great! The ts482 chip was all of 60 cents, and it took minimal circuitry to add composite audio input and a volume control. I can't say I hear any noise, even with my cheap bench power supply. I updated the schematic to put the capacitors in the correct location. |
| Richard Crowley:
--- Quote from: jeffheath on February 17, 2019, 04:15:48 am ---...I updated the schematic to put the capacitors in the correct location. --- End quote --- The correct location for the capacitors is between the pot and the input resistors. --- Quote from: Zero999 on February 14, 2019, 09:21:34 am ---The capacitors should be after the potentiometers, otherwise the bias point of the circuit will shift, as the volume is adjusted. A capacitor is needed to block the DC voltage to the potentiometer. --- End quote --- You may not notice it immediately but the DC from the op-amp will cause premature deterioration of the pot with increased noise over time. |
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