Matrix12x Posted November 24, 2009 Report Share Posted November 24, 2009 On the MB6582.... Does anyone else think the headphone volume is way low? I have to double check my resistor values I think. Quote Link to comment Share on other sites More sharing options...
nILS Posted November 24, 2009 Report Share Posted November 24, 2009 The outputs are at line level and not headphone outs. A headphone amp should solve that ;) Quote Link to comment Share on other sites More sharing options...
Futureman Posted November 25, 2009 Report Share Posted November 25, 2009 On the MB6582.... Does anyone else think the headphone volume is way low? I have to double check my resistor values I think. The summed out is pretty low compared to the individual outs. Nothing wrong with that tho.. Quote Link to comment Share on other sites More sharing options...
Matrix12x Posted November 26, 2009 Author Report Share Posted November 26, 2009 Yeah, I think I am going to breadboard a quickie opamp headphone amp to put in there.It's way low in mine, almost inaudible. The line outs have loads of signal though. :-) Quote Link to comment Share on other sites More sharing options...
Wilba Posted November 26, 2009 Report Share Posted November 26, 2009 The mixed output isn't a headphone output, it's just passive mixed with 10K resistors, hence very low output level. Not much I could do about that, no room on the PCB for a headphone amp, plus I heard (perhaps incorrectly) that the audio outputs swing up to 9V, making a single supply amp running on 9V difficult or impossible. I don't really know, though. Perhaps using PSU Option B (generating a 12V supply) combined with 8580/6582 SIDs (which will output 9V max) is a scenario suitable for a headphone amp supplied with 12V. If someone comes up with a good circuit, please share it! :) Quote Link to comment Share on other sites More sharing options...
Smithy Posted November 26, 2009 Report Share Posted November 26, 2009 Not to forget, the impedance value of your headphones will also have an effect on the overall volume. Quote Link to comment Share on other sites More sharing options...
Matrix12x Posted November 27, 2009 Author Report Share Posted November 27, 2009 Most cheap headphones are about 600 Ohms am I correct? I thought the low impedance ones were about 100-150 ohms. I figure a simple circuit using a dual opamp like a 5532, a 1uF DC block to a 10K ohms on the non inverting input, 10K to gnd as R1 at the inverting input, 100K as Rf, and a 56 pF cap in the feedback to limit the BW, and maybe a 100-150 ohm series output resistor feeding a 1uF DC block to my headphones. I'll probably play with the feedback resistors value to match it to the gain I need. I have used this IC with as little as +/- 5VDC. A voltage divider to float the audio signal on the input at some offset will allow single supply operation. I'll breadboard something next week and let you know the results. Quote Link to comment Share on other sites More sharing options...
seppoman Posted November 27, 2009 Report Share Posted November 27, 2009 A voltage divider to float the audio signal on the input at some offset will allow single supply operation. you could either remove the electrolytic cap at the audio out that does AC couple the signal, or if the gain of the transistor circuit is too high (didn't bother to investigate this) you could even grab the output signal directly from the SID output (I think I remember it does swing around 4.5V with not too much of amplitude, maybe look up the datasheet), buffer it with an opamp and do a complete active preamp/mixer stage. In the last case, better solder the wires instead of a connector, the SID doesn't like hot-plugging on its output very much. S Quote Link to comment Share on other sites More sharing options...
Smithy Posted November 28, 2009 Report Share Posted November 28, 2009 (edited) Most cheap headphones are about 600 Ohms am I correct? I thought the low impedance ones were about 100-150 ohms. Most cheap headphones i know of are usually under 60 (Sixty) Ohms, maybe thats what you meant? You'd really need an impedance that low for use with mp3 players, otherwise they'll be far too quiet, and will require a headphone amplifier to get a decent amount of volume. Edited November 28, 2009 by Smithy Quote Link to comment Share on other sites More sharing options...
Matrix12x Posted November 30, 2009 Author Report Share Posted November 30, 2009 sorry, I added that extra zero. Most of my cheaper headphones at home are less than 64 ohms. Quote Link to comment Share on other sites More sharing options...
rosch Posted November 30, 2009 Report Share Posted November 30, 2009 as far as i know (and i might be wrong) many regular cheap headphones have about 32 ohms while 600 ohms are high quality studio headphones. Quote Link to comment Share on other sites More sharing options...
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