Northern Oak 0 Report post Posted August 1, 2003 It's a "glorified CMOY" design, the only addition being the unity gain buffer at the output stage. 10k resistor in blue is your potentiometer. You need a good one here, else you may end up with unbalanced left and right channels. Alps has good tolerance, difference is less than 0.2dB. The 1uF capacitor acts as a filter for your input ac signal. IC1a is the the gain amp, i.e. it amplfies your input voltage by a scale factor, depending on the resistor values that you have chosen. The resistors are the 1K and 10K in green. For this diagram, the gain is 11, cause it's a non-inverting amp, so it's (10K divide by 1K) plus 1. You got to practise caution when choosing the gain for IC1a because too much and you will cause the amp to clip in no time but too little and you will need to crank up the volume control by quite a fair bit. IC2a is the unity gain amp or buffer. I couldn't recall how much current the opa2132 can provide, but it's definitely lesser than the EL2002/2001 buffers. Each buffer is itself a unity gain buffer with a max output current of 120mA. An advantage of the buffer is that it protects IC1a's output from being "loaded" by your cans impedance. Okay, that's all I can say for now. BTW, the buffers ain't cheap, probably 2.5 times the price of the OPA2132 and if you add 4 per channel, that means you need 8 of them. Maybe it's more cost effective to use the OPA2132. Share this post Link to post Share on other sites
Wortel 0 Report post Posted August 1, 2003 Thanks for the info Northern Oak. I read through it very carefully. I will use some of what you said to make my parts selections. Share this post Link to post Share on other sites
snowparang 0 Report post Posted August 1, 2003 what's the bypass/crossmix thing for? An active crossover circuit? Gain of 11 is a bit too low, do you know the limit of the opamp? How about x30? Share this post Link to post Share on other sites
Northern Oak 0 Report post Posted August 1, 2003 Passive Crossfeed -> Channel Mixing -> It fills the voids in the sound stage spanning from the left ear to the right ear so that it will sound more like a speaker setup. Based on my past experience, it may be better to push the gain higher, perhaps somewhere between 15~18 but maybe not to x30. If you're bent on getting x30, it may be wiser to up the rail voltage from +/- 4.5V to +/- 9V instead. Share this post Link to post Share on other sites
Wortel 0 Report post Posted August 1, 2003 So I will need 2 9V batteries? I suppose I can accomadate that. Im not gonna really be using it for portable anyway. Share this post Link to post Share on other sites
snowparang 0 Report post Posted August 1, 2003 Passive Crossfeed -> Channel Mixing -> It fills the voids in the sound stage spanning from the left ear to the right ear so that it will sound more like a speaker setup. Based on my past experience, it may be better to push the gain higher, perhaps somewhere between 15~18 but maybe not to x30. If you're bent on getting x30, it may be wiser to up the rail voltage from +/- 4.5V to +/- 9V instead. hmm...maybe. Cause I'm not really building a portable one but one for my PC, will be tapping the 12V DC from the PSU so can get +-6V... I'm not sure about opamps, but can I just use any level of supply voltage? There should be a minimum and max? sorry me a newbie.... Share this post Link to post Share on other sites
jasonhanjk 0 Report post Posted August 1, 2003 Yes you can. Yellow and black wire. Share this post Link to post Share on other sites
Northern Oak 0 Report post Posted August 1, 2003 will be tapping the 12V DC from the PSU so can get +-6V... May I know what PSU are you referring to? but can I just use any level of supply voltage? There should be a minimum and max? sorry me a newbie.... Yes, there's a minimum and a maximum supply voltage : +/-2.5V to +/-18V. jasonhanjk: hmmm, what are you referring to? Share this post Link to post Share on other sites
Wortel 0 Report post Posted August 1, 2003 The wires from a computer PSU. My new one has heaps of extra wires. pretty thing it is Yellow wire is the 12v connector. jason : black wire dont matter, all black wires are grounds. Share this post Link to post Share on other sites
Northern Oak 0 Report post Posted August 1, 2003 okie, no problem with the PSU. Share this post Link to post Share on other sites
Firefox 0 Report post Posted August 1, 2003 The wires from a computer PSU. My new one has heaps of extra wires. pretty thing it is Yellow wire is the 12v connector. Good luck on that then... Computer PSU's are all switching units and are very noisy. Share this post Link to post Share on other sites
Wortel 0 Report post Posted August 1, 2003 My new psu is quite quiet. dual fan unit. I don't want to make a PSU powered amp though. Maybe later on. Share this post Link to post Share on other sites
Northern Oak 0 Report post Posted August 1, 2003 (edited) Mechanically quiet but what about electrically? Point to ponder. Edited August 1, 2003 by Northern Oak Share this post Link to post Share on other sites
Wortel 0 Report post Posted August 1, 2003 Mechanically quiet but what about electrically? Point to ponder. Point taken. and I dont want to tie a headamp inot my PSU. Share this post Link to post Share on other sites
Northern Oak 0 Report post Posted August 2, 2003 Forgotten to add that your K501 would sound better with the CMOY if you used more than 1 buffer. 3 would be okay, I guess. Share this post Link to post Share on other sites
