------=_20041019100555_75225 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 8bit > Hey all, > > I've been in a major "clean-up" mode lately and as part of this, I decided > to > have just one pair of speakers on my desk, but still use them from all 3 > computers. So I need a *simple* 4-channel (1 extra for future use) stereo > line-level mixer. I'd appreciate some help with this design... > > My initial (and hopefully final :-) thought is to do this with a single > op-amp > per channel... Hi Neil, How about just doing a zero-voltage summing bus? The quality should be fine(when compared to the ground loops you'll likely have with three computers), and you can do stereo with just a dual opamp, or use a quad if you want to uninvert the signal. Attached is a diagram of the left or right channel. If you run it single supply you'll need t provide vref and also use an output cap. Cheerful regards, Bob ------=_20041019100555_75225 Content-Type: image/gif; name="mixer.gif" Content-Transfer-Encoding: base64 Content-Disposition: attachment; filename="mixer.gif" R0lGODlhDgNtArMAAAQCBPz+/Hx+fAAA3igAANNwIEQ5SQCC3iRwpgTpugB1AAAAAAEgOgDgaQCQ AACBACH5BAAAAAAALAAAAAAOA20CAwT/MMhJq7046827/2AojmRpnmiqrmzrvnAsz3Rt33iu73zv /8CgcEgsGo/IpHLJbDqf0Kh0Sq1ar9isdsvter/gsHhMLpvP6LR6zW673/C4fE6v2+/4vH7P7/v/ gIGCg4SFhoeIiYqLjI2Oj5CRkpOUlZaXmJmam5ydnp+goaKjpKWmp6ipqqusra6vsLGys7S1tre4 ubq7vL2+v8DBwsPExcbHyMnKy8zNzs/Q0dLT1NXW19jZ2tvc3d7f4M0CE+PkFeXh6eqW6ALt5O7r 8vOP7e8U6Bbu+/z9/vv0Ago0865cvgAH8ZlIOLChQysFJRxkKPEExYcYMyq5N25ihosf/0BqHEnS B0eE5z6miFeypUse9xB6xCASRM2XOHNaNCdx5oWbIXUKHSoEaMh/SJMqXcqUJdGnAo12kLqDKtSr 1qyqXKIVq1doXfU1Cfu1rDKyPJmgNcuW2Nq1N+C2nesLrVwbd+nqxUU2bw2/ewPLaqpUCmDBiNse TszY6+LGkIk+jkwZ5+TKmElezsz54ebOOQHQ/Qy6tDzSplODQ6269TbWrmNnlU1bKOzauMXl3q2Z t2+Mt38LBxZ8uPFdxY8rt5V8ufNYzZ9LZxV9uvVT1a9rF5V9u/dO3b+LxxR+vPlJ5c+rb+R0vftb AN/LpxV/vn1Y7e/rd5V/v39V/f0nYP8pAQ5oICgFHqjgJgku6CA76T0oIUERTmhhGA1eqGEiGW7o YSAdfijiHiGOaKIdJZ6oYhwprugiGy2+KOMZMc5ooxg13qhjFznu6CMWPf4oJEQVDmkkDEEeqaQT SS7pZBIxNvnklDGEKCWVWCJ50ZVZdvlCflx6KaYL8YQ55pksEKammWiKyY8KRbb5YXtSxinnhQXW J4Kddz5opVZ89nlglHsKaig+pAV66H1sbqDoou81ysGjkJ4n6VSVonmpo5m2uSlNncr5aUqhivoZ paW6Nyqqqaq6pU8xkdpqn/0ZpFBFuIo1q6FO5RNTrLfuymtHwaJE7JbCCsoSSMeiBGr/sp76qkGz yEI7Zq3TGuvsT9Z6mSCyzT7bLZbMZpsrt+OSa+6525abLpUivUkCq+9Ktxm99Tp3b75P7svvkv7+ e2TAAg9JcFwhUIVvwdocjJdULY7KcE4O00CsBxdjuvDEs81wm62YbsupyBxXVrEMwIp7U8olQ3Zy lcWKSzK67Lbc2MtfyirzzDrzbDNiOJOp684+17zxz7p5jPDQTKfVdM1IP7fm1P8QDbXPFCX0JtVM RT3P0UE97fTYMReNAthee4I2xmKT7e7VcKa9ztohk91zvGWnKbc6dNdt9rk1sbxC33tfQvjIf+e6 MtxxF74aGiBPyrhClx3uOHqQJ26O/1EZI3n5N5Y7CjHEFn/uTejrsm1T6aZzgzqOrbs+WOyvzU57 Nq9jeDvutu/eMX6+X5M7GMMHP0jxXiBvPCDKc9H88n08r4X00OtBPZDVS3P9FdtnX0f3VYDvvRzi T1H++G+cH4X66MPYe/tnvQ8/Muw/Uf/8NMqPfzH3j7W/LlxbCin69z+2ELCAZTkgAh2zQB8psIFQ eSAEJTPBG0mwgjq5IAa5MjUAbVBGGvxgS0Iowt6UUEUkPGFGUqhCz7TQRCx84UBiKMOi9AN4NfQQ DXN4Gh5uaIc+TAcQg/g4Ik5oiEbsBhKTWDsmOmiJTsQGFKP4OyoOaIpWnAYWsxiNLf9y8Rle/GLS xLifMJIxfmfUjxnTeIw1spF/b7SPG+MojDnSkTh3jFQeVbXH9dixj8gBpKUEaZ4/KstpEzEk5giZ MHggsieZUeSd7JEWaWFGkqLanOLyBo8AYrINn9SUJrGWukKVJJRnOglD8LaQUzKykbjq3OQ0h7gV vnJ1ivNJKeeFyjL00k2V1OVWVmLLW6pOZJaU3OCAY8zB3XCYcPKkNNekv2ayrnFQqqY1UbZMrmhz m54jplq+CU6hWeRRvyxBOsdlFyiscwTvtFZf1kfOcqZJmoappz2Pp899gqif/vxDPGEZUA4BtKB8 GCguEXoIhYaNoYZw6DEhSgiJ+o3/ooKwqDIxyk/ocLSiB/0oHTRaS5H6gaS7NCmJQtrDh050YCzl Gy1lYhOUCi+mQqSlLLNl0yryx5WzdBZQImekntJMI4IL1uKCCkKcgq5nTAscJ3Vk1LbNEKoxY6Xd dlRVrF7VqlrbZVfB6FQlHjVv1fKqBcuKnGkmBZpbzRrRbujWAFpnrFulXw5WabW05nVp9mIrAHUg TKi+babcnA5emVpHwqqVZFpFLMzstVjJ/iI4SX0k4rJTWUfoCYfOwOxfN6nM7nRWEZ8VbC6Ks9Nn DdWy4fyNxNgBFpjodKatrYpxZkuJ0+rNtkdZKBB8yyHiwrYXySGdcH9g3OLWorln/+stZWcB3Z0s crqgHWMkqssI3hqUrNe9jncjWtvwame8HQ2tdMeDXuaVVxLchUR73Qte+H5nvv+s73a3g9+Mvne/ d8VrfOe1XqlVdsDwLLBy+tvQ/8p3OQxGBIJNad/dNnfCBAWwbKuL4eXWw8KrdfCHjxNhCYvYs/ry bYdd+mADJ+ydK37piLErOu6cmD3nfdUAb9xd74DJojG+6Iz52xGSBnmjGvZxXZ+5iCOXdMhETm2C e6zfFhP5HEnyopNTiuMcTytHWuZxk8XLOQqjVsxnpvFkx1xlKIP4L11Wr3mFM94wtxnFb8aBneVc 4Q0Dl818TrJv5rtn7Vp5OOgtNP8z/rjlPHhX0ctgtJrXnOZAHzrFSqOypd2M6Z/o6VdWI++d40xm nYH6apBGY5+vDLhKxpXUi1awkpFJOW2FuhCNvjWgWV2ucJ3VxKPWdKn/Si24AnvTeA6wVbWV2+M6 Gs3fnfRUi63r9Bqa0yTmMmmr7d9g71pfIwsr41KdDEkrdlLzFHZ+sedMFN31mpUeqZCpkJciy/vc mf72HKSahXo7kkXvzne8v/dkev/2327I9UoFHm13a5ue3cRywgOeWH3fm9tMOrg+tqdw68EbsDIu OF4W/muDR5wm1Ov4sxn+sJq6XLcex7j/Tv6R56kcD0HLWZl3/ueVL9udGq+xLyn/TumR3/booiX5 Y4FOc3ST4eZ3yHkLMuvqjSY95j+3X9AxljuoO7ziRp9lMqHJGil/far2M1NYShxbqX2c4ZH9W2Gr JC+so30sdY/uQizndYKzHOzjXra4PeYPpY+Wg0y27jmdR/S2/92veeWrxQpv98NvhPJ6Xwnd+q6J JRMm1HIt+cy25vnSm/70AMEnlpsiE9S73q09wXxNwcb5fQ8drKIfPZnyjvPcM4n3rfzSxmpPPoII /viWhyfbx5l1tagdZfgiPsBvP9q5F2syGpS836EP8cAa//BjVxnge998NSSKUtKHQ/Oovm1zVS6h Mre5nhXFvrxnLfHMyRzS2fZ+/8MnX/57xSfqk0zCFF/yx3P893fbt3TJNz0wESf0Mk07AyzWRx9p EDHKNX4LyICM1W8mUSGskm5NQ4Ec+ArSozAZ5nhn91hIQX09sHwNGATtdFYkeHcedYPkF3/6N1zh gX6ZdzdjU4HUpVq683A2yHhDEGFmZwRwEXpVF4S8cGA+p4P5UwT4hX9HIBdO2H6QFYVE+AX8toFJ CBtVk03YFFVKVX4/hYMXZ4TuAyWoUYZZuHW3Aitq2ApS6BAQWGSv14d9OHVCt3pu8YValIWYBXxE 4G8NQ4jaY4XNsYRJ2HTVkIcN0YMppIVNlF1RIYM0VCeZaIIu9IENFny8w4ab+P+AA5eCPoWHoRiA 7KF6paiJAUGG6UcdjNhFcVGLrGiKs/gXuriGskgPg6d53nKLIqaFv8iLtqiHd4hyRWV6OwZG0FiC zqhS6gRtuNSCL2eN1+htZtaBkMSNindtpBiDMMhIfaeIR0hT4niGsSaJTteO8KhX81iN8liPxqCO 8XiPdFhu/Shxi0I1HuSNqgiQ/JgzBOlhCHeQCIls3WiQDKmCqiZOCxmREumPEXeOHJWOeqORH8WR 7WaReoaNImmGDtk6sreMJ1mSzLeSLLkRJPmSVhiTMhmJCVmTiUiTODlcOrmTJtGTPtlz7xiU3nST RPmTRnmUQhlpSgmTSdmUewX/lFAJZ085lWFHjlbJXFKZlUXHlFxpky75lSNZlWJ5kfRYllpJlmgJ iGq5lvgIR275glsZlz84lHQZlW15l+Vol3p5lXzZl283kYAZmBg5mFQZlvylWbHnkUWEmOeFcFsY GSCpR+HIM/ECiybkmOI1Stonc57ZUppJcRejNQ0ygyMxmXwUS0UDeVOGVHOZbarJmjFobJX4mrsV TLQJjrnZi3kJm+0SmdSIZLXZm7fZauEYd+P4VaEpHx3iF35YV8Y4CtPoJ/9YFNHJUHcRKJTok5jY kqBIlG+BTteJUKY5c8EokyKYccqInpipnudpmN4JjPDJdO9ZF9R0O9s5n+75/536qXXr2Z9IkJ8A 6pT1OaA5+Z8GeqAFmqAyOJ4M6o67GGlYiJ8O+qB1GaEWyoQVmqEPyZ8cqqAe+qHWiaAiCnMLWqJj eaIo6pcYuqJIqaIuqoADGaMvGqI06lgkeqMymgrJSKE5qqNdqZK4RieI+FmRaRCQ6GmJlKRQuJir R6RMCkw/inWxQifsQoCWxH51eH0X9SuC06N1saGw84TtN3aUxBPhR3ZNullcimqhIqD0haayYoeu dhI2SKeWV6Vp6HuTJKbEA1c1SGsVYafgN6frqKdkuo6p5KdgWHP2Z6hVBzJCeKWdFKWqWam+UiuM uSBwelKIkqh42i6cyYB4Sv86M2F9YIpcjNqoW0qpe7pto0mqkIpYsoSozViMU5qDl2qcZFqlRJU4 oYqAvfqZUgqjUfeqgsqrovpvaSoztipkBEisuGqsUYeISkqaJWKtKNdeE5opnQqkhDmj4JqiNjqu 4cqj5jp/qwqklmoKqSo37YoK7xo1m9pt6bp7IXavWgIf+sp9Ftiv/pqrAKtOizWvKDlWBhs79dqG A+uLq5Cwu7Ow6dOw6iquFEt3LXqxU4ewGrt7BduxIbmuNyqx/gey2/hcJqt8g5WyewJdEIs0JFuy LBtc/zqzBPtiCGKzZ7MyA/WyjvMtDuWzl/Nj7qqzG8uORWu09zSdqai0e8f/JeTmtDhbka3ZtFJL sxu3drB2tVw3FYCytVz7ZQUpcrgWtl7LoqNotvZ4mFZrttwKtmF7hXAbt1fXtm5LhnOrtkh7rtam t57Gtg3nt2vbkHYruFT7lutmuIFYqa8KnGmruPsYrVw4m/AHucEluct6qzJruRtnNtTGp/bKufbY a7YGuokrup+Kdp+ruZWHugFCus0WtYp7WENDu8eGup6bVcSWt4Z7mUEiu73Lt6HrusJ7uqIrdXGK u8grULhLud94u8S7o0HqhsHJls27vPd0svuIl9dbvIAorJLDWs2rm8/LOq+1fzjavdJrTpqjpVrK vsrrvScXhsCqqIirt9hb/5dxt7/pG7/ru3W2G8Dc678aKJGyecADPL6E95x5AnoO/KSt53kKjDyd iVWsKbQTpDzD+DSHhcEZ/H3Vt3TNqsDVySN3esLkS8IsNqbtm6cprMIhV4Tn+1oe/MH5A76cUsMQ dIKjo5AwfL9bgII+/MMUScQPa8QZi8RJq8ToysRN7MTYAcXyKsVRTMUEYsVXjMXSqcVbzMWhoMMi CsYfKsYcSsYZasYWisYPqsZ0eXpe/MZwHMdyPMd0XMd2fMez20F4vMd83Md+/MeAHMiCPMgsmZKE fMiInMiKvMiM3MiO/MiQHMmSPMmUXMmWfMmYnMmavMmc3Mme/MmgHMqiPA3KpFzKpnzKqJzKTBwB ADs= ------=_20041019100555_75225 Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit _______________________________________________ http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist ------=_20041019100555_75225--