<html><head><meta http-equiv="Content-Type" content="text/html; charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class="">I was looking at this online image and it shows only two wires connected. So the schematic is probably correct.<div class=""><br class=""></div><div class=""><img apple-inline="yes" id="76540881-2E2A-45F1-BF7A-4404E0B3A32B" src="cid:04F62E70-9D23-4031-9CF3-EEF25740003C@altus-escon.com" class=""></div><div class=""><br class=""><div><div class="">Ben</div><div class=""><br class=""></div><blockquote type="cite" class=""><div class="">On 5 Oct 2020, at 17:37, Michael E Caloroso <<a href="mailto:mec.forumreader@gmail.com" class="">mec.forumreader@gmail.com</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><span style="caret-color: rgb(0, 0, 0); font-family: Menlo-Regular; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; float: none; display: inline !important;" class="">That's a pretty strange in/out technique.</span><br style="caret-color: rgb(0, 0, 0); font-family: Menlo-Regular; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none;" class=""><br style="caret-color: rgb(0, 0, 0); font-family: Menlo-Regular; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none;" class=""><span style="caret-color: rgb(0, 0, 0); font-family: Menlo-Regular; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; float: none; display: inline !important;" class="">Suffice to say, don't put too much faith in schematics as they often</span><br style="caret-color: rgb(0, 0, 0); font-family: Menlo-Regular; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none;" class=""><span style="caret-color: rgb(0, 0, 0); font-family: Menlo-Regular; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; float: none; display: inline !important;" class="">are not 100% accurate. Errors are known to be intentional to deter</span><br style="caret-color: rgb(0, 0, 0); font-family: Menlo-Regular; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none;" class=""><span style="caret-color: rgb(0, 0, 0); font-family: Menlo-Regular; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; float: none; display: inline !important;" class="">copycats.</span><br style="caret-color: rgb(0, 0, 0); font-family: Menlo-Regular; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none;" class=""><br style="caret-color: rgb(0, 0, 0); font-family: Menlo-Regular; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none;" class=""><span style="caret-color: rgb(0, 0, 0); font-family: Menlo-Regular; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; float: none; display: inline !important;" class="">MC</span><br style="caret-color: rgb(0, 0, 0); font-family: Menlo-Regular; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none;" class=""><br style="caret-color: rgb(0, 0, 0); font-family: Menlo-Regular; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none;" class=""><span style="caret-color: rgb(0, 0, 0); font-family: Menlo-Regular; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; float: none; display: inline !important;" class="">On 10/5/20, Ben Stuyts <</span><a href="mailto:ben@stuyts.nl" style="font-family: Menlo-Regular; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px;" class="">ben@stuyts.nl</a><span style="caret-color: rgb(0, 0, 0); font-family: Menlo-Regular; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; float: none; display: inline !important;" class="">> wrote:</span><br style="caret-color: rgb(0, 0, 0); font-family: Menlo-Regular; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none;" class=""><blockquote type="cite" style="font-family: Menlo-Regular; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; text-decoration: none;" class="">I don’t see any sonic advantages. If the offset voltage on the output of<br class="">IC1B isn’t exactly 0 (set by R63) you will have audible clicks anyway.<br class=""><br class="">As far as I can see from online images, the switch is not on the pcb. So it<br class="">saves one wire to solder/assemble. Maybe it was just for economical<br class="">reasons.<br class=""><br class="">Ben<br class=""><br class=""><br class=""><blockquote type="cite" class="">On 5 Oct 2020, at 16:25, ColinMuirDorward <<a href="mailto:colindorward@gmail.com" class="">colindorward@gmail.com</a>> wrote:<br class=""><br class="">Thanks Ben!<br class="">What's the advantage of doing this, rather than using a switch connected<br class="">to the output buffer that toggles between either the processed or the<br class="">unprocessed signal?<br class="">Less click?<br class="">Colin<br class=""><br class=""><br class="">On Mon, Oct 5, 2020 at 12:43 AM Ben Stuyts <<a href="mailto:ben@stuyts.nl" class="">ben@stuyts.nl</a><br class=""><<a href="mailto:ben@stuyts.nl" class="">mailto:ben@stuyts.nl</a>>> wrote:<br class=""><blockquote type="cite" class="">On 5 Oct 2020, at 05:28, ColinMuirDorward <<a href="mailto:colindorward@gmail.com" class="">colindorward@gmail.com</a><br class=""><<a href="mailto:colindorward@gmail.com" class="">mailto:colindorward@gmail.com</a>>> wrote:<br class=""><br class="">Here <<a href="http://www225.pair.com/audio/waltzingbear/Schematics/Urei/545.JPG" class="">http://www225.pair.com/audio/waltzingbear/Schematics/Urei/545.JPG</a>><br class="">is the schematic for the Urei 545 PEQ. I understand that it's a highpass<br class="">filter followed by four BP SVFs summed into the dry signal, then a<br class="">lowpass filter.<br class="">I'm stuck on the in/out switch, though. What's going on here? I know what<br class="">it's supposed to do, but I don't understand how it works.<br class=""></blockquote><br class="">The switch connects the output of IC1b directly to the output stage IC7.<br class="">The output of IC1b is very low impedance and is connected directly to the<br class="">+ input of IC7. Therefor, the processed signal (coming in via R52) is<br class="">completely attenuated (short circuited you might say) by IC1b’s output.<br class=""><br class="">There might be some bleed but it is attenuated by R52 (10k) over the<br class="">output impedance of IC1b (extremely low).<br class=""><br class="">Ben<br class=""><br class=""><br class=""><br class="">--<br class=""><a href="https://www.instagram.com/colinmuirdorward/" class="">https://www.instagram.com/colinmuirdorward/</a><br class=""><<a href="https://www.instagram.com/colinmuirdorward/" class="">https://www.instagram.com/colinmuirdorward/</a>><br class="">-<br class=""><<a href="https://www.instagram.com/colinmuirdorward/" class="">https://www.instagram.com/colinmuirdorward/</a>><br class=""><a href="https://www.instagram.com/ssdp_synthesis/" class="">https://www.instagram.com/ssdp_synthesis/</a><br class=""><<a href="https://www.instagram.com/ssdp_synthesis/" class="">https://www.instagram.com/ssdp_synthesis/</a>></blockquote></blockquote></div></blockquote></div><br class=""></div></body></html>