tag:blogger.com,1999:blog-8559314700259794131.post3767214335594258377..comments2024-03-16T17:35:18.893+01:00Comments on Eddy Bergman.com: Synthesizer Extra's No. 01: SIMPLE AD/AR using the 7555Eddy Bergmanhttp://www.blogger.com/profile/13286799069112368259noreply@blogger.comBlogger12125tag:blogger.com,1999:blog-8559314700259794131.post-36163737200920829552023-06-03T19:53:24.396+02:002023-06-03T19:53:24.396+02:00Yes that is also true, however on a AD/AR output i...Yes that is also true, however on a AD/AR output impedance is not that critical because we're only pulling current from it occasionally or in pulses. The output impedance of opamps is usually very low, upto 190 Ohms in your average opamp, so in the case of the opamp output of an oscillator, where we draw a signal from the output constantly, it is helpful to up that a little to 1K to protect the output against running hot over time. That's why it is standard to use 1K on VCO outputs. However that VCO signal usually goes into an other opamp and opamp input impedances are infinitely high so it that case 1K isn't going to make any difference. But if that signal goes into a transistor input the impedance might be lower so for safety, and to be sure, we use 1K on VCO outputs and because it really doesn't matter you should always use 1K on an opamp output, then you're always good to go. So your point is valid. :) (I hope that made sense ^___^ )Eddy Bergmanhttps://www.blogger.com/profile/13286799069112368259noreply@blogger.comtag:blogger.com,1999:blog-8559314700259794131.post-16323217866021720592023-06-03T19:39:14.777+02:002023-06-03T19:39:14.777+02:00Oh so that's what those are for. I thought it ...Oh so that's what those are for. I thought it had something to do with the low output impendance / high input impendance rule of thumb modular systems tend to have (or so i've read they tend to have, don't know if that's true).Timhttps://www.blogger.com/profile/18270474139946317284noreply@blogger.comtag:blogger.com,1999:blog-8559314700259794131.post-9543581188369056892023-06-03T19:21:19.660+02:002023-06-03T19:21:19.660+02:00Yes it's a good practise to do that and you ca...Yes it's a good practise to do that and you can put a 1K in if you like. They are used to protect the output of the opamp against short circuits when putting in or pulling out the patch cables, however all modern opamps have short circuit protection built in so it's not absolutely necessary these days but it certainly can't hurt to use them.Eddy Bergmanhttps://www.blogger.com/profile/13286799069112368259noreply@blogger.comtag:blogger.com,1999:blog-8559314700259794131.post-23055453554269019262023-06-03T19:07:37.672+02:002023-06-03T19:07:37.672+02:00Hi Eddy, wouldn't it make sense to put a 1k re...Hi Eddy, wouldn't it make sense to put a 1k resistor on the output socket like most outputs on most modules have? Timhttps://www.blogger.com/profile/18270474139946317284noreply@blogger.comtag:blogger.com,1999:blog-8559314700259794131.post-46720905143729389602022-02-19T18:46:08.843+01:002022-02-19T18:46:08.843+01:00I'm afraid I don't have a schematic for th...I'm afraid I don't have a schematic for the final version I did but it's just adding a few very simple extra's like an opamp buffer stage on the output and an extra opamp with a gain of 2 for 0-10V. It's really basic stuff but I'm afraid you'll have retrace it if you want a schematic. I would love to see the schematic you create (and check it over for you if you want) and even add it to this article (with full credit given of course) if you would like that. I look forward to seeing it.Eddy Bergmanhttps://www.blogger.com/profile/13286799069112368259noreply@blogger.comtag:blogger.com,1999:blog-8559314700259794131.post-499354599065343172022-02-19T18:27:32.813+01:002022-02-19T18:27:32.813+01:00Hello! Thanks a lot for sharing your work! I am no...Hello! Thanks a lot for sharing your work! I am now working on a dual eg version of your design based on 7556 and was wondering if you have the schematic of your final version layout? Just thought i ask you first before i retrace(could make an error..). Would gladly share it here when im done.Anonymoushttps://www.blogger.com/profile/13803571255280427015noreply@blogger.comtag:blogger.com,1999:blog-8559314700259794131.post-9766166630079689702021-12-10T18:03:51.359+01:002021-12-10T18:03:51.359+01:00Thanks for the compliment! I'm glad you find t...Thanks for the compliment! I'm glad you find the site helpful. As for the resistors. The value doesn't really matter as long as they are the same or close to the same because they are used as voltage dividers. So whether it's 2K2 or 22K doesn't matter as long as both resistors are the same or close to the same so they divide the voltage in half.Eddy Bergmanhttps://www.blogger.com/profile/13286799069112368259noreply@blogger.comtag:blogger.com,1999:blog-8559314700259794131.post-63910623143013749492021-12-10T16:27:07.540+01:002021-12-10T16:27:07.540+01:00Nice work! I've built the LMNC AD/AR but this ...Nice work! I've built the LMNC AD/AR but this one looks the business, and I've re made the layout to use one TL074 (had a ton of them hanging around). Can I just check that in your second layout the resistors labelled 20k and 22k should be 2k and 2.2k (or 3.3k in my case)? Or have I missed something (wouldn't be the first time!)<br /><br />Absolutely love you site. It's helped a lot over the last year.Anonymoushttps://www.blogger.com/profile/03974225278230659646noreply@blogger.comtag:blogger.com,1999:blog-8559314700259794131.post-53346921036936671702021-03-18T11:48:25.179+01:002021-03-18T11:48:25.179+01:00sameguy again. nevermind I forgot to add a cruical...sameguy again. nevermind I forgot to add a cruical component. namely the transistor *facepalm* I will test it further when I've done the faceplace, but it seems to work like inteded with the NE555P and I forgot to mention I use TL082 for the Opamps because I've got several laying around. THANK YOU so much for your work and dedication! greetingsknopslhttps://www.blogger.com/profile/09656746636816147729noreply@blogger.comtag:blogger.com,1999:blog-8559314700259794131.post-41925048775691763502021-03-18T11:41:27.907+01:002021-03-18T11:41:27.907+01:00sameguy here. the thing is I had to switch two com...sameguy here. the thing is I had to switch two components. the 7555 -> NE555P and the two Log Pots are Lin Pots. I am getting no signal on the LED or on the output. is that even possible? The pots can't be the problem am I right?knopslhttps://www.blogger.com/profile/09656746636816147729noreply@blogger.comtag:blogger.com,1999:blog-8559314700259794131.post-65381999201609328072021-03-08T10:48:59.949+01:002021-03-08T10:48:59.949+01:00You can try it and it might work but the normal NE...You can try it and it might work but the normal NE555 has some problems that the 7555 does not have. For one, it can have oscillations on top of the squarewave output (see my article on the 81 LED chaser) and it also consumes a lot more power than the 7555 does. But try it and see if it works. I bet it will work.Eddy Bergmanhttps://www.blogger.com/profile/13286799069112368259noreply@blogger.comtag:blogger.com,1999:blog-8559314700259794131.post-73925513015136821002021-03-08T10:29:31.331+01:002021-03-08T10:29:31.331+01:00I have a question about the IC 7555, can I use a N...I have a question about the IC 7555, can I use a NE555 instead and have the same or a similar effect?knopslhttps://www.blogger.com/profile/09656746636816147729noreply@blogger.com