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Post by mobius on Dec 24, 2018 16:53:43 GMT
While I unfortunately have not had a lot of time for building anything at all lately, I've also been running into an additional hurdle with a lot of the circuits I've been coming across in my researching making pretty heavy use of op amps. Those circuits and the common op amps being used typically require a dual power supply with greater voltages than what can be obtained with AE's 0..5V and a voltage divider/virtual ground. Being new to the synth-DIY hobby my parts bin does not have an assortment of op amps to experiment with, much less those that can run on the lower power that AE provides.
So I've been trying to find some op amps to order that I could use to try out some of those circuits with my AE. I do have an LM324 that I used to breadboard up a simple AR envelope and it seems to be working ok, but I was wondering what op amps y'all have been using, if any, in your AE circuits? And any best/better op amps to use over others?
Just realized I probably could pop the fronts off of some of the modules and see how the magic is done by Robert, but still a question I'd like to throw out and see what everyone has been using.
Cheers!
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Post by robertlanger on Dec 24, 2018 18:15:45 GMT
Hi, my standard opamps are LMV358 (dual), LMV324 (quad) and MCP602. These are all so called rail-to-rail opamps, meaning they work close to the supply voltages.
The MCP is the "better" one and goes down to 15 millivolts above the ground level.
Maybe the LMVs are available only as SMD, the MCP602 is also available as THT part.
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Post by mobius on Dec 24, 2018 18:17:26 GMT
Great - thanks Robert!
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Post by thetechnobear on Dec 24, 2018 18:19:00 GMT
I don't know much about the advantages of various opamp  but one thing , I learnt early on was that often I needed 'rail to rail' opamps, this will get quite a bit closer to your min/max voltage levels, before clipping. I use MCP6002 or MCP6004, which are rail-to-rail , and easy to get hold of... im sure theres load of others those. I guess these are more expensive, but this is a non-issue given the quantity I use ( I used a MCP6002 on the belamini project you can see it in that post ) the other thing, Ive found trimmer pots a useful thing to have around, if you need accurate offset or scaling... though I admit, finding space on AE circuits can be challenging , as to date, Ive been fairly frugal with the HP I allow for my DIY modules (which I usually later regret  ) |
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ben
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Post by ben on Dec 26, 2018 23:34:41 GMT
I've tried for the sake of trying a super cheap op-amp with TDA2030A 'cause it was cheaper to buy one from eBay (China) than actually building one myself, but it turned out to be too noisy and impossible to use in any way (maybeee for spring reverb or smthn similar, maybe..), but not for the general mixing etc. So I wouldn't recommend buying or building this one for sure. BTW, my guess is that you can try to buy some small modules that can change the voltage from 5 to 9, 12, 12+/12- etc. on eBay and Amazon, and play with that, just make sure you don't "overheat" the final output. I'm also a newbie so don't take my word for granted, I'm just experimenting a lot, including all of that op-amps and voltage stuff sorry don't know how to insert smaller size images in this forum. Good luck and looking forward to what you'll come up with! P.S.: big thanks to Robert Langer for giving some advices regarding to the mixer schematics.  |
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ben
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Post by ben on Jan 16, 2019 10:05:08 GMT
Does any of you have any idea why I'm having crackling sound out of LMV358 op-amp? Did any of you had the same issue? I've soldered three of those and all of them had the same issue (so it shouldn't be a problem of soldering, I guess..). It seems like the amplifier is working, fed signal in and it amplifies the sound, but also with some artefacts which are impossible to miss. For 1uf and 0.1uf I've used electrolytic capacitors instead of ceramic - could this be an issue? Used schematics from here: cdn.sparkfun.com/datasheets/BreakoutBoards/SparkFun_OpAmp_Breakout-LMV358.pdf |
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Post by admin on Feb 27, 2019 9:32:21 GMT
Hi ben, do you have an update on your DIY project? The photo above looks impressive and I'd love to hear a demo of what it does! |
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ben
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Posts: 124
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Post by ben on Feb 27, 2019 13:24:09 GMT
Hi ben , do you have an update on your DIY project? The photo above looks impressive and I'd love to hear a demo of what it does! do you mean amplifier? The schematics which I've shared above work well, it seems I just had an issue with soldering flux, it was shortening my circuit. After a proper cleaning with isopropyl alcohol everything works well. But before I found out about this problem - ordered a few LM358 soldered boards on eBay ( LM358 eBay link), actually 5 for 3.75$. Just had to change pots to a bigger ones/more usable. Regarding to the sound samples - lately had no time to record any, will try to do something this weekend... Here's a photo with 358 amp in the first grey/AE modular row:  ![]()  |
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Post by admin on Feb 28, 2019 21:32:34 GMT
Here's a photo with 358 amp in the first grey/AE modular row: Wow! This looks amazing! I didn't know that you were so far advanced in building your own modules. Would you mind taking some time and show off each one separately with a short description what it does, maybe a clue on how you built it and a sound demo? This is exactly the kind of DIY spirit that I think the AE system with its "safe" 5v is all about. Great work! |
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