Electronics > Beginners
Op amp based preamp supply. Charge pump, single vs symmetrical & ripple
dazz:
--- Quote from: dazz on November 28, 2018, 12:34:03 am ---Those are just great simple, compact solutions, than you. If I can find those for cheap it's a done deal
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I meant to write "thank you" there, sorry about that.
--- Quote from: Hero999 on November 28, 2018, 09:52:51 am ---
What are the budget constraints?
Is just just a one off hobby project? Will it be made and sold commercially in small quantities i.e. 5 or so? Or are you going to make 1000s? It's often cheaper to use a module, once the cost of all of the parts, assembly and board space is taken into account.
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It's not a commercial product, I'm simply designing the PCB and publishing the gerber files for DIYers, so one-offs typically. Re: budget constraints, well, I don't have a figure in mind, just thought it made sense to use cheap components that are readily available regardless of where you live. The idea of building this thing was posted in a spanish forum by someone else, I believe using components that can only be purchased at mouser or digikey, with shipping costs and all, doesn't make too much sense. There's already a "cheap" solution available here:
http://tagboardeffects.blogspot.com/2014/01/bipolar-voltage-converter.html
https://tagboardeffects.blogspot.com/search?q=3005
--- Quote from: Hero999 on November 28, 2018, 09:52:51 am ---How about using two 9V batteries or a 12VAC mains adaptor?
A voltage doubler circuit with the 78L08 and 79L08 could provide a +/-8V supply when running off the mains and batteries can give +/-9V directly. It's possible to get sockets with a built-in switch to disconnect the batteries, when running off mains power.
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I'm going to put a 9V input for those who want to use the pcb's supply and also V+ and V- inputs for those who prefer to use an external supply like those you suggest, or one of those cheap ebay +15V/-15V converter boards. The pcb is going to be 80x40 mm anyway because it's meant to be fitted in a 1590BB enclosure with pcb mounted pots like these Since I need those pcb dimensions to get proper spacing between pots (see pic 1 for initial pcb design) I have plenty room to include the optional power supply.
I think I might be able to make it work with +9/-9 but spec said that it wouldn't sound the same as running it at +15/-15:
--- Quote from: spec on November 27, 2018, 03:44:41 am ---PS: if you run the opamps from +-9V, as you suggested, the sound would change, not due to headroom or noise considerations but because the opamp itself is operating from lower rails. This effect is not so marked in newer opamps, but more so with the older opamps.
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--- Quote from: b_force on November 28, 2018, 11:03:56 am ---What happened to the LT1615 , LT3460, LT1316 idea?
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--- Quote from: Hero999 on November 28, 2018, 11:24:34 am ---Going by the prices of those ICs in Mouser, it was probably deemed too expensive. I don't see the point in doing hobby electronics on a shoe string budget. If you really want to save money, there's plenty of cheap junk available.
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Point taken. But it's not just about the money, smd components complicate things for DIYers.
Zero999:
Since you want a symmetrical power supply, then how about using a boost converter to get 24V to 30V, then a rail splitter, such as the TLE2426 to get the 0V point?
http://www.ti.com/lit/ds/symlink/tle2426.pdf
dazz:
--- Quote from: Hero999 on November 30, 2018, 08:48:39 am ---Since you want a symmetrical power supply, then how about using a boost converter to get 24V to 30V, then a rail splitter, such as the TLE2426 to get the 0V point?
http://www.ti.com/lit/ds/symlink/tle2426.pdf
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According tho this I can do pretty much the same thing with an opamp as a voltage follower, is that right? I'll try both anyway. I've ordered 7660s, 2577's, and MC34063's to try for the boost converters/inverters in different configurations. Will also try 7815s, 7915s, 7824s to regulate and filter the rails when needed, pi filters, and I'll get a few flyback transformers to try this: https://www.hobby-hour.com/electronics/flyback-regulator-lm2577.php.
But yeah, I think the simplest approach is boost converter + filter + rail splitter. I already have a preamp based on TL082's with a virtual ground, not even a rail splitter, just a resistor divider, and it works great as long as the supply rail is properly filtered (using a 7809 for that one)
At the end of the day, as always, the ultimate objective is to learn and I have plenty things to try already.
T3sl4co1l:
If you're going to the trouble of a boost converter, you might as well do a buck-boost or SEPIC or the like, with a coupled inductor, so you get everything in one stage without any fumbling with rails. :-+
Tim
dazz:
--- Quote from: T3sl4co1l on November 30, 2018, 04:48:21 pm ---If you're going to the trouble of a boost converter, you might as well do a buck-boost or SEPIC or the like, with a coupled inductor, so you get everything in one stage without any fumbling with rails. :-+
Tim
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I had no idea that such a thing existed, thank you.
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