ISO: Op-Amp Boost-Only Design
I'm searching for a schematic/layout for a *transparent boost-only circuit based around an op-amp. I tried a of couple transistors-based circuits, but they weren't performing as I was expecting. The last build had its guts ripped out and is now a passive attenuator with a 500k ohm pot, dimming LEDs and 3PDT wiring -- love it for guitar.
I've got packs of TL0XX op-amps sitting around, so if I can chuck one on a board, that'd be swell.
Know of any? I've searched around, but didn't find what I was looking for.
*as transparent as possible.
Put in electrolytic caps that are rated for 18V+ and run it at 18V. Doesn't get more transparent than this.
Is your google broken? :) I found this pretty quickly, it's a minimal parts count op-amp buffer.
I'm sure it will work fine as drawn for bass, but if you're concerned about bass rolloff you could substitute a 220nF cap on the input for the 100nF that's specified. If you're OCD about "tone" you might want to put in non-polarized 10µF electrolytic caps in place of the standard polarized electrolytics. I would also add power supply filtering and a polarity protection diode if this is going to be built into a stompbox.
My Google is only partial; I'm at work and the best websites are blacklisted.
Thanks for the links, guys. I'll go through this list when I get home -- none of these damned links work here. :rollno:
I am concerned about frequency loss, so I'll be considering those mods.
This one seems to work! Yeah, same website, but .com instead of .ca works.
I recommend looking at the datasheet for whatever op amp you plan on using. There is usually a reference schematic in there that will be minimal parts and very transparent. You might need to change some of the caps for the right frequency range, but it'd be a good place to start.
If you don't have a way to run pedals at 18V, try getting your hands on an ICL7660S or a MAX1044 and slap them in there used as voltage doublers (schematic can be found on the net, e.g. in their datasheets).
You don't need non-polarized caps in there btw, good polarized ones will do the trick as well, although using a non-electolytic 1uF cap on the input would work just as well. I doubt one can hear the difference between those (1uF, 10uF, polarized/non-polarized/non-electrolytic) though.
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