I have about a jillion TL074s laying around making my fingers itch to use them. Obviously it would not be anything like a reference amplifier but...
I keep thinking it would be neat (not practical, fast or terribly easy, but neat) to make an amplifier out of these things with an ouput of several watts... like maybe 10-20W. I'm guessing i'd have to have at least one of them ( ! ) be a buffer on the front, with the rest configured as unity or low-gain followers. bridge/parallel times a whole bunch maybe. How many TL074s do you need to put out several volts across a 4-ohm speaker anyway?
aside from the obvious size and hassle, with possibly some funky capacitances and inductances in all the wiring, what other things are stupid about this?
It's a good thing I have a wife to keep me from wasting *all* my time...
I keep thinking it would be neat (not practical, fast or terribly easy, but neat) to make an amplifier out of these things with an ouput of several watts... like maybe 10-20W. I'm guessing i'd have to have at least one of them ( ! ) be a buffer on the front, with the rest configured as unity or low-gain followers. bridge/parallel times a whole bunch maybe. How many TL074s do you need to put out several volts across a 4-ohm speaker anyway?
aside from the obvious size and hassle, with possibly some funky capacitances and inductances in all the wiring, what other things are stupid about this?
It's a good thing I have a wife to keep me from wasting *all* my time...
sss said:u can make a stereo 30 band graphic equalizer with that many op amps , u gotta be crazy triying to make a 20w amp out of them , u cant even us a heatsink
also u need a 8 (or more) layer pcb for that many op amps
mmmmm...2x20WPC, with a 30 band eq for each... only 150 devices required...
why would I need an 8 layer PCB? I'm thinking more along the lines of a few 8-inch square pieces of veroboard! and sure I could use a heatsink...or maybe a whole BUNCH of little ones. Our good friends at Aavid Thermalloy have several DIP heatsinking options. Of course, I could make a common heat sink out of one big flat one... drill a few holes by every op-amp package, and mount all the other components on the underside of the PCB... and screw the PCB down to the heatsink with the amps inbetween, with a little white grease...about 100 screws should do it... then 60 pots for the adjustments...
tiroth said:
Would you please explain how you arrived at this number?
as for the servos: did you miss the "offset voltage indicator" thread? I'd only need 44 little potentiometers (which I do have BTW) along with 44 or 88 LEDs (which I don't have). That, plus 45 minutes to trim out the zero on all the individual amplifiers. Then three days to tune the EQs to suit the room...along with the DIY RTA I could make out of another 15 opamps...
Alcaid said:If they bother you that much you could always send them to me so your fingers stop itching
I might even pay the postage
They don't itch *that* much!
OpAmp amps are possible, though
This project might not fly, but very good amps have been built out of OpAmps. See
http://headwize2.powerpill.org/projects/showproj.php?file=meier3_prj.htm[/URL]
Norman
This project might not fly, but very good amps have been built out of OpAmps. See
http://headwize2.powerpill.org/projects/showproj.php?file=meier3_prj.htm[/URL]
Norman
I could tell you, but then I'd have to kill you...
I get them free from work.
When a PCB fails on a customer device, It's almost never because of the opamps. So on the ones that are not surface mount, there are usually one or two (depending on model) good lm324 or tl074s. I have been saving them because I am a bit of a pack rat. I asked my boss specifically about using 'trash' devices and he doesn't care what I do with them. I can even sell them or things I put them in...but according to the nondisclosure agreement, any circuits I come up with are property of the company.
I get them free from work.
When a PCB fails on a customer device, It's almost never because of the opamps. So on the ones that are not surface mount, there are usually one or two (depending on model) good lm324 or tl074s. I have been saving them because I am a bit of a pack rat. I asked my boss specifically about using 'trash' devices and he doesn't care what I do with them. I can even sell them or things I put them in...but according to the nondisclosure agreement, any circuits I come up with are property of the company.
Hey, if you want to build something for the sheer craziness of it, knock yourself out. You will end up spending $50 in pots unless you get them free or surplus, in order to build something with much poorer performance than a $4 LM3875. On the other hand, with the output impedance so high already, you may not have to worry about circulating ground currents. (but maybe they will just fry the opamps, hard to say)
speaker said:
Yes.
This is an idea that is probably a year away if it ever will be built. It was like a song stuck in my head that I couldn't get rid of so I made a thread about it.
As for the pots... There are 2-4 of them on ALL the PCBs on all our analog controllers. Bourns 3299 mostly, some 3262. I have loads of them as well.
How high is the output impedance of 200+ TL07x opamps in parallel?
Gosh thanks!I am beginning not to be surprised at how willing people here are to answer even dumb questions. Very helpful.
I was about to start thinking about heat dissipation in the individual packages and as a whole, and it occurred to me that even with LM324s we're talking less than a watt each, easily handled by little sinks on each. If I were to go with one big heatsink for the whole thing, it would likely be such a big piece of aluminum that it would never even get warm. cool.
Stocker said:
ahem. I know they are not ideal. To say that TL074s suck at audio is to put down a whole BUNCH of commercial gear that sounds just fine to a lot of people. LM324s you may have more of a point but for those of us with ringing ears and who mostly use music for background noise anyhow, even LM324s would probably satisfy "most" people if they didn't know they were there...
And I get them free at work because they are trash, and because my work has about as much to do with audio as anthropology.
But thank you for your constructive criticism
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