It's pretty common among home builders to have the input impedance/resistance on an input to be fed by an electric guitar to be as high as possible.
But the gear I want to emulate doesn't have a real high impedance -- 390kOhms to be exact. If I wanted to use a good old 5532 op amp here, would that be too high a resistor for its noninverting input?
But the gear I want to emulate doesn't have a real high impedance -- 390kOhms to be exact. If I wanted to use a good old 5532 op amp here, would that be too high a resistor for its noninverting input?
That's a lot of current noise, so, yes, I'd absolutely be running a FET-input with that.
We're talking more like <1 kOhm input/feedback impedances for BJT inputs to be lower noise.
We're talking more like <1 kOhm input/feedback impedances for BJT inputs to be lower noise.
not ideal, the input noise current in 300k would be 5x worse than the 5534 noise V
and ~150 mA input offset from i_n flowing in 300k could be a problem depending on gain, output coupling
a cheap classic would be the TL07x series, but not really a noise improvement
at a few bucks the OPA164x series (only smt) would be a modern choice unless low battery operation were important
and ~150 mA input offset from i_n flowing in 300k could be a problem depending on gain, output coupling
a cheap classic would be the TL07x series, but not really a noise improvement
at a few bucks the OPA164x series (only smt) would be a modern choice unless low battery operation were important
Thank you.
What I have in there now is a 2134 but I think that they're a little brighter and harder sounding than I would prefer. I'm not particularly fond of the TLO72 either.
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What I have in there now is a 2134 but I think that they're a little brighter and harder sounding than I would prefer. I'm not particularly fond of the TLO72 either.
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err
opa213x are fine for their age, more recent than 5534/072 but the OPA164x are on fully complementary process and have exceptional input common mode linearity - at 300 k source Z the OPA164x should have clearly measurable lower distortion, in addition to fine noise and i_b performance
opa213x are fine for their age, more recent than 5534/072 but the OPA164x are on fully complementary process and have exceptional input common mode linearity - at 300 k source Z the OPA164x should have clearly measurable lower distortion, in addition to fine noise and i_b performance
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The "crossover" for implementing FET devices versus BJT is generally considered to be about 4KΩ----above that input impedance, FET will be quieter; below 4K, a BJT wins. The OPA1642 is the best of the FET devices, methinks.
Source impedance of 390k is considered a high impedance. The thermal voltage noise of 390k resistor is close to 65nV/sqrt(Hz), thus an pre-Amp with low current noise is the best choice. Considering the voltage noise, a simple TL072 will do the trick, there is no point in swapping to fancy, expensive OPAs. And, btw, did you ever disassemble an active pre-amp/ eq for for acoustic guitar? Guess what you find there? It's TL062 or TL064 One of the cheapest JFET OPAs. With lowest current consumption - longest battery life. Doing its job
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Maybe my solution would be to ask for recommendations on dual FET opamps that are sensibly hi-fi, have good output drive, and sound a little smoother and mellower than the opa2134. I actually like the 5532 for guitar applications, it's almost tubey. But I guess it's a no-go here.
If I buy an SMT chip and some adapters from ebay, do they come with solder on them, just heat and serve? Or am I expected to supply the solder and flux?
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I've not bought any myself so I'm just making a guess here but I reckon they'll be intended to be hand-soldered, not oven-baked.
The OP didn't specify a SOURCE impedance of 390KΩ; he indicated wanting to emulate an amplifier with an input(LOAD) impedance of 390KΩ. Figuring on an average guitar pickup source impedance of ~10K (source resistance and reactance (Z=√ (R2+X2)), an OPA1642 will deliver about 11 db less noise and 36 db less distortion than a TL072---certainly a significant difference. And faster, too. For a coupla $$ more, it's well worth it.
I wasn't going to bring it up, but thank you.
Does anyone have any observations regarding the tonal balance of the OPA1462?
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Does anyone have any observations regarding the tonal balance of the OPA1462?
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Might as well take the cash you would use for the 1642 and fill your toilet with Perrier. Same end effect.
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Might as well take the cash you would use for the 1642 and fill your toilet with Perrier. Same end effect.
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The whole problem with the world is that fools and fanatics are always so certain of themselves, and wiser people so full of doubts. Bertrand Russell
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Might as well take the cash you would use for the 1642 and fill your toilet with Perrier. Same end effect.
__________________
The whole problem with the world is that fools and fanatics are always so certain of themselves, and wiser people so full of doubts. Bertrand Russell
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Serves me right to be silly enough to respond to a thread where the OP is describing the sound of opamps
If you can hear tonal imbalance from an opamp, you're using it wrong.
If you feel the need for a precision opamp in your guitar chain, you're a geek in your basement, a not a musician with a real world performance setup that will have an order or two magnitude higher noise floor
If you feel the need for a precision opamp in your guitar chain, you're a geek in your basement, a not a musician with a real world performance setup that will have an order or two magnitude higher noise floor
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