Silou
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CorrectI believe the person who asked required the opamp to be pin compatible with 4556 in DIP8 or soic8 in Objective 2, at least easily convertible.
CorrectI believe the person who asked required the opamp to be pin compatible with 4556 in DIP8 or soic8 in Objective 2, at least easily convertible.
Two 4556 can already give 200ma of output current.
You need to look at the voltage vs current graph. It's easily 100ma for normal use cases. 100ma at 7V rms. Adding more is possible but very not elegant in o2 without redo the board.For practical purposes it is a little less than that.
80mA (for symmetrical distortion free signal) per opamp = 160mA for 2, but this is peak current so 'merely' 115mArms.
To increase current capabilities perhaps adding 1 dual opamp (with VERY short wiring to the boards) and 2 extra resistors would be the easiest and best way to go about this.... in this particular O2 case.
I know how to interpret the data and calculate the actual valuesYou need to look at the voltage vs current
Nah. https://www.audiosciencereview.com/...be-hybrid-cth-and-jds-o2-headphone-amps.3928/I know how to interpret the data and calculate the actual values
Ths3120 and opa2674 are CFA, which has to have specified Rf instead of directly connecting together.
CFA won't be stable with 0ohm feedback resistance.Huh?
CFA won't be stable with 0ohm feedback resistance.
But the output of each opamp is directly connected to the inverting input in the pcb layout in Objective 2. Unless redo the pcb, it will not work with o2. Or maybe he wasn't answering the guy who asked about o2?I think he means the feedback resistor is not necessarily in the way of connecting the outputs together.
But the output of each opamp is directly connected to the inverting input in the pcb layout in Objective 2. Unless redo the pcb, it will not work with o2. Or maybe he wasn't answering the guy who asked about o2?
It wasn't me.So, to summarize so far: you would need an op amp with low noise(?), stable at +1 gain and compatible with an existing PCB (no feedback resistor allowed, only PDIP or SOIC case).
Couldn't you specify these to start with? There are options (you already got a few, there are more, but then I'm sure you'll come up with more requirements). Do you have a point to make in perpetrating this charade?
Maybe noob question, all opamp have noise, when sample amplified by opamp it also add noise/square root hz? Or I am wrong? Is this audible?
If used in gain stage you will measure and even hear the diff. of noise between opamps.Maybe noob question, all opamp have noise, when sample amplified by opamp it also add noise/square root hz? Or I am wrong? Is this audible?
hmmm. That not exactly correct is it?That's funny, 'cause I've been arguing for years that the O2 gain stage is needlessly low-noise (generally swamped by typical sources), compromising on real-world distortion performance instead as the NJM2068 breaks a bit of a sweat at high levels. I've been suggesting upping feedback resistor values by a factor of 2 even in the regular version, especially if you need the 6.5X gain. (Things are a bit more relaxed in 2.5X, a lot more so in 1X.)
If you do the math, both NJM2068 and NE5532 have an equivalent input noise level of below -120 dBV (1 µV) in the stock 6.5X gain circuit (1k5/274R). That's -126 dBFS relative to a 2 Vrms DAC output. There should not be any meaningful difference left at a DAC dynamic range of about 116 dB or less (or 110 dB if you're stuck with onboard audio levels).
If noise down that far is even audible to begin with, your gain staging needs some work to say the least.
Of course you can find a scenario in which the noise difference between the two types becomes plainly audible - input shorted, excessive gain, full volume, sensitive headphones / IEMs. But is that a realistic use case? Hell no. If you were to connect your regular source under the same conditions, you'd be getting a ton of noise and ear-bleeding levels.
Opamp noise becomes critical when handling really low-level signals. We're talking phono or microphone inputs, where nominal signal levels may be mere millivolts. A line-level input just isn't as demanding by far.
Always depends on what you are looking at. On the input side, you'll have some given input signal and noise levels to compare to, so it's most useful to look at input-referred performance.The noise that matters is the output noise not the input referred noise. Also how input referred noise has anything to do with gain?
Pretty much. In practice, it is dwarfed by source noise and both get attenuated into oblivion.However tho, the SNR is preserved because the volume control is after the gain stage. There's potential clipping issue but you get lower noise with higher gain(i would argue it's meaningless on the other hand). The pot is the actual reason that the noise of gain stage is not audible.
To be fair, at least some of these grass growing detectors are meant to be used with a 10 ohm output impedance, making things several dB less critical. Noise requirements for IEMs seem to be somewhat relaxed in general due to all the blood circulating racket generated just by having something plugged into your ear... I don't think you need a great deal less than 20 dB SPL or so. Feel free to point me towards observations indicating the contrary though.In o2, the output stage is relatively noise free especially for the time but 2uV is not exactly low noise, some iems produce audible noise even with 0.8uV noise. -120dBV is not so clean when sensitivity is over 145dB/V.