Hi,
I need some advise, as was planning to replace some Op amps in a blue tooth receiver.
Please advise on the op amps I can swap for, for best sonics. I would not like to go overboard (price-wise) with Burson etc., however if there is anything reasonable, I surely would appreciate.
These are the ones currently installed:
NJM5532 operational amplifier for RCA (DIP8 dual operational amplifiers)
NJM4556A for 3.5mm auxiliary to headphone
What could the above stated be replaced with ? Will discrete opamps make a huge difference ?
Thanks once again.
Regards,
d.
Attached is a picture:
I need some advise, as was planning to replace some Op amps in a blue tooth receiver.
Please advise on the op amps I can swap for, for best sonics. I would not like to go overboard (price-wise) with Burson etc., however if there is anything reasonable, I surely would appreciate.
These are the ones currently installed:
NJM5532 operational amplifier for RCA (DIP8 dual operational amplifiers)
NJM4556A for 3.5mm auxiliary to headphone
What could the above stated be replaced with ? Will discrete opamps make a huge difference ?
Thanks once again.
Regards,
d.
Attached is a picture:
Attachments
Thanks for the advise and help. I was leaning towards the LM4562 for the line output, however, couldn't find a dip8 version. I believe I can use the SOIC version with a dip8 adapter.
I presume it will work though, as I don't understand whether the voltage and other specs are interchangeable between the two.
I have rudimentary knowledge of electronics as you may have noticed.
I presume it will work though, as I don't understand whether the voltage and other specs are interchangeable between the two.
I have rudimentary knowledge of electronics as you may have noticed.
LME49720 is same as Lm4562, basically the part number was changed when TI aquired National Semi.
Mike
Actually, the part number was changed before the TI acquisition. National went from two letters (LM) to three around 2007ish. LME = audio. LMP = precision. LMV = general purpose opamps. Etc. The LM4562 just happened to be developed around the time of the change. That's all.
You are correct, though. The LM4562 and LME49720 are the same part. Same die. Different number on the package. That hasn't stopped people from arguing the opposite, however.
Tom
Usually it is low gain that needs a bigger dose of compensation?
Of course reading the datasheet is always a good idea.
That's a good rule of thumb. The issue with rules of thumb is that they're sometimes wrong. This is one of those cases.
The "discrete opamps" I've looked at have had -40 dB/dec AVOL slope with a pole-zero pair centred around the unity-gain frequency (UGBW). This causes the AVOL slope to change from -40 dB/dec to -20 dB/dec around UGBW, and back to -40 dB/dec beyond UGBW, which allows the opamp to be used as a buffer with 45-60 º phase margin (on a good day).
Without external compensation, these opamps will suffer from degraded phase margin once you configure them for a gain beyond unity. Around 6-12 dB of gain, I would expect significant ringing, and at 20 dB gain, they're guaranteed to be unstable without external compensation. Thus, I have grave concerns with using "discrete opamps" in gain stages, including RIAA stages, unless proper compensation is added.
In case of the "discrete opamps" it's absolutely mandatory. Brushing up on feedback theory is a good idea too...
I should say that I think I have come across one "discrete opamp" that had a -20 dB/dec AVOL slope, thus would be stable at gains beyond unity. I don't remember which one. Most that I've seen have had the -40 dB/dec slope with pole-zero compensation near UGBW.
Tom
Swapping the op amp will make a difference. However, any lack in those you've already got installed can be attributed to support and/or power circuit.
So, any benefit of op-amp swapping in this case comes from putting in a chip that has requirements which are a closer match to the support and power circuits.
That is unorthodox and possible and backwards.
The orthodox fix is to repair the support and power circuits to closer match the needs of your chips.
Op-amp swapping, which looks easy, is actually the hard way.
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You must work with more arcane DOAs than I have seen.
In pro audio a classic is the Jensen 990. This is supplied stable at any gain. There are a few others from older consoles with more-or-less wide gain ranges, and these too are "universal compensation". (Some, like 2520, don't go to unity gain well because of crude input stages of small common-mode range....)
https://www.technicalaudio.com/pdf/...ted/Jensen_JE-990_opamp_JAES_reprint_1980.pdf
The John Hardy Company 990 Discrete Op-Amp
DIY JE-990 Discrete Operational Amplifier
I'd think any "audio op-amp" which was ONLY stable near unity gain would be a very special-purpose hammer.
Thanks for the warning.
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I don't work with "discrete opamps". I don't see the point. I can get better performance for way less with an actual opamp. I occasionally have clients who requests that I design in a "discrete opamp", which is the only reason I'd ever bother with them.
Would you consider the Sparkos "discrete opamps" arcane? They feature the exact AVOL characteristic I described earlier (data sheet).
BTW: Of the three "opamps" you linked to, only one (the top one) features a data sheet with an AVOL curve. It also features 0.01 % THD, or about 300-1000x worse than current opamps. Meh... Still not interested.
Tom
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I very very much doubt you will hear any difference.
Besides expectation bias, of course.
If anything, get a better Bluetooth receiver, as a whole element; you don´t have the current schematic, you don´t know what those Op Amps actually do, you don´t have a specific problem to correct and even if you had, nothing points to OP Amps as culprits.
Non designers often believe (wrongly, VERY wrongly) that a "better design" means the same old tired one but with "better parts".
Well, it does not work that way, as *any* real Designer can tell you.
Besides expectation bias, of course.
If anything, get a better Bluetooth receiver, as a whole element; you don´t have the current schematic, you don´t know what those Op Amps actually do, you don´t have a specific problem to correct and even if you had, nothing points to OP Amps as culprits.
Non designers often believe (wrongly, VERY wrongly) that a "better design" means the same old tired one but with "better parts".
Well, it does not work that way, as *any* real Designer can tell you.
I don't work with "discrete opamps". I don't see the point. I can get better performance for way less with an actual opamp. I occasionally have clients who requests that I design in a "discrete opamp", which is the only reason I'd ever bother with them.
Would you consider the Sparkos "discrete opamps" arcane? They feature the exact AVOL characteristic I described earlier (data sheet).
BTW: Of the three "opamps" you linked to, only one (the top one) features a data sheet with an AVOL curve. It also features 0.01 % THD, or about 300-1000x worse than current opamps. Meh... Still not interested.
Tom
The discrete opamps that I think Samuel Groner designed for Weiss have excellent specs, but I'm sure they have a price tag to match. Probably the only ones worth even remote consideration.
https://weiss.ch/files/downloads/op1-bp/OP1-BP-Datasheet-R1.pdf
Excellent specs indeed. -150 dB THD! That's an engineering feat. Unfortunately, it has the same AVOL characteristic as many other "discrete opamps", thus will feature marginal stability at higher gains. You can see the AVOL curve on page 8 of the data sheet you link to. Also note that due to this gain characteristic, the transient response (page 14) shows significant ringing.
The interesting thing is that these "discrete opamps" are designed much like an actual opamp. The main difference between designing an opamp in an IC and designing one on a PCB is that on the PCB you can get better control over absolute values (±0.1% resistor tolerance is easy to find), whereas ICs offer much, much better matching between devices than you can ever hope to achieve on a PCB.
Tom
An interesting trick: If you run a stereo op-amp as a parallel amplifier, it is possible to manufacturer that audiophile 'black background' for a dime.
What I was wondering is, if that can be applied as a voltage regulator?
Most single chip regulators are good for tone, but either cause or fail to prevent smashed-flat soundfield. If that's the power source, then swapping the amplifier doesn't make the slightest bit of sense. Even if I might seem weird, I'd rather think about swapping the power source for one that is made for music.
Also wondering how to do that?
P.S.
The thing is: If given such a large head start on quality, at the power locale, then afterwards, embellishing the amplifier should be a lot easier and more effective. It isn't possible to make good decisions when running on poor power. So, the first step in quality improvement is...
What I was wondering is, if that can be applied as a voltage regulator?
Most single chip regulators are good for tone, but either cause or fail to prevent smashed-flat soundfield. If that's the power source, then swapping the amplifier doesn't make the slightest bit of sense. Even if I might seem weird, I'd rather think about swapping the power source for one that is made for music.
Also wondering how to do that?
P.S.
The thing is: If given such a large head start on quality, at the power locale, then afterwards, embellishing the amplifier should be a lot easier and more effective. It isn't possible to make good decisions when running on poor power. So, the first step in quality improvement is...
I'm sorry, this doesn't seem to make sense. Why would all "chip regulators" cause "smashed-flat soundfield"? They aren't all the same despite being encased in black plastic with pins sticking out. This claim seems dubious at best, I'd have to say. Not to mention the high PSRR of typical op-amp circuits.
You can get a "black background" with one op-amp too.
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