The Quad 405 did the same. The jury is still out on that one. To make something very fast and cheap is a cunning plan. I have speculated about video amps for phono stages. This one might be worth trying. Noise reduces to 10 nV by about 1 kHz. When stated 3 rd harmonic is usally < -70 dB. This would be less for audio. The class A trick can be used as output current is generous. If you look at the noise graph it looks lower than the claim. Hard to say as others do not always offer the same.
http://docs-europe.electrocomponents.com/webdocs/05b0/0900766b805b0ba0.pdf
http://docs-europe.electrocomponents.com/webdocs/05b0/0900766b805b0ba0.pdf
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From the horses mouth!
https://e2e.ti.com/support/amplifie...gn_notes/upgrading-op-amps-in-audio-equipment
https://e2e.ti.com/support/amplifie...gn_notes/upgrading-op-amps-in-audio-equipment
A few of these choices strike me as a bit dubious. While OPA164x make sense as a TL07x replacement assuming adequate rail decoupling, I kinda doubt that their output stage performance can really equal OPAx134 (4 mA quiescent, +/- 35 mA vs. 1.8 mA, +36/-30 mA), and they are only specified for +/- 18 V where OPAx604 will support up to +/- 24 V and actually only become really good towards the upper end. At +/- 15 V and with no particular output loading though, why not.
They quite correctly point out the suitability of OPAx209. Their noise performance is quite excellent (2.2 nV, 0.5 pA). I imagine these should do really well as an NJM2068 replacement, and generally in many standard audio circuits now involving 4560s-4580s, LM833, OP275 etc. (Do mind that the output stage is a little less powerful than the 4580's, more on 4565 level there.)
It's a bit of a shame that they're only making these parts in surface mount packages.
They quite correctly point out the suitability of OPAx209. Their noise performance is quite excellent (2.2 nV, 0.5 pA). I imagine these should do really well as an NJM2068 replacement, and generally in many standard audio circuits now involving 4560s-4580s, LM833, OP275 etc. (Do mind that the output stage is a little less powerful than the 4580's, more on 4565 level there.)
It's a bit of a shame that they're only making these parts in surface mount packages.
I read the other day MC33078 and LM833 are related. From memory this seems unlikely. Motorola talk about both in some engineering notes and seem to say same familly and 33078 better.
I think when I ran some tests at 24 V with OPA types they stop giving any extra after 18 V. Thus it seems they are safe but not doing more. It was a bit sad as I was trying to get the most out of a class A design with ouput buffers. I could be wrong.
I think when I ran some tests at 24 V with OPA types they stop giving any extra after 18 V. Thus it seems they are safe but not doing more. It was a bit sad as I was trying to get the most out of a class A design with ouput buffers. I could be wrong.
So many times I spec'd these on purpose for quality, but only ever if paralleled drive.
Actually I've never tried them as stereo amplifiers, because that didn't look like a good idea. Really--never even tried that. Well, it wasn't even worth considering.
But, I have used a whole lot of these in tandem mode, and they're very fine for that.
So, what should you replace one of these with? Two of them. Unfortunately, it costs 6 more cents for audiophile mode. Oh well.
Actually I've never tried them as stereo amplifiers, because that didn't look like a good idea. Really--never even tried that. Well, it wasn't even worth considering.
But, I have used a whole lot of these in tandem mode, and they're very fine for that.
So, what should you replace one of these with? Two of them. Unfortunately, it costs 6 more cents for audiophile mode. Oh well.
This was to see where it went. NE5532 BD135/136. I have often played with this circuit hoping one day to find a use for it. Never have as yet. The theory is if the loop is very fast it will close. Not really. At 1 kHz it is doing something. Some place the BD135/6 with the collectors to the load and the power rails as bias via resistors. That I am sure will work if stability can be ensured.
Not sure what the load was . 30 R perhaps?
Nigel,
Thanks for the posted data, very interesting.
I recently made up a small amp of a couple of watts in a very similar simple way. BD139/140 diode biased with 2k2 from +Vcc to cathode and 1k1 from -Vcc to anode of the diode string. I used LF353 (it's what I had) and closed the loop from output to opamp -in with 12k // 22pF to give v/v of 11. It managed just about 3W into 4 Ohms and slightly better into 32 Ohms. It actually sounded far better than I would have believed (I was only trying to make a cheap parts bin line driver) and I'd love to see the THD.
It worked better than I hoped for a 'lunch break' project and my love for composite/boosted opamp was born
Unfortunately, the provided documentation is advertisment-purposed and cannot be relied upon for application purpose. The documentation is just for selling. This will be inconvenient! You'll have to pretend that the mystery part shipped without documention and then measure for applicability.
You know, just like all class ab chips?
I suggest, don't admit if that was a surprise. Instead, just re-phrase the same comment into illustrating how the part was mis-used.
You know, just like all class ab chips?
I suggest, don't admit if that was a surprise. Instead, just re-phrase the same comment into illustrating how the part was mis-used.
Yeah, it is a really lovely part; however, the outputs are so flimsy as far as linearity is concerned that it is not suitable for the stereo use for which it is marketed. To be clear, the datasheet markets it for uses for which it is not suitable! That is what it has in common with most Class aB chips available. Given that the problem is so very commonplace, then I claim that it is not reasonable to misuse a part capable of lovely output.
Therefore what you see here are probably examples of refitting a stronger part into to socket of a circuit that shouldn't have used this part.
In fact, if you don't have two sockets for stereo, then don't (mis)use this part.
cheap and low cost ... usually found in many china made car preamps and car amplifiers ... i have mine replaced them with either TL072's or NE5532's
That looks like a good plan to replace a fake part that didn't work with one of specs that meet the design goals.
It is likely that there are 4558 variants available that just can't meet design goals. it is in that case when replacement is advisable.
It will take greater board space to defeat wishful thinking; and, when greater board space isn't the thing to do, then just install a stouter part. That plan works just fine.
There is a catch here however ... i had 2 same car preamplifiers with 4558 inside ... one of them replaced with TL072 and another one with NE5532 ... despite the improved sound quality with either TL072 / NE5532 ... the preamp that has TL072 made some noise during turnoff ... the one with NE5532 didnt make any turn off noise at all ... so some caution is advised when considering opamp replacement with different models ... i still dont know why the TL072 made the noises
The '072 is notoriusly and badly behaved when power is removed. I guess it is the same mechanism as the phase reversal when a 072 is used as a voltage follower and the input goes high, close to the power voltage.
On the '4558 : I use it to test if a new construct works at all. If it blows, I won't got to bed crying. Had it been a LME49720 in TO99 on the other hand....
Besides, the 4558 is not so bad as some make it out to be. I've used in a RIAA (three 20dB gain stages, active) , and must admit I was surpriced how well it sounded.
I guess that in order to make the best of it (4558), you definitely need to consider the limitations of this opamp, staying within this envelope.
The worst ever ? Hardly.
For audio the LM358 takes cake. But then again, it was never intended for audio use. But is was and is dead cheap, works on low voltage and has low standing current, 2 AA cells , and you are good to go.
On the MC33078/LM833:
Go to TI's homepage and find the datasheets or these devices, print them out.
Take the first of each, put one on top of the other and hold them up against a bright light. Apart from the names, do you see any differens? No ?
Now try with page 2. And 3 and 4... 24.
QED: TI regards these two as identical. Which one of the original designs was chosen is anyones guess, no schematics is revealed.
On the '4558 : I use it to test if a new construct works at all. If it blows, I won't got to bed crying. Had it been a LME49720 in TO99 on the other hand....
Besides, the 4558 is not so bad as some make it out to be. I've used in a RIAA (three 20dB gain stages, active) , and must admit I was surpriced how well it sounded.
I guess that in order to make the best of it (4558), you definitely need to consider the limitations of this opamp, staying within this envelope.
The worst ever ? Hardly.
For audio the LM358 takes cake. But then again, it was never intended for audio use. But is was and is dead cheap, works on low voltage and has low standing current, 2 AA cells , and you are good to go.
On the MC33078/LM833:
Go to TI's homepage and find the datasheets or these devices, print them out.
Take the first of each, put one on top of the other and hold them up against a bright light. Apart from the names, do you see any differens? No ?
Now try with page 2. And 3 and 4... 24.
QED: TI regards these two as identical. Which one of the original designs was chosen is anyones guess, no schematics is revealed.
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