I bought a car dvd recently. Everything is fine except ... the sound quality. For fun, I would like to upgrade the JRC4558 chips (and TDA7338 probably) on the circuit board to some better ones to see if there's any improvement. My question is, is OPA2132U a good drop-in replacement for it? What's the difference between OPA2132U and OPA2132UA?
Also, it seems there are many other chips that I could use, e.g. OPA2228, OPA2134, etc. Which one is better?
Any suggestions are welcome! Thanks!
Also, it seems there are many other chips that I could use, e.g. OPA2228, OPA2134, etc. Which one is better?
Any suggestions are welcome! Thanks!
Reviving an old thread, but this one didn't get far the first time around so I figured I'd give it a kick and see if it wakes up.
Following from AndrewT's advice, I'd simply like to ask; is there another opamp (or opamps) that is similar enough in design to the various 4558 chips, and well-behaved enough, that it could be dropped into a circuit with a reasonable expectation of working? Let's ignore whether this might be considered an "upgrade" for now.
Assume in this case that the circuit was well-designed to begin with, and that the 4558 was chosen due to low cost, not due to some unique performance benefit of the 4558.
Another way to look at it; despite it being a "bad idea", if you had to choose one opamp to blindly drop in to a circuit built around 4558 chip(s), what opamp would you drop in there?
(Answers of "NJM4558", "MC4558", etc. don't count.
)
Following from AndrewT's advice, I'd simply like to ask; is there another opamp (or opamps) that is similar enough in design to the various 4558 chips, and well-behaved enough, that it could be dropped into a circuit with a reasonable expectation of working? Let's ignore whether this might be considered an "upgrade" for now.
Assume in this case that the circuit was well-designed to begin with, and that the 4558 was chosen due to low cost, not due to some unique performance benefit of the 4558.
Another way to look at it; despite it being a "bad idea", if you had to choose one opamp to blindly drop in to a circuit built around 4558 chip(s), what opamp would you drop in there?
(Answers of "NJM4558", "MC4558", etc. don't count.
)
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Toss up between an LM4562 (much higher power consumption) or a TL072 (great all rounder). Honest answer... I'd probably go with the TL072 based on your criteria.
I always used TL072 in place of 4558 for common works. Is stable in all applications I have tried.
By the way, every chinese or low priced consumer product uses them (and maybe it grow in trees or is sold by weight), for filtering 1-but DAC who have too much RF hash to 4558 liking (and 4558 most times only distort the RF hash and not recude it at all!). My usual upgrade to these products is an passive RC filter and direct to RCA or using JFET buffer. Great sound difference thanks to HF/RF hash true filtering, even an 6/dB passive filter works beter than slow 4558 with "engineering" filter (this is an place where measurements go hand-by-hand with listening impressions).
A '4558 also is quite slow and would still be working fine in layouts that would qualify as horribly sloppy by today's standards (but occasionally crop up in late-'70s gear).
Even if it were a '90s receiver where 4558s would have been used for cost reasons and layout and supply bypassing actually are fine, I would still look at the circuit in any case. In some positions an upgrade would be just a waste of time (like an input buffer in front of a 50k volume pot), others may actually be exploiting the high-impedance (for a bipolar) input with low capacitance nonlinearity, while in yet others significant upgrades are to be expected due to better output driving and whatnot.
If decoupling is half-decent and somewhat higher power consumption is acceptable, you can always upgrade to a 4560 or 4565. (I'm not sure what to name with a similar power envelope and bipolar input.) Similar input characteristics, but progressively faster and beefier. Anything beyond those just adds more ifs: 4556A (similar input characteristics, faster, but a lot more power-hungry, even though that goes along with excellent output driving as it's a headphone driver), 5532 (a lot more power hungry, higher bias currents, though good output driving and lower noise), NJM4580 (more power hungry but less so than 5532, current output potentially even higher), 2068 (still quite economic, very low Vnoise, but suitability for high-impedance surroundings questionable, higher bias currents), LM833 (kinda similar to NJM2068), MC33078 of one kind or another, and so on.
This upgrading business tends to be particularly fun if they were really thrifty and opted for ancient (but then cheap) SIP package parts. You're not exactly drowning in replacement options for those, I think I've seen 4565s and 2068s.
BTW, a circuit optimized to work well with a 4558 is likely to be less well-performing than it could when just dropping in another type with no change in passives.
EDIT: Good point re: RF hash immunity. Hanging a '4558 on the output of a 1-bit DAC, unfiltered, clearly is not a good move, and the trusty '072 may actually work better there. I wouldn't want to be using one after a 100k volume pot or in non-inverting a tone control though.
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Great info from everyone, even though I only truly understand a fraction of it.
It is an equalizer. It contains:
2x - JRC4558D ("original, vintage!" I could probably pull these and sell them to some guitar freak for an effects pedal )
8x - MC4558
I do not know the function of each opamp, and I do not have a schematic. The EQ cost me $30 and sounds very good to me, but I cannot leave well enough alone. If I completely mess it up I won't be heartbroken.
It is an equalizer. It contains:
2x - JRC4558D ("original, vintage!" I could probably pull these and sell them to some guitar freak for an effects pedal
)8x - MC4558
I do not know the function of each opamp, and I do not have a schematic. The EQ cost me $30 and sounds very good to me, but I cannot leave well enough alone. If I completely mess it up I won't be heartbroken.
Great info from everyone, even though I only truly understand a fraction of it.
It is an equalizer. It contains:
2x - JRC4558D ("original, vintage!" I could probably pull these and sell them to some guitar freak for an effects pedal
8x - MC4558
I do not know the function of each opamp, and I do not have a schematic. The EQ cost me $30 and sounds very good to me, but I cannot leave well enough alone. If I completely mess it up I won't be heartbroken.
Hi,
5532 for the input and TL072's for the rest. Possibly 5532 for the output.
rgds, sreten.
I removed the board from the chassis a few days ago. Flipped it over and tried to map out some simple stuff like inputs and outputs, and couldn't make heads or tails of anything. The traces go through a series of switches to enable/disable line EQ and tape EQ functions, etc. and I end up losing track of what's going where.
At least it still works after re-assembly.
I'll post some pics on the weekend. Some of you nerds will be able to take one look and say what's going on. (I use the term "nerds" in the most loving way possible here, of course. I am a nerd myself, I just chose a different subject to nerd out on.)
4558's are everywhere and cost around £0.10 each here.
Described as 'The RC4558 device is a dual general-purpose operational amplifier, with each half electrically similar to the µA741, except that offset null capability is not provided' which I suppose says it all. They are hopelessly outclassed these days, yet still appear in modern equipment.
The RF issue is something I first read about and looked into some years ago and I think there more than a grain of truth to it. I also think its why the 5532 got a mixed reception among in the audio world because 5532's were the quality device of choice used in most CD players of the 80 and 90's
I think you have seen the posts of mine on the second sourced LM833 from TI that has a much improved output stage. Its an interesting device.
SIP outline was quite widely used some years ago. I've got some 5532's in SIP form
A couple of pics:
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
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