I looking for 4pcs of DIP8 versions of JRC4558 (JRC4558D?) opamps.
I know they are the "worst opamps ever" http://www.diyaudio.com/forums/showthread.php?threadid=67906 ), however when I replace them into my speakers with LM4562 (I know, I know, waiting for the AD8599 SOIC samples to be soldered on DIP8 socket and inserted into the sockets...) then oscilation happen.
http://www.diyaudio.com/forums/showthread.php?s=&threadid=124628
A big one. Noise to signal is like 1:1 (if the noise is not stronger, lol) ...
Regardless, I wonder if I can obtain them somewhere to test out if was my modifications that caused the oscilation, or if the circuit need to be changed for the LM4562 or other sensitive and fast opamp...
I know they are the "worst opamps ever" http://www.diyaudio.com/forums/showthread.php?threadid=67906 ), however when I replace them into my speakers with LM4562 (I know, I know, waiting for the AD8599 SOIC samples to be soldered on DIP8 socket and inserted into the sockets...) then oscilation happen.
http://www.diyaudio.com/forums/showthread.php?s=&threadid=124628
A big one. Noise to signal is like 1:1 (if the noise is not stronger, lol) ...
Regardless, I wonder if I can obtain them somewhere to test out if was my modifications that caused the oscilation, or if the circuit need to be changed for the LM4562 or other sensitive and fast opamp...
as long as you don't drive a load less than 5k, the TL072 will make for a nice, less noisy drop-in replacement. if you want actual specs, look up RC4558 or LM1458 at www.datasheetarchive.com
then look up TL072. another good fet input replacement would be LF353. all dual opamps are pinned out the same.
then look up TL072. another good fet input replacement would be LF353. all dual opamps are pinned out the same.
anatech -
Agreed. The amplifier played reltively nicely with them onboard too, so... They are not great, but they will do for most of the low-end applications.
Thanks for suggestions. What about NE5532 then? I just tested them and believe or not, again oscilations, even in the default scheme...
http://s232.photobucket.com/albums/...on=view¤t=opmps_genius_SW-51_HT_mod.gif
Now it is possible that these more modern opamps just does not handle ZERO gain, as the circuit seems to have?!
unclejed613 - less that 5k? That should not be the case, as the input resistance of TDA amplifiers are around 20k or so...
Thanks. But can they handle zero gain?
I think I will change the R9 to 12k or 15k, witch should introduce some gain and stabilize (fingers crossed?) the opamps... What do you think?
Agreed. The amplifier played reltively nicely with them onboard too, so... They are not great, but they will do for most of the low-end applications.
Thanks for suggestions. What about NE5532 then? I just tested them and believe or not, again oscilations, even in the default scheme...
http://s232.photobucket.com/albums/...on=view¤t=opmps_genius_SW-51_HT_mod.gif
Now it is possible that these more modern opamps just does not handle ZERO gain, as the circuit seems to have?!
unclejed613 - less that 5k? That should not be the case, as the input resistance of TDA amplifiers are around 20k or so...
Thanks. But can they handle zero gain?
I think I will change the R9 to 12k or 15k, witch should introduce some gain and stabilize (fingers crossed?) the opamps... What do you think?
RC4580
JRC version ---> NJM4580
http://semicon.njr.co.jp/njr/hp/fileDownloadMedia.do?_mediaId=152
TI version ---> RC4580
http://www.ti.com/lit/gpn/rc4580
Operating Voltage . . . ±2 V to ±18 V
Low Noise Voltage . . . 0.8 μVrms (TYP)
Wide GBW . . . 12 MHz (TYP)
Low THD . . . 0.0005% (TYP)
Slew Rate . . . 5 V/μs (TYP)
JRC version ---> NJM4580
http://semicon.njr.co.jp/njr/hp/fileDownloadMedia.do?_mediaId=152
TI version ---> RC4580
http://www.ti.com/lit/gpn/rc4580
Operating Voltage . . . ±2 V to ±18 V
Low Noise Voltage . . . 0.8 μVrms (TYP)
Wide GBW . . . 12 MHz (TYP)
Low THD . . . 0.0005% (TYP)
Slew Rate . . . 5 V/μs (TYP)
Hi trodas,
The NE5532 is unity gain stable. Therefore, your decoupling caps are not sufficient, or defective. Something is fishy there, poor PCB design? I say this because I've never had an NE5532 oscillate when dropping into a spot occupied with a 4558, 1458 or anything like those.
You may be stuck with the 4558 as the manufacturer may have "fixed" a bad design with a slow op amp. Hard to say. You could install 1 uF ceramic caps across to power supply pins. Avoid using signal ground as the return. That might actually be your problem.
-Chris
The NE5532 is unity gain stable. Therefore, your decoupling caps are not sufficient, or defective. Something is fishy there, poor PCB design? I say this because I've never had an NE5532 oscillate when dropping into a spot occupied with a 4558, 1458 or anything like those.
You may be stuck with the 4558 as the manufacturer may have "fixed" a bad design with a slow op amp. Hard to say. You could install 1 uF ceramic caps across to power supply pins. Avoid using signal ground as the return. That might actually be your problem.
-Chris
abbacat66 - thank you, this is interesting. However I would preffer the original 4558 anyway, because the noise I hearing now is TERRIBLY ANNOYING, and I did not fully believe in the "compatibility" anymore
The Japan site is nice and informative (there is the NJM4558D infos: http://semicon.njr.co.jp/njr/hp/pro...oductId=115&_moveKbn=PRODUCT_DETAIL_MOVE_SPEC ) but no sample order?
Where I can obtain these then?
janneman - Yes. I run it like that right now.
Noisy as hell
Even with the C7 present it seems to me (but I could remember it wrong, of course) was the noise a bit smaller...
Suggestions what to do to stop the oscilations are more that welcome.
The Japan site is nice and informative (there is the NJM4558D infos: http://semicon.njr.co.jp/njr/hp/pro...oductId=115&_moveKbn=PRODUCT_DETAIL_MOVE_SPEC ) but no sample order?
Where I can obtain these then?
janneman - Yes. I run it like that right now.
Noisy as hell
Even with the C7 present it seems to me (but I could remember it wrong, of course) was the noise a bit smaller...
Suggestions what to do to stop the oscilations are more that welcome.
Hi trodas,
Pull what you need from a Japanese stereo or something. Even VCRs may have some. Then, they are free except for your labour.
Jan is on the same track as I am here. It looks like you may have to play with C117 and C7. Those compensate your op amp. Try pulling C117 & C118 first. You must do both sides as high frequency oscillation on one side will be picked up by the other side. You may need to reduce C7 & C8 also. Just try it. The 5532 would be a good baseline to start with as they sound good and are easy to use.
C1 is an RFI filter and may also add HF stability. C3, C9 and C13 are DC blocking capacitors. C13 blocks DC from input bias currents. Odd there is no DC return for the input of IC3. Must be biased from the inside, and there is an excellent reason to include a cap there. C9 prevents noise when using the volume control due to DC output offsets from your 4558 (the "D" indicates an 8 pin dip, "DD" is the quiet version). C3 protects the 4558 from external DC offsets. Each of these has a reason to exist and therefore should remain in circuit.
If you have an oscilloscope, you can monitor for oscillations. A 'scope is a basic requirement for doing this kind of work.
Pull what you need from a Japanese stereo or something. Even VCRs may have some. Then, they are free except for your labour.
Jan is on the same track as I am here. It looks like you may have to play with C117 and C7. Those compensate your op amp. Try pulling C117 & C118 first. You must do both sides as high frequency oscillation on one side will be picked up by the other side. You may need to reduce C7 & C8 also. Just try it. The 5532 would be a good baseline to start with as they sound good and are easy to use.
C1 is an RFI filter and may also add HF stability. C3, C9 and C13 are DC blocking capacitors. C13 blocks DC from input bias currents. Odd there is no DC return for the input of IC3. Must be biased from the inside, and there is an excellent reason to include a cap there. C9 prevents noise when using the volume control due to DC output offsets from your 4558 (the "D" indicates an 8 pin dip, "DD" is the quiet version). C3 protects the 4558 from external DC offsets. Each of these has a reason to exist and therefore should remain in circuit.
If you have an oscilloscope, you can monitor for oscillations. A 'scope is a basic requirement for doing this kind of work.
anatech - yep, I wish I got access to some, but I don't. Dead stuff is already thrown away, so... no luck yet, I'm stuck with the noise
Well, currently the C7, C8, C33, CC34, C59 and C60 are gone. Also are currently the C117, C118, C119, C120, C121 and C122 gone too.
It is true that I cannot remember if I even tried to run the opamps with just the C7 & spol. present while the C117 & spol. absent. Maybe not.
Still I think that putting there a 10 or 22pF C7 & spol. is maybe better that the 100pF original.
NE5532 oscilate just worser that LM4562 in this circuit, dunno why.
True. Same goes for C99, just check the switchboard scheme that is before the electronic scheme: http://img519.imageshack.us/my.php?image=geniussw51hometheaterelba4.gif
From the TDA7269, okay. But datasheet say that this is just 500nA, so I think C13 is unnecessary. 500nA the pot surely can handle
C9 do a terrible job then. When the pot become unclean over time, it become noisy a bit. Not much, but at some anges... But okay, we need one decoupling cap in the loop.
Even the DC offset from opamp should not be that high that high (it is already decoupled on the input) it require a cap there. Regardless if C3 stay, C9 has no bussines of be there.
True again. From Genius point of view, there is no knowing what will get connected on the input and hence they has to protect their circuits even from very high input DC offset.
In DIY world, we already know what get connected there. My moded X-Fi with LM4562 opamps, planed replacement for AD8599 ones. Current DC offset is 200mV, witch is not a problem since the opamps gain is 1 (or 2?) and then 200 or 400mV on the output is not going to clip or distort my audio signal in any way.
I hope that AD8599 output DC offset will be even lower and that the removal of the muting transistors on the X-Fi output will also decrease the DC offset and noise as well
True. I have a basic scope, a Allison Technology 440 Scope Plus
http://img147.imageshack.us/my.php?image=eurocase400wpsu9yh6.jpg
http://www.atcweb.com/tpi440.htm
and I already did some measurments. On the output from the amp, on rigth speaker, I measured a AC - 115,9kHz, 97.5mV, DC - 163.7mV
115kHz?!
I hear something completely different. So the primar oscilation is at 115kHz and I hear some sort of lower harmonic. Shame I can't choose to measure the harmonic, tough. I willing to bet it is somewhere near 5kHz.
PS. I ordered a sample of the 4pcs TI 4580 chips. I wonder if they will oscilate as well in this circuit.
Well, currently the C7, C8, C33, CC34, C59 and C60 are gone. Also are currently the C117, C118, C119, C120, C121 and C122 gone too.
It is true that I cannot remember if I even tried to run the opamps with just the C7 & spol. present while the C117 & spol. absent. Maybe not.
Still I think that putting there a 10 or 22pF C7 & spol. is maybe better that the 100pF original.
NE5532 oscilate just worser that LM4562 in this circuit, dunno why.
True. Same goes for C99, just check the switchboard scheme that is before the electronic scheme: http://img519.imageshack.us/my.php?image=geniussw51hometheaterelba4.gif
From the TDA7269, okay. But datasheet say that this is just 500nA, so I think C13 is unnecessary. 500nA the pot surely can handle
C9 do a terrible job then. When the pot become unclean over time, it become noisy a bit. Not much, but at some anges... But okay, we need one decoupling cap in the loop.
Even the DC offset from opamp should not be that high that high (it is already decoupled on the input) it require a cap there. Regardless if C3 stay, C9 has no bussines of be there.
True again. From Genius point of view, there is no knowing what will get connected on the input and hence they has to protect their circuits even from very high input DC offset.
In DIY world, we already know what get connected there. My moded X-Fi with LM4562 opamps, planed replacement for AD8599 ones. Current DC offset is 200mV, witch is not a problem since the opamps gain is 1 (or 2?) and then 200 or 400mV on the output is not going to clip or distort my audio signal in any way.
I hope that AD8599 output DC offset will be even lower and that the removal of the muting transistors on the X-Fi output will also decrease the DC offset and noise as well
True. I have a basic scope, a Allison Technology 440 Scope Plus
http://img147.imageshack.us/my.php?image=eurocase400wpsu9yh6.jpg
http://www.atcweb.com/tpi440.htm
and I already did some measurments. On the output from the amp, on rigth speaker, I measured a AC - 115,9kHz, 97.5mV, DC - 163.7mV
115kHz?!
I hear something completely different. So the primar oscilation is at 115kHz and I hear some sort of lower harmonic. Shame I can't choose to measure the harmonic, tough. I willing to bet it is somewhere near 5kHz.
PS. I ordered a sample of the 4pcs TI 4580 chips. I wonder if they will oscilate as well in this circuit.
Hi trodas,
The first step would be to install bypass caps from the power supply pins directly to what we will call our "dirty ground". This will not be connected to the signal ground until it reaches the power supply. If you examine the existing bypass caps, you may find that they are connected to your signal ground. If that is the case, disconnect them and create your own ground to run back. Return the circuit to original condition and check it's operation. From here on in, you must take notes to be clear on what you do, and the results.
Each change will need to be addressed in an organized fashion. Then you will find it easier to keep on track and learn something in the process.
Hi dietcoke,
Hi yangsmm,
One thing to think about is that a faster op amp will generally oscillate more readily than a slower one. Other factors may change things slightly - as in this case.
-Chris
Well, if the NE5532 oscillates, you probably have layout problems with the PCB board. It's a pretty well mannered op amp, and hard to mess up with. So you must attack the root of the problem rather than try to just patch it up. I strongly suspect the 4558s were installed because they worked.
The first step would be to install bypass caps from the power supply pins directly to what we will call our "dirty ground". This will not be connected to the signal ground until it reaches the power supply. If you examine the existing bypass caps, you may find that they are connected to your signal ground. If that is the case, disconnect them and create your own ground to run back. Return the circuit to original condition and check it's operation. From here on in, you must take notes to be clear on what you do, and the results.
Each change will need to be addressed in an organized fashion. Then you will find it easier to keep on track and learn something in the process.
May do. You'll have to see. I would recommend using a relay to replace your muting transistors if you can.
The high frequency oscillation will cause audible noise due to a few possible effects. One, the output stage draws current and you may get a form of higher frequency motorboating where you are hearing the envelope of the high frequency as it is modulated. With power amplifiers, you may also hear hum as the supply delivers high current. The other common effect is rectification. The following stage can not reproduce the high frequency and may detect the high frequency as the earlier stages are driven into non-linear operation. Either way, you get some indication. This can easily be seen with an oscilloscope. Yours is not the best tool for the job, an inexpensive analog 'scope would work just fine.
Hi dietcoke,
Well, it's a better op amp, but it is designed to drive output lines and headphones. I'm thinking that the NE5532 might be better here. The NJM4556 is better at driving headphones than a straight NE5532.
Hi yangsmm,
There is no one "best" op amp. You want to choose the right tool for the job. Blindly replacing one op amp for another is not the answer. I've seen older numbers replaced with newer types where the original part performed better in that application.
One thing to think about is that a faster op amp will generally oscillate more readily than a slower one. Other factors may change things slightly - as in this case.
-Chris
i just looked at the schematic. C7 is an integrating cap. it turns the op amp into a low pass filter to keep it from oscillating. the turnover frequency is about 900khz. i agree with anatech. there might be PC layout issues or power supply bypassing issues at work here, so they tacked on the 100pf caps to make it behave. there don't appear to be any other stability factors at work here. a 5532 has a 10Mhz bandwidth, and the 4558 is 2.5Mhz, and both are internally compensated. there does appear to be something strange that happens between 100khz and 200khz that might have something to do with the phase margin. my vote is put the 100pf cap back in, and go as high as 300pf if you have to.
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