NJM5532 to two OPA627
Hi all
My CDP has a NJM5532 opamp in the output stage. I am interested in changing this for something better.
I know that opamps like OPA2134 and OPA2604 are drop in replacements physically, however, are any changes to the circuit/surrounding components required or advised?
I am also interested in replacing the dual opamp with two single opamps like OPA627.
Are the Brown Dog adaptors used for this any good?
Do they introduce additional problems by moving the opamps further away from the PCB/groundplane?
Is there another/better way to do this?
Looking at the layout of the components surrounding the opamp in my CDP, it appears that they are spread quite far apart and connected by long traces.
What is likely to happen if you move the opamp to a separate board and construct an identical, but less widespread, circuit around it? The opamp would be further from the main PCB and groundplane but closer to its decoupling caps etc?????
Hi all
My CDP has a NJM5532 opamp in the output stage. I am interested in changing this for something better.
I know that opamps like OPA2134 and OPA2604 are drop in replacements physically, however, are any changes to the circuit/surrounding components required or advised?
I am also interested in replacing the dual opamp with two single opamps like OPA627.
Are the Brown Dog adaptors used for this any good?
Do they introduce additional problems by moving the opamps further away from the PCB/groundplane?
Is there another/better way to do this?
Looking at the layout of the components surrounding the opamp in my CDP, it appears that they are spread quite far apart and connected by long traces.
What is likely to happen if you move the opamp to a separate board and construct an identical, but less widespread, circuit around it? The opamp would be further from the main PCB and groundplane but closer to its decoupling caps etc?????
Hello!
To use the 134, 604 or 627 you definitely need to at least put 0,1uF caps as close to the psu pins as possible to the ground...and additionally to see what you can do to improve the psu to the analogue section...see the chip specs for more info
I use Brown Dogs to hold two 627s, can't say I have noticed any drawback. The OPA627 gives a better 3D sound stage compared to the OPA2604 or 2134 - in my CD at least.
You could always try to decouple each opamp on the Bown Dog - IF any of the opamp pins are connected to ground, that is...
t
To use the 134, 604 or 627 you definitely need to at least put 0,1uF caps as close to the psu pins as possible to the ground...and additionally to see what you can do to improve the psu to the analogue section...see the chip specs for more info
I use Brown Dogs to hold two 627s, can't say I have noticed any drawback. The OPA627 gives a better 3D sound stage compared to the OPA2604 or 2134 - in my CD at least.
You could always try to decouple each opamp on the Bown Dog - IF any of the opamp pins are connected to ground, that is...
t
Hi Tom
Yes, that space is a real bonus. With a little bit of shielding to line it, you could put a range of things in there.
I was thinking of putting a Tent XO2 clock and XO supply in there. It's quite close to the original crystal.
You could even put an extra transformer and power supplies in there.
Yes, that space is a real bonus. With a little bit of shielding to line it, you could put a range of things in there.
I was thinking of putting a Tent XO2 clock and XO supply in there. It's quite close to the original crystal.
You could even put an extra transformer and power supplies in there.
Before discarding the NE5534 for something else, I'd spend some time making calculations for voltage noise and current noise performance, because the specifications can be quite deceptive. Sure, the specified current noise may be thousands of times greater than that of other opamps, but people seem to forget that the openloop gain and input impedance should also be part of the calculation. I'm a bit rusty here, but AFAIK some of the popular alternative opamps that have been suggested here (OPA2134, OPA2604...) have very high impedance JFET inputs, which means that the current noise has to be extremely low for the opamp to be any good.
The boastful claims of 0.000000000001 THD are useless information, whereas the corresponding graphs of THD vs Gain are much more informative. In some cases they show that distortion increases 10 times when the gain is increased 10 times. This means that almost all of the distortion is at low amplitude, indicating a B-class output stage with a very non-linear crossover step (optimized for low power consumption above all else) and is therefore unsuitable for many hifi audio applications. The datasheet for the OPA2350 however shows that the distortion increases only 1.5 times from 0.004% to 0.006% when the gain is increased from 1 to 10. This indicates that the output stage is class-AB with a much smoother transition.
CM
The boastful claims of 0.000000000001 THD are useless information, whereas the corresponding graphs of THD vs Gain are much more informative. In some cases they show that distortion increases 10 times when the gain is increased 10 times. This means that almost all of the distortion is at low amplitude, indicating a B-class output stage with a very non-linear crossover step (optimized for low power consumption above all else) and is therefore unsuitable for many hifi audio applications. The datasheet for the OPA2350 however shows that the distortion increases only 1.5 times from 0.004% to 0.006% when the gain is increased from 1 to 10. This indicates that the output stage is class-AB with a much smoother transition.
CM
Hi All,
Slightly off topic but I replaced 4 pcs of NJM353 with 4 unit of dual OPA627 on adaptor with high hopes in the preamp section of my 4-channel amplifier:
Phonon340C 10112008013 on Flickr - Photo Sharing!
However, the SQ had suffered with reduced volume, loss of details and very slow sounding ...... being the electronic noob as I am, I just realised that the input current of the dual OP627 is 14mA against the LM353 at 3.6mA. Is this the most likely reason for the poor SQ or just I need to:
- remove some compensation capacitors mentioned here or
- remove some input rail resistors to handle the higher current as advised else where??
Meanwhile, I have order OPA2107 with input current requirement of same 3.6mA to try again but would certainly hope for some guidance on how to use dual OPA627 properly in the replacement of NJM353 as I had already spent some serious $ on them.
Thanks and regards,
Richard
Slightly off topic but I replaced 4 pcs of NJM353 with 4 unit of dual OPA627 on adaptor with high hopes in the preamp section of my 4-channel amplifier:
Phonon340C 10112008013 on Flickr - Photo Sharing!
However, the SQ had suffered with reduced volume, loss of details and very slow sounding ...... being the electronic noob as I am, I just realised that the input current of the dual OP627 is 14mA against the LM353 at 3.6mA. Is this the most likely reason for the poor SQ or just I need to:
- remove some compensation capacitors mentioned here or
- remove some input rail resistors to handle the higher current as advised else where??
Meanwhile, I have order OPA2107 with input current requirement of same 3.6mA to try again but would certainly hope for some guidance on how to use dual OPA627 properly in the replacement of NJM353 as I had already spent some serious $ on them.
Thanks and regards,
Richard
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You need to measure the rails to the opamps and confirm they are clean and correct.
You need to make sure the PSU can supply the additional current without overheating any regulators etc.
And you really need to use a scope to see what's happening. The OPA627 is a high speed device and may be unstable. Opamps can't just be swapped around without you realising the implications and looking to see if the application is suitable
You need to make sure the PSU can supply the additional current without overheating any regulators etc.
And you really need to use a scope to see what's happening. The OPA627 is a high speed device and may be unstable. Opamps can't just be swapped around without you realising the implications and looking to see if the application is suitable
Hi Mooly,
Thanks for the advice ... indeed feeling foolish just taking many of the threads on "op-amp rolling" on the surface and not getting into details nor realizing the complexity. For now, I will be glad to just be getting just marginally improved or similar SQ with similarly spec'd OPA2107 in place of the original NJM353. If even OPA2107 is not a good bet that all will be well electronically, do share your thoughts on recommendation on viable alternatives or I really have to get back to putting some LF353s since the original NJM353s had been destroyed and hard to get from ebay. Thanks again, Richard
Thanks for the advice ... indeed feeling foolish just taking many of the threads on "op-amp rolling" on the surface and not getting into details nor realizing the complexity. For now, I will be glad to just be getting just marginally improved or similar SQ with similarly spec'd OPA2107 in place of the original NJM353. If even OPA2107 is not a good bet that all will be well electronically, do share your thoughts on recommendation on viable alternatives or I really have to get back to putting some LF353s since the original NJM353s had been destroyed and hard to get from ebay. Thanks again, Richard
The LF353 is similar to the TL072... surprisingly good really.
I still like the OPA2604 for sound quality as the distortion spectrum has even harmonics as the predominating feature.
Working with surface mount technology,
http://www.diyaudio.com/forums/parts/127924-working-smd-how-do-without-specialised-tools.html
I still like the OPA2604 for sound quality as the distortion spectrum has even harmonics as the predominating feature.
Working with surface mount technology,
http://www.diyaudio.com/forums/parts/127924-working-smd-how-do-without-specialised-tools.html
Yeah, I suspected that and I always look at the distortion in gain of 10 or so.
Check out the OPA1641/1642 (which I was recommending formerly)
Yes, it is: 4,5 MHz is slow and it won't misbehave. The OPA1642 is not that much faster, though
Hi Mooly,
I feel more wasted now that you mentioned LF353 (or my case NJM353) is actually quite good ... just felt that the NJM353 is old and surely there is some modern compatible op amp after 15 years that will improved over it. Guess I will not be looking at OPA2604 since the input current is 10.5mA instead of 3.6mA for the original NJM353 and the planned OPA2107 at 4mA ... as not to repeat the same disappointment with the 14mA dual OPA627.
Aside to Andrea,
---------------
I am looking for direct replacement with just IV op amp and will not be capable to look into major mod like have different stage to 'pipe' different op amp. Will try the recommended OP1642 and the OP2107 to decide. Thanks nevertheless
Regards,
Richard
I feel more wasted now that you mentioned LF353 (or my case NJM353) is actually quite good ... just felt that the NJM353 is old and surely there is some modern compatible op amp after 15 years that will improved over it. Guess I will not be looking at OPA2604 since the input current is 10.5mA instead of 3.6mA for the original NJM353 and the planned OPA2107 at 4mA ... as not to repeat the same disappointment with the 14mA dual OPA627.
Aside to Andrea,
---------------
I am looking for direct replacement with just IV op amp and will not be capable to look into major mod like have different stage to 'pipe' different op amp. Will try the recommended OP1642 and the OP2107 to decide. Thanks nevertheless
Regards,
Richard
Hi Andrea, Noted and thanks.
Aside to Mooly,
unfortunately i do not have the schematic and only the shot of the amp in discussion as follows:
Phonon340C 10112008013 on Flickr - Photo Sharing!
As you can see, there are 5 PSUs but no sure if 4 are for the 4 channels throughout preamp to output or just 1 for preamp and 4 for output .... please bear with an electronics noob.
If not due to higher current of dual OP627, it will then be even more beyond my capability if it relates to all the other R and C mod that is needed to optimise with this change for NJM353 to OPA627. Any further advice is certainly appreciated.
Regards,
Richard
Aside to Mooly,
unfortunately i do not have the schematic and only the shot of the amp in discussion as follows:
Phonon340C 10112008013 on Flickr - Photo Sharing!
As you can see, there are 5 PSUs but no sure if 4 are for the 4 channels throughout preamp to output or just 1 for preamp and 4 for output .... please bear with an electronics noob.
If not due to higher current of dual OP627, it will then be even more beyond my capability if it relates to all the other R and C mod that is needed to optimise with this change for NJM353 to OPA627. Any further advice is certainly appreciated.
Regards,
Richard
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