Hello everyone!
I have a stereo integrated amplifier ROTEL RA-930AX with opamp NE5532AN (img : http://www.repo.intilinux.com/DSC01418.JPG). I wanted to replace it with a better one. For example: OPA2604. It's a good choice?
I have a stereo integrated amplifier ROTEL RA-930AX with opamp NE5532AN (img : http://www.repo.intilinux.com/DSC01418.JPG). I wanted to replace it with a better one. For example: OPA2604. It's a good choice?
Im not a believer in replaceing Opamps just for the sake of it .... especially if you don"t know what the Opamp is doing in that particular place in the circuit .....
You can replace a opamp in a Circuit with another with better specs and still get worse results ...... The designers at Rotel probably chose the NE5532 for a reason ......
I would personally leave it as it is unless you really think that the NE5532 is holding your amp back from sounding good ....
If you are really set of swapping in another opamp try the LM4562 , it is one of the best speced Dual Bipolar opamps out there .....
LM4562 - Dual High Performance, High Fidelity Audio Operational Amplifier
Cheers
You can replace a opamp in a Circuit with another with better specs and still get worse results ...... The designers at Rotel probably chose the NE5532 for a reason ......
I would personally leave it as it is unless you really think that the NE5532 is holding your amp back from sounding good ....
If you are really set of swapping in another opamp try the LM4562 , it is one of the best speced Dual Bipolar opamps out there .....
LM4562 - Dual High Performance, High Fidelity Audio Operational Amplifier
Cheers
OPA2604... yes it's a good choice, the one I would use...
and search the forums
it's the one of the most asked questions
http://www.diyaudio.com/forums/chip-amps/154106-best-sounding-audio-integrated-opamps.html
http://www.diyaudio.com/forums/chip-amps/82610-best-sounding-dual-opamps.html
and search the forums
it's the one of the most asked questionshttp://www.diyaudio.com/forums/chip-amps/154106-best-sounding-audio-integrated-opamps.html
http://www.diyaudio.com/forums/chip-amps/82610-best-sounding-dual-opamps.html
Hello, you're right. But I want to try. In truth I have chosen the lm4562 and opa2104 as possible substitutes. I'll let you know how it will test. I will use a socket to restore the original.
I bought them both ... see when they arrive ...
Hi Antony.
Have you seen this thread on the Rotel RA-920AX
http://www.diyaudio.com/forums/solid-state/169537-rotel-ra-920ax.html
There is a link for the 920AX service manual on post 3.
The 920AX is supposedly very similar to the 930AX
The op amp circuit that you are attempting to upgrade is the RIAA Phono Stage. Unless you are using a record deck it is largely irrelevant to the sound of the amplifier.
The 10uf (orange) caps are in the phono eq circuit and increasing the value will increase sub-sonic rumble using the record deck.
The op amp in the signal path all the time is IC 501 which is another dual op amp. It probably would be worthwhile replacing the electrolytics on the op amp voltage rails C 415 C 416 C505 & C506 Voltages are quoted as 17.5V +ve and 17.7 V -ve. Any op amp subtitution you use will need to be able to take 36 Volts
If all the component numbers on the 920AX circuit are similar to the 930AX I would look at replacing C 411 C412 C501 C502 C601 C602 These are 10uF 25V signal coupling capacitors. Replace these with similar or larger value (22uf or 47uf). The other critical capacitor is the feedback capacitor which is listed on the 920 circuit as C605 & C606 100uF 25V. Probably best replaced with another 100uf Cap. All of these capacitors could be bi-passed with a 0.1 uf polyester capacitor. Usually I tack the bi-pass cap on to the new electrolytic leads on the bottom of the PCB and then trim the leads.
You should be able to do these mods with minimal cost - Use decent low ESR capacitors such as Panasonic FC or Elna Silmics - Check what will fit on the PCB and use a capacitor with a generous voltage rating as these tend to be better sounding parts.
If you want to continue with more mods you may need to replace the main power capacitors depending on the age and condition of the amplifier.
Have you seen this thread on the Rotel RA-920AX
http://www.diyaudio.com/forums/solid-state/169537-rotel-ra-920ax.html
There is a link for the 920AX service manual on post 3.
The 920AX is supposedly very similar to the 930AX
The op amp circuit that you are attempting to upgrade is the RIAA Phono Stage. Unless you are using a record deck it is largely irrelevant to the sound of the amplifier.
The 10uf (orange) caps are in the phono eq circuit and increasing the value will increase sub-sonic rumble using the record deck.
The op amp in the signal path all the time is IC 501 which is another dual op amp. It probably would be worthwhile replacing the electrolytics on the op amp voltage rails C 415 C 416 C505 & C506 Voltages are quoted as 17.5V +ve and 17.7 V -ve. Any op amp subtitution you use will need to be able to take 36 Volts
If all the component numbers on the 920AX circuit are similar to the 930AX I would look at replacing C 411 C412 C501 C502 C601 C602 These are 10uF 25V signal coupling capacitors. Replace these with similar or larger value (22uf or 47uf). The other critical capacitor is the feedback capacitor which is listed on the 920 circuit as C605 & C606 100uF 25V. Probably best replaced with another 100uf Cap. All of these capacitors could be bi-passed with a 0.1 uf polyester capacitor. Usually I tack the bi-pass cap on to the new electrolytic leads on the bottom of the PCB and then trim the leads.
You should be able to do these mods with minimal cost - Use decent low ESR capacitors such as Panasonic FC or Elna Silmics - Check what will fit on the PCB and use a capacitor with a generous voltage rating as these tend to be better sounding parts.
If you want to continue with more mods you may need to replace the main power capacitors depending on the age and condition of the amplifier.
Ok. Thank you!
This is the technical manual : http://www.repo.intilinux.com/rotel%20ra-930ax/RA-930AX-TM.pdf
So I prepare to replace them:
You'll find the recommended capacitors.
OPA2604 datasheet : http://www.repo.intilinux.com/rotel ra-930ax/opa2604.pdf
NE5532AN datasheet (original opamp) : http://www.repo.intilinux.com/rotel%20ra-930ax/NE5532FE%20(originale%20montato).pdf
High Resolution : http://www.repo.intilinux.com/rotel ra-930ax/rotel_mod.JPG
More photos : http://www.repo.intilinux.com/rotel ra-930ax/DSC01419.JPG
http://www.repo.intilinux.com/rotel ra-930ax/DSC01417.JPG
This is the technical manual : http://www.repo.intilinux.com/rotel%20ra-930ax/RA-930AX-TM.pdf
So I prepare to replace them:
An externally hosted image should be here but it was not working when we last tested it.
You'll find the recommended capacitors.
OPA2604 datasheet : http://www.repo.intilinux.com/rotel ra-930ax/opa2604.pdf
NE5532AN datasheet (original opamp) : http://www.repo.intilinux.com/rotel%20ra-930ax/NE5532FE%20(originale%20montato).pdf
High Resolution : http://www.repo.intilinux.com/rotel ra-930ax/rotel_mod.JPG
More photos : http://www.repo.intilinux.com/rotel ra-930ax/DSC01419.JPG
http://www.repo.intilinux.com/rotel ra-930ax/DSC01417.JPG
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Rotel RA-
I always have some Rotel on hand in my "collection" of amplifiers, and I'm following them since the early 9xx models.
Although all models have almost identical output section, the pramp/chips usually varies between the models, to such extent I suspect the are putting inside whatever they have on hand. Thus, I have seen for example RA-970BX with NE5532, AD712, OPA2604, AD711, OPA275...being different only the letter BX, BX2 and so on.
Also the RA-1060, and some other models - you can find with OPA2134, NE5532 and/or OPA2604.
Recently I purchased an mint Rotel RA-1070 which comes with OPA2604, and - although sound very good, I started changing opamps, in hope I can obtain any improvements; I did not change the gain resistors (thus it is original setting g=6)
Here is my experience (Classe CAP-2100 serving as reference amp, Krell KAV250mk2 as source and Dynaudio Confidence C1, speakers)
OPA2604 (original) - the sound is very relaxed, dynamic, with anususal ease and non-fatigue; however, in the mid-high tonality something is harsh and a bit murky. Although the details are fairly, there is not clean sound
The sibling OPA2134 is much worse than 2604; althoug more polite, it is lifless; very good for listening MP3 or tuner, but nod for high end-ish sound which we are expecting from the top-cat Rotel inegrated
The 2132, another contender to be miles ahead of 2604, does not shine; it is more similar to 2134 than to 2604, although lot peaple says it is just more selected opa2604. However, it is better than most other tryed, bat not so relaxed.
OP275 - this chip is interesting: actually, to my ears it soundr pretty much like 2604 tonally, with wide soundstage, good front-to-back rendering, crisp and very impactfull...but, somehow it is like OPA2604 put one the steroids - everything is a bit too wide, to deep , too high, and to explosive. It is not possiible this is the only chip it has right, since no other is alike.
AD826 - although clean,wide stage, (too) polite, the soundstage has no hight. Something is missing here. AD827 and 828 are very similar, with the former the bass is boomy compared to 826, and the later excels in term of stage and airiness, but that seems unreal. The listener becames part of the scene (well, almost), but on the long run, it is not listenable with vrious music style (eg. you cannot listen hevy metal, or some elctronic music, but it is excellent for small jazz ansamble)
LM6172 - this is interesting one, has very good mid-bass resolution, excellent highs and attack, but somehow it's missing ability to layer the stage. Everything is two dimensional. And it is a bit veiled in upper mids. Otherwise, very dynamic and assuringly.
Very similar is the momentary star performer, LM4562. This chip has everything right, clean, clear, airy...but missng impact on the bass region. Thats not Rotel as shoud be, using this chip, although probably the best in term of distortion.
Now, what to do? Does anybody has some tweak here? How to obtain a maximom from the 2604?
Actually, thix opamp is really excellent intended chip, but something it should be done with it to give the best from itself. I feel something has to be done in the circuitry/passive components to be optimized. Rotel always uses gain of around 6, but in older models this is done via 10k/1,8k resistors, somwhere 2,9k/580R, and somtimes lesser values. I cannot undarstand this
Some people says for OPA2604 and OP275 the suplly voltage should be around 20V, but I did not tried yet.
I always have some Rotel on hand in my "collection" of amplifiers, and I'm following them since the early 9xx models.
Although all models have almost identical output section, the pramp/chips usually varies between the models, to such extent I suspect the are putting inside whatever they have on hand. Thus, I have seen for example RA-970BX with NE5532, AD712, OPA2604, AD711, OPA275...being different only the letter BX, BX2 and so on.
Also the RA-1060, and some other models - you can find with OPA2134, NE5532 and/or OPA2604.
Recently I purchased an mint Rotel RA-1070 which comes with OPA2604, and - although sound very good, I started changing opamps, in hope I can obtain any improvements; I did not change the gain resistors (thus it is original setting g=6)
Here is my experience (Classe CAP-2100 serving as reference amp, Krell KAV250mk2 as source and Dynaudio Confidence C1, speakers)
OPA2604 (original) - the sound is very relaxed, dynamic, with anususal ease and non-fatigue; however, in the mid-high tonality something is harsh and a bit murky. Although the details are fairly, there is not clean sound
The sibling OPA2134 is much worse than 2604; althoug more polite, it is lifless; very good for listening MP3 or tuner, but nod for high end-ish sound which we are expecting from the top-cat Rotel inegrated
The 2132, another contender to be miles ahead of 2604, does not shine; it is more similar to 2134 than to 2604, although lot peaple says it is just more selected opa2604. However, it is better than most other tryed, bat not so relaxed.
OP275 - this chip is interesting: actually, to my ears it soundr pretty much like 2604 tonally, with wide soundstage, good front-to-back rendering, crisp and very impactfull...but, somehow it is like OPA2604 put one the steroids - everything is a bit too wide, to deep , too high, and to explosive. It is not possiible this is the only chip it has right, since no other is alike.
AD826 - although clean,wide stage, (too) polite, the soundstage has no hight. Something is missing here. AD827 and 828 are very similar, with the former the bass is boomy compared to 826, and the later excels in term of stage and airiness, but that seems unreal. The listener becames part of the scene (well, almost), but on the long run, it is not listenable with vrious music style (eg. you cannot listen hevy metal, or some elctronic music, but it is excellent for small jazz ansamble)
LM6172 - this is interesting one, has very good mid-bass resolution, excellent highs and attack, but somehow it's missing ability to layer the stage. Everything is two dimensional. And it is a bit veiled in upper mids. Otherwise, very dynamic and assuringly.
Very similar is the momentary star performer, LM4562. This chip has everything right, clean, clear, airy...but missng impact on the bass region. Thats not Rotel as shoud be, using this chip, although probably the best in term of distortion.
Now, what to do? Does anybody has some tweak here? How to obtain a maximom from the 2604?
Actually, thix opamp is really excellent intended chip, but something it should be done with it to give the best from itself. I feel something has to be done in the circuitry/passive components to be optimized. Rotel always uses gain of around 6, but in older models this is done via 10k/1,8k resistors, somwhere 2,9k/580R, and somtimes lesser values. I cannot undarstand this
Some people says for OPA2604 and OP275 the suplly voltage should be around 20V, but I did not tried yet.
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Thanks for sharing your impressions eddie. When I design using opamps I prefer the inverting configuration, but that's not really something you can easily change.
The lower the value of the feedback network resistors, the lower the noise, however in my experience noise (pure white noise as opposed to hum etc) is the least of the issues in audio. Also the lower value resistors require an opamp capable of driving them fully. Devices such as the older TL072 are happier with loads over 3k or so.
It's always worthwhile (essential) to use a 'scope and squarewave test the various stages to see any unwanted behaviour or whether the compensation is optimal for the device being used. Also make sure the devices are bypassed at the supply pins with a small cap.
The lower the value of the feedback network resistors, the lower the noise, however in my experience noise (pure white noise as opposed to hum etc) is the least of the issues in audio. Also the lower value resistors require an opamp capable of driving them fully. Devices such as the older TL072 are happier with loads over 3k or so.
It's always worthwhile (essential
) to use a 'scope and squarewave test the various stages to see any unwanted behaviour or whether the compensation is optimal for the device being used. Also make sure the devices are bypassed at the supply pins with a small cap.I think OPA2604 (and, fairly almost all above tried chips) has enough current capability to drive almost anything in thier path.
It is interesting, the same feeling that "something more should be done" I have even with the old good NE5532 - this opamp is somehow "at home" with the all kinds of music. If it ywould have the cleaness of, say, LM4562 -it would be a real star here.
It's always worthwhile (essential
Unfortunatelly, I have no scope, and I'm even not a tech (but MD
) and the only instrument I have is my ear (OK, and Classe amp as some reference).I'm impressed how good decoupling of the opamps Rotel made - good BG caps, small MKP and sometimes additional ceramics. Even the dastest opamps (AD828) works perfectly and without any sign of oscillations.
What still amazes me is that we are able to pick up on what in reality are microscopic differences between the best devices... and to get the very best from a system means taking the whole system as "a whole".
The NE5532 is the device that (so the folks that know say) 95% of the stuff we ever listen too has passed through... yet adding another different device to the chain is audibly obvious in some cases.
There was an interesting write up on the 5532 as used in DA convertors (CD players) and how it was put forward that hf hash could cause non linearities due to the input stage configuration of the 5532.
I'm still unsure on it... as a pure gain block correctly implemented it seems pretty transparant... but in one or two other applications I have found it definitely does unpleasant things to the audio... things that swapping for say a TL072 corrects. Things I can't explain...
The NE5532 is the device that (so the folks that know say) 95% of the stuff we ever listen too has passed through... yet adding another different device to the chain is audibly obvious in some cases.
There was an interesting write up on the 5532 as used in DA convertors (CD players) and how it was put forward that hf hash could cause non linearities due to the input stage configuration of the 5532.
I'm still unsure on it... as a pure gain block correctly implemented it seems pretty transparant... but in one or two other applications I have found it definitely does unpleasant things to the audio... things that swapping for say a TL072 corrects. Things I can't explain...
Has anybody tested discrete drop-in replacement modules for NE5532, OPA2604 etc? Like these:
DEXA Technologies Discrete Audio Op-Amp
Semiconductor Burson Op Amp
DEXA Technologies Discrete Audio Op-Amp
Semiconductor Burson Op Amp
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