Replace NE5532AN

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#21
Mooly said:
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.
Click to expand...

I received once advices for NE5532 implementation in DA conversion, which is interesting and not obvious at first sight: supply 7812 reg, as close as possible to supply pins (and no bypass at all(!?) -> on the output of the chip resistor - fairly low 33R-> 4,7uF poly cap, and after that->100k to GND. The signal iz taken from this point. The point is, this chip works best if it is stressed for high current output, and the cofiguration of R/C on output is inverse of usual practice as can be seen in most of the CDP schematics.

I tried this on some old Rotel RCD971, and there is significant difference in sound, really, especially on the quieter bacground and more real stage, noise but I don't know if it works in preamp configuration.

Interesting to note I was told this solution is taken from some Studer proffessional broadcast CDP, so it might really be very carefull design.
 

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#22
Usual reason for putting a low value resistor on an opamp output is to ensure stability into capacitive loads... even lead capacitance. The 4.7uf eliminates DC offset, the 100k providing a true ground reference (0 volts) at the other side. The only load on the opamp output is the 100k...

Don't quite follow what you mean tbh 🙂

Sometime the output from a DAC is fed into a low value resistor to ground such as 33 ohm, and that converts the DAC's current to voltage. An opamp is then used to amplify that.
 
#24
eradoncic said:
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.
Click to expand...


Replacing done!. I agree with you: the sound is very relaxed, dynamic, with anususal ease and non-fatigue. I also noticed a more detailed treble. Definitely a step forward (to me) ... a recommended upgrade or at least try!
 
#26
antony28 said:
Replacing done!. I agree with you: the sound is very relaxed, dynamic, with anususal ease and non-fatigue. I also noticed a more detailed treble. Definitely a step forward (to me) ... a recommended upgrade or at least try!
Click to expand...


Glad you tried;
However, I still did not found anything how to improve opa2604 soundind by changing gain resistors 🙁

For example - for gain approx. G=7 (which is preset in many Rotel amps), they are using 3,9k/680R to ground, in NFB loop. This can be acheived either by many resistor combinations (e.g 12k/2k, 20k/3,9k...etc, in both "directions", lower or higher than used).
Still the main question remain: how the NFB resistors value should be used, and what the effect will be on the sound 😕

Now I'm trying OPA637 (on Brown dog adapter) as a drop in replacement od 2604, and I must say - all this rave about 627/637 is objective - this one sounds really good, better than 2604 albeit on the same familly-sound, but much more clean and full bodied, excellent dynamic.
 
#28
NE5532 newcommer replacements

Well, this is a small update for anybody interesting to replace opamp in rotel gear
Recently I'm trying the new TI opamps: OPA827 and OPA2211 as a replacement for OPA2604

These newcommers are rally excellent, not only per specs but also sonically.
For those who prefer BJT input, the OPA2211 is stunning - at least to me (and for this application) it is the best NE5532 replacement I have heard in terms of it's special character. The 2211 has everything the old chip has extending the weak points of the older, much more clean, with firm and focused bass (my personal biggest personal complain) and excellent midrange/highs.

The JFET 827 is another excellent opamp, I would say OPA627 killer (at least considering the price/performance ratio) - works perfectly, and adding cleannes older FET chips were insufficient.

Sonically, it is almost identical to 627/637 familly - fullbodied, very clean and clear; it is better to 2132/2134 by good margin, although I prefer 2132 for it's sonical delicate balance; the only complain was a bit brush highs which is impossible to fix whatever I've done (incl. carlosfm "receipe"). Well, 827 is better without any adiitional care on the circuits.
 
#29
Hi
I have tested the Burson opamp and comparier with what i believe is the best opamp (AD744/AD811) by Walt Young. This AD744/AD811 combination has previous been compaired with opa2604, OPA 627, AD844, and was then a vinner. The Burson opamp is lightyears ahead the AD744/AD811.....
 
#30
Looking at the data sheet for the AD744 it is quite an impressive device but as such requires utmost care in it's implementation... I would hesitate to recommend it as a straight plug/play swap for more frequently encountered devices such as the 5534. The AD811 is a video amp, again the same applies perhaps more so.

What were you testing the Burson in just for interest...
 
#31
Well: I have been using the AD744/AD811 combination for years and has been very satisfied with the overall sound. This summer i Made a new Preamp and decided to compare the AD744/AD811 combination with the burson op-amps. The reason was that it has alway been said to me that discrete components sounds better then op-amps. I must say that the burson op-amps proved this by 100%. You should give it a try and I sure that you will positive surprised.
Regarding how to hook up the AD744/AD811 combination please see http://waltjung.org/PDFs/ADI_1993_Seminar_Audio_Drivers.pdf
Figure 8.57
 
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