Op-Amps, who knew?

[Karl vd Berg]

@wyn palmer , just one question: I tried briefly the OPA2228 and it has a pretty nice sound, but it's not unity-gain stable and is much faster than the OPA2227. Being a bit reluctant to use the 2228 in any equipment, afraid of any possible oscillations or instabilities, etc...
Where would you suggest it's application?

 

[wyn palmer]

@wyn palmer , just one question: I tried briefly the OPA2228 and it has a pretty nice sound, but it's not unity-gain stable and is much faster than the OPA2227. Being a bit reluctant to use the 2228 in any equipment, afraid of any possible oscillations or instabilities, etc...
Where would you suggest it's application?

Looking at the open loop gain/phase characteristics I would agree with the claim that it's optimized for gains of 5 or greater, as it has a phase margin of about 45degrees when the open loop gain is 14dB, but with no capacitive load as far as I can tell. 45degrees is about as low a phase margin as you'd like to see...
It, theoretically, is unity gain stable, but not really unless a cap across the feedback R is used as described in the data sheet, and even then "it ain't pretty". The actual small signal square wave response at a gain of 10 is pretty decent.
I wouldn't like to suggest any particular applications. It's not particularly quiet, not particularly stable, doesn't seem to be recommended into lower loads than 10k for good distortion- not really anything that in my limited view stands out, although the overall set of specs seems pretty capable.

 

[pwauk12]

@wyn palmer -thanks for this, it matches my "perception' that it was more brittle and had accentuated high end (not in a good way)- on the next NAD I do I will put in a 2134 in one channel and a 4562 in the other and see if there is any measurable difference

 

[mjw21a]

I found LM4562NA to be significantly better than NE5532. Much wider sound stage and very laid back. That said when I changed to 2x Burson V5i-D and 2x Burson V6 Vivid Duals in my Muji Studio DAC II or took the performance of that DAC to beyond my wildest dreams.... The DAC actually outperforms my $30k (Australian) vinyl setup. Quite incredible. Nothing else has been upgraded in the DAC at this time. Considering tube coupling caps and output caps though

 

[wyn palmer]

I found LM4562NA to be significantly better than NE5532. Much wider sound stage and very laid back. That said when I changed to 2x Burson V5i-D and 2x Burson V6 Vivid Duals in my Muji Studio DAC II or took the performance of that DAC to beyond my wildest dreams.... The DAC actually outperforms my $30k (Australian) vinyl setup. Quite incredible. Nothing else has been upgraded in the DAC at this time. Considering tube coupling caps and output caps though

Hi- MattyW from Brisbane?
The problem is that it's pretty well impossible to comment on completely subjective conclusions like yours, other than to once more observe the whole subjective/objective argument at work. However, I would really appreciate it if someone would actual provide me with a tear down or at least a set of real specs for the Burson amps. The only real evaluation of them that I can find is now dated as it wasn't of any of the current models. However it was highly derisive towards their technical qualities...

 

[mjw21a]

Beyond my ability I'm afraid. Still, I'm never removing them.... Not ever.

 

[urarnut]

having done this to a number of NAD 2200/2600/2700- there is a noticeable and measurable improvement in the performance, the distortion and noise is lower and better signal to noise- which sonically to me, sounds like more detail, better transparency and better dynamics.

That said, I also replace all the electrolytics and some of the ceramic caps as well.

as to op amp choice- as the original op amps (2043DD) are BJT, I replace them with other BJT opamps- 4562 in this case.

I realize this is an old thread but, I wonder if you have done this same mod for the 7600 which is supposed to include the same amp. I could not find the the 2043DD or similar on the schematic or parts list. Can you tell me what position in the schematic of the 7600 this opamp would go? Thanks for sharing your knowledge.

 

[pwauk12]

There are a few 2043 in the 7600, IC961,IC 351 and IC501.

there are also some 4558- you can research on AK to see if they are worth changing

 

[urarnut]

There are a few 2043 in the 7600, IC961,IC 351 and IC501.

there are also some 4558- you can research on AK to see if they are worth changing

Thanks. These are on the "main Volume", "Tape Selector", and "Audio Accessory" PCBs respectively. Is that right?

 

[pwauk12]

yes