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Aiyima 04 Op-Amp Problem

Joe Smith

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Looking for advice/counsel...I recently purchased an Aiyima 04 amp with the standard TI NE5532P op-amps. Using with a 24v/5a power supply. One of the Amazon review posters sung the praises of swapping in OPA627AU amps...there were a number of alternative ones mentioned as being "better" or "warmer" than the stock chips, so I thought I'd give that a try.

Found a seller that looked credible with those chips mounted to dip8 sockets, at a good price. Got them today and swapped them in, being careful to get the pin orientation correct. Upon powerup, got a high pitched noise from the amp, powered down immediately. Inserted old chips back, fortunately, the amp seems fine at least.

Did I get bad units or does the squeal indicate some sort of voltage mismatch? The chips don't have a TI or BB logo, just marked as BBOPA 627AU 0008.
 

somebodyelse

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The OPA627 is a single opamp while the 5532 is a dual, so you'd need 2 x 627s per adapter board to make an equivalent with a matching pinout. If you've only got one 627 on the adapter board it's not going to work.

When you say the seller 'looked credible' do you mean a reputable source like Farnell, RS, Mouser, Digikey etc. or do you mean someone on ebay, ali etc? Given the current high price of the 627 from the former the chance of fakes on the latter is unfortunately high.

The squeal indicates oscillation, one of the risks of opamp rolling. This time it was audible, but it can happen at ultrasonic frequencies. If you don't have an oscilloscope you might want some sacrificial speakers in case you fry a tweeter. I'd encourage you to do some measurements before and after if you can, and some properly controlled listening tests to see if you can really hear the difference as it's easy to get caught up in the process and mislead yourself - been there, done that ;)
 
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Joe Smith

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I'm not great at soldering items this small. Is there a reputable seller who has the 1656 genuine TI chips already mounted to a dip8 socket? I think I will return these 627's. Hopefully my tweeters are OK, I will check on that. It's a pair of Baby Advents.
 
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Joe Smith

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Hmmm... Was the main reason I bought the 04, thinking to try some different plug and play op amps. Ah, well. The stock sound is OK.
 

DVDdoug

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The "magic" of op-amps is their nearly infinite gain is combined with negative (corrective) feedback making raw op-amp performance much less critical. If there's anything wrong with your amplifier, swapping op-amps probably won't help. Is there something wrong with the sound? Noise, distortion, frequency response?

Some tube amplifiers are made with the opposite philosophy so that swapping tubes can change the sound. But since tubes age and their characteristics very from part-to-part, that approach makes performance less reliable/predictable

If you have a higher-gain mic preamp or phono preamp, a lower-noise op-amp might reduce the noise. Otherwise I wouldn't expect much difference.

Upon powerup, got a high pitched noise
A long time ago I built a preamp and the 1st attempt turned into an RF oscillator instead of a preamp... At first I was impressed at how quiet it was (before connecting an input). Then there was a little pop and one side of my power amp had blown. My tweeters were OK. The frequency was probably so high that the voice coil inductance saved them, or maybe the amp just blew first. I didn't have an oscilloscope so it's only by deductive reasoning and a bit more in-depth studying of op-amps that I figured-out what had happened. In then, I successfully re-designed the preamp and repaired the power amp.

Did I get bad units or does the squeal indicate some sort of voltage mismatch?
It's probably just wired wrong, since it's not a drop-in replacement. ;)
 

somebodyelse

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Hmmm... Was the main reason I bought the 04, thinking to try some different plug and play op amps. Ah, well. The stock sound is OK.
Don't worry - the 5532 isn't the limiting factor in the A04, and changing it for a 'better' pin-compatible opamp is unlikely to have made a measurable or audible difference under controlled listening conditions. Listen sighted and excited and you'll probably swear it sounds different - that's just how the brain works, and why the controls are important. It's just more convincing when you experience it first hand than when someone tells you about it.
 

Tangband

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Looking for advice/counsel...I recently purchased an Aiyima 04 amp with the standard TI NE5532P op-amps. Using with a 24v/5a power supply. One of the Amazon review posters sung the praises of swapping in OPA627AU amps...there were a number of alternative ones mentioned as being "better" or "warmer" than the stock chips, so I thought I'd give that a try.

Found a seller that looked credible with those chips mounted to dip8 sockets, at a good price. Got them today and swapped them in, being careful to get the pin orientation correct. Upon powerup, got a high pitched noise from the amp, powered down immediately. Inserted old chips back, fortunately, the amp seems fine at least.

Did I get bad units or does the squeal indicate some sort of voltage mismatch? The chips don't have a TI or BB logo, just marked as BBOPA 627AU 0008.

use lm4562 .
I have done the switch on my two Aiyima a04 . The sound gets better and theres no problems.
 
OP
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Joe Smith

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The ones I would up getting as replacements are Burr-Brown OPA2134PA. But, they made the 24v/4.5a power supply make more noise when I tested power on without speakers. Is that normal? I ordered these directly from TI so I know they are OEM chips... I have some test speakers I can try them with, but I don't want to fry anything if I can avoid it.
 

JohnYang1997

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Just use opa1642 or opa1656. The circuit has high resistance so current noise is quite important. Opa827 is good too but same as 627 it's single opamp you need those adapters that have opamp both sides.
Or simply stick with the stock 5532 which is adequate for the circuit.
 

pma

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The ones I would up getting as replacements are Burr-Brown OPA2134PA

They will be fine.
The mistake you made is that you had used single opamp OPA627 in place of the dual opamp NE5532. This is a huge mistake as they have different pin connections and doing so you could have destroyed the amplifier and speakers. You must first check datasheets before doing any opamp swapping. And do not believe the incompetent amateurs who make suggestions on a forum without checking and understanding what you are doing.

The noise with OPA2134 is in fact lower than with NE5532 and LM4562. AIYIMA is designed with high values of resistors so the resistor noise and current noise dominates. You will get no improvement with SOTA opamps.

A07_OPA2134_noise__RCfilter.png A07_LM4562_noise__RCfilter.png A07_5532_noise_RCfilter.png
 
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Joe Smith

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They will be fine.
The mistake you made is that you had used single opamp OPA627 in place of the dual opamp NE5532. This is a huge mistake as they have different pin connections and doing so you could have destroyed the amplifier and speakers. You must first check datasheets before doing any opamp swapping. And do not believe the incompetent amateurs who make suggestions on a forum without checking and understanding what you are doing.

The noise with OPA2134 is in fact lower than with NE5532 and LM4562. AIYIMA is designed with high values of resistors so the resistor noise and current noise dominates. You will get no improvement with SOTA opamps.

View attachment 136275 View attachment 136276 View attachment 136278
Thanks! They do sound good and when using with the 32v/5a supply that came with the Aiyima a07, the amp sounds very good, though I am preferring the a07 with stock op-amps to the a04 with the modified ones. I may swap the BB 2134 amps into the a07 eventually. Thanks for the advice, PMA. Fortunately, I think I did not damage the amp or the speakers as I turned the amp off quickly with the 627's.
 

Tangband

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Thanks! They do sound good and when using with the 32v/5a supply that came with the Aiyima a07, the amp sounds very good, though I am preferring the a07 with stock op-amps to the a04 with the modified ones. I may swap the BB 2134 amps into the a07 eventually. Thanks for the advice, PMA. Fortunately, I think I did not damage the amp or the speakers as I turned the amp off quickly with the 627's.
Out of curiosity - wich of the amplifiers do you prefere ? A07 or A04 ?
 
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Joe Smith

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I think the a07 is the better amp, subjectively, I need to do more testing and flip those op-amps. But I really like the a07 so far. The higher power supply did not open up the a04 much beyond what I was hearing with the lower-power brick. For the cost difference, I'd say the a07 is the one to go for.
 

Colin James Wonfor

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Just a note;- The OP27 and OP37 are good opamps the OP37 is crap below gains of 100 it can burst into oscillations.
I also had the problem on AD797, this beast is track decoupling and track bothered.
 

LTig

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Just a note;- The OP27 and OP37 are good opamps the OP37 is crap below gains of 100 it can burst into oscillations.
I also had the problem on AD797, this beast is track decoupling and track bothered.
Hmm, I had no problem with AD797 at 20 dB gain when I replaced the LT1082 in my MC phono stage a few years ago. However I've read in Douglas Self "Small signal Audio Design" that early versions of the AD797 were difficult to stabilize and later versions not. Maybe the designer @scott wurcer can comment on this.
 

Colin James Wonfor

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Not to squash D.S. work but I spent a whole year at Cambridge Audio (Richer Sound) fixing is designs so I have no confidence in D.S. designs but would love to be able to write like him but with facts.
 
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