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Need opamp replacement advice
Need opamp replacement advice
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Old 13th June 2021, 06:45 PM   #1
jason7381 is offline jason7381
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Default Need opamp replacement advice

Hey Guys.
I've recently purchased a headphone amp from aliexpress (based on beyrdynamic a1) and I'm not too happy from the sound quality (esp the bass). I was thinking of replacing the opamps, but got into a bit of a snag! So basically, it has two NE5532P's which appear to be fake, according to this post:
Fake Op Amp Tester? My Op Amps Genuine or Fake?
They have 19YLDZM markings on em. Now, here's the tricky part, I've used my multimeter and measured 24.38V (VCC - and +) which I presume to be the voltage they're running on. I've also looked at the official TI datasheet, and 22V is the max:
https://www.ti.com/lit/gpn/NE5532
Is there something I misunderstood in the datasheet? Anything wrong with the way I've measured the voltage? Does this mean I'd have to get replacement opamps that are capable of withstanding 24V? And if so, any suggestions? Thanks.
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File Type: jpg NE5532P Dual Pinout.JPG (4.0 KB, 149 views)
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Old 13th June 2021, 06:54 PM   #2
Mooly is offline Mooly  United Kingdom
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Need opamp replacement advice
The absolute max voltage rating is 44 volts and this is the voltage between pins 4 and 8.

So if you are seeing +24 on pin 8 and -24 on pin 4 then yes, the device is being used outside its absolute max rating.

How that 44v is made up doesn't matter, you can have +15 and -29 or +40 and -4 and so on.
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Old 13th June 2021, 07:08 PM   #3
jason7381 is offline jason7381
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I appreciate the fast response Mooly! But that sounds a bit confusing. To re-iterate, my multimeter was autoranging on DCV, negative (black) probe was put onto pin 4, and the positive (red) probe was put onto pin 8, and the reading was 24.38 on both opamps. Not sure how you've reached 44. And where does it say on the NE5532P's datasheet that it's 44 btw? I've only saw 22 as the max. I need to get this voltage thing figured out before I could look for compatible replacements.
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Old 13th June 2021, 07:44 PM   #4
tomchr is offline tomchr  Canada
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If you measure from pin 4 to pin 8 and see 24.4 V, you're fine. That's a bit more than half of the specified 44 V supply voltage (22 V -> 44 V total).

If you suspect the opamps are fake, why not try a genuine pair? You can get them from Mouser: Mouser Electronics

Something like the LM4562 or OPA1656 would work well also. Note that the OPA1656 is only available in a surface mount package. If your opamps are socketed, you'll need an adaptor if you want to use the OPA1656.

Tom
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Old 13th June 2021, 07:49 PM   #5
bucks bunny is offline bucks bunny  Germany
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If your amp works, replacing the op-amps will not change bass response at all, even if these are fakes. There are no "low bass" fakes on the market. Fakes are noisier and have more THD, that's all.
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Old 13th June 2021, 07:53 PM   #6
jason7381 is offline jason7381
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Quote:
Originally Posted by tomchr View Post
If you measure from pin 4 to pin 8 and see 24.4 V, you're fine. That's a bit more than half of the specified 44 V supply voltage (22 V -> 44 V total).

If you suspect the opamps are fake, why not try a genuine pair? You can get them from Mouser: Mouser Electronics

Something like the LM4562 or OPA1656 would work well also. Note that the OPA1656 is only available in a surface mount package. If your opamps are socketed, you'll need an adaptor if you want to use the OPA1656.

Tom
Thanks for your assistance Tom! I think I'm starting to get it. So, the voltage specified in the datasheet is per each VCC pin (- and +) individually? And when measuring the voltage using a multimeter between pins 4 and 8, the end result is in fact a combination of both? I.E 24V means each pin receives 12V?

And for the record, mine are DIP8 and are non-soldered (removable, sitting in sockets). And after reading various opamp opinions, I'm leaning more towards trying OPA2228/OPA2107/OPA2134,





Quote:
Originally Posted by bucks bunny View Post
If your amp works, replacing the op-amps will not change bass response at all, even if these are fakes. There are no "low bass" fakes on the market. Fakes are noisier and have more THD, that's all.
How can you be so sure? What would affect bass response then?
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Old 13th June 2021, 08:10 PM   #7
bucks bunny is offline bucks bunny  Germany
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everything else! how can you be sure it is the opamp?

Fake opamps that still work are re-stamped LM358, the cheapest crap on the market. They are noisy and low end, but bass response is not affected. period.
btw, did you measure frequency response to backup your claim?

Last edited by bucks bunny; 13th June 2021 at 08:15 PM.
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Old 13th June 2021, 08:32 PM   #8
jason7381 is offline jason7381
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Quote:
Originally Posted by bucks bunny View Post
everything else! how can you be sure it is the opamp?

Fake opamps that still work are re-stamped LM358, the cheapest crap on the market. They are noisy and low end, but bass response is not affected. period.
btw, did you measure frequency response to backup your claim?
Well, I can't be 100% sure, lets say it's a gut feeling! It's not my headphones (as they have good enough bass with other sources) and it's not like the bass on this headphone amp is non-existant, its just under-emphasized. Also, I've seen various opamp threads (where people did state that they've noticed bass differences with different opamps). Apart from the opamps though, it also has 2x BD139 & 2X BD140 transsitors (which I was thinking of replacing with 2SC5171 & 2SA1930 as I've read it provides some degree of improvment) and it also has 2X BC546 & 2X BC556, which I was thinking of leaving as-is. And no. I don't have the gear (osciliscope I'd imagine) to measure the frequency response I'm afraid.
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Old 13th June 2021, 10:46 PM   #9
johnmath is offline johnmath  Australia
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If you can post a schematic with values for the Ali Express headphone amp the circuit can be analysed. Most likely the low frequency output is limited by one or more capacitor values in the circuit that are too small, possibly as a cost saving or to fit them in a limited space.
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Old 13th June 2021, 11:48 PM   #10
bucks bunny is offline bucks bunny  Germany
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Quote:
Originally Posted by jason7381 View Post
Well, I can't be 100% sure, lets say it's a gut feeling! .
And I have a quite strong feeling you are barking at the wrong tree.
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