Do all OPA2134PA's sound the same?

G'day all, this is something that I can't explain. Today I obtained some replacement OPA2134PA's for two that I accidentally blew up yesterday (yes, reversed power supply leads).

Anyway these replacement OPA2134's are from a different manufacturer, and I never thought the originals sounded that great. Anyway these OPA2134's sound fantastic. I'm wondering why? Are counterfeit dual op amps a possibility? Regards, Felix.
 
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G'day mate, yes it's a strange one, as the original OPA2134's in use sounded rather 'dry sounding' to me, if that makes any sense!

In fact when the originals were first installed I remember thinking that they didn't sound as good at the LM833's in there previously! But these OPA2134's sound nothing like the original ones. These replacements sound clean, crisp and dare I say it....musical. So I don't know.

Likewise I would have thought that an OPA2134 is an OPA2134! That's why I wondered about possible counterfeits. Yes these are Texas Instruments dual op amps. Regards, Felix.
 
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Op amp failures!

G'day all, I think I'm having a bad run with op amps of late because strange faults with op amps and particularly with the OPA2134 keep happening!

The other day one of my DIY stereo headphone amps suddenly failed on the right channel. A lot of difficult and painful fault finding followed and the failure was found due to several causes, namely a chance diode failure (a red LED to be specific used as part of a constant current source), and also the complete failure of the right channel of the OPA2134 input stage.

How common is that? It had been working happily for a couple of years then suddenly failed on the right channel without warning. Why, I wonder? Regards, Felix.
 
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sandyK

Member
2007-04-27 12:54 am
Sydney
G'day all, I think I'm having a bad run with op amps of late because strange faults with op amps and particularly with the OPA2134 keep happening!

The other day one of my DIY stereo headphone amps suddenly failed on the right channel. A lot of difficult and painful fault finding followed and the failure was found due to several causes, namely a chance diode failure (a red LED to be specific used as part of a constant current source), and also the complete failure of the right channel of the OPA2134 input stage.

How common is that? It had been working happily for a couple of years then suddenly failed on the right channel without warning. Why, I wonder? Regards, Felix.

Felix
If you are talking about the Silicon Chip headphone amplifier from the Studio Series Preamplifier, then the most common causes appear to be due to poorly soldered joints in the area of the red LED.

SandyK
 
G'day mate, yes that's the kit. Not a bad design at all. I use this one as a part of my general microphone preamp monitor amp set up for my weekly voiceover recording work for our National Ham Radio news service.

It was perfectly reliable until it failed this week, right in the middle of the weekly recording session! 'Murphy' I guess! Regards, Felix (vk4fuq).
 
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... a chance diode failure (a red LED to be specific used as part of a constant current source)...

FWIW, I read this a couple of days ago:

"Beware of the very low melting point of the LED encapsulant and don't stress the leads before soldering. Otherwise the plastic when it softens transmits the stress to the bond wire and if you are very lucky it will break then and there. If you are very unlucky it will break at some indeterminate time later"

From Mic Preamp Schematic Collection
 
It's very likely that the OPA2134 has been "blessed" with several die shrinks for cost and yield improvement during its lifetime. When the analog IC houses were in their prime, and I was working for a major customer (Harris) I remember receiving notices of pending die shrinks, which detailed changes in non-data-sheet parameters, or shifts in typical values; min-max of course were almost never changed, and then only for the better.
 
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I came to this thread through a google search for "opa2134 counterfeit". I bought 5 2134s from ebay to build a Rod Elliott's P88 on breadboard (i fully intend to buy it as soon as i can afford it). I rebuilt the first stage twice already (no second stage yet, until i can fix the first), the last iteration seems to *work*, meaning it does amplify signal (140mv input, higher output), but the sound is AWFUL!

It sounds like a mistuned FM radio, completely distorted if i raise the volume even a little on the source and whenever there is a voice in the signal it's all "robotic". I'm gonna rebuild it a third time but i don't see how it can do its job if i mis-wired something but do it so badly.

The other components are
  • MKT caps rated for 100V (signal)
  • MKT caps rated for 63v (bypass on the opamp power pins).
  • 1% Resistors, from china as well (standard values for 3db gain)

Also, the opa2134s lack the "dent" between pin 1 and 8 that i saw on every other DIP package i've ever seen (not many, but still dozens of them).

I'm starting to think i ran into a counterfeit batch. This could very well be just a bad case of mis-wiring on my part (i'm very very very much of a newbie) but the weird distortion i'm getting is so fishy!

Anyone has info about this?
 

Mooly

Administrator
Paid Member
2007-09-15 8:14 am
I bought 5 2134s from ebay to build a Rod Elliott's P88 on breadboard ...................

It sounds like a mistuned FM radio, completely distorted if i raise the volume even a little on the source and whenever there is a voice in the signal it's all "robotic". I'm gonna rebuild it a third time but i don't see how it can do its job if i mis-wired something but do it so badly.

Anyone has info about this?

You mention a "breadboard layout" and that could (and without seeing its impossible to say) be the problem.

Maybe post a picture of your project :)
 
I will rebuild it as i don't trust my skills. I have a Szekeres headphone amp made on breadboard a couple years back and it sounds quite fine so i don't think that's the problem :)

I want to say that i never said the project itself sounds bad. I'm willing to bet my pajamas that it will sound great once i get it right. I was complaining about my board, which is very likely badly soldered and/or has a counterfeit active element.

I will post a pic as soon as i make a third revision, i want to be extra-sure that i didn't get something wrong in this revision. Give me two or three days :) thanks for your help and sorry for hijacking the thread! :p
 

AngelP

Member
Paid Member
2012-07-12 9:11 am
Stansted
OPA2134PA counterfeit revisited

Hi, I know this thread stopped many years ago, but I hope that some fresh observations could perhaps revive it.

Firstly, the OPA2134PA is a fantastic amplifier engineering achievement that came out of the analog team at Burr Brown (now Texas Instruments - as everything else). It is widely used in high end professional audio equipment and quite rightly so.

Unfortunately, it also comes at a hefty price and so fraudsters seem to have found it another moneyspinning target.

I recently bought a few pieces of this amp from an otherwise reputable UK supplier. Only to find that the DC offset suddenly was at - or above the datasheet values. So, I had a closer look and had to realise that the new DIP's I bought looked a bit different from what they should look like.

If you look at the pics, the one to the top left is an original BB , the one to the bottom left is the new "2134" and the amp to the right / in the back is a dirt cheap old bugstandard TL072.

The first thing to notice on the "new" is the abscense of the nook between pin 1 and 8. Secondly, the print and pin1 dot mark are different. So, perhaps it simply comes from a different authorised 2134 production fab facility? I think not.

Compare the plastic mould and the lead frame points at the edge of the amps - the "new" amp mould is rounded and the visible frame pin points are more spaced apart (ok it is dificult to see on the pic) compared to tighter spacing on the original OPA2134.

But the "new" 2134 case fits the 072 build to the T - and I am willing to bet my last dirty PJ that this is a counterfeit TL072 re-marked as a OPA2134. That would also make sense of the measurements.

Take a look at ebay - you should now be able to spot these fake duds just from looking at the pictures. Unfortunately, some sellers display original pics and send you cr*p counterfeit devices anyway.

The disturbing thing is that fakes now seem to have infiltrated into the inventory of reputable suppliers as well. That's scary!

Or what?
 

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Angel, I believe you are correct in that the chips you just got are fakes. I have 2 OPA134s purchased from DigiKey several years ago and they have the BB logo and all of the writing in white. This was not too long after I learned TI had purchased Burr-Brown and I think TI was still using the BB name. Looking at the TI web site, the current chips (OPA134, 2134, and 4134) all now have the TI logo on them in white and have the notch in the end by pin 1 but do not appear to have the dot by pin 1.

And I agree with you, the real OPA134 series are very good op-amps. Hope this helps.

Ken