Burr Brown OPA134 ?

[John Noll]

I recently obtained an MCI JH110C that the original owner modified by swapping the chips in the Repro and Output cards with OP134 and OP2134's. The electronics are oscillating, most noticable right after powering up.

I'm still waiting for a manual/schematics to be shipped from Blevins. Are these Burr Brown chips replacements for 5532 and 5534's? I want to replace them with the original chips to see if the high frequency oscillating goes away.

 

[mcs]

They are not always direct replacements. The newer "faster" chips may need extra PS decoupling caps, and different feedback networks to stop them from oscillating.

Best regards,

Mikkel C. Simonsen

 

[John Noll]

Exactly. That's why I want to replace them with originals. Should I put 5534's where the OP134's are and 5532's where the OP2134's are? Or do I have that backwards?

Anyone have an MCI JH110C Repro schematic handy? Thanks.

 

[SonsOfThunder]

[quote author="mcs"]They are not always direct replacements.[/quote] This is one of my favorite devices...and you are correct!

The newer "faster" chips

Its not just that they are faster, they are FET input where the 553x are bipolar input.

may need extra PS decoupling caps

Probably...also the PS might not be up to the task.

and different feedback networks to stop them from oscillating.

Maybe not...usually putting FET input OAs in place of bipolars is not so bad...IIRC the other way around can be bad.

HTH! :thumb:

 

[DrFrankencopter]

If you think the original owner knew a little bit about what he was doing, you might assume that they replaced TL071 and TL072's with the 134 and 2134s. These are FET input op-amps, and would make a better sub than for a 5532 or 5534. Actually, the 5532/5534 are hard chips to sub out, as they seem to sit in an optimal spot in terms of input impedance, noise and distortion...they're just an all round good audio IC.

If the burr brown chips are oscillating, you probably need much more compensation. Is there a cap going across the feedback connection? If not, this is your problem right there...try stuffing about 22-50pF in there and see if things stabilize.

Cheers,

Kris

 

[John Noll]

I replaced the BB chips with 5532 and 5534's and the oscillation problem subsided. I'm still waiting for the manual from Blevins, so I don't know for sure if those chips are the original spec, but it makes sense that they would be.
Thanks for all of the suggestions.

 

[Moby]

I replaced all my op/amps in soundcraft 1624 console with opa134/2134, including ne5534 in VG summing with opa627. No problems with oscilating, works nice. I tried with opa637 for summing, but hardly oscitaled, so i give up :wink:

 

[Svart]

what exactly are they doing to make you think they are osc.? can you see it on a scope? I would think about keeping those opamps and just decoupling them with some good caps right at the pins.. even though the 5532/5534 combo is great, why go back when you can move forward?

:green: :guinness:

 

[Ethan]

Yup, as has been suggested, since it appears to be the opamps try decoupling the high speed opamps directly from the power pins to ground on the underside if you can with 0.1uF's.

 

[Svart]

I guess it would be important to ask what kind of sound color and quality you are looking for..

the general thought for the parts are as follows

opa(X)134 warm and lightly scooped in the upper mids, more "musical"
opa(X)604 slightly clearer, more detailed high end, good all around.
ne5532(5534) crisp but fairly uncolored, the one you want for more purity.
tl071(2) similar to the 5532?? anyone?

of course the more chips of one type you have in the audio path, the more pronounced the "sound" of the chip will be.

thats my take on these chips from testing recently.

i've swapped out a quite a few chips in various pieces of equipment with no osc. problems.. even a few opa627s.. maybe your problem lies elsewhere?

:guinness:

 

[John Noll]

Back to my original post -
I had recently purchased a very nice MCI JH110C 1/2" machine that had some high frequency oscillation issues. I noticed most of the chips in the repro and balanced i/o boards were Burr Browns. I wanted to try the stock chips but wasn't sure what they should be as the manual/schematics I ordered from Blevins hadn't arrived yet (still don't have them). I assumed that they should be 5532's and 5534's. Someone here suggested that that was correct. I put in some 5532's and 5534's and the problem went away.
I wasn't modifying a circuit for better performance, just trying to find out what the original spec chips were. The machine sounds pretty damn good as it is, so I don't want to mod it, just eliminate the annoying oscillation. The previous owner had passed away, so I couldn't ask him what he had done to the machine.

 

[fatboy135]

reopening that topic:
as far as I mod the tl audio pa1 from a friend of mine I notice that it becomes a great oscillate of 1 MHz into the final stages where it is great amplification, so I think that opa2134 are great for very small signals but they are so awful on great amplifiers stages

 

[Twist Turner]

Hey, I didn't get a manual from Blevins either, so far I've been waiting about 10 years for him to get me one...................I finally gave up about 5 or 6 years ago and picked one up on ebay, if I hadn't just moved and had the manual packed somewhere, I'd look up what the proper chips are for you.

 

[fatboy135]

oops, I swap my conclusions on the schematics paper, as far as I research the opa2134 is so nice for typical amplification stages but they are awful perfect oscilators on followers stages.
I´m replacing the opamps of tlaudio pa1. We were trying the opa2134 and now we will try the opa275.
We also replace the signal coupling and decoupling caps by evox rifa and wima and also the electrolytic caps with elna low noise purposes...

 

[JayDee]

has anyone tried burr brown opa in our diy projects ?

ssl mix bus
or
calrec eq ?

any difference ?
any mods (oscillating?)?

is it worth a try ?

jay

 

[fatboy135]

Hi I had just replace the tl072 from my Triaxis with a burr brown opa2134 yesterday.
The matter was that the triaxis has tubes and one tl072 on the audio signal path. The trouble was that the tubes gets a lot of signal and the tl072 becomes to saturate even with a voltage divider.
So I need to increase the dinamic range from the triaxis, the tl072 only achieves +/- 13 volts on a 15 volts symetrical feed, with the opa2134 is nearly a rail to rail it gets about +/-14.5 volts allowing me to have more dinamicals and avoiding the classical ic clipping.
There wasn´t any oscillate, but... on a tl audio I modded I installed that op amps and becomes a nicely 1 MHz oscillate, inaudible for the human ear, it only consumpts watts.

 

[craigb]

I really like the OPAx134's as well. A while back I was breadboarding a compressor circuit, and had used a TL072 because I had some laying around. It was being used as a unity gain inverting input, and a buffer output. When I first swapped in the OPA2134 it was literally a jaw dropping difference. The increase in clarity of the high end was amazing. I had to swap back and forth a couple of times to believe it. Very nice sounding chip, IMO.
:shock:

 

[fatboy135]

When I first swapped in the OPA2134 it was literally a jaw dropping difference. The increase in clarity of the high end was amazing.

Totally agree it happens the same to me. But I couldn´t understand how changing a simply ic on a circuit could develop new sounds, it is a mystery for me

 

[JayDee]

[quote author="craigb"]I really like the OPAx134's as well. A while back I was breadboarding a compressor circuit, and had used a TL072 because I had some laying around. It was being used as a unity gain inverting input, and a buffer output. When I first swapped in the OPA2134 it was literally a jaw dropping difference. The increase in clarity of the high end was amazing. I had to swap back and forth a couple of times to believe it. Very nice sounding chip, IMO.
:shock: [/quote]

did you mod something ? feedback caps ?

 

[craigb]

did you mod something ? feedback caps ?

Nope, I just swapped the chips.