[viggen]

Thanks Jon.  Yah cost me $50 to get a single Muses02 op amp.  So I see the $$ value but is the SQ upgrade meaningful?

[MttBsh]

Product description is a little confusing (Chinese effort to translate to English - a lot better than I could translate English to Chinese!) but saw no option for more than 1 set of outputs, darn.

[viggen]

is this what you were looking for?


4. Unbalanced RCA output + full-balanced XLR output

[MttBsh]

is this what you were looking for?


4. Unbalanced RCA output + full-balanced XLR output

I was looking for all unbalanced (RCA). 2 or more inputs and 2 outputs (one output to my amp and one to my subs)

[unfairlane]

wonder whether the upgraded op amps version is worth it.  or, hunting down your own opamps like bursons.

  Good question!  I found mine to be annoyingly forward in the midrange. Mine came with 10xOPA627 and 4xMUSE8020

It was strikingly hard and shouty in the midrange with original op amps fitted. I was about to replace it but a friend reminded me to try some op-amp rolling before I gave it up.

As the OPA627 is known for being musical components, I was only left with the option of replacing the four MUSE's. I had four LME49720 lying around so I put them in place in the sockets without any further hopes. The preamp is unrecognizable. It no longer shouts, female vocals no longer have any harshness but sound very clean and realistic.

Possibly the most dynamic preamp I've heard. Reference level.

[viggen]

which LME49720 version to get?

there's two on this site:

https://www.mouser.com/c/semiconductors/audio-ics/audio-amplifiers/?m=Texas%20Instruments&series=LME49720

LME49720NA/NOPB

LME49720MAX/NOPB

[viggen]

I was looking for all unbalanced (RCA). 2 or more inputs and 2 outputs (one output to my amp and one to my subs)

u can use adapter.

https://www.amazon.com/gp/product/B07GJTCY6L/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

[unfairlane]

which LME49720 version to get?

there's two on this site:

https://www.mouser.com/c/semiconductors/audio-ics/audio-amplifiers/?m=Texas%20Instruments&series=LME49720

LME49720NA/NOPB

LME49720MAX/NOPB

  Hi there!

   I bought the LME49720NA/NOPB and they really did it

[viggen]

  Hi there!

   I bought the LME49720NA/NOPB and they really did it

Thanks!

[viggen]

I got lucky and found a used one on audiomart.  I haven't opened it up to see what op amps are in there.  But, it sounds great as is.  For the price, this is ridiculously good.  I am not a fan of blue velvet potentiometers.  Maybe this could be swapped out for further improvement but I am not dying to do so.  I can leave it as is. 

Just opened it up and all op amps are JRC 5534DD.

[viggen]

So, this is what happened.  I replaced every 5534 opamp with LME49720NA.  Logically speaking, they should all work right?  Well, it didn't sound right.  When using the balanced output, I get scratchy, low volume sound.  So, I put back 2 of the 5534 opamps in the red position:



Afterwards, the unbalanced inputs works but not the balanced.  So, I put 4 of the 5534 opamps back in the blue position and the balanced input sounded fine.  But, when switching to unbalanced output, it still sounded scratchy, low volume.  So, I swapped back all the other 5534s.  Now, the preamp creates a buzzing sound.  And, the opamp closest to the blue transformer started to create smoke. 

So, did I break this preamp, and is there a way to un-break it?

Side note, the 5534 in the position closest to the blue transformer had a crack on it.  So, possibly the op amp was over heating even before the op amp swapping? 

 

[SET Man]

So, this is what happened.  I replaced every 5534 opamp with LME49720NA.  Logically speaking, they should all work right?  Well, it didn't sound right.  When using the balanced output, I get scratchy, low volume sound.  So, I put back 2 of the 5534 opamps in the red position:



Afterwards, the unbalanced inputs works but not the balanced.  So, I put 4 of the 5534 opamps back in the blue position and the balanced input sounded fine.  But, when switching to unbalanced output, it still sounded scratchy, low volume.  So, I swapped back all the other 5534s.  Now, the preamp creates a buzzing sound.  And, the opamp closest to the blue transformer started to create smoke. 

So, did I break this preamp, and is there a way to un-break it?

Side note, the 5534 in the position closest to the blue transformer had a crack on it.  So, possibly the op amp was over heating even before the op amp swapping?

Hey!
   Never a good thing to see and smell smoke out of any audio components.

   Yes, sound like something went very wrong there. Hard to tell what is the damage without looking into it closely. But I think you something shorted. Sometime when you remove op-amps in and out especially if you're not careful it might cause the legs of the op-amps to bent and cause a short sometime internally. Or sometime simply because you put it in the wrong way.
   
    Anyway, before you put in new op-amps. It is best to look and measure to see if any other components in there are burnt like the resistors, caps and even the PCB traces.

   Well, I'm not an expert on this perhaps others with more knowledge will chime in. Good luck!

   

[viggen]

The legs seem to be fine at least during my uninstalling and reinstalling the op amps.  And, I did make sure the orientation of the new matched that of the old op amps.

I don't know how to measure.  And, the cost to fix this would probably be more than the pre is worth.  So, I'd just bin this to paper weight.

Thanks SET man, for your response.

[Doublej]

Since the 5534 in the position closest to the blue transformer had a crack on it before you replaced anything, my guess is the unit had a problem before you touched. It was likely just a matter of time before it would have been on the fritz even if you had not touched it.

[GeorgeAb]

Usually, when an op amp fails it does not have sufficient current to take out input, feedback or output components. Usually when something is working and items are being swapped and then it goes bad it is likely that the swapping was the reason. If an op amp is inserted incorrectly it will short the rails (+15V, -15V power supplies) and draw enough current internally to destroy itself. If the power supply is not taken out (you still have +15V and -15V without noise on it, it is just a matter of removing bad op amps and replacing with known working op amps. Good luck.

I have also found that swapping op amps with same pin outs that the higher speced op amps can oscillate but it all depends on how it is configured in circuit. 

Just a note on clones. My experinece with clones is to buy empty board and case, then purchase components from a reputable source such as Mouser Electronics, then populate boards yourself. Did this for a headphone amp, that is sitting in a closet somewhere.     

[viggen]

Doublej.  I think that might be the case but oh wellz.  Perhaps that's why the seller never replied my emails after the pre was sold.  It was just about tracking # and such... way before I opened the pre up.

George, I got the LME from mouser.  The 5534 who knows the source but was sounding very good before the op amp swap. 

After I swapped in the LME and 5534 and using balanced input and output, the sound was noticeably different.  Much calmer with blacker background.  Didn't get a chance to listen to it long enough to determine whether it was actually better.  The 5534 did have its own attributes such as sounding more solid and weighty.

[Sabaselfsit]

I also like this pre amp very much. So if anyone is "on the fence" thinking about this; go for it. Mine has the 1611 OP Amp. All I did to it was change the volume knob because I didn't like the feel of the 'flat' one on there, and the power iec inlet. The oem iec inlet had a very loose fit, and I felt like the power cable could just fall out by itself almost. Replaced it with a Furutech gold.

[viggen]

Thanks Saba going to get some OPA1611 too.

As for my unit, found out what happened. 



The op amp that smoked, some bad soldering.

My friend who quality checked this preamp said I should use single op amp.  The LME49720 is a dual.  And, I should replace all my old op amps as they are likely bad after the first one smoked as they are railed.

[viggen]

So for those who wants to use dual op amp with this preamp, maybe you can use this converter:

https://www.aliexpress.us/item/3256802311085851.html?gatewayAdapt=glo2usa4itemAdapt



My engineering friend told me the pins on dual and single op amps are different so best not to use dual with this pre though I did hear the pre with the LME installed and it sounded pretty good.  I ordered converters just now and will update in a week or so.

I did install some OPA134PA in place of the 5534 in the mean time and it sounds pretty good.  I plan to install the LME after I get the adapters.  I also have a pair of Muses02 which I think I will try where it relates to the RCA input or the output.

[viggen]

I only use the RCA input.  So, I can make do not using the empty slots below:



Correct me if I am wrong, but the 4 op amps in the top right of the picture is the amplifier stage and has the most influence?

Does anyone know what the pair on the bottom does?