OP275 opamp replacement help.

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Glen1

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Joined 2005
#1
I just have an enquiry about a replacement for a OP275 op amp.
I have a Musiland DA10 which uses the OP275 opamp and I have read that this op amp is only satisfactory and gains in performance can be made by swapping it out for a different model. I'm new to the diy game so just looking for advice on different options and the best way to go about this project.
I have attached a photo with the op amp right in the middle. The dac has already had the caps chaged to blackgates.

Ta,
Glen.
 

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#2
Hi Glen. There is a wide range of opamps which will work and sound different from what you have. Better? Who knows? The OP275 has lots of fans for its mellow sound. An AD8620 will sound dramatically different and possibly better if you want more detailed and upfront sound. Are you comfortbale desoldering SMDs?
 
#3
analog_sa said:
Hi Glen. There is a wide range of opamps which will work and sound different from what you have. Better? Who knows? The OP275 has lots of fans for its mellow sound. An AD8620 will sound dramatically different and possibly better if you want more detailed and upfront sound. Are you comfortbale desoldering SMDs?
Click to expand...

Thanks for the reply. I actually like the sound of the dac. I'm using it for streaming with a Squeezebox SB3 and the sound it produces is extremely close to my tubed output Droplet cdp. I've read that there's heaps of op amps available and they are all different. I guess I'm just after a little more refinement that what I'm getting now. I don't want anything more forward. Apparently the 627 is pretty good but some say it's layed back. A person on HeadHifi repalced his 275 with a LM4562 and claims that it tidied up things even more. Mods recommended for the dac are change the caps, the op amp, the diodes and remove the ac filter. Mine has the caps and ac filter done.
I wouldn't attempt to do the de-soldering especially given I hear that surface mounts can be diabolical if you damage the tracks. I'll be able to find a suitable tech to do it for me.
 
#7
The LM4562 is probably the best choice if you already enjoy the 275. I would recommend buying a cheap hot air station and doing your own desoldering - takes very little time and effort.

Tantalums are the yellow surface mount capacitors close to the opamps. PS = power supply
 
#8
OP275 is a dual opamp with hybrid bipolar/FET inputs....I assume that makes it behave like a FET input opamp, but I don't know, having not used it.

The AD8620 seems appropriate. I also like OPA2107 - the data doesn't support me on that one, so your mileage is highly likely to vary. The "common" opamps (which would have been considered excellent just a few years ago, but I digress) such as OPA2132 are likely a downgrade from the existing OP275.

Most of the commonly accepted "best" opamps, such as AD843 and OPA627 are only available in single packages. There exists a browndog "footprint" adapter -I don't know how well it works, I've never tried it.

EDIT: Isn't the LM4562 bipolar input? I wouldn't have thought it wise to just drop it into a circuit.
 
#11
I tried some different opamps in a headphone amp - I really liked the AD825. It's had a clear and pretty yet meaty and dynamic sound. The AD825 is mono only, but there's a new generation of similar opamps it seems, and those are in stereo: AD8599.

Here's a writeup: http://www.head-fi.org/forums/f6/ad8599-bloody-good-256805/

It's not an really an "established" opamp, but it's my current object of curiosity. Maybe you'd like to try it?
 
#12
TheSeekerr said:
- but then, analog_sa is an expert, and I'm not, so he can probably tell us why I'm wrong.
Click to expand...


Feeling sarcastic today? 🙂

Actually the 8620 is probably not going to work for very long due to max supply voltage limited at 13v. Not sure about the Musiland but it's quite likely it runs the rails above 15v.


I can't imagine any issues pertaining to input stage being bipolar or fet. The bipolars may produce higher offset but this is definitely not a problem with the LM4562.
 
#14
Glen1 said:
Apparently the 627 is pretty good but some say it's layed back. A person on HeadHifi repalced his 275 with a LM4562 and claims that it tidied up things even more.
Click to expand...

I can't really tell you which opamp to use, it depends on too many variables. Currently I've just started experimenting with an old CD-player myself. As already has been said is that the OP275 is dual whereas the OPA627 is single. A dual-opamp to 2x-single-opamp converter needs to be fabricated or bought and soldered on the board.

I wouldn't attempt to do the de-soldering especially given I hear that surface mounts can be diabolical if you damage the tracks. I'll be able to find a suitable tech to do it for me.
Click to expand...

With the right equipment removing a surface mounted device is actually easier than removing a through hole device. The more pins there are the bigger the difference, which becomes even bigger when components are soldered lead-free (RoHS compliant).
The "right equipment" is nothing more than a hot air blower with precise controls for air speed and temp and a small nozzle (NOT a paint stripper) and some fine tweezers. I realize that this is easier said than done as I do this for a living and have a lot of experience...
Another option to remove the opamp - which destroys it, though - is to carefully cut each pin near the casing and lift the opamp. The remains of the pins can then easily be desoldered one by one using an iron. Make sure not to apply any force as that is usually the cause of damaged islands and tacks...
 
#17
Mooly said:
Somebody mention working with SMD 🙂
http://www.diyaudio.com/forums/showthread.php?s=&threadid=127924&highlight=
Click to expand...


kristleifur said:
As we're on the topic of SMD and desoldering, here's a really nice introductory video: http://tangentsoft.net/elec/movies/tt04.html - Tangent Tutorial 4: How to Desolder Electronic Parts

SMD is not that bad!
Click to expand...

I can only say that, IMO, some of these methods greatly increase the risk of damaging or even lifting pads off the PCB. I admit that I did enough damage to know my dos and don'ts by now :blush: .
Mooly's technique might work on lead containing solder but I have my doubts when it comes to lead-free stuff. Even now that I'm becoming more and more familiar with it do I sometimes still consider desoldering Pb-free stuff a :cuss:.

My golden rule is that the only safe way to remove a component is to do it without force. That either means completely removing or at least completely melting the solder on all joints simultaneously. It applies to SMDs as well as THDs.


Off-topic: I noticed the instructor in the video uses the same soldering iron as we have at work: JBC. IMO that is the best you can get. These have an inductive heating element inside the tip. Heating a stone cold tip to operating temperature takes about 2 seconds (no typo). Changing tips and continuing work takes 5 seconds. The other benefit of that quick response is that when you solder difficult joints (lots of copper sucking the heat away) these irons hardly need more time so you don't heat up the component too much.
 
#18
A lot depends on what you get use to. I have seen many boards ruined with profesional equipment. The way I posted is safe. You can see and "feel" every leg on the package is free.
Some years ago I won a bet against a field rep selling PACE SMD desoldering and rework stations.
He too could not believe I could remove a 100 legged IC quicker and neater than with the station. I won 😀
 
#20
I had some 8599s put in a processor. Really nice sounding opamps. Really is the best of the AD and BB worlds. If I had it to do over again, I would put these in my Benchmark DAC1 in place of the 2107s that are in there now. Not that the 2107s are bad.
 
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