Just discovered the weird world of Op-amp swapping....

[chebby]

Was just reading some reviews of my Firestone Audio Fubar II USB DAC (looking for tips on optimising iTunes/WMP settings) and came across people who like to swap things called op-amps in their equipment. (Crazy bar-stewards!)

Seems my DAC has this thing called an OPA2604 and lots of people who are into this Op-amp 'rolling' say this other thing called OPA2107AP sounds better, warmer, more detailed etc.

Who am I to disbelieve them?

A quick search revealed that people even sell these things on ebay and they only cost a few quid.

Hmmmm.

Are they easy to swap? Do I have to buy oscilloscopes and soldering irons and fast-furriers analysis software or a tunnelling-scanning electron microscope? Do I need to do this in a concrete bunker away from innocent bystanders or can I just pop out some chip and pop another in?

Are these OPA2xxx thingies idiot proof? Can they be put in the wrong way around or are they made so that they are impossible to put in the wrong way?

Do I need 20 years in the electronics industry and a degree before attempting this?

(I will unplug it first.)

Thanks.

 

[Anonymous]

Such op amp tweaking has been alive and kicking in the Quad modifiers world for a long time. Going to do mine next year with a full board change. I'm not sure that I'll bother trying a lot of different chips though...

 

[chebby]

Further research shows that Firestone Audio actually ENCOURAGE this activity and make 'user tuning' (with different op-amps) a plus point of the design.

Hopefully when I open the cover I will find one of these sockets....

and hopefully (again) there is no soldering involved.

igglebert, are my hopes well founded? Is is that easy? Are these things just push fitted?

(I assume I should touch some bare metal surface to discharge static first like when fitting new RAM.)

 

[Olli1324]

Yes, with those sockets it is simply a matter of pulling out the old one and shoving in the new one. The only thing you have to do is make note of that semicircular indentation on one end of the op amp (you can see them in the picture you posted earlier) and make sure it matches up with the mark the will be on the socket (or at least, I assume the socket will be marked too.... I'm pretty sure it will be, but you can always look at the position of the semi circular mark on the original op amp to get the orientation correct).

Of course, I would only try this with recommended op amps, so as not to encounter potential instabilities and what not.ÿ

 

[chebby]

Thanks.

 

[chebby]

OK I am going to order one OPA2107AP (DIP 8) from RS online.

Price is a bit steep (£14) compared to the plethora of ebay traders from Hong Kong, but at least I know I will get a genuine, unused, Burr Brown (Texas Instruments) item rather than some counterfeit.

Unless any of you DIYers know of a rock solid, trustworthy, online components vendor who will not sell me something used (recovered from old equipment in a shack in Jakarta) or bogus.

Thanks.

 

[Anonymous]

chebby:igglebert, are my hopes well founded? Is is that easy? Are these things just push fitted?
Are they push fitted? Depends on the kit. I think a lot of stuff these days has surface mounted components. One of the beauties of my old school Quad is that I have a socket.

Is it that easy? I doubt it. Electronics is never that easy! I'm not an EEng but the below quote re Quad 405 suggests to me there's a few considerations:

'If you feel you must change the op-amp consider the input bias current specification which generally gets worse as gain bandwidth product (GBWP) increases - FET input devices like TLE2071, OP134 and OPA604 are all good for audio and have very low input bias current required for the low output voltage offset in this design'

(www . dc-daylight.ltd.uk/Valve-Audio-Interest/QUAD/QUAD-405-Modification/QUAD-405-Mods.html, d.c. daylight LTD)

I think that in terms of the Quad 405 you can lower some of the noise created in the early stage of the power amp. All else being equal it sounds like it should be a simple matter of substituting a low quality component with a good one, but how it interacts with the circuit design must be a consideration.

Let us know what happens. Perhaps you should add a packet of fuses to the order

 

[chebby]

I have found out that the op-amp in the Fubar (OPA2604) fits into an 8 pin (DIP 8) socket so removal/replacement should be OK.

I have checked on quite a few forums and found that the OPA2107AP is a very popular and favoured replacement for the OPA2604 in the Fubar USB DAC and other applications (headphone amps etc.)

I have compared the data sheets for pin configurations, input voltages etc etc, and cannot see any problems....

http://docs-europe.electrocomponents.com/webdocs/0026/0900766b80026053.pdf

http://docs-europe.electrocomponents.com/webdocs/00ac/0900766b800ac268.pdf

It seems the OPA2107AP is a valid drop-in alternative to the OPA2604.

Let me know if those data sheets show anything that would cause you concern.

Thanks.

 

[PJPro]

Tangent does a review of several op-amps. See here. If there is a single op-amp in your amp, it's going to be a dual channel.

Incidently, I've used a DIP8 socket in my headphone amp to allow op-amp rolling. Still having one or two issues with it at the moment, hence the lack of recent updates!

 

[PJPro]

Tangent also gives some advice somewhere on his site about how to extract an op-amp from the DIP8 socket. They can be a little difficult to remove. You also need to take precautions against static.

I recently swopped out my op-amp and used a pair of needle-nosed pliers to do it. Placed the whole lot on a metal baking tray on the gas cooker as I believe that the hobs are earthed.

The op-amp was a little difficult to remove but managed it with a bit of force. I have heard of others levering the op-amp up using a small screwdrive...a little bit at one end....at little bit at the other. Clearly, what you want to avoid is breaking the board or breaking a connection.

Latly, make sure you put the op-amp in the right way round.

 

[JoelSim]

chebby:Price is a bit steep (£14) compared to the plethora of ebay traders from Hong Kong, but at least I know I will get a genuine, unused, Burr Brown (Texas Instruments) item rather than some counterfeit.

ÿ

It'll probably turn your Fubar into a calculatorÿ

 

[chebby]

OK I finally found what I needed (apart from DIY chatter on places like head-fi) to confirm that the OPA2107AP is a safe choice.

I found a Q&A forum on Firestone Audio's own website where the designer of the Fubar II USB DAC (David Lin) answered a question (about using the OPA2107 instead of the OPA2604) and confirmed it was a completely compatible and safe choice.

I have just placed the order to RS components and it should arrive tomorrow or Saturday.

Also the Firestone Audio 'Supplier' PSU arrived today in a big box (from Russ Andrews) addressed to the wife, but I am not allowed to open that until Christmas morning, so that particular upgrade will remain to be heard for another 2 weeks.