OPA541 and OPA549

[Mad_K]

I have just done a comparison test of these chips for my own girly-man amp, and I thought I'd share.

I used P.Daniels minimized circuit. 600VA 18-0-18 trafo = +/-26VDC rails. Standard components.

Remember these are only first impressions.
I hadn't really expected much difference between the chips, and I certainly didn't expect the audio quality they produced!

OPA549 (max +/- 30V, 8A/10A continous/peak)= BIG sounding chip! Heavy bottom, a little laid back. Reminded me of the Audio Note Kit Two I used to have. Very nice.
http://focus.ti.com/docs/prod/productfolder.jhtml?genericPartNumber=OPA549

OPA541 (max +/-40V, 5A/10A cont./peak, FET input)= More neutral. More open and detailed, but not fatigueing. My preference so far. Sounds more like my Aleph 30.
http://focus.ti.com/docs/prod/productfolder.jhtml?genericPartNumber=OPA541

 

[Asen]

Have you made a comparison with LM3875?

Thanks

 

[Mad_K]

No, because I can't get it. They only have the LM3886 where I buy my parts, and National wouldn't sample me any. Haven't tried the 3886 either. I have tried the TDA2050 though. I found it to be much more colored, and a lot less stable.

I have to moderate the differences mentioned above, after switching back and forth a couple of times (and a few hours of burn-in). They seem a lot more alike now. The 549 clearly has more power, and less percieved distortion. I also added a 0,1uF between the rails and between testing them, and it seems this made up most of the sonic difference mentioned above. (First 549 without, then 541 with and now 549 with the 0,1uF). I think they would be more alike with 35V rails on the 541.

For my first clone, I'm going with the 549...

 

[argo]

Mad_K

Did you bought the opa chips in Norway or you got samples from Ti?

argo

 

[Mad_K]

They where samples😉

I also tried to disconnect the 0,1uF now = did not sound much different, a little darker perhaps..

 

[lawbadman]

Hey Mad_k,
Did you use a regulated power suppy for your OPA549 and OPA541 amplifier?
If you do use a reg PSU, do you have a circiut diagram so thas I can build one?

Thanks

 

[Mad_K]

No reg. supply, sorry...🙁

 

[pundip]

Mad_K,
I am thinking about building an amp based on the opa541. What current limiting resistors did you use? Also does anyone know if the opa541's have thermal protection?

 

[Mad_K]

Mad_K,
I am thinking about building an amp based on the opa541. What current limiting resistors did you use? Also does anyone know if the opa541's have thermal protection?

Didn't use any😎 Since this was only a test-setup...


Read the datasheet, it's all there😉

 

[pundip]

Hi,
Are you going to be using current limit with your gc? I am not sure I should just short the limit pin to output out limit resitor

 

[Mad_K]

I depends on what load you are going to drive, and wether you are going to short the outputs😉.

I would use a 0,1 ohm for opa541am or a 0,15 ohm for opa541ap ina final design. Caddock MP930 looks good here...

 

[Matttcattt]

Mad_K,
I am thinking about building an amp based on the opa541. What current limiting resistors did you use? Also does anyone know if the opa541's have thermal protection?

Didn't use any😎 Since this was only a test-setup...


Read the datasheet, it's all there😉

Hi,
Are you going to be using current limit with your gc? I am not sure I should just short the limit pin to output out limit resitor

I depends on what load you are going to drive, and wether you are going to short the outputs😉.

I would use a 0,1 ohm for opa541am or a 0,15 ohm for opa541ap ina final design. Caddock MP930 looks good here...

i am using the OPA541 and OPA549. im glad you found them good. i just shorted the current limiting pin to output on the OPA541, and to -v on the OPA549.

 

[Mad_K]

I just left CL pin floating on my latest incarnation with opa541. Maybe I should tie it to the output instead

I'm not shure wether we are current limited at max, or if we now have no CL at all😕

Anyways, it sounds GOOD!

 

[millwood]

the datasheet for the opa541 has very detailed instructions on how to calculate the current sensing resistor and its wattage requirement. check it out.

 

[Mad_K]

🙂

 

[Mad_K]

Didn't use any😎 Since this was only a test-setup...


Read the datasheet, it's all there😉

I depends on what load you are going to drive, and wether you are going to short the outputs😉.

I would use a 0,1 ohm for opa541am or a 0,15 ohm for opa541ap in a final design. Caddock MP930 looks good here...

the datasheet for the opa541 has very detailed instructions on how to calculate the current sensing resistor and its wattage requirement. check it out.

Ahaaa

Where does it say wether you are current limited or not if you use 0 ohm CLR?

 

[millwood]

Where does it say wether you are current limited or not if you use 0 ohm CLR?

the answer critically depends on the voltage drop off the zero ohm CLR, 🙂

 

[Mad_K]

Ahaaa

Where does it say wether you are current limited or not if you use 0 ohm CLR?

-found it here:

http://www-s.ti.com/sc/psheets/sboa057/sboa057.pdf

(table 1)

CLR=0 Ohm -> CL=10A (peak)


😉

 

[millwood]

the 10A limit is the internal limit on the output devices (that's how the amp is spec'd).

the limit on the positive and negative side is slightly different (about +/- 10%).

 

[Mad_K]

That's what I figure too. I guess it lets the smoke out when you draw more than that continously 😎