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Old 2nd March 2003, 06:54 PM   #41
PMA is offline PMA  Europe
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OPA549 (or OPA541 etc.) is not the best solution for hi-end amp. You should not use higher gain than 2x - 4x. The circuit has low GBW (1 MHz) and there is not enough feedback for higher frequencies, this resulting in rapidly rising distortion at higher frequencies.
I would recommend this circuit as a car or basement amplifier, no hi-fi.
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Old 2nd March 2003, 11:42 PM   #42
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Quote:
Originally posted by PMA
OPA549 (or OPA541 etc.) is not the best solution for hi-end amp. You should not use higher gain than 2x - 4x. The circuit has low GBW (1 MHz) and there is not enough feedback for higher frequencies, this resulting in rapidly rising distortion at higher frequencies.
I would recommend this circuit as a car or basement amplifier, no hi-fi.
Curious...IMHO the OPA 548/9 sound better than the LM3875/3866 in the inverted GC circuit.

I cannot argue with your figures, as I don't know enough theory to do so, and you are probably correct... just curious as to why this is!
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Old 3rd March 2003, 09:53 AM   #43
Mad_K is offline Mad_K  Norway
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Quote:
Originally posted by PMA
OPA549 (or OPA541 etc.) is not the best solution for hi-end amp. You should not use higher gain than 2x - 4x. The circuit has low GBW (1 MHz) and there is not enough feedback for higher frequencies, this resulting in rapidly rising distortion at higher frequencies.
I would recommend this circuit as a car or basement amplifier, no hi-fi.
Then the LM3875 isn't much suited eithter since it only has 2MHz GBWP.
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Old 3rd March 2003, 11:05 AM   #44
protos is offline protos  Greece
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Quote:
Originally posted by PMA
OPA549 (or OPA541 etc.) is not the best solution for hi-end amp. You should not use higher gain than 2x - 4x. The circuit has low GBW (1 MHz) and there is not enough feedback for higher frequencies, this resulting in rapidly rising distortion at higher frequencies.
I would recommend this circuit as a car or basement amplifier, no hi-fi.
There always seems to be a disagreement between the theorists and the practical people in this forum.
As peter daniel has said many times in the other gainclone thread ,to paraphrase " Why don't you try both and see what you prefer?". After all it is very simple to do with these chips. I personally have redone listening tests and still prefer the OPA 549 as sounding more tonally neutral and correct. 3875 sounds quite a bit zingy and blarey to me but only if you A/B otherwise it's ok. But ok is not what we are about as fanatics is it?
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Old 3rd March 2003, 05:18 PM   #45
PMA is offline PMA  Europe
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protos,
I do not try to say that OPA549 is better than 3875 or vice versa
BTW, I do not think that I am a theorist (please visit my www to check it)
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Old 3rd March 2003, 06:30 PM   #46
MBK is offline MBK  Singapore
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hmmm, could you guys elaborate about the difference between OPA548 and LM3886 sound qualities? I built the amps for my active system using OPA548 and am very happy with it. Then again I never compared them to anything else either...

Now for an extension of the system I wanted to try the 3886 from gainclone fame... maybe I should stick with OPA548 after all?

My OPA548 circuit incidentally is using a non-inverting configuration that Siegfried Linkwitz recommends for the ... LM3886. (at http://www.linkwitzlab.com/images/graphics/3886amp.gif)

Beautiful picture of the , err, "finished" OPA548 amps below... (the chips are underneath the home depot door stopper aluminium rail heat sink)

Regards

Markus
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Old 10th March 2003, 04:50 PM   #47
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Default build in a OPA549 amp

Hi guys, I'm thinking of building a OPA549 amp. Do I have to use a regulated power supply for it, or is a normal power supply ok. If it does need a regulated power supply can someone give me a circuit diagram?
What gain is best for this amp, I have seen 2-4X in this thread, anyone agree with this?

Thanks
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Old 10th March 2003, 07:58 PM   #48
Bricolo is offline Bricolo  France
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what about the opa541?
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Old 30th June 2013, 03:34 AM   #49
xrk971 is offline xrk971  United States
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Quote:
Originally Posted by carlmart View Post
National seems to have cut sending samples outside of the USA. I don't get them in Brazil anymore and a friend told me in Argentina neither. Apparently Europe is too.

BB and ADI keep delivering.

Pity BB does not include their OPA512 in their sample program, which is TO3 and goes up to +/-50v, probably delivering close to 100W. Looks like an LM12 version.


Carlos
I am still wondering if anyone in this forum has used the OPA512 for audio - I have used it as a closed loop servo voice coil actuator driver and it works very well. Should be able to deliver 10 amps at 100 volts into 8 ohms or 100 watts. They don't give samples because these sell for $144 ea and only require a big heatsink, two resistors, a couple of bypass caps, and an input coupling cap for a full blown 100 watt hi fidelity amplifier.

http://www.ti.com/lit/ds/symlink/opa512.pdf
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Old 28th February 2014, 07:53 AM   #50
PMA is offline PMA  Europe
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I can provide you with a set of measurements on my old OPA549 amplifier prototype. OPA549 has low idle current and low slew rate, and pronounced cross over distortion. These features make it very bad sounding amplifier, in case you have a comparison with good amplifiers. Measurements are taken at about 4Vrms output voltage with 6.8 ohm load. THD vs. freq plot is similar to manufacturer's datasheet.
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