Suggestions for the OPA549

[Leolabs]

What is the usable gain setting and do signal/feedback caps are required???Can it be build using the usual approach of a normal 3875 GC(ie only low capacity caps are employed,hand-wiring.....)

[Ipanema]

OPA549 is unity gain stable. You can use it as monolitic F4.

Pinkmouse likes it a lot. He can give a better suggestion.

[juma]

I used it this way :
http://www.diyaudio.com/forums/showt...48#post1029948
with impressive result.
This configuration (SuSy) alows for some distortion and class AB artefacts cancelation and sounds much better than single chip topology. Look for "Bivoj" thread where Pavel published some real life measurments with single-chip amp with OPA549. Regulated PS helps a lot. I used LT1083 fot that.

[pinkmouse]

Originally posted by Ipanema
Pinkmouse likes it a lot. He can give a better suggestion.

Indeed!

My favourite implementation is inverting, with gain of 8, and for general use, at least 6800uF on the rails, (you can go slightly less for mid/high only, and more for bass, if you're using an active crossover). With this setup you can use a 15-0-15 traffo, but if you want all the power available, you will need a preamp or buffer with about 2 x gain, (I use the OPA627 for preference), and increase the rails to about 30V.

[Upupa Epops]

Ask PMA to audio quality of this amp...

[juma]

There is a way to make a better sounding single-chip-per-channel OPA549 implementation (picture in attachment). Its sound character is dominated by first IC (AD823 sounded very good to me, AD797 even better).
This version is inspired by Walt Jung's article "Composite Line Driver With Low Distortion" published in ELECTRONIC DESIGN ANALOG APPLICATIONS, Issue June 24, 1996.

[Ipanema]

Is this a nested feedback design?

[Gcollier]

Originally posted by Ipanema
Is this a nested feedback design?

Looks that way to me I'll have to give this application a try, it works great for preamps.

I have been using the OPA549 in my "upstairs" audio system for some time now and am very happy with it. For optimal sound quality follow Pinkmouse's suggestions and keep the gain low and use a preamp. The OPA549 does not have the gain bandwith to provide peak performance when used at high gains, but can provide plenty of output current. Honestly having tried most of the common chips (4780, 3886, 3876, 3875, 1875, OPA541) I have absolutely no complaints about the OPA549 as long as it is used within it's limitations. If anyone is interested I can post the board files that I have been using, its a 2 sided design, non-inverted, can be used as either a stereo pair or paralelled. I originally built it as a sub amp, but it worked out very nicely when the wife asked for an amp to use upstairs...who was I to refuse

[juma]

Hi Gcollier,
I used AD823 because it swings rail to rail (it has to give bigger part of total voltage gain), and it sounds very good. If you plan to lower the gain of OPA549 to 2x or even unity, it would be good to use an OpAmp with higher PS voltage capability (OPA552 endures +-30V) instead of AD823. Regulated PS improves the sound in this case also. I used a pair of LM338s as regulators for OPA549.

[jaudio]

Is the pin layout for the AD823 correct?

http://www.diyaudio.com/forums/attac...amp=1175883958