Musical Fidelity A2 preamp AD797 oscillate

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#21
It is really interesting with the distortion thing, but I have played before with many opamps (almost every opamp from BB and AD) and I don't think this is the case.

The sound is really superb and very transparent, wide soundstage etc - it is almost a rule when mixing AD797 with OPA627 (in my Cdplayers) - they almost always sound really good.

I'll try to replace AD797 with something else. I'll try AD845/OPA627 AD8020 etc.

For sure it is going to be interesting. Sadly the 797 is a difficult opamp 🙁
 
#22
sviru said:
Hi guys. I have made pcb which made possible using four ad797 instead of one QUAD Opamp MC33078-D. What improvement in sound quality - great. But there is one problem. When I turn the volume pot close to miniumum there is a BUZZZZ sound in the speakers. When I touch the volume pot BUZZZING sound gets noticeably smaller. Volume pot is a metal one.

This really bothers me. AD797 gets hot/warm while working - but not that much so You can't touch it.

With 797 this amp sound the best and I need to o something with this.

Decoupling of 797 is made by two tantalum caps from -V and +V pins. Maybe to far away from the supply pins of the opamp?

Please help. Thnx.
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just a though from a beginner datasheet says 1k max input impedance any way you can lower your z in?

did try distortion cancelation also datasheet?

seems from other threads this is important

Glen
 
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