I'd forget about the audiophool caps and simply use a standard 100uF electrolytic coupling cap.
To Joerg, the reason large caps are used like this is that any non-linearities they generate are minimised as the Zc component becomes an increasingly tiny fraction of the load.
My 'standard' audio output coupling cap is 100uF and 10uF for inputs and internal ac coupling. Even high end mixing consoles do it this way.
You can also forget about any LF -3dB point issues. :-)
Graham
Well, I'd use film caps if they were available at larger values and didn't cost so much.
I'm surprised at the dried out electrolytics. The normal types are specced at
85C. I do know of electrolytics drying out in one specific audio console that ran really warm though. The standard fix is to substitute 105C parts.Never had an issue with dried out electros in any gear I've designed btw.
Graham
I remember reading about a nice feature of zeners: when they fail, they'll short circuit. But that was long ago...
Meindert
Since this amp creates it's own "ground" with the zeners, a 5% drop of B+ would be a 5% drop of both supply voltages of the opamps and hence not noticeable on the signal.
I once designed a high quality class A headphone amplifier which appeared to have about 1Vpp ripple on *one* of the supply rails (bipolar supply). This wasn't noticeable on the outputs at all because the feedback of the opamps cancelled it.
Meindert
Hello Meindert,
The ones in the metal housing tried to become spacecraft after shorting.
Regards, Joerg
Not to mention the supply voltage rejection ratio.
Graham
Why would they fail ?
Entirely off the top of my head, I recall the TL072 draws 2.8mA typical.
I reckon a 68k 3W ( runnung at 1.5W dissipation ) should do the job myself.
Graham
Hello Graham,
Typically, yes. But the data sheet says 2.5mA per channel max so that would be 5mA total.
Regards, Joerg
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