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In Reply to: RE: An interesting JFET-based active XO design from TNT Audio ... posted by andyr on March 30, 2014 at 18:34:24
Andy,You're essentially taking a step backward with those designs. You already have a superior design implemented in your system currently.
Discrete components have no inherent advantage regarding feedback usage or lack thereof. Much depends upon the topology utilized and not the packaging of the devices.
DC offset correction could easily be added to your existing op-amp designs to avoid the use of blocking capacitors if you have heartburn with those. A servo can employed or a static offset correction circuit.Cheers,
Dave.
Edits: 03/30/14Follow Ups:
Are you saying that there is no feedback in Rod's opamp-based XO?
And re. your statement " DC offset correction could easily be added to your existing " ... it would be hard to add extra components to the P09 PCB.
Regards,
Andy
No, I'm not saying that. I'm saying that there is actually feedback employed in those JFET buffer stages. (It's not obvious, but it's there.) Most folks just analyze schematics looking for global feedback loops and if they don't see one assume it's a "no-feedback" design.
Of course, all this presumes that feedback is a bad thing. Many good audio design engineers would disagree with that. :)
"Easily" is not the correct word. Sorry. However, you could scab some daughtered breadboard type things into the P09 pcb and achieve. Probably though, the best approach would be to use different active crossover boards that have servo correction built on already. I've seen some nice DIY boards on DIYaudio.com a few years back. There was even a group buy IIRC.
Regardless, you should achieve a good result using those buffered passive circuits and it will be an excellent learning experience.
Cheers,
Dave.
Completely disagree. Op amps sound very compromised compared to zero feedback fet buffers. This is based on years and years of listening to opamps and other circuits.
Edits: 03/30/14
Completely disagree with your disagreement. I think we'll probably have to agree to disagree. :)
I accept your subjective evaluations. By definition they are incontrovertible.
Cheers,
Dave.
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