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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 are you using laser trimmed op-amps such as the OPA2134? Your xo's are old (just like us) and I'm thinking you may have TL072's which Rod Elliott says are fine for this application but I don't think they are laser trimmed. Laser trimming minimizes DC offset. Just a thought.
Edits: 03/30/14Follow Ups:
But R U sure 'laser trimming' removes DC offset? :-))
I measured some DC offset ... which was not a problem with my present amps bcoz they have an input coupling cap.
Regards,
Andy
Well, I thought the purpose of laser trimming was to eliminate the DC offset but more knowledgeable people than I (that means the rest of you guys) could correct me. In any case, the offset should only be a few mv ( <10) without trimming and almost all the newer opamps are trimmed.Have you discussed it with Rod Elliott to see why the problem exists?
BTW I have toyed with the idea of changing the OPA2134s but have never gotten around to it. Can you really hear a difference between the AD826 and OPA2134. At this point in my life I have reached audio nirvana as I can barely hear my wife in the background when I am listening. I think that is what is meant by a "blacker background" because when I get done with my listening sessions, there seems to be a dark cloud in the room :).
BTW since you seem to be headed toward a JFET DIY have you given thought to making it balanced rather than single- ended?
Edits: 04/01/14 04/01/14
No, neo. :-((
The rest of my system is not balanced and I do not have the design knowledge to do anything more than just use Grey Rollin's schematics and calculate the component values appropriate for my slopes & knee frequencies.
Regards,
Andy
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