#9 here: http://www.diyaudio.com/forums/showthread.php?s=&postid=357726&highlight=#post357726
Adding zobel makes no change.
Adding zobel makes no change.
#42 http://www.diyaudio.com/forums/showthread.php?s=&threadid=25793&perpage=40&highlight=&pagenumber=2
Oscillation occur, zobel is suggested, but everything is fine after changing ground connections.
Oscillation occur, zobel is suggested, but everything is fine after changing ground connections.
Peter Daniel said:Fred,
If I still was a moderator, I would ask you to stay on topic. Go back to your other favourite thread, if you have nothing (else related to the main subject) to say.
I didn't expect you'd be a game for GC boards
To make it clear for you, I'm looking for actual cases where Zobel was find useful, not theoretical. I don't know why this bothers you.
It doesn't. On the subject of moderation, your not a moderator, you resigned remember?
I believe I am still on topic. Your efforts to say otherwise smell of censorship. Maybe an official moderator can step in to make the judgment call. The measurements have been shown and you wanted to know more about moamps setup. I think you need enough theory to ask him what the capacitance of the speaker wire is. One can only wonder why you are trying so hard not to understand how the network works and how much capacitance is enough to be problematic without a zobel. What exactly is your agenda? You seem to think mine is selling everyone zobel networks I guess. I would just like people to understand how the circuit works and seem to be joined by others in this desire. Efforts to the contrary and self-serving motivations hardly contribute to learning and the free exchange of factual and verifiable information on the forum. This is not a matter of opinion type discussion or indecipherable theory. This is very straight forward electronics and an excellent subject for measurement and simple circuit explanations. Tell me in whose interest you are speaking and what is hurt (other than maybe your pride) by an understanding of how a zobel works. I really don't understand what you are afraid of .....
#1 http://www.diyaudio.com/forums/showthread.php?s=&postid=268209&highlight=#post268209
amp oscillates, zobel no help
amp oscillates, zobel no help
Fred Dieckmann said:
It doesn't. On the subject of moderation, your not a moderator, you resigned remember?
I believe I am still on topic. Your efforts to say otherwise smell of censorship. Maybe an official moderator can step in to make the judgment call. The measurements have been shown and you wanted to know more about moamps setup. I think you need enough theory to ask him what the capacitance of the speaker wire is. One can only wonder why you are trying so hard not to understand how the network works and how much capacitance is enough to be problematic without a zobel. What exactly is your agenda? You seem to think mine is selling everyone zobel networks I guess. I would just like people to understand how the circuit works and seem to be joined by others in this desire. Efforts to the contrary and self-serving motivations hardly contribute to learning and the free exchange of factual and verifiable information on the forum. This is not a matter of opinion type discussion or indecipherable theory. This is very straight forward electronics and an excellent subject for measurement and simple circuit explanations. Tell me in whose interest you are speaking and what is hurt (other than maybe your pride) by an understanding of how a zobel works. I really don't understand what you are afraid of .....
Read again, I'm not concerned with Moamp setup, I know it's good.
I merely suggested that other people setups may not be up to the task.
#26 http://www.diyaudio.com/forums/showthread.php?s=&postid=259811&highlight=#post259811
amp oscillates, adding coupling cap to ground resistor (from -IN) solves the problem
amp oscillates, adding coupling cap to ground resistor (from -IN) solves the problem
#40 http://www.diyaudio.com/forums/showthread.php?s=&threadid=19783&perpage=40&highlight=&pagenumber=1
Hissing problem, a guy adds additional series resistor with 10 turns of wire ari=ound it, hiss is gone
Hissing problem, a guy adds additional series resistor with 10 turns of wire ari=ound it, hiss is gone
#1 http://www.diyaudio.com/forums/showthread.php?s=&postid=206709&highlight=#post206709
Zobel slightly modified, nevertherless still distorting. Placing higher value series resistor at the output helps.
Zobel slightly modified, nevertherless still distorting. Placing higher value series resistor at the output helps.
moamps said:
Doesn't this pretty much say it all? Moamps has demonstrated an example which, it seems to me, is a classic. If you're going to ask people to describe a problem wherein a zoebel either did or did not fix it - then they should be required to present evidence equivalent to what Moamps has provided here. Otherwise, we can argue forever about what the "problem" was (e.g. it didn't have as much "air" or "forwardness" as when I used zipcord for speaker interconnect) - and what the ultimate "solution" was (e.g. "I packed the cables in ice for two hours and it really opened the sound")...
All this argument isn't advancing DIY without some evidence and real discussion instead of personal bickering is it? Let's see some real proof instead of conjecture and intuition only...
I'd be happy to make some test equipment available if need be.
Bill
"Absence of evidence is not the same as evidence of absence" - Carl Sagan
You are missing a bigger picture here, jam. After the search is over, we might ask a modearator to change the title to "GainClone Troubleshooting Thread".
It may become helpful to anybody having problem with their amps, providing of course Fred's post will be removed, as they might be causing too much confusion.
It may become helpful to anybody having problem with their amps, providing of course Fred's post will be removed, as they might be causing too much confusion.
#10 http://www.diyaudio.com/forums/showthread.php?s=&postid=196902&highlight=#post196902
oscillation problems, lots of advise from the forum (no doubt zobel as well), changing bypass caps to more regular type helps.
oscillation problems, lots of advise from the forum (no doubt zobel as well), changing bypass caps to more regular type helps.
Hi Peter,
Douglas Self has a section in his book about his experiments with Zobel networks. Here's a quote from part of it.
"...I removed the standard 10 Ohm / 0.1 uF Zobel from a Blameless Class-B amplifier with CFP output and the usual NFB factor of 32dB at 20 kHz. With an 8 Ohm resistive load the THD performance and stability were unchanged. However, when a 0.47 mH inductor was added in series to roughly simulate a single-unit loudspeaker, there was evidence of local VHF instability in the output stage; there was certainly no Nyquist instability of the global NFB loop."
Though you may strongly disagree with his anti-subjectivist rants, there's tons of tidbits of info like this in the book, making it well worth reading.
Douglas Self has a section in his book about his experiments with Zobel networks. Here's a quote from part of it.
"...I removed the standard 10 Ohm / 0.1 uF Zobel from a Blameless Class-B amplifier with CFP output and the usual NFB factor of 32dB at 20 kHz. With an 8 Ohm resistive load the THD performance and stability were unchanged. However, when a 0.47 mH inductor was added in series to roughly simulate a single-unit loudspeaker, there was evidence of local VHF instability in the output stage; there was certainly no Nyquist instability of the global NFB loop."
Though you may strongly disagree with his anti-subjectivist rants, there's tons of tidbits of info like this in the book, making it well worth reading.
#3 http://www.diyaudio.com/forums/showthread.php?s=&postid=180276&highlight=#post180276
Is there a Zobel in that picture? I couldn't figure it out.
Is there a Zobel in that picture? I couldn't figure it out.
#1354 and #1661 http://www.diyaudio.com/forums/showthread.php?s=&threadid=9112&perpage=40&highlight=&pagenumber=42
Amp oscillates, adding Zobel didn't help. Thread is too long to find what helped.
Amp oscillates, adding Zobel didn't help. Thread is too long to find what helped.
#976 http://www.diyaudio.com/forums/showthread.php?s=&postid=138206&highlight=#post138206
Hey Jam, who was paying for that lunch?
Hey Jam, who was paying for that lunch?
That's about all I could find on Zobel in Chip Amp section.
I believe, there is more inf0, but I'm not that dedicated to look for it. From whatever I posted here, it is not really clear if Zobel was definitely neccessary to remove oscillations. In some cases it seems like other fixes were actually better.
That is exactly how I remember all those troubleshoothing posts. It was always a first suggestion to try Zobel, but it later appeared that something else was to blame.
I believe, there is more inf0, but I'm not that dedicated to look for it. From whatever I posted here, it is not really clear if Zobel was definitely neccessary to remove oscillations. In some cases it seems like other fixes were actually better.
That is exactly how I remember all those troubleshoothing posts. It was always a first suggestion to try Zobel, but it later appeared that something else was to blame.
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