The only IC based amp (hate the word "gainclone") was Marchand's PM21 based on the LM3886. It used a zobel consisting of a .01uF cap and a 5.6R resistor. Not the "conventional" values. I didn't try it without the zobel but certainly it continues to function quite well a few years later with one.
Re: X Ray vision
Nice try Fred, but looking at the drilled holes on the board and missing components (front and right), I would rather suspect that both the resistor and capacitor forming Zobel are missing. Underneath traces also indicate that this was a place for Zobel. Why isn't not installed? Maybe for testing purposes?
Fred Dieckmann said:
Nice try Fred, but looking at the drilled holes on the board and missing components (front and right), I would rather suspect that both the resistor and capacitor forming Zobel are missing. Underneath traces also indicate that this was a place for Zobel. Why isn't not installed? Maybe for testing purposes?
X-Ray vision?
"Is there a Zobel in that picture? I couldn't figure it out." - all quotes are from PD
Maybe because you can't see through the PCB? You know who to ask if you are actually want to know, the guy that designed it. Tell him I sent you........
"I'm not much of subjectivist or objectivist. I'm always after the best solutions, whatever they are. That's why I'm doing this research."
This could be part of your research. I fully agree with you on the objectivist part.
"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 necessary to remove oscillations. In some cases it seems like other fixes were actually better.
That is exactly how I remember all those troubleshooting posts. It was always a first suggestion to try Nobel, but it later appeared that something else was to blame.'
I don't think a Zobel is a cure for poor layout, grounding, and decoupling. I notice everyone wants leave off the 0.1 uF high frequency decoupling caps as well. I have expressed concerns about this as well in the past. If you are going to use just electrolytic caps the layout and grounding are even more of an issue to get right and the caps had better have a very low ESR and ESL. Another example of second guessing the guys at National Semiconductor that can get you in trouble. A Zobel is not going to cure a poor layout for the power supply cap connections to the IC. Read the data sheets for the amplifier chips and see how much importance is placed on these issues.
"I'm not that dedicated to look for it." Here is something I could not agree with more. I'm am releived that there issomething in this debate that we see eye to eye on.
"Is there a Zobel in that picture? I couldn't figure it out." - all quotes are from PD
Maybe because you can't see through the PCB? You know who to ask if you are actually want to know, the guy that designed it. Tell him I sent you........
"I'm not much of subjectivist or objectivist. I'm always after the best solutions, whatever they are. That's why I'm doing this research."
This could be part of your research. I fully agree with you on the objectivist part.
"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 necessary to remove oscillations. In some cases it seems like other fixes were actually better.
That is exactly how I remember all those troubleshooting posts. It was always a first suggestion to try Nobel, but it later appeared that something else was to blame.'
I don't think a Zobel is a cure for poor layout, grounding, and decoupling. I notice everyone wants leave off the 0.1 uF high frequency decoupling caps as well. I have expressed concerns about this as well in the past. If you are going to use just electrolytic caps the layout and grounding are even more of an issue to get right and the caps had better have a very low ESR and ESL. Another example of second guessing the guys at National Semiconductor that can get you in trouble. A Zobel is not going to cure a poor layout for the power supply cap connections to the IC. Read the data sheets for the amplifier chips and see how much importance is placed on these issues.
"I'm not that dedicated to look for it." Here is something I could not agree with more. I'm am releived that there issomething in this debate that we see eye to eye on.
Attachments
"Whose side are you on?"
"That would be telling"
1.) Who can't read the 'scope trace that moamp posted? Looks fine to me. Those of us who have built our share of amps have seen that more times than we care to admit.
2.) Using the example of a CFP output that D.Self refers to is really disingenuous here. Those stinking things oscillate if you look at them wrong. I should know. See #1 above.
3.) It is hard to make a product idiot proof, because idiots are so damn clever. If there is a way to make CAT 5 cable even more capacitive than it already is.......and therefore blow up an amp......rest assured that there is at least one out there with your product in their crosshairs.
Consider yourself lucky if it is only one.
Jocko
"That would be telling"
1.) Who can't read the 'scope trace that moamp posted? Looks fine to me. Those of us who have built our share of amps have seen that more times than we care to admit.
2.) Using the example of a CFP output that D.Self refers to is really disingenuous here. Those stinking things oscillate if you look at them wrong. I should know. See #1 above.
3.) It is hard to make a product idiot proof, because idiots are so damn clever. If there is a way to make CAT 5 cable even more capacitive than it already is.......and therefore blow up an amp......rest assured that there is at least one out there with your product in their crosshairs.
Consider yourself lucky if it is only one.
Jocko
Hi,
Probably....and it appears he still has hopes for winning the Nobel prize too.
Still, IMHO he's absolutely right in what he says here.
Oscillations are more often than not caused by instability in the circuit proper and if that's the case Zobel networks can attempt at masking them but sooner or later something going to smoke...
What I usually do before even thinking about hooking up a speaker is doing all kinds of torture tests on the amp with dummy loads iso speakers.
If everything passes that succesfully then only the most unfortunate of unfortunate situations are going to upset the amp to the point where it can oscillate into self-destruction.
Note, I am only talking about topologies that do not require a Zobel network per definition.
So what should you do?
If it were me I'd take a gamble and play the same game the software publishers play; use Joe Consumer as a test bed, but only after I'd gain enough confidence in my product though.
Come to think of it, all these problems could be swept under the table with a simple output trannie...Mucho better than all Nobels and Zobels combined.
Handy stuff and those fancy cables with their crazy capacitance are only trying to limit/filter the HF bandwidth in the first place...
But that's another chapter entirely...
Errr...Frankenstein out of the basement yet?
Cheers,
Probably....and it appears he still has hopes for winning the Nobel prize too.
Still, IMHO he's absolutely right in what he says here.
Oscillations are more often than not caused by instability in the circuit proper and if that's the case Zobel networks can attempt at masking them but sooner or later something going to smoke...
What I usually do before even thinking about hooking up a speaker is doing all kinds of torture tests on the amp with dummy loads iso speakers.
If everything passes that succesfully then only the most unfortunate of unfortunate situations are going to upset the amp to the point where it can oscillate into self-destruction.
Note, I am only talking about topologies that do not require a Zobel network per definition.
So what should you do?
If it were me I'd take a gamble and play the same game the software publishers play; use Joe Consumer as a test bed, but only after I'd gain enough confidence in my product though.
Come to think of it, all these problems could be swept under the table with a simple output trannie...Mucho better than all Nobels and Zobels combined.
Handy stuff and those fancy cables with their crazy capacitance are only trying to limit/filter the HF bandwidth in the first place...
But that's another chapter entirely...
Errr...Frankenstein out of the basement yet?
Cheers,
Know!? He doesn't even suspect! *
"Nice try Fred, but looking at the drilled holes on the board and missing components (front and right), I would rather suspect that both the resistor and capacitor forming Zobel are missing. Underneath traces also indicate that this was a place for Zobel. Why isn't not installed? Maybe for testing purposes?" - who else but PD.......
What is this the P-A design espionage school or an example of the GR "I saw a picture so I know what he is doing in the design school"? You would think somebody so passionate about Chip amps would keep an eye on the competition. Or just maybe........... he was trying to cash in on the lucrative Zoble free market! Is this humor, thick headiness, or an attempt at slander? It sure doesn't appear to be research or the desire to learn anything, not even what the competition is doing!
Your competition would probably like to thank you for moving the topic in the direction of his products. He is shy about using the forum to promote his work and I am sure he appreciates you using the forum to share the spotlight with his products as well as yours. It was the act of a gentleman and I tip my hat to your generosity!
You are, if not a gentleman and a scholar, surely a gentleman.
Please give me the opportunity to retire for the evening. You are providing so much fun for me that I could go on all night. I know you have amps to build and I have taken up way to much of your time. Such indulgences will make me very unpopular with your customers and I ask their forgiveness.
Thanks for playing,
Fred, who must go to bed.
* Mark Twain quote
"Nice try Fred, but looking at the drilled holes on the board and missing components (front and right), I would rather suspect that both the resistor and capacitor forming Zobel are missing. Underneath traces also indicate that this was a place for Zobel. Why isn't not installed? Maybe for testing purposes?" - who else but PD.......
What is this the P-A design espionage school or an example of the GR "I saw a picture so I know what he is doing in the design school"? You would think somebody so passionate about Chip amps would keep an eye on the competition. Or just maybe........... he was trying to cash in on the lucrative Zoble free market! Is this humor, thick headiness, or an attempt at slander? It sure doesn't appear to be research or the desire to learn anything, not even what the competition is doing!
Your competition would probably like to thank you for moving the topic in the direction of his products. He is shy about using the forum to promote his work and I am sure he appreciates you using the forum to share the spotlight with his products as well as yours. It was the act of a gentleman and I tip my hat to your generosity!
You are, if not a gentleman and a scholar, surely a gentleman.
Please give me the opportunity to retire for the evening. You are providing so much fun for me that I could go on all night. I know you have amps to build and I have taken up way to much of your time. Such indulgences will make me very unpopular with your customers and I ask their forgiveness.
Thanks for playing,
Fred, who must go to bed.
* Mark Twain quote
Attachments
Re: "Whose side are you on?"
At VHF though? I'd expect the local loop instability of the CFP to be at a much lower frequency than VHF, a few MHz maybe. IOW that a VHF instability is most likely a parasitic rather than loop-related.
I didn't intend to be misleading with this.
Jocko Homo said:
At VHF though? I'd expect the local loop instability of the CFP to be at a much lower frequency than VHF, a few MHz maybe. IOW that a VHF instability is most likely a parasitic rather than loop-related.
I didn't intend to be misleading with this.
Credit were credit is due.
This not my amp! i would have been proud to have designed it though. I believe the network might have been removed to show the rest of the board more clearly......... the other pictures of his amps appear to have the Zoble. Sorry for any confusion. Why don't you call RSN and ask him. Again, please tell him I sent you. I could be completely wrong of course. It may have been a clever ruse to throw the audio spys off the scent. I am glad to hear there is room for improvement. It was sufficient enough of a design, to reportably sound better than one of your amps and with much less of an investment, but I haven't heard either and so will only pass on the report to me. Maybe they were using the wrong speaker cables..........
I really must go to bed before the laughter wakes my wife up.
Peter Daniel said:
This not my amp! i would have been proud to have designed it though. I believe the network might have been removed to show the rest of the board more clearly......... the other pictures of his amps appear to have the Zoble. Sorry for any confusion. Why don't you call RSN and ask him. Again, please tell him I sent you. I could be completely wrong of course. It may have been a clever ruse to throw the audio spys off the scent. I am glad to hear there is room for improvement. It was sufficient enough of a design, to reportably sound better than one of your amps and with much less of an investment, but I haven't heard either and so will only pass on the report to me. Maybe they were using the wrong speaker cables..........
I really must go to bed before the laughter wakes my wife up.
I needed a zobel
Hi,
I built the following amp (call it Geenkloon) two years ago and designed it and built it with Zobel. Hoewever for the second amp I missed the 22nF cap at the time and decided not to use the Zobel in the second amp for a while (and forgot about it later).
It turned out that during this period I did not need it, and I must say I never noticed a remarkable difference between the channels too. I more or less decided to go for a minimal clone next time. Even the 22uF cap should disappear.
Last week I opened up both boxes and changed the attenuator for another type. When connecting the amps again one channel was definitely instable (I reached the power switch in time to save the speaker). Of course I thought I made a mistake in the components just changed and even changed back to the old switch. After an hour or so decided to find another cap and connect the zobel since everything else was the same.
The zobel worked, quite to my surprise. I used the same speakers (B&W) I used for a longer time for my DIY projects and I used the same speaker cable (ordinary copper of 4 meters in length). The zobel is gonna stay in ..
Have a look at my project pages, to see I soldered everything of the amp except the attenuator on just a few square cm. Unfortunately I cannot go back to exactly the same amp since over the last two days I changed the caps for Black Gates. It sound great already.
Maarten
http://www.platenspeler.com/gainclone.html geenkloon project
Hi,
I built the following amp (call it Geenkloon) two years ago and designed it and built it with Zobel. Hoewever for the second amp I missed the 22nF cap at the time and decided not to use the Zobel in the second amp for a while (and forgot about it later).
It turned out that during this period I did not need it, and I must say I never noticed a remarkable difference between the channels too. I more or less decided to go for a minimal clone next time. Even the 22uF cap should disappear.
Last week I opened up both boxes and changed the attenuator for another type. When connecting the amps again one channel was definitely instable (I reached the power switch in time to save the speaker). Of course I thought I made a mistake in the components just changed and even changed back to the old switch. After an hour or so decided to find another cap and connect the zobel since everything else was the same.
The zobel worked, quite to my surprise. I used the same speakers (B&W) I used for a longer time for my DIY projects and I used the same speaker cable (ordinary copper of 4 meters in length). The zobel is gonna stay in ..
Have a look at my project pages, to see I soldered everything of the amp except the attenuator on just a few square cm. Unfortunately I cannot go back to exactly the same amp since over the last two days I changed the caps for Black Gates. It sound great already.
Maarten
http://www.platenspeler.com/gainclone.html geenkloon project
Attachments
Currently in the process of building a GC. But my current setup uses braided catV cable for the tweeter after the (external) crossover filters.
From what is said earlier in this thread it seems that CATV cable is definitely a NONO with gainclones due to the high capacitance of the cable. Is this true or do I have a problem grasphing the real issue here.
And if yes what can I do to prevent oscillation?
From what is said earlier in this thread it seems that CATV cable is definitely a NONO with gainclones due to the high capacitance of the cable. Is this true or do I have a problem grasphing the real issue here.
And if yes what can I do to prevent oscillation?
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