Not exactly a zobel but...
Late arrival, but still in time?
Peter, the only way I could put back my Kimber 4TC speaker cable back in my system was to put two paralleled 0.47 ohm 3watt carbon resistors in series with the output on my GC power amp.
As you know, the Kimbers are mid/high capacitance cables.
The difference in sound was from almost no treble to a fantastically open and detailed treble.
Also, without the resistors it seamed that my amp was not man enough for my speakers, bass was affected too.
To get to this final result I tested almost all kinds of combinations possible with Zobels, with no satisfying results.
You can imagine this was intensive work, and always listening to the results.
After this, I always use these resistors on the output of my GCs.
They play much better with whatever cable and on whatever system you connect it.
Unfortunately, I can't prove this by words, so you'll have to trust what I say.
Or catch the first plane to Lisbon and I'll show you.
BTW, my final solution, after all, is to put a resistor (2.35 ohms seams spot on) on the chip's output, as you always do with op-amps.
Peter Daniel said:
Late arrival, but still in time?
Peter, the only way I could put back my Kimber 4TC speaker cable back in my system was to put two paralleled 0.47 ohm 3watt carbon resistors in series with the output on my GC power amp.
As you know, the Kimbers are mid/high capacitance cables.
The difference in sound was from almost no treble to a fantastically open and detailed treble.
Also, without the resistors it seamed that my amp was not man enough for my speakers, bass was affected too.
To get to this final result I tested almost all kinds of combinations possible with Zobels, with no satisfying results.
You can imagine this was intensive work, and always listening to the results.
After this, I always use these resistors on the output of my GCs.
They play much better with whatever cable and on whatever system you connect it.
Unfortunately, I can't prove this by words, so you'll have to trust what I say.
Or catch the first plane to Lisbon and I'll show you.
BTW, my final solution, after all, is to put a resistor (2.35 ohms seams spot on) on the chip's output, as you always do with op-amps.
I tried Mills 0.22, 5W resistors at the output, but I didn't notice any improvement, except for additional sonic signature of the resistors. My cables are easy load though.
Although your entry is not exactly what I was asking for, it's better than nothing and actually proves my point (that Zobel is not a universal fix). So if you don't have any of those (Brian's) boards, send me your address and I'll send you one
Although your entry is not exactly what I was asking for, it's better than nothing and actually proves my point (that Zobel is not a universal fix). So if you don't have any of those (Brian's) boards, send me your address and I'll send you one
moamps said:
To me it is not any problem. I do not know if your amp has problems with a bit strange cabling around though. Positive supply cap oriented thus to enable at least 5-6cm longer traces… Then bypass caps mounted to the strange positions, are you bypassing the inputs? You have to bypass the chip inputs, not the PCB inputs.
http://www.diyaudio.com/forums/showthread.php?postid=255696#post255696
Yes. It's something normal for RC network.
Please calculate F(-3dB).
Please guys, (like Fred says) read some (simple) books.
Leach, Slone, Self .....
What is the point is that the improvement is not necessary a consequence of the protected stability under the load, just a simple fact of low passed signal.
I am not sure what and why am I advised to calculate and read???
Like Fred…?
Pedja
Peter Daniel said:
Although your entry is not exactly what I was asking for, it's better than nothing and actually proves my point (that Zobel is not a universal fix). So if you don't have any of those (Brian's) boards, send me your address and I'll send you one
Is that your point? Then why didn't you say so in the first place.
I think everybody would have agreed with you then. I thought
your argument was that the Zobel filter is never a (required) fix.
Of course a Zobel filter cannot prevent all imaginable problems.
Carlos,
Did all the Zobels you tried cause more oscillation than the
series resistor solution, or are you talking about sonic
preferences?
Peter Daniel said:I tried Mills 0.22, 5W resistors at the output, but I didn't notice any improvement, except for additional sonic signature of the resistors. My cables are easy load though.
Although your entry is not exactly what I was asking for, it's better than nothing and actually proves my point (that Zobel is not a universal fix). So if you don't have any of those (Brian's) boards, send me your address and I'll send you one
In post 59 I gave my experience with Zobel, and to my surprise it actually worked to get my amp stable.
I guess my entry is exactly not what you were asking for
as it does not prove your point.Too bad, apparently those entries do not get the boards
Maarten
Hi,Pedja said:
My whole PCB is 11cm long; where did you find those 5-6cm?
Look to PCB design below.(Elektor design with Zobels)
My intention is caps bypassing.
Also, this isn't HF design.
Also, this isn't design witch I want to sell to anybody.
Are you educated PCB designer?
Regards
Attachments
Christer said:
It was my point all the time, as I stated it already in this thread and in the other threads. Zobel might be of help, but in case of LM3875 chip, when it oscillates, other "fixes" are much more effective. Those include better layout, better grounding and series, output resistor (sometimes with parallel inductance) at the output.
platenspeler said:
In post 59 I gave my experience with Zobel, and to my surprise it actually worked to get my amp stable.
I guess my entry is exactly not what you were asking for
Too bad, apparently those entries do not get the boards
Maarten
I guess it wasn't what I was aking for. I was specifically asking for links to previous posts on this (or the other) forum showing that Zobel was helpful in reducing oscillations. Only one post in this thread qualifies for that so far, and it is a post #20. So don't get upset. I'm showing again my original request, so you can see for yourself I'm not making anything up:
Peter Daniel said:
As to the Carlos prize, I said it's better than nothing, and since it again proves my point why not distinguish that attempt.
But send me your address and I'll forward a board for you as well.
Peter Daniel said:
OK, so he didn't post a link to a previous post but only gave testimony to his experience of a Zobel being helpful in reducing oscillations.
Well, since his post is now a part of this forum history, I hereby post a link to it in full compliance with your original request.
http://diyaudio.com/forums/showthread.php?postid=398248#post398248
RHosch said:
OK, so he didn't post a link to a previous post but only gave testimony to his experience of a Zobel being helpful in reducing oscillations.
Well, since his post is now a part of this forum history, I hereby post a link to it in full compliance with your original request.
http://diyaudio.com/forums/showthread.php?postid=398248#post398248
Clever attempt and technically it qualifies. Send me your address
For future reference, I will not accept any submissions with posts made after May 20, 2004
Hello,moamps said:
I did not say you want to sell that design. I wanted you to realize that you may have some problem with PS decoupling, yes for the high frequencies. Now I am disappointed if you in fact confirmed you do not give much attention to this issue. Usually it is wrong to think about amplifiers neglecting HF.
If you seriously do not see a way to reduce your PS local decoupling caps traces (seen by the chip) for at least 5-6cm in two steps, I just do not see much reason to talk with you about PCB design. None education could help. As about your PCB, this uneducated PCB designer is just interested to know do you have a driving license?
I do know Elektor’s (7-8/98) “100W single IC amplifier” article and yes, that board is obviously, considering PS caps, quite clumsy designed.
I can not understand your reason to post Leach in part where he talks some of the things I have already said in this thread. Might be you post just to have a post, but whatever it is, you just do not know what you posted. However, Leach’s recommendation for suited location for Zobel is quite funny. If you find a time, tell some here to mount Zobel on the output terminals because Leach recommends this… (Ok, I have some further thoughts on this but I’ll refrain from offering them as long as I see here play dead approach.)
Pedja
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