@Igla this is essentially the same thing I did. If I took a hammer and flattened my main ground wire it would be the same. If you look at the gaincard pictures posted at
Mick Feuerbacher Audio Projects
you'll se a similar thing, but just for one channel. I just got less turn on/off thump when I connected all the signal ground to a single point and then connected that point to the main ground with a very thin wire. This thin wire has a bit more resistance and makes it less likely that any stray noise from the power supply would end up at the amp input. So if you get no thump in your current setup let it be. I followed Peter Daniels building instructions and check out decdun.me.uk, I found this image there
Mick Feuerbacher Audio Projects
you'll se a similar thing, but just for one channel. I just got less turn on/off thump when I connected all the signal ground to a single point and then connected that point to the main ground with a very thin wire. This thin wire has a bit more resistance and makes it less likely that any stray noise from the power supply would end up at the amp input. So if you get no thump in your current setup let it be. I followed Peter Daniels building instructions and check out decdun.me.uk, I found this image there
Attachments
Thanks for the answer mrVetz. I also have LM3875 gainclone wired in the same manner with a copper ground plane and it has no hum, no noise, no thump and no oscillations. The same goes for LM1875 GC - with copper plane I had no problems. But when I tried to wire it as you did (grounding done with wires and not with cooper plane) I got hum and large DC offset. The attached picture shows how I did it. Perhaps I should select different signal ground point - at the cinch or at the pot? Is there something I'm missing?
Regards
Regards
Attachments
post42.
this diagram does not have a MAG.
The speaker return is connected to the PSU Zero Volts.
The pot, PSU Cinch (RCA) and 1k0 are connected to the signal Ground.
The double bridge connects to some intermediate point away from the PSU.
There is a fourth common point between the two amplifiers.
This an excellent example of "how not to do it" !!!
this diagram does not have a MAG.
The speaker return is connected to the PSU Zero Volts.
The pot, PSU Cinch (RCA) and 1k0 are connected to the signal Ground.
The double bridge connects to some intermediate point away from the PSU.
There is a fourth common point between the two amplifiers.
This an excellent example of "how not to do it" !!!
Anyone out there who wants to show an machanical engineer how to do a proper grounding in some lousy chip amp he built? Not a single one?
AndrewT; ''how not to do it'' is not much of a help for me. Rather show me ''how to do it''.
I have a feeling that this forum is somehow unfriendly to some members. This is the third time I'm asking for help with no answer. I'm also a member of other forums - some woodworking forums and a few local forums. When I asked for help on those forums I always got it. I know I don't help other members on this forum. This is because I don't know nothing about amps and other electrical stuff. I just see a schematic and I try to solder it because I like to solder and listen to the music and I have a great pleasure if it works. Do I have to become a member of some dedicated circle on this forum or should I cange the flag and country name? Would this help?
You know what; I don't want no help from such a forum.
AndrewT; ''how not to do it'' is not much of a help for me. Rather show me ''how to do it''.
I have a feeling that this forum is somehow unfriendly to some members. This is the third time I'm asking for help with no answer. I'm also a member of other forums - some woodworking forums and a few local forums. When I asked for help on those forums I always got it. I know I don't help other members on this forum. This is because I don't know nothing about amps and other electrical stuff. I just see a schematic and I try to solder it because I like to solder and listen to the music and I have a great pleasure if it works. Do I have to become a member of some dedicated circle on this forum or should I cange the flag and country name? Would this help?
You know what; I don't want no help from such a forum.
Grounding is a very complicated subject that I like many others don't completely understand. Many factors are at play that require different techniques. I have read all the popular articles and excerpts from multiple books on the subject and aside from somewhat muddying the waters further I can conclude that the right way or the recommended way does not always work 100%. Other factors may be at play. If andrew thinks that the way you have done it is an example of the wrong way to do it then try something else. Also most of the people on here seem to be willing to help, if no one is giving you a solid answer as to what will it may be because we are not sure or maybe we are currently working or sleeping or doing all the other things that make up life. This is supposed to be fun remember.
I'm so sorry. I have overreacted. You know, one of those days.
It's just a simple LM1875 gainclone with no zobel filter and capacitor from negative input to ground.
The thing is that when I wire it with ''ground plane'' (photo on #39) I got no problems (low DC offset and no hum). AndrewT answered me that this is a good grounding. I do all my gainclones like that.
Then I was reading about split grounds - to ground separately signal grounds in one point and power grounds in second point and then put them together in one point. That kind of grounding is suppose to give even better sound. So, first I tried the grounding like on the other picture. This is inverted GC but I guess the principle stays the same. I got large DC offset and big hum. Then I tried all sorts of combinations trying to split grounds and the result was always the same - DC offset of more then 100mV and hum. I have also tried the same wiring as mrVetz did (post #9). It didn't work for me. How weird. I don't understand what am I doing wrong. I was doing that for three days then I just desoldered my LM1875 gainclone. Now I'm listening to LM3875 GC which also has ''ground plane'' and all the grounds from RCA, pot, loudspeakers, power caps and ICs are going throug separate wires to that plane. I have also tried to put all the grounds from left channel together in one point and from right channel to other point and then connect both points together with a thick piece of wire with a ground from the bridges in the middle (third picture - from Peter Daniel users manual) . It didn't work.
In those three days of soldering grounds I've got a ''grounding bug'' which just won't let me be.
I want to figure this out just for a piece of mind. How come that this works everywhere else just not in my amps?
Damn, it's already eleven and I have to wake up early.
I hope my english was good enough to understand.
By the way; how did Peter split signal and power grounds on his PCB? As I believe he has separated grounds but I just can't get it. All I can see is a ground plane on the PCB and all the grounds are going to that plane.
Regards
It's just a simple LM1875 gainclone with no zobel filter and capacitor from negative input to ground.
The thing is that when I wire it with ''ground plane'' (photo on #39) I got no problems (low DC offset and no hum). AndrewT answered me that this is a good grounding. I do all my gainclones like that.
Then I was reading about split grounds - to ground separately signal grounds in one point and power grounds in second point and then put them together in one point. That kind of grounding is suppose to give even better sound. So, first I tried the grounding like on the other picture. This is inverted GC but I guess the principle stays the same. I got large DC offset and big hum. Then I tried all sorts of combinations trying to split grounds and the result was always the same - DC offset of more then 100mV and hum. I have also tried the same wiring as mrVetz did (post #9). It didn't work for me. How weird. I don't understand what am I doing wrong. I was doing that for three days then I just desoldered my LM1875 gainclone. Now I'm listening to LM3875 GC which also has ''ground plane'' and all the grounds from RCA, pot, loudspeakers, power caps and ICs are going throug separate wires to that plane. I have also tried to put all the grounds from left channel together in one point and from right channel to other point and then connect both points together with a thick piece of wire with a ground from the bridges in the middle (third picture - from Peter Daniel users manual) . It didn't work.
In those three days of soldering grounds I've got a ''grounding bug'' which just won't let me be.
I want to figure this out just for a piece of mind. How come that this works everywhere else just not in my amps?Damn, it's already eleven and I have to wake up early.
I hope my english was good enough to understand.
By the way; how did Peter split signal and power grounds on his PCB? As I believe he has separated grounds but I just can't get it. All I can see is a ground plane on the PCB and all the grounds are going to that plane.
Regards
Attachments
AndrewT; please don't take it personaly. I had a bad day and sometimes on such a day we react as we shouldn't.
First questuon: Lets say I will stick to ''ground plane'' as I call it. Can I attach all grounds where I want on that plane or should I put them on specific points on that plane- for example: speaker grounds closer to power capacitor grounds, RCA and pot grounds closer together and away from power grounds?
SoIL4x4: As far as my knowledge goes I have tried everything (not just something else) to split grounds and nothing worked like I described in my previous post. Well, it suppose to be fun but I took this grounding too much seriously but I can't figure it out. That's why I have asked for help.
Here is my second question: Obviously the wiring in post #42 is wrong. How should I do it if I want to split signal and power grounds?
Regards
PS
I know my english is not very good so perhaps my questions sound arogant or there is something else wrong with my writing. Please feel free to tell me, how to form questions on different way.
First questuon: Lets say I will stick to ''ground plane'' as I call it. Can I attach all grounds where I want on that plane or should I put them on specific points on that plane- for example: speaker grounds closer to power capacitor grounds, RCA and pot grounds closer together and away from power grounds?
SoIL4x4: As far as my knowledge goes I have tried everything (not just something else) to split grounds and nothing worked like I described in my previous post. Well, it suppose to be fun but I took this grounding too much seriously but I can't figure it out. That's why I have asked for help.
Here is my second question: Obviously the wiring in post #42 is wrong. How should I do it if I want to split signal and power grounds?
Regards
PS
I know my english is not very good so perhaps my questions sound arogant or there is something else wrong with my writing. Please feel free to tell me, how to form questions on different way.
Hey GloBug,
I like this photo, showing how you have connected caps to amp board. Are you also using the Audio Sector rectifier/power-supply-board?
I can't see it in your photo, so I'm not sure how those connect on the powersupply end. Or, I'm thinking that maybe those caps and wiring is the rectifier, as if you built it point-to-point??
AlexQS
There is some good information on this page concerning a point-to-point wired gainclone- http://dogbreath.de/Chipamps/GainCardCopy/GainCardCopy.html
It's not an LM1875, but it should still be applicable.
It's not an LM1875, but it should still be applicable.
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