Hi
Could someone give me a kick up the **** with this project and explain the grounding to me please?
Here is the circuit: click here
Are all the ground points simply starred together? Where are they then connected? And what does the turntable ground wire connect to?
Thanks!
BTW, I posted this q elsewhere but to no reply so sorry if you've read it before.
Could someone give me a kick up the **** with this project and explain the grounding to me please?
Here is the circuit: click here
Are all the ground points simply starred together? Where are they then connected? And what does the turntable ground wire connect to?
Thanks!
BTW, I posted this q elsewhere but to no reply so sorry if you've read it before.
Konnichiwa,
No, implied (but not drawn well - I have been getting better in using this now) are two main star grounds, namely power ground and signal (input) ground. However, there really should be three star points, one for the MC stage, one for the Phono EQ input signal current loop and one for the power/output current loop. Finally both input and MC star are connected to the main power/output loop star ground.
To the metal (or copper foil lined non-metallic) case, which in turn is also connected to the power/output loop ground.
Basically, remember that there is no such thing as "ground", it's a fiction, a myth, a story told to little enginner childrens by their mom. In reality current always flows in loops and if you wish to control where the current flows you MUST collect all currents flowing out of a given node and return them to that node (Kirchoffs law), only then can you be sure that there is unwanted signal current flowoing in your "ground" which will then shift the "ground" (I prefer actually the term reference) away from being a solid "reference" to being a signal modulated and distorted reference.
So, think "Where will the current flow" and forget "ground".
Sayonara
Ropie said:
No, implied (but not drawn well - I have been getting better in using this now) are two main star grounds, namely power ground and signal (input) ground. However, there really should be three star points, one for the MC stage, one for the Phono EQ input signal current loop and one for the power/output current loop. Finally both input and MC star are connected to the main power/output loop star ground.
Ropie said:
To the metal (or copper foil lined non-metallic) case, which in turn is also connected to the power/output loop ground.
Basically, remember that there is no such thing as "ground", it's a fiction, a myth, a story told to little enginner childrens by their mom. In reality current always flows in loops and if you wish to control where the current flows you MUST collect all currents flowing out of a given node and return them to that node (Kirchoffs law), only then can you be sure that there is unwanted signal current flowoing in your "ground" which will then shift the "ground" (I prefer actually the term reference) away from being a solid "reference" to being a signal modulated and distorted reference.
So, think "Where will the current flow" and forget "ground".
Sayonara
Thanks, Evil One.
So I assume all the 'ground' points marked "0" are signal and the GND point is the actual power/output loop. I have omitted the MC section as I don't have any use for it at present. I am building in a wooden, foil lined case.
Thanks for the ground advice, though I wish my mum was an engineer!
So I assume all the 'ground' points marked "0" are signal and the GND point is the actual power/output loop. I have omitted the MC section as I don't have any use for it at present. I am building in a wooden, foil lined case.
Thanks for the ground advice, though I wish my mum was an engineer!
OK, I think this is what you are saying:
An externally hosted image should be here but it was not working when we last tested it.
Phono Preamp Finished
http://www.ampchipdiy.com/phpBB2/viewtopic.php?p=4606#4606
Thanks Thorsten. Pictures soon.
http://www.ampchipdiy.com/phpBB2/viewtopic.php?p=4606#4606
Thanks Thorsten. Pictures soon.
Problematic developments
Hi,
Well, I had this wonderful preamp working and sounding really great for a month or so (with the recommended battery supply) but a chance look inside the case one day showed that the 2200uF supply caps on the +V rail were bulging on top
They are Panasonic FCs rated at 50V and it's just the +V rail caps on both channels that are affected. I'm absolutely sure I have them the right way round and each cap 'sees' around 11.2V or so (though the -V rail caps see closer to 11.9V). How could they start bulging - is it possible that my grounding could be causing the problem? And are the bulging caps now too damaged to use (I have some spare 2200uFs but they are Elnas rated at only 16V)?
Thanks in advance for any help.
Hi,
Well, I had this wonderful preamp working and sounding really great for a month or so (with the recommended battery supply) but a chance look inside the case one day showed that the 2200uF supply caps on the +V rail were bulging on top
They are Panasonic FCs rated at 50V and it's just the +V rail caps on both channels that are affected. I'm absolutely sure I have them the right way round and each cap 'sees' around 11.2V or so (though the -V rail caps see closer to 11.9V). How could they start bulging - is it possible that my grounding could be causing the problem? And are the bulging caps now too damaged to use (I have some spare 2200uFs but they are Elnas rated at only 16V)?
Thanks in advance for any help.
There has been a development. I took the thing apart and checked the circuit over - couldn't find any mistakes as far as I could tell.
Now, the thing plays happily for about an hour then the sound starts to distort and eventually fizzles out. Then the volume and selector switch pop at every step. If I leave it alone for a while and switch it on again it works fine for a while before the problem re-occurs.
Anyone have any idea, please?!
This preamp sounds great when it works....
Now, the thing plays happily for about an hour then the sound starts to distort and eventually fizzles out. Then the volume and selector switch pop at every step. If I leave it alone for a while and switch it on again it works fine for a while before the problem re-occurs.
Anyone have any idea, please?!
This preamp sounds great when it works....
Re: Problematic developments
Hi,
Are you ABSOLUTELY SURE that they are wired in correct polarity? Bulging tops suggests either duff capacitors or inverted capacitor polarity.
Sayonara
Hi,
Ropie said:Well, I had this wonderful preamp working and sounding really great for a month or so (with the recommended battery supply) but a chance look inside the case one day showed that the 2200uF supply caps on the +V rail were bulging on top
They are Panasonic FCs rated at 50V and it's just the +V rail caps on both channels that are affected.
Are you ABSOLUTELY SURE that they are wired in correct polarity? Bulging tops suggests either duff capacitors or inverted capacitor polarity.
Sayonara
Hi,
Thanks for replying
>> Bulging tops suggests either duff capacitors or inverted capacitor polarity.
The caps can't be duff as they are the second pair to do this. I have been over the circuit several times and am convinced I have them the right way round. Wouldn't they have blown by now (after over a months use) if they were inverted?
Thanks for replying
>> Bulging tops suggests either duff capacitors or inverted capacitor polarity.
The caps can't be duff as they are the second pair to do this. I have been over the circuit several times and am convinced I have them the right way round. Wouldn't they have blown by now (after over a months use) if they were inverted?
Konnichiwa,
IU can't really say, but if everything is wired correctly the Capacitors would be connected across a 12V Battery. Connecting a 50V Capacitor in correct polarity across a 12V Battery cannot cause any issues. The Cap's may or may not have blown up, they may just be on the side where they run hot but not yet are close enough to catastrophic failure to blow up. What would happen though is that the affected battery discarges much fater than the other, which would explain the "fadeout" after 1 Hour or so.
At any extent, if the circuit is wired as shown with capacitors in correct polarity then what you describe cannot happen... So there is a wiring fault somewhere, no idea where is the capacitors are not inserted with wrong polarity....
Ciao T
Ropie said:
IU can't really say, but if everything is wired correctly the Capacitors would be connected across a 12V Battery. Connecting a 50V Capacitor in correct polarity across a 12V Battery cannot cause any issues. The Cap's may or may not have blown up, they may just be on the side where they run hot but not yet are close enough to catastrophic failure to blow up. What would happen though is that the affected battery discarges much fater than the other, which would explain the "fadeout" after 1 Hour or so.
At any extent, if the circuit is wired as shown with capacitors in correct polarity then what you describe cannot happen... So there is a wiring fault somewhere, no idea where is the capacitors are not inserted with wrong polarity....
Ciao T
Elna Cerafine BOUM!
Last month I experienced a capacitor blow up when I switched on my Joplin amplifier the first time. The light blue cloud of thick smoke was very nice, but I was quite disappointed because it was an Elna Cerafine that I acquired to replace the cathode bypass capacitor.
It was wired correctly, since I installed another capacitor in the same way and it worked without problems. Do these problems happen frequently?
Carlo
Last month I experienced a capacitor blow up when I switched on my Joplin amplifier the first time. The light blue cloud of thick smoke was very nice, but I was quite disappointed because it was an Elna Cerafine that I acquired to replace the cathode bypass capacitor.
It was wired correctly, since I installed another capacitor in the same way and it worked without problems. Do these problems happen frequently?
Carlo
Thanks for replies
Yes, actually, one of the batteries is discharged much more than the other. The bulging caps are showing the same V as the more rapidly discharging battery. I have a power switch and led connected as shown (oh, now I see that switch is in the wrong place! - could that be the cause of the problems?? go easy on me please
)
Yes, actually, one of the batteries is discharged much more than the other. The bulging caps are showing the same V as the more rapidly discharging battery. I have a power switch and led connected as shown (oh, now I see that switch is in the wrong place! - could that be the cause of the problems?? go easy on me please
)An externally hosted image should be here but it was not working when we last tested it.
Ropie said:(oh, now I see that switch is in the wrong place! - could that be the cause of the problems?? go easy on me please
An externally hosted image should be here but it was not working when we last tested it.
You'd be better to use a double switch for + and - rails.
Use a resistor on the led
, and connect it between + and - rails.
carlosfm said:
You'd be better to use a double switch for + and - rails.
Use a resistor on the led
Thanks, Carlos. I see since I drew the diagram that a double switch is needed. The led actually has a built in resistor ( I suppose I should have shown it on the drawing) though shouldn't it actually go between + and 0V rails, or doesn't it matter?
bulging caps, possible cause
Hi, Ropie.
I have finished an El Cheapo phono pre a couple of days ago.
What a fantastic little preamp...
I was searching some topics about grounding and found this thread.
Time ago I had a problem similar to yours with the PS caps in my line preamp: the problem, apparently, was caused by the ubication of the on/off power switch. When it was connected after the rectifier -in the + dc line-, the spark caused by the operation of the switch apparently was very huge -very audible and annoying-; after a couple of days I noticed that the caps were bulging on top.
then I installed the switch on the 220 AC line, before the trafo, and with a 100n 400v cap across the terminals. The problem was over. Some time later I read something about that the arcing phenomena in switches is worst on dc than on ac. I don´t know really if it is so, but in my case the trick worked flawlessly
Maybe this information would be helpful to you. Cheers.
Hi, Ropie.
I have finished an El Cheapo phono pre a couple of days ago.
What a fantastic little preamp...
I was searching some topics about grounding and found this thread.
Time ago I had a problem similar to yours with the PS caps in my line preamp: the problem, apparently, was caused by the ubication of the on/off power switch. When it was connected after the rectifier -in the + dc line-, the spark caused by the operation of the switch apparently was very huge -very audible and annoying-; after a couple of days I noticed that the caps were bulging on top.
then I installed the switch on the 220 AC line, before the trafo, and with a 100n 400v cap across the terminals. The problem was over. Some time later I read something about that the arcing phenomena in switches is worst on dc than on ac. I don´t know really if it is so, but in my case the trick worked flawlessly
Maybe this information would be helpful to you. Cheers.
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