I have recently built a preamp, 4 gainclones and a separate power supply.
I have included a rough schematic of the whole deal.
There are a few issues. There is a soft Hum when it is on. It does now change with the POT or the input, and the amps dont get hot, so I doubt that it is oscilation. Besides, it sounds like 60 Hz.
When I have all 4 amplifiers powered on, and have all 4 connected to the preamp, there is a hum. The buzz sortof depends on which of the amplifiers is connected. Since there are 4 of them, that leave 16 possiblibies, I did not try them all, but it changes depending on which ones are plugged into the preamp. I am guessing this is some sort of ground loop issue.
Also, if I connect the grounds of the two power supply circuits together, the hum gets louder.
Also on a side note, when I turn a fan on, on the other side of the room, I get a decently loud click through the speakers, and also when I turn the whole thing on, I get a pretty loud click as well.
If anyone could help, I would be very apreciative.
I have included a rough schematic of the whole deal.
There are a few issues. There is a soft Hum when it is on. It does now change with the POT or the input, and the amps dont get hot, so I doubt that it is oscilation. Besides, it sounds like 60 Hz.
When I have all 4 amplifiers powered on, and have all 4 connected to the preamp, there is a hum. The buzz sortof depends on which of the amplifiers is connected. Since there are 4 of them, that leave 16 possiblibies, I did not try them all, but it changes depending on which ones are plugged into the preamp. I am guessing this is some sort of ground loop issue.
Also, if I connect the grounds of the two power supply circuits together, the hum gets louder.
Also on a side note, when I turn a fan on, on the other side of the room, I get a decently loud click through the speakers, and also when I turn the whole thing on, I get a pretty loud click as well.
If anyone could help, I would be very apreciative.
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Hi Paul,
regarding the click on turn on, a 100nf cap (X2 type) across your power switch should solve it.
As for the clicks due to turning on other appliances, I had a similar problem. I tried the common mode supply filter mentioned here
and I found that it reduced the click quite a bit. But I had to power both the amp and the source (in my case a discman) through this filter. I used an inductance of about 2mH (calculated, not measured), and I guess a higher value would have gotten rid of the click completely.
Hope that helps.
- Ashwin
regarding the click on turn on, a 100nf cap (X2 type) across your power switch should solve it.
As for the clicks due to turning on other appliances, I had a similar problem. I tried the common mode supply filter mentioned here
and I found that it reduced the click quite a bit. But I had to power both the amp and the source (in my case a discman) through this filter. I used an inductance of about 2mH (calculated, not measured), and I guess a higher value would have gotten rid of the click completely.
Hope that helps.
- Ashwin
Hey matt, thanks for the tip.
I am not sure what you mean by it though. If you mean taking the earth connection on my AC input module and connectiing it to both the ground connections on the amplifier supply and the preamp supply... I have tried that, and the humm got louder. I will try again, but I am not sure if it will work.
Please specify if you meant somthing else...
Paul Hilgeman
I am not sure what you mean by it though. If you mean taking the earth connection on my AC input module and connectiing it to both the ground connections on the amplifier supply and the preamp supply... I have tried that, and the humm got louder. I will try again, but I am not sure if it will work.
Please specify if you meant somthing else...
Paul Hilgeman
no no...uh there are 3 connections in the all plug. The bottom one is the ground. Use an adapter to make sure that the ground connection never gets into the wall socket. ie...only the 2 "hot" prongs from the power plug actually get plugged into the wall.
http://www.partsexpress.com/pe/show...4&St3=-48068791&DS_ID=3&Product_ID=3050&DID=7
use something like this...its the fastest way to try it
-Matthew K. Olson
http://www.partsexpress.com/pe/show...4&St3=-48068791&DS_ID=3&Product_ID=3050&DID=7
use something like this...its the fastest way to try it
-Matthew K. Olson
And also possibly the most dangerousSorry Paul, only trying to help. I had a problem w/ ground stuff too in my gainclone a while back. MOAMPS suggested that try something.... is your hum more like a buzz or a hum? b/c I had a 120hz buzz i think...wasn't loud.... what I had to do was ground everything at 2 "star" grounds... this ended up being grounding the gainclone at the ground point on the power supply caps ...the 1kuf ones that are attached to the chip. Then I took 1 wire off of there and went to chassis...this is where the ground met w/ the power supply ground coming off the main power supply caps. In your case, if you aren't using big main ps caps, i think the ground would come from the middle of 2 bridge rectifiers. Anyway, i don't know if this'll help... hope its not as dangerous as lifting the ground from the wall.
-Matthew K. Olson
ps...i'll find a link for ya to that diagram
here
http://www.diyaudio.com/forums/show...d=13858&perpage=15&highlight=hum&pagenumber=2
-Matthew K. Olson
ps...i'll find a link for ya to that diagram
here
http://www.diyaudio.com/forums/show...d=13858&perpage=15&highlight=hum&pagenumber=2
moamps said:
Indeed, they do. But they are rigorusly tested to make sure that they meet the safety requirements. If you're not absolutely certain which tests are required to legally meet double insulated requirements, you don't have the test gear or knowledge. Earthed eqipment is much simpler.
Edit: This is serious. Don't ever remove earth bonds.
Ok... I sheilded my RCA cables, and added in the line filter. The clicks when I change the speed settings on my fan have been reduced. There is much less of a HF click when I change speeds, but there is still a click, maybe with the maximum frequency in the click being about 1000Hz.
The humm has gone way down, probably 10dB or so lower than it was, so low that I cant hear it at all from the listening position, or even from halfway between the listening position and the speaker. The only place that I can actually hear it is within less than 12" from the speaker.
so... thanks guys.
-Paul Hilgeman
The humm has gone way down, probably 10dB or so lower than it was, so low that I cant hear it at all from the listening position, or even from halfway between the listening position and the speaker. The only place that I can actually hear it is within less than 12" from the speaker.
so... thanks guys.
-Paul Hilgeman
ground loop
"We will want to ground the chassis to circuit ground, and for safety it is desirable to also earth
ground the system through the third conductor of the AC line cord. This occasionally results in
ground loop noise, and if it does, I recommend grounding the system to earth through a 10 ohm
5 watt resistor as an alternative to simply floating the chassis."
This is what Nelson Pass had to say about this issue, so there, maybe that helps.
"We will want to ground the chassis to circuit ground, and for safety it is desirable to also earth
ground the system through the third conductor of the AC line cord. This occasionally results in
ground loop noise, and if it does, I recommend grounding the system to earth through a 10 ohm
5 watt resistor as an alternative to simply floating the chassis."
This is what Nelson Pass had to say about this issue, so there, maybe that helps.
Safety issues
Please also read this thread:
http://www.diyaudio.com/forums/showthread.php?s=&threadid=18188
It has relevance to 2 pin mains issues, and conformance.
Please also read this thread:
http://www.diyaudio.com/forums/showthread.php?s=&threadid=18188
It has relevance to 2 pin mains issues, and conformance.
Re: Safety
I'm not too good with the techical terms. Circuit ground refers to the PCB grounds? And they both go to a 10 resistor (is 12 ohm okay?) and then to the star ground, where my earth ground goes to the AC line cord. Do I have this correct?
I'm asking because I had a slight buzzing noise from the tweeter and woofer on both channels and I tried to get it to go away. And relised my power strip (that my gainclone is plugged into) had no ground wire where it plugs into the wall (although all the plugs on the power strip have ground wires for some reason). So I plugged my gainclone into the wall and the slight buzz turned into a pretty loud and very noticeable buzz.
EC8010 said:
I'm not too good with the techical terms. Circuit ground refers to the PCB grounds? And they both go to a 10 resistor (is 12 ohm okay?) and then to the star ground, where my earth ground goes to the AC line cord. Do I have this correct?
I'm asking because I had a slight buzzing noise from the tweeter and woofer on both channels and I tried to get it to go away. And relised my power strip (that my gainclone is plugged into) had no ground wire where it plugs into the wall (although all the plugs on the power strip have ground wires for some reason). So I plugged my gainclone into the wall and the slight buzz turned into a pretty loud and very noticeable buzz.
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