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Old 24th November 2012, 11:08 AM   #21
syklab is offline syklab  Hong Kong
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Quote:
Originally Posted by MagnumOpus View Post
Actually, both channels are humming, but it's barely audible, and not with stuff playing.
Can you post some picture of your power supply module and the amp board with all the hockup wire.
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Old 27th November 2012, 02:26 AM   #22
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The suspense! My question, his question, a race against time.
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Old 27th November 2012, 02:50 AM   #23
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Hi,
Read the voltage of both rails with the voltmeter selector switch in AC. It will tell you if you have ripple in the PS supply. The reading should be almost zero. Hold the probe until the reading settle. It takes some time to settle.
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Old 29th November 2012, 05:13 PM   #24
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I am so busy with work and training these days, thank you guys for your response. I will check as soon as I have the time, and post some pictures
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Old 20th December 2012, 08:25 PM   #25
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If I replace the input resistor with an LDR will it still provide the same protection? I could always put the resistor inline with my pre-amp, for plugging in "unsafe" things I guess.
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Old 22nd December 2012, 01:40 PM   #26
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Ok, time to install a switch.

How the hell do I hook this up?

Boutons ON/OFF Bipolaires - Bouton On-Off INOX 250V 3A
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Old 22nd December 2012, 02:40 PM   #27
wlowes is offline wlowes  Canada
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Default hum and hiss

Quote:
Originally Posted by MagnumOpus View Post
Actually, both channels are humming, but it's barely audible, and not with stuff playing.
Your physical layout likely produces the hum and hiss. You have the signal running past the power supply and transformer to the amp and then back past all of that to the speaker posts. Anywhere you run unshielded signal wires in close proximity to AC you will likely pick up AC noise on the audio circuit.

2 things will likely help if you want to keep this layout.
First, all your AC wires should be twisted. This will cancel out common mode noise.
Second, be sure to keep as much separation from the signal wires away from the AC. If there is still some noise, use shielded wire for the small signal wire and keep lots of separation from the speaker wire and the AC.

I have a Peter Daniel amp that is so quiet you can literally put your ear to the speaker at full volume and hear nothing. The quieter you make this amp, the better the music will sound. I actually used a block of thick copper for the heat sink and laid it out such that the signal section was on one side of the copper and the AC on the other. Worked perfectly for past 5 years making very good music.
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Old 22nd December 2012, 03:19 PM   #28
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Quote:
Originally Posted by wlowes View Post
Your physical layout likely produces the hum and hiss. You have the signal running past the power supply and transformer to the amp and then back past all of that to the speaker posts. Anywhere you run unshielded signal wires in close proximity to AC you will likely pick up AC noise on the audio circuit.

2 things will likely help if you want to keep this layout.
First, all your AC wires should be twisted. This will cancel out common mode noise.
Second, be sure to keep as much separation from the signal wires away from the AC. If there is still some noise, use shielded wire for the small signal wire and keep lots of separation from the speaker wire and the AC.

I have a Peter Daniel amp that is so quiet you can literally put your ear to the speaker at full volume and hear nothing. The quieter you make this amp, the better the music will sound. I actually used a block of thick copper for the heat sink and laid it out such that the signal section was on one side of the copper and the AC on the other. Worked perfectly for past 5 years making very good music.
Thank you I will perhaps try something later on when I install the power switch.
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Old 22nd December 2012, 07:18 PM   #29
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I put the AC socket on the front of the amplifier to keep it away from the signal.

Twisting wires doesn't actually stop common mode noise, but it lowers peak common mode noise which is the most offensive (subject to phase shifting etc). Twisting wires in power cords even for regular 60hz is desirable for the same reason, common mode noise or not. There is a canceling affect of the shifted signal.

That power button in the link. Wire the incoming positive to C1, and then the out going positive to NC1. NC1 stands for normally closed (off), but you can turn it on. Then if your transformer puts out 24v or less, you can attach V+ and PG+ to the LED.
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Old 23rd December 2012, 02:07 AM   #30
wlowes is offline wlowes  Canada
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I made a power cord described in TNT audio. Basically heavy gauge wire twisted, inside a tube with safety ground outside twisted in opposite direction. Easy to see it makes a strong improvement on this amp. Still I had missed the twisting of AC wires from IEC socket to transformer and on to rectifiers. This too made an easy to hear improvement.
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