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Post by darkarn on Apr 7, 2021 13:47:28 GMT
Looks like you need to run a wire from the RCA shield to ground. That can be safety ground, copper water piping or central heating with all metal piping. Seems risky since the closest ground I can think of is those on the wall sockets?
I am wondering if this is due to my volpot's wiring. I am using only one wire to connect both of its ground pins to the ground
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solderdude
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Post by solderdude on Apr 8, 2021 4:57:37 GMT
That can't be it. They are connected on the PCB anyway.
I would be more concerned about the long wires on the other pins of the volpot.
On the PCB these wires are kind of screened by the groundplane.
I would try to use the safety ground. Just buy a plug with safety ground pin and connect the safety ground to the RCA shield.
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Post by darkarn on Apr 8, 2021 6:06:53 GMT
That can't be it. They are connected on the PCB anyway. I would be more concerned about the long wires on the other pins of the volpot. On the PCB these wires are kind of screened by the groundplane. I would try to use the safety ground. Just buy a plug with safety ground pin and connect the safety ground to the RCA shield. The long wires you mentioned are for both channels; without them I cannot even hear any audio. I had to do it this way since I am not able to solder the volpot to the PCB due to blocked holes.
So am I right to say that it is either I try to clear those holes and solder the volpot to the PCB, or I use the safety ground method and connect to RCA shield (which RCA shield should I be using by the way)?
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solderdude
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Post by solderdude on Apr 8, 2021 16:59:44 GMT
Hard to say.
I would solder the potmeter wires as short as possible to the bad on the top side of where the potmeter was.
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Post by darkarn on Apr 8, 2021 19:17:10 GMT
Hard to say. I would solder the potmeter wires as short as possible to the bad on the top side of where the potmeter was. I see, I'll most probably want to work with a more proper soldering and desoldering station if I am going for this, so I am thinking of going with the safety ground idea you mentioned since that sounds easier for a temporary workaround
Which RCA shields should I connect the safety ground to?
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Post by solderdude on Apr 9, 2021 9:31:00 GMT
You can use the output RCA shields for instance as most folkd don't use these.
Just connect the shield of only 1 RCA to safety ground and see if this helps in your case.
It might, it might not.
When it helps make a more permanent cable/wire for it.
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Post by darkarn on Apr 9, 2021 9:44:04 GMT
You can use the output RCA shields for instance as most folkd don't use these. Just connect the shield of only 1 RCA to safety ground and see if this helps in your case. It might, it might not. When it helps make a more permanent cable/wire for it.
I am using the output RCAs to my powered monitors though (JBL LSR 305), won't that create a ground loop?
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Post by darkarn on Apr 9, 2021 18:54:53 GMT
I tried the safety ground idea, it didn't work
Right now the only way for the buzz to go away is if I hover my hand over the left capacitor
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Post by solderdude on Apr 9, 2021 20:37:55 GMT
Could be hum is picked up by the tube.
Relocating does not change this ?
Try placing the amp in a metal box (large tin can).
When possible connect an RCA shield with a wire to the metal of the box.
This way you can find out if it comes from external.
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Post by darkarn on Apr 10, 2021 10:52:36 GMT
Could be hum is picked up by the tube. Relocating does not change this ? Try placing the amp in a metal box (large tin can). When possible connect an RCA shield with a wire to the metal of the box. This way you can find out if it comes from external.
Unfortunately relocating didn't change it.
The largest tin can I have is not big enough for the amp and wires to fit in, so I used it to cover the top half of the amp (covering the capacitors and tube). This did not work too.
However, I replaced and resoldered the wires to the volpot so that they are as short as possible and free of oxidisation. I also used two wires instead of one for the ground pins of the volpot. The buzz is reduced, but still not eliminated. This meant that I am still unable to use the full volume range of the amp. What I noticed is that when I pressed onto the volume attenuator at the top right (e.g. to switch the volume attenuator on/off by moving the jumpers), the buzz get significantly louder
Am I right to say that if the volpot is mounted back to its original location, these will be resolved?
Will a linear power supply or atomicbob's Noise Nuke help too?
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Post by solderdude on Apr 11, 2021 15:58:49 GMT
The attenuator is the input signal. When you touch it you introduce hum so that's normal.
Can't say if placing the volpot back helps. Did you run a wire from the metal part of the volpot to the groundpad next to it ?
It is possible some of the hum comes in via the mains adapter. Can't say if this is the case here.
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Post by darkarn on Apr 11, 2021 16:09:07 GMT
The attenuator is the input signal. When you touch it you introduce hum so that's normal. Can't say if placing the volpot back helps. Did you run a wire from the metal part of the volpot to the groundpad next to it ? It is possible some of the hum comes in via the mains adapter. Can't say if this is the case here.
I have resoldered a new and sturdier piece of bare/non-insulated copper wire from the groundpad to the metal part of the volpot, still same issue |
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Post by solderdude on Apr 12, 2021 11:57:21 GMT
When touching the RCA shield does this reduce the same way as hovering above the capacitor/tube or touching the top of the capacitor ?
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Post by darkarn on Apr 13, 2021 21:13:06 GMT
When touching the RCA shield does this reduce the same way as hovering above the capacitor/tube or touching the top of the capacitor ?
It doesn't; touching the capacitors is the only way that can reduce the buzz on the left channel reliably.
Not sure if this is relevant, but if I do not plug anything to the RCA out jacks, there will be another kind of buzz that can be heard on both channels (on top of that buzz on the left channel)
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Post by solderdude on Apr 15, 2021 17:07:18 GMT
Buzz is on 1 channel only ?
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