Hey everyone. I have the ms-22b with a pretty good hum and I also sometimes pick-up radio stations. I wanted to try the things mentioned here, but I needed a little clarification.
Earlier someone said they disconnected the yellow wire that was connected from board to chassis and the hum disappeared. Then he said he installed a mini 69 circuit to this wire between board and chassis. Does this mean he reconnected that wire? If so, why since it fixed the hum problem by disconnecting it? Is it safe to disconnect it?
Second, somebody split the incoming phono input ground leads. After I unsolder them, where do I then connect them to? Same place or somewhere different?
Thanks for the help,
Evan
Earlier someone said they disconnected the yellow wire that was connected from board to chassis and the hum disappeared. Then he said he installed a mini 69 circuit to this wire between board and chassis. Does this mean he reconnected that wire? If so, why since it fixed the hum problem by disconnecting it? Is it safe to disconnect it?
Second, somebody split the incoming phono input ground leads. After I unsolder them, where do I then connect them to? Same place or somewhere different?
Thanks for the help,
Evan
Hi Evan, personally I found the 69 circuit unnecessary if you isolate the input grounds. When you gain access to the rear of the RCA sockets you will find that on both the input and output sockets, the manufacturers have soldered the ground tags together and terminated both Black wires (one for each channel). What you need to do is temporarily remove the Black wires then unsolder the two tags away from each other. When you have done this, reconnect the respective Black wire to its Ground Tag. Hopefully the attached simple sketch will help you.
You may have a different issue with RF interference, this is not due to a Ground loop but something else. Have you tried using the Ground post on the MS22B as this may help. Les
You may have a different issue with RF interference, this is not due to a Ground loop but something else. Have you tried using the Ground post on the MS22B as this may help. Les
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Hi Les, thanks for getting back to me so quickly. The diagram seems pretty clear to me. So I won't be desoldering them from the board, but from the tabs at the jacks at the back of the unit?
The RF is less of a concern because I usually can't hear it unless my ear is near the speaker, also the hum drowns it out! I am using the ground post on the yaquin and it helps to slightly reduce the hum.
Evan
The RF is less of a concern because I usually can't hear it unless my ear is near the speaker, also the hum drowns it out! I am using the ground post on the yaquin and it helps to slightly reduce the hum.
Evan
Hi Evan, I did both input and output but the inputs are the important ones. You will not cure hum completely due to the power transformer magnetic fields inducing it into the front end Triodes. If you are lucky, you can prove this by vertically dangling a large screwdriver between the valves and the transformer housing, moving the screwdriver around and you will hear variations in mains hum level. At least you can reduce it to an acceptable level doing the wiring change. It is not a very clever design, which is one reason I re-designed it. Even the heater regulator is fed from the wrong place as it sees some of the smoothing capacitor ripple current - such a basic mistake to make with the PCB tracking!
Thanks Les, I just saw your post, but I went ahead and did both input and output last night. Glad to hear that's ok. After changing just the input grounds, the hum did not go away, but after doing the output too, it reduced it significantly to a level that I'm pleased with.
One other problem. I'm using a preamp/amp with home theater bypass and I get a really bad hum when it's on ht bypass with the yaquin ms-22 in the chain. Any other input is fine and it's gone if I unplug the Yaqin. Also, it disappeared when I used a cheater plug without a ground for the Yaqin, but after doing the wiring change on the pre the cheater plug actually causes a hum when playing lp's, so I ditched the cheater plug which I like anyways because it's safer, but now I stuck with unplugging the Yaqin when I watch tv or movies. Any ideas or just keep unplugging it?
Evan
One other problem. I'm using a preamp/amp with home theater bypass and I get a really bad hum when it's on ht bypass with the yaquin ms-22 in the chain. Any other input is fine and it's gone if I unplug the Yaqin. Also, it disappeared when I used a cheater plug without a ground for the Yaqin, but after doing the wiring change on the pre the cheater plug actually causes a hum when playing lp's, so I ditched the cheater plug which I like anyways because it's safer, but now I stuck with unplugging the Yaqin when I watch tv or movies. Any ideas or just keep unplugging it?
Evan
Hi Evan, it is hard for me to advise as I do not have enough information on your other units. Is the Home Theater Pre running on two core cable? If so, have you tried reversing the connection of the power supply? You may have to resort to something like this:-
Stereo Audio Isolation Transformer | eBay
I am considering the same myself to isolate the ground currents emanating from my PC.
Ground loops can be one of the most frustrating things to clear, the isolating transformer may offer a quick fix.
Les
Stereo Audio Isolation Transformer | eBay
I am considering the same myself to isolate the ground currents emanating from my PC.
Ground loops can be one of the most frustrating things to clear, the isolating transformer may offer a quick fix.
Les
Hi Les, I'm not sure what you mean by 2 core cable. All 2 channel sources run through a Peachtree Nova Pre/Amp/Dac, video sources run through a Pioneer a/v receiver and the receiver's L/R front outs feed the Peachtree's H/T bypass. If you mean 2 wire power cord, the Pioneer uses a two prong cord and the Peachtree uses 3 prong. The Pioneer connects to the Peachtree with RCA cables. Does this help?
Evan
Evan
I mean just the power cords as that is where you seem to have an issue. You are probably grounding a slightly hot signal ground to earth via the Yaqin. Have you tried reversing the Pioneer plug to see if that helps? I find the present practice of supplying audio equipment with just 2 core cable very hard to swallow. At the end of the day, if all of the connectors are isolated then fine, but most signals come out with a circuit ground which makes me think a Ground connection should be applied. When I first purchased my Yaqin amp, the whole metal chassis was floating! I warned Yaqin about this and from thenceforth all of their amps have a solid Ground connection. The bottom line seems to be that you have an earth current flowing down the screens of the interconnects due to a difference in potential between at least two of your units. If you can get hold of a power isolation transformer then you will not need a ground on the unit it supplies, hence you will not get a ground current flowing through the leads, that's another possible way of removing the ground hum loop.
Hi Evan, sorry about that, totally my ignorance. I thought you guys still used the straight two pin plugs. Not been to the States since my trip to San Francisco in 1970, must get over there again sometime. Been to Washington, Fort Lauderdale, Key West, Norfolk, Williamsburg and San Diego as well. But not Texas, one place I would like to visit before my curtain comes down 
I digress! - Do you still get the hum with the Yaqin plugged in but switched off? If so then the Yaqin is doing nothing more than provide another ground return for whatever other unit has a slightly hot chassis. This may be caused by the presence of, for example, suppressor capacitors in a unit especially if fitted with a switched mode power supply. Just keep trying various connection options but as stated earlier, you may need some ground breaking transformers to eradicate it completely.
I digress! - Do you still get the hum with the Yaqin plugged in but switched off? If so then the Yaqin is doing nothing more than provide another ground return for whatever other unit has a slightly hot chassis. This may be caused by the presence of, for example, suppressor capacitors in a unit especially if fitted with a switched mode power supply. Just keep trying various connection options but as stated earlier, you may need some ground breaking transformers to eradicate it completely.
Les, no problem. Texas is okay; I've been to most of the other places you mentioned and I'd say they're nicer.
I get a hum with the Peachtree in h/t bypass and the Yaquin plugged in and switched off. No other inputs on the Peachtree hum and it doesn't matter if the Pioneer a/v receiver is on or not. I haven't tried unplugging the rca's from pioneer to peachtree to see if it still hums when not connected. By the way, the hum does not increase with the volume.
Evan
I get a hum with the Peachtree in h/t bypass and the Yaquin plugged in and switched off. No other inputs on the Peachtree hum and it doesn't matter if the Pioneer a/v receiver is on or not. I haven't tried unplugging the rca's from pioneer to peachtree to see if it still hums when not connected. By the way, the hum does not increase with the volume.
Evan