M3500 & MSR-16 Noise

R

rorohello

Member
Hi you guys it's me again. Still having a blast with the m3500 and msr16 in my garage. Thank you for the help with the group's panning on the other thread.

My other question has to do with grounding. I have snakes connected on all 16 channels via the tape in and direct outs.

If I don't have the tape deck plugged in. There's absolutely no noise on the board. Either in the stereo mix or doing to group Outs to the TL Audio Summing mixer.

Soon as I plug the tape deck into my power conditioner however there's a very noticeable noise floor. This happens regardless of whether or not the tape machine is turned on. Unplug it and again back to total silence.

The tape machine is in a metal rolling rack. Am I supposed to try and ground the tape machine or the board in some way?
 
Describe the noise. Hum? White noise?

Am I correct in assuming the MSR-16 has a two-wire power cord without ground? And what about the power supply for the M-3500? The PS-3500? Is it also a two-wire power cord without ground?
 
Other things I can mention:

This is occurring with all of the effects sends muted. And all monitor channels muted except for the 6 channels active for the drum ebrain line ins.

If I have the tape machine plugged in. The noises there whether or not the record armed switches are engaged on 1-6 or not.

Noise also goes away if I bring down the channel fadees on all (1-6).

And again the board is completely silent with no noise if I just unplug the tape machine.
 
Also...when playing back from tape to the monitor channels it's much less noticeable..

I could live with it... But hoping there might be something easy I'm missing.
 
No. Even just a TRS to TRS or TS to TS cable…hell an RCA cable tip to tip will tell you if it makes a difference in the buzz. If there is a screw or binding post on the back of either labeled as ground touch the cable/wire to those, or find some point you know is actually bonded to the metal chassis of each. Your just trying to get the ground reference common between the console frame and the tape machine chassis. It should already be common because you said both have 3-wire power cords with ground, but I don’t know how they handled getting the PS-3500 chassis common with the console frame, nor can we verify without opening stuff up if the ground conductor of either power cord actually connects to the device chassis. You can test this with an ohmmeter or DMM set to resistance, measure between the chassis and the ground pin of the respective power cord. It should be a dead short. But before that it’s easy just to grab any length of wire or a cable and touch that from chassis to chassis with everything g powered up and monitor to see if the wire/cable contact between the device chassis’ makes any difference.
 
I had an EB Tech Hum X. Put it on the tape deck plug and problem solved.

I'll check threads here about grounding as I get more stuff unpacked.
 
Okay, so, yes you have a ground loop. Using the Hum X is NOT the right way to fix the problem…it’s fine as a VERY temporary measure, but the 3-wire power cord with ground lug is there for your SAFETY. The Hum X breaks continuity of that ground lug.

Is the console and tape machine connected to the same wall outlet?

What happens if you remove the Hum X, and connect a wire between the chassis of the M-3500 console frame and the PS-3500 chassis?
 
What ground lug? I don't see a ground lug on either the deck or the mixer.

What can happen with the Hum X installed long term?

They are connected to different outlets right now. I tried both ways before the Hum X and they both had the noise.
 
rorohello said:
What ground lug? I don't see a ground lug on either the deck or the mixer.

What can happen with the Hum X installed long term?

They are connected to different outlets right now. I tried both ways before the Hum X and they both had the noise.
Click to expand...
The ground lug or prong of the power cable. Re-read my post.

If you don’t have a dedicated ground point on any of the chassis then you just have to figure it out.

What can happen long term if you use the Hum X? Again, re-read my post. The ground conductor is there for your safety. If you use the Hum X and there is a failure, partial or otherwise, of your building AC power neutral leg, and the device is not grounded, you’re at risk for being the neutral leg and having current flow through you. That’s what the ground is there for.

The Hum X is a band-aid fix of the worst kind in my opinion. If you’re comfortable with the risk and the band-aid approach, then that’s you’re prerogative. But I don’t recommend it.

EDIT: I stand corrected…the Hum X “works by placing the unit on the end of the power cord of the equipment that has a ground loop and then plugging the Hum X into any standard 15 amp outlet. The Hum X filters out unwanted voltage and current in the ground line that cause ground loop hum, while simultaneously maintaining a solid, safe ground.”

So you tried plugging the console and the tape machine into the same wall receptacle and you still had the hum issue?

I’m curious to know what happens if you try my suggestion, remove the Hum X and bond the power supply chassis to the console frame with a wire. And if that does nothing also try it the other way, bond the console frame to the tape machine chassis with a wire.

Bottom line, you have either an audio ground loop issue, or a voltage differential between your chassis. That *should* be mitigated by the fact both devices (the console power supply and the tape machine) have 3-wire power cords with a ground conductor, but, again, we don’t know how the ground conductor is bonded to each chassis, and we also don’t know if the console frame is bonded to its power supply chassis. I have to look at the schematics to see how this was handled, at least on paper.

Again, if you’re okay with band-aid, I’ll save us both time trying to rectify the issue.

But if you’re interested in trying to resolve the issue in a more correct way that maintains safety and affords relatively noise-free audio, I’m willing to try and help.
 
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sweetbeats said:
What happens if you connect a wire from the tape machine chassis to the console chassis?
Click to expand...
Here’s the one piece of advice that is the easiest to try, but hasn’t been yet. (AFIK)

Don’t have wire?

Yes you do ;)

You gotta at least have a guitar cord.
Just touch the tip to the chassis of the mixer and the other tip to the chassis of the MSR16
 
Ok I will try it today.

Yes, the noise was there when connected to the same outlet and to different outlets.

The Hum X has 87 positive reviews on Sweetwater and is currently out of stock there. It has 4 out of 5 stars out of 780 on Amazon.

They have been sold in the U.S. now for over 20 years.

I think if there was a safety issue with it, there would be something negative written up somewhere right?
 
Okay I stand corrected and I’m editing my post above…the Hum X “works by placing the unit on the end of the power cord of the equipment that has a ground loop and then plugging the Hum X into any standard 15 amp outlet. The Hum X filters out unwanted voltage and current in the ground line that cause ground loop hum, while simultaneously maintaining a solid, safe ground.”

So you still have your safety ground, and your noise is gone.

So if you’re good with that then you’re done.

I just know I wouldn’t be.

It gets good reviews because it works. But that doesn’t exonerate the fact it is a band aid fix to a fundamental problem in your ground scheme, and me personally I want to address the root cause, not band aid fix it. But there are lots of folks such as yourself that are happy to put the band aid on and move forward, and, as I said earlier, that is totally your prerogative…no judgment here, that’s just totally not for me.

Glad you had a solution.
 
I read and value your posts across many of my machines Sweetbeats. So I will investigate a more thorough solution.

I first still have to think through layout and workflow in this garage!
 
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