Audio Interference on MS-100BT- troubleshooting log

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stubbsonic
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Re: RF interference solutions? Ferrite bead?

Post by stubbsonic » Fri Mar 16, 2018 12:09 am

The isolation transformer arrived just in time for me to try it this evening. The short report is that it DID seem to work! (YAY!) Because of the nature of the venue and the show, I didn't have a good opportunity to test it intensely, but I heard no wireless coming through my system when I used my boosted sounds.

However, one downside with the product I got (PylePro PHE400) is that all the high end went away (dramatically!) and I lost a lot of level. I was able to do a radical shape on the graphic EQ (basically a diagonal line from lower left to upper right); and got it to sound reasonably good (still with some loss at the very upper end).
Last edited by stubbsonic on Fri Mar 23, 2018 1:13 pm, edited 1 time in total.
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Re: RF interference solutions? Ferrite bead?

Post by NucleusX » Fri Mar 16, 2018 10:07 am

First thing i would do is contact Pyle Audio for more information as to why this might happen.
From what i see, the PHE400 has no power, so no buffer. Maybe you should look into one of
the Radials, as they include buffering in some of their better loop/routing pedals. I know you
own the Radial BigShot EFX, but it might've been the wrong weapon of choice. These things
can be difficult to solve, so i think the key here will be patience during your trial and errors.
Maybe you should try the G3n or G5n, it might eliminate the need for all this MS-100BT effort.
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Re: RF interference solutions? Ferrite bead?

Post by stubbsonic » Sun Mar 18, 2018 8:24 pm

I contacted Pyle (no word yet from them).

I also contacted Radial and their response suggested that the signal & tone loss was probably due to an impedance issue, and "loading on my pickups"-- so a buffer would help with that. I have a Fulltone 2B so that should sort the tone loss issue. He said that the Pyle used a lower quality transformer so he suggested that if I wanted something with better fidelity to try something called an SB-6 (stagebug) which is a dedicated isolation transformer for about $100. I was able to return the Pyle transformer and get the SB-6 instead.

As a side note, I have already ordered a G3n which (if it doesn't have the same issue) will actually be a little better for these theatre gigs-- especially when it comes to choosing between patches (the MS-100BT is a little clunkier for patch changes).

However, I want to continue to experiment and solve the issue as I really like the MS-100BT and would like to continue to be able to use it at this gig.
Last edited by stubbsonic on Fri Mar 23, 2018 1:16 pm, edited 1 time in total.
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stubbsonic
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Re: RF interference solutions? Ferrite bead?

Post by stubbsonic » Fri Mar 23, 2018 12:24 am

I tried the StageBug SB-6, but unfortunately, the issue returned. I tried it with the above mentioned signal path (a buffer out front) but it didn't help.

Since it is a stereo isolation transformer, I also tried putting the left channel before the input side, and the right channel after the output side-- isolated on both sides-- still no help!!

I'm pretty sure that the cheaper Pyle iso worked, apart from the loss of level and tone/impedance issue. Ideally, I should have tried the Pyle iso with the buffer, and called it a day if it worked. But I returned it too quickly! (Assuming if the Pyle worked, the Radial would work better).

After tonight's show, I tried using the SB-6 without the buffer, and it actually sounded pretty good and maintained most of the level but I wasn't able to test the issue at that time. So I may try that on the next show to see if that helps at all.

For any of you who are tracking this saga, I do now have the G3n that I can also try out, but I wanted to see if I can resolve the MS-100BT issue--
Last edited by stubbsonic on Fri Mar 23, 2018 1:19 pm, edited 1 time in total.
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NucleusX
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Re: RF interference solutions? Ferrite bead?

Post by NucleusX » Fri Mar 23, 2018 9:42 am

With passive pickups (no buffering), the resistance of them increases with more coil winds. If the pickup is wound too
much with too much resistance, inductance starts to rise and changes the reactance and impedance characteristics of
your input circuitry. It basically creates its own filter, and translates that to a drop in high end. Seems the same thing
is happening to you with your transformer, as its also subject to the same principles. I think the solution here will
require buffering at some point. Doesn't matter where you end up in your journey, as long as you keep posting your
progress during the process. People reading this can learn all sorts of things from it. Thanks for the updates.
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stubbsonic
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Re: Audio Interference on MS-100BT- troubleshooting log

Post by stubbsonic » Mon Mar 26, 2018 10:36 am

I've updated the original post of this thread, and will give a few more details here.

Yesterday before my show, I met with the sound guy and we tinkered with the guitar rig & sound system. A major revelation was that the bleed coming into my guitar rig was not limited to wireless mics, but was coming from the entire house mix (apparently), including wired mics.

I placed isolation transformers at various points in my signal path: pre and post MS-100BT, or between the feed from the direct out on my amp and he house; with or without lifted grounds. None of these got rid of the issue.

Plan B was to use the G3n which I had just ordered instead of the MS-100BT. I could tell the issue was not gone, but the level of the "bleeding" signal was noticeably lower. It was low enough to not cause the issues it caused with the MS-100BT (feedback during boosted solo moments). So that's what I used in the show last night and it was fine.

The fact that this signal is somehow coming through the rig-- raises several new questions:

1. How is the signal coming in to my guitar rig?
2. Why is it worse with the MS-100BT?
3. Is there a possible solution that will improve it so either MS or G3n will not have ANY sound system bleed?
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Re: Audio Interference on MS-100BT- troubleshooting log

Post by stubbsonic » Wed Mar 28, 2018 3:13 pm

After realizing that the sound "bleeding" to my amp is "the general mix", it occurred to me that some theaters have a secondary system for the hearing impaired. I asked the sound guy and he confirmed this to be the case.

They have a system called an "induction loop" (also called a "Hearing Loop") that broadcasts to hearing aids and to special boxes that audience members can borrow. He also said there is a wire that is supposed to block those magnetic signals from getting to the stage. After a little research I think that blocking wire is called a "cancellation loop" which, I theorize might carry an out of phase version of the signal-- which, itself, could be picked up by my pedal.

Right now this is my #1 suspect. I think if I can learn a little about this broadcast format, I might be able to block it more effectively.
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Re: Audio Interference on MS-100BT- troubleshooting log

Post by stubbsonic » Thu Mar 29, 2018 9:07 am

Ok. It's an induction loop. [see above, and I've updated the first post].

Crazy idea. Get one of the hearing-assistance receiver boxes from the front desk. Then, using a passive mixer, input my pedal in one channel, input the receiver box into another channel but invert the phase of receiver input, then carefully find perfect cancellation level.

(It's possible that I wouldn't need to invert the signal, depending on how my guitar coils affect the phase of the signal).
Last edited by stubbsonic on Thu Mar 29, 2018 1:24 pm, edited 1 time in total.
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Re: Audio Interference on MS-100BT- troubleshooting log

Post by Jim_Fogle » Thu Mar 29, 2018 10:44 am

Zoetrop, please delete this post. I've tried and received the error message I can not delete posts.
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Re: Audio Interference on MS-100BT- troubleshooting log

Post by stubbsonic » Mon Apr 16, 2018 1:56 pm

The problem signal vanishes when I use the selector positions 2 & 4 on my strat. So it is a single coil issue. However, my bass, which has humbucking sidewinders, still exhibits the problem.

That said, I'm intrigued about trying a dummy coil. That's were you put a pickup without pole pieces into the guitar and near where you want cancellation. I think for the amount of time and hassle, it might make more sense for me to pick up a different strat with noiseless pickups. I do love my strat and would miss it, but that does seem like a relatively painless solution.
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