Increased noise floor when running thru PBC...

R

Raynov1

Member
I've noticed that when i run through the PBC i have an increased noise floor. I have it setup with the first 6 loops in front and the last 4 in the loop. Even when only running the front 6 (with none of the loops on) the noise floor is increased. I've tried turning off the buffers and such but it makes no difference.

My amp setup is a Mesa Triaxis preamp and a Mesa 2:90 poweramp. Signal chain: gtr > wah > into PBC 1-4 > various pedals in 1 thru 6 > 5-6 out to input on Triaxis > 2:90 power amp. (Omitting 7-10 going to loop on Triaxis in this example)

Even with nothing connected to any of the 6 loops and the loops off, just Gtr in 1-4 then 5-6 out to input of Triaxis, the noise floor is noticeably increased.

Any thoughts on why? Or anything i can try to minimize it? I dont typically run a noise gate as its not bad even on high gain patches....but with the increase in the noise floor i think I'll have to....
 
It's almost like a ground loop kind of sound. I recorded it with a video camera. The camera leveled out the without/PBC (made a bit louder) and the with/PBC (made a bit quieter) so they sound like they are the same volume on the clip.....but the 2nd half of the clip starting at ~:36 second mark is actually louder in person. The Triaxis isn't actually a very quite preamp on high gain sounds so i do get a manageable amount of hiss but you'll hear past the :36 second mark that it's definitely a different (and louder in person) sound just running through the PBC with all loops off and all buffers on (or off, makes no difference). See youtube clip below.

 
I tried some different cables and different outputs on the PBC and one interesting thing is if i go in to the 1-4 input and out the A output, so all 10 loops in front of the amp.....the amount of hiss added is crazy. Switch back to either of the other outputs, 1-4 out or 5-6 out, and its back to what you hear in the clip.

My setup previous to this was going out of the Triaxis into a GCX which has an Eventide 4000 and a TC G Major in the loops then out to the 2:90 poweramp. No added noise running that. I'm trying to go smaller with the PBC and run a couple of Factor pedals and eliminate the heavy rack cases :)
 
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How are you powering the PBC? What happens if you go into In 7-10 and use output A?
 
I've powered it with either the power supply from one of the Eventide pedals, which is 12v and 1200ma i believe....and also with an Eventide PowerFactor version 1 (Cioks) 12v outlet.

I haven't tried using 7-10 in front of the amp. I've used 7-10/out A in the loop and i dont notice any noise using a TimeFactor in parallel.

I'm going to pick up a Voodoo Iso 5 (i need a couple more outlets) and it also has a 12v outlet.

Think its power related? I know that can cause noise if I'm not powering it correctly.... or maybe its just a ground loop and maybe i need to lift the ground on the my pedalboard powerfactor power source?
 
It could be either issue - I would start with guitar into In 1-4 and Out 5-6 into amp, nothing in the amp's effects loop, nothing in the PBC's loops. Make sure that's not noisy first - if it is noisy, then it's either the PBC or the power supply. The ISO 5 will be a good thing to test with - the Voodoo Lab supplies with 12VDC/400mA output are pretty quiet.
 
Ok so i picked up an ISO 5. Powering it from that made no change. Sounded the same as when i was using the PowerFactor (Cioks). What i did try that seemed to work was i had a Behringer HD400 Hum Destroyer laying around and added that between the 5-6 out and the Triaxis input and also between A out and the Triaxis loop return (configuration was PBC loops 1-6 in front of amp, Loops 7-10 in loop). That seemed to quiet things down a lot.

If i didn't run it in both places, before Triaxis input and before Loop return on the Triaxis, I got that noise/hum back. I guess it's possible to have a ground loop in more than one spot?

Knowing now that seems to be the issue, is using the Hum Destroyer (or similar) my only alternative? Or are there other things i can try?

If something like the Hum Destroyer is my only alternative, I know Ebtech and Radial also make units as well (more expensive), didn't know if there were any quality or sound benefits between the Behringer and Ebtech or Radial. I try to stay away from Behringer as, in my experience, it usually doesn't hold up through continued use but this seems to be such a simple thing, didn't know if it mattered.
 
Definitely if the transformers helped, then it was a ground loop. You can continue to use the transformers for sure. I haven't tried the Behringer unit, but most of the other ones seem pretty similar, with the exception of the Radial units. They use the larger and more expensive Jensen transformers, which have a better frequency response than the cheaper transformers. Although, for guitar purposes, the cheaper ones still work pretty well. The output B jack on the PBC uses one similar to what you find in Ebtech.

Another option is to make cables that have the ground disconnected on one end. This should also solve the problem. The advantages of this approach are that you don't need to buy transformers, and that there are no tone coloration issues. The disadvantages are that you now have special cables you have to keep track of, and some have told me that this approach can add a little noise of its own (although I have yet to hear such noise).
 
An update....i ended up not using the Behringer unit as i found it was causing signal attenuation. Not sure if it was the unit i had was defective (it's pretty old and has been bounced around a lot) or if that is just how they are. I re-routed all the audio cables away from all the power cables and got it so i only needed to use a transformer in one place (5-6 out) instead of two (5-6 out in front of amp and A out for the loop). I ended up using an RJM Tone Saver and used the ISO output (5-6 out - into Tone saver - ISO out on Tone saver - to Input on amp). No more signal attenuation and no more buzz. Looks like it's all good.

Used it live last night for the first time and everything was as quiet as it normally is....

Also, in my testing i found that the loud hiss i was getting when running all 10 loops in front of the amp (nothing actually connected to the loops as i was just trying to isolate the ground loop) was caused by loop 10 being set to parallel. Apparently if that loop is in front of the amp, is in parallel mode and nothing is connected to it, it adds hiss (at least in my case). Changing it back to series made the hiss go away. I'm assuming this goes for any of the other loops that can be set to parallel. I don't think that is actually a problem with the PBC, but if anyone else happens to find extra hiss maybe that is something to look for (empty loop in front of the amp set to parallel).
 
Glad I found this thread. I recently got a PBC. Initially my display screen was a bit wonky ito how the information was displayed. I was informed that I needed to adjust the contrast to improve the visibility. I basically had to set it to 100% so that i can see all areas of the screen, otherwise it was kind of disappearing on the corners.

That being said i recently acquired a custom junction box designed by @Goodwood Audio and experienced an increase in floor noise through the PBC. After re-wiring the whole board and going through quite a bit of tests I found that the noise came / was generated through the PBC. Similar to the above scenario when running through the PBC alone, therefore no loops activated I get increased noise. Testing guitars straight into amp was fine, but as soon as I go through the PBC in and utilise either the Out1/4 or 5/6 or A/B I experienced increased noise, regardless of the buffers been switched on or off. I also utilised the junction boxe's ground lift switch to no avail. So I'm wondering whether the PBC is actually faulty or is there something else at play here?
 
Pieter Hefer said:
Glad I found this thread. I recently got a PBC. Initially my display screen was a bit wonky ito how the information was displayed. I was informed that I needed to adjust the contrast to improve the visibility. I basically had to set it to 100% so that i can see all areas of the screen, otherwise it was kind of disappearing on the corners.

That being said i recently acquired a custom junction box designed by @Goodwood Audio and experienced an increase in floor noise through the PBC. After re-wiring the whole board and going through quite a bit of tests I found that the noise came / was generated through the PBC. Similar to the above scenario when running through the PBC alone, therefore no loops activated I get increased noise. Testing guitars straight into amp was fine, but as soon as I go through the PBC in and utilise either the Out1/4 or 5/6 or A/B I experienced increased noise, regardless of the buffers been switched on or off. I also utilised the junction boxe's ground lift switch to no avail. So I'm wondering whether the PBC is actually faulty or is there something else at play here?
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I'm actually having the same issue with my set up.

I use "silent" 4/5 cable method set up where the first 6 loops are run into the front end of an amp which is then sent to a load box and speaker sim unit (two notes torpedo captor X) which then gets sent back to loops 7 - 10 and lastly out in stereo. I get an increased noise floor (about -40db) when Im plugged into the first 6 loops, but get no noise floor increase when I plug directly into the amp (which gets routed back into 7-10). I tested by plugging my guitar directly into the input of the PBC, disconnecting all cables, and going directly into the amp after loop 6 and get the increased noise floor. The unit is powered by a Strymon Zuma, 9V 500ma.

I also went ahead and tested using a DI box with a ground lift switch, which decreased the noise, but also attenuated the signal by about 10 - 15db.

At this point I think that I've isolated it to the noise coming from the PBC at the first 6 loops, is there anything I can do to mitigate this?
 
JamesCardoza said:
I'm actually having the same issue with my set up.

I use "silent" 4/5 cable method set up where the first 6 loops are run into the front end of an amp which is then sent to a load box and speaker sim unit (two notes torpedo captor X) which then gets sent back to loops 7 - 10 and lastly out in stereo. I get an increased noise floor (about -40db) when Im plugged into the first 6 loops, but get no noise floor increase when I plug directly into the amp (which gets routed back into 7-10). I tested by plugging my guitar directly into the input of the PBC, disconnecting all cables, and going directly into the amp after loop 6 and get the increased noise floor. The unit is powered by a Strymon Zuma, 9V 500ma.

I also went ahead and tested using a DI box with a ground lift switch, which decreased the noise, but also attenuated the signal by about 10 - 15db.

At this point I think that I've isolated it to the noise coming from the PBC at the first 6 loops, is there anything I can do to mitigate this?
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You sholdn't be getting that much noise. What happens when you turn off buffer #1?
 
rjmmusic said:
You sholdn't be getting that much noise. What happens when you turn off buffer #1?
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Thanks for getting back.
when i turn buffer #1 off there is no change in sound. This also goes for the other two.
I tested out a few more things tonight:
If i plug my guitar directly into the amp and have the amp/cab sim routed to my pedalboard i get no noise, the moment i add the PBC to the input of the amp the noise comes back.

also when i jumper the send (to amp input) and receive (from amp cab sim) and run the whole board into the front end of the amp I don’t get the noise.

my next step is to get a ground isolation box and test out various points where I can isolation noise from to see if that will help as well.
 
Ah, I had assumed that you were talking about hiss, but it sounds like it's hum. Hum is pretty much always a grounding issue, and the results you reported seem consistent with that. First thing to try is move the connection to the amp's loop return from Out A to Out B on the PBC (if it isn't there already), and turn on the Iso B and Mono Output switches. That will add isolation to the return connection. If that's not enough, you may need to add a second isolation transformer between the amp send and In 7-10.
 
Having the same exact issue/noise problem with my RJM PBC 10. Ground loop noise problems for sure between PBC and Amp. Signal flow looks like this:

Guitar
-> buffer
RJM PBC10
L1 - Cali76 compressor
L2 - PitchFork
L3 - empty
L4 - empty
OUT 1-4/IN 5-6 - Volume pedal (Getting ground loop hum)
L5 - empty
L6 - empty
OUT 5-6/IN 7-10 - Diezel VH4S Amp Parallel FX Loop Send (getting ground loop hum)
L7 - Mobius (parallel)
L8 - Timeline (parallel)
L9 - Bigsky (parallel)
L10 - Mercury 7 (parallel)
OUT A/B - Diezel VH4S Stereo Parallel FX Return (Getting ground loop hum)

The ground loops are happening between the send returns to the amp, and a strange noise through the volume pedal, but only when sweeping the volume pedal in between full on and off positions. Looks like a total of 4 points for potential ground loops. So temp solution for now is my pedalboard guy is gonna try adding ground lifts for each in/out through my custom built input/output box on pedal board that goes to and from amp...thats the cheapest solution at the moment, then may try adding transformers from there if needed. And still utilizing the ISO button on PBC as well. Kind of a bummer :(.
 
UPDATE: Ground Lift switches turned on on all of my send/returns to amp(minus the input to amp, which is the main ground) solved all the ground loop noise issues.

Nick
 
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