Pitch block and wireless don't play well together (?)

Rex

Rex

Dignified but Approachable
Tonight I ran into what appears to be an incompatibility between the pitch block and my wireless unit.

I plugged my Ultra into the church's FOH tonight for a little tone tweaking. I fed the Axe-FX with my wireless unit (an Audio-Technica ATW-R14 operating on UHF) so I could walk the house and see what it sounded like from different positions.

All went as I expected until I pulled up a patch containing a pitch block. The patch is the stock Ballet Slippers preset with a low-level delay near the end of the chain to make it sound "more like the record." ;) When I struck the first chord, I heard a wavering quality in the sound. Now, I'm used to a little pitch hunting when playing chords through a pitch block, but this was different. This was a faster quivering that modulated the sound more deeply. The difference was obvious, and it didn't sound good.

I checked my tuning; I was still in tune. The battery in the wireless transmitter was fresh. On a whim, I turned off the transmitter and cabled straight into the Ultra — the problem vanished. I went back through wireless, and the problem returned.

I checked some of my other patches, comparing wired to wireless. In each case, the result was the same: my ears couldn't tell the difference between wired and wireless, once the Ultra's input knob was adjusted properly — except on that darn pitch block patch.

For what it's worth, I've got everything housed in a four-space rack. There's the wireless receiver in the top space, a Furman power unit below that, and the Axe-FX at the bottom.

I'm stumped on this one. Does anyone have an idea what might cause this?
 
Are you using the rear input? Make sure it's the left. Preferably go into the front.
 
Sounds to me like your wireless is putting out high frequency "trash" that's confusing the pitch module. If you have no luck with changing inputs try a low pass filter on the output of the wireless receiver. A first order filter with a resistor and a cap on the output of the receiver might solve the problem.

My cheapo Nady wireless puts out tons of garbage above the audio band that causes problems with my Digitech TSR-24 processor (an outdated but very flexible processor). I'm not familiar with your unit.

I would think that the AXE-FX would have an input filter to get rid of that junk before the audio hits the A/D, but perhaps it's somehow an induction into the digital circuitry that bypasses the input filtering.

I don't know. It just a wild guess. Putting a scope on the output of the receiver should tell you a lot if you have access to an oscilloscope.

Good luck!
 
Thanks for the quick reply, Cliff.

I plug my guitar into the front jack. The wireless unit is "permanently" patched into the right rear jack to avoid having to run a cable from the back of the rack to the front, and to allow me to switch between a solid-body and an acoustic without messing around with cables. I'd read in other posts that this was a workable solution, and it was, up until tonight.

What is it about plugging into the right rear jack that would cause me problems?
 
sampleaccurate said:
Sounds to me like your wireless is putting out high frequency "trash" that's confusing the pitch module.
Click to expand...
Wow... two instant replies! Thanks, sampleaccurate.

You may be onto something. If high-frequency junk could make it past the input filtering (I'm assuming that filtering is there; I don't know for sure), it might play heck with the digital version of the signal that feeds the pitch detector. On the other hand, the receiver was still on and connected to the Axe-FX when I cabled straight in, so it might not be a dirty signal.

sampleaccurate said:
...try a low pass filter on the output of the wireless receiver. A first order filter with a resistor and a cap on the output of the receiver might solve the problem.
Click to expand...
I'd rather not hang an RC circuit off the back of the receiver (need to shield it and such). Can you recommend reasonably-priced wireless rigs with clean output?

sampleaccurate said:
...perhaps it's somehow an induction into the digital circuitry that bypasses the input filtering.
Click to expand...
I would expect induction into the digital circuitry to cause all sorts of havoc, and not selectively target the pitch shifter.

Thanks for the advice.
 
Rex said:
Thanks for the quick reply, Cliff.

I plug my guitar into the front jack. The wireless unit is "permanently" patched into the right rear jack to avoid having to run a cable from the back of the rack to the front, and to allow me to switch between a solid-body and an acoustic without messing around with cables. I'd read in other posts that this was a workable solution, and it was, up until tonight.

What is it about plugging into the right rear jack that would cause me problems?
Click to expand...

Pitch tracking/Envelope detection isn't done on the right rear or effects loop. Just the front and rear left.
 
Thanks to everyone who chimed in with great ideas. I did some experimenting this evening, and here's what I found.

1) Hard-cabled into the front jack: Sounds fine. This was my control state;

2) Wireless into the left rear jack: Sounds fine. I couldn't tell it from (1);

3) Wireless into the right rear jack: Sounds crappy and quivery;

4) Wireless into either Input 2 jack: Sounds crappy and quivery;

5) Setting pitch source to Local Mono: Fixed the problem halfway — there's still some crappiness;

6) Setting pitch source to Local Poly: Fixed the problem almost completely.

So it looks like only the front jack and the left rear jack will work with wireless (at least with my wireless) on pitch-shifted tones, unless you choose the Local Poly pitch source. My experiments showed that pitch tracking — both local and global — is performed on all inputs, but with varying degrees of success.

I'm happier now,because I can still have an all-in-one dual-guitar rig without swapping cables, as long as I'm careful about selecting the pitch source (for this particular patch, anyway). And I don't have to throw away all the time I took cutting a patch cord to length, drilling internal holes in my rack, and routing the cord between side panels in the rack to keep it dressed out of the way of incoming power cords.

But I'm left with some questions: What's the root cause of the problem, why is the Axe-FX only susceptible to it on some of the inputs, and what is the secret sauce that makes some inputs immune? I'm inclined to concur with sampleaccurate's idea that ultrasonic noise at the output of the wireless unit confuses the pitch detector, and maybe only the front and left-rear inputs have adequate filtering to block the noise. But it's just guesswork. I don't really know.

Thanks again for all the quick and thoughtful help.
 
If you try a cable to the other inputs I think you'll rule out wireless as being part of the issue. It's purely based on which input is used because the global pitch detector only analyzes the left channel of input 1--either the front or the rear left jack.

With pitch tracking on, the block makes adjustments based on the detected note. The global detector isn't providing any useful info when the notes aren't arriving at the input it's analyzing. Local track modes use a L+R sum of the input to the block itself so that's why they'd usually be an improvement over global in this example.
 
Bakerman said:
If you try a cable to the other inputs I think you'll rule out wireless as being part of the issue.
Click to expand...
Now, why didn't I think of trying that? Thanks for pointing that out. I tried what you said, and sure enough, the problem is independent of whether I'm using wireless.

But there's still global pitch detection going on at those other inputs. The resulting notes are at the correct pitch. They're just warbly.
 
A fixed interval shift will always be at the correct pitch. That alone doesn't mean global detection is working. What tracking allows for fixed shifts is adjusting something (splice length, I'm guessing) based on the current note to reduce the warble you're describing.
 
Can you help me understand that better? I'm having a hard time understanding how a pitch block can produce the right pitch — with the global pitch source selected — unless it's detecting pitch.
 
I think it's something like this: Small chunks of audio have their speed changed then get pieced together to form the output signal. The old:new speed ratio is what determines the interval, and that's constant for a fixed harmony. Octave up is always 1:2, etc. Tracking allows additional fine-tuning of what's happening (maybe setting splice length to a whole number of cycles) but even when that's not working you still get a discernible pitch at the chosen interval.
 
I think I'm starting to get it. If I understand right, there's pitch detection at each input, but global pitch tracking is only applied to the left side of Input 1. Is that correct?
 
I've been using detection/tracking interchangeably. There's no tracking specific to any of the other inputs, just the option of local tracking when sending those signals to a pitch block.
 
recently something strange happened_ still related to a possible conflict between pitch block and wireless

I played my first gig using the new line6 g90 wireless and everything seemed fine

even feedback when needed was there etc etc
BUT when I moved into the "noise" section of whole lotta love, for which I use some patches heavy on delays and pitch shifting (that i got from this forum by the way) the sound wasn't quite right...I was getting a lot less.....well a lot less noise and it was coming out waaaay too calm....definitely not how it is supposed to sound. the particular effect generated by echoes and complex pitch shift was almost gone completely as the patches had been reduced to say 30% of their potential.

difficult to explain but it's as if the use of wireless creates a limitation to these particular patches...
the gig before I was using the same exact patches and setup, but a normal cable instead of wireless...

anyone had similar experiences?? :| :oops:
not quite sure how to solve this problem
 
The problem I was having turned out to be related to which input I was using, and not related to wireless at all. The front input and the left side of rear Input 1 worked fine. The right side of rear Input 1 gave me problems, unless I switched the pitch tracking to Local Poly (switching to Local Mono was a 75% fix for me).
 
I always use the front input

anyone else experience any chance of sound to any patch with pitch block in it using a wireless system?
 
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