Wah squeal with TB-pedals behind it turned of

nitefly7

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1,056
So this week I started noticing that my wah produces a squealing sound when in the heel-down pos when it's connected to my pedalboard interface (custom made, non-DIY, buffered input + fx-loop/patchbay + isolated tuner out).

Interface =
Guitar input
fx send (+ tuner out)
fx return
Amp output

The squealing sound goes away if I:
- connect my guitar -> wah -> to the ‘FX return’ jack
- use a buffer in front of the Guitar input (guitar -> wah -> buffer -> Guitar input)
- use a buffer in the interface loop (guitar -> wah -> Guitar input -> ‘fx in’ -> buffer -> ‘fx out’ -> Amp-output
- put a True Bypass pedal (Maxon SD9/Xotic SP comp) in front of the interface, with the effect on (guitar-> wah -> TB pedal turned on -> Guitar input -> ‘fx in’/‘fx out’ -> Amp output)

any thoughts on why the squealing sound occurs?
 

stinkfoot

Member
Messages
6,138
I wonder if you have crosstalk in the interface, which is resolved when you stick a buffer in between the wah and the rest of the chain. If you skip the guitar in -> fx send bit, and connect the wah directly to the first pedal, does it still squeal?
 

nitefly7

Member
Messages
1,056
I wonder if you have crosstalk in the interface, which is resolved when you stick a buffer in between the wah and the rest of the chain. If you skip the guitar in -> fx send bit, and connect the wah directly to the first pedal, does it still squeal?

Yeah, an answer from the guy that had taught me so much during these years of GAS :)

Turns out, while the interface is equipes with an isolation transformer for the tuner output, I didn't spec the interface to have a buffered in ...

Still; the squeal only occurs when I'm connected to the interface's input (and, also when I'm connected to the tuner output which is supposed to be isolated/parallel with the interface's output).
It's not there when I skip the guitar in -> fx send and plug into the interface's fx return (or again, the tuner out)
If I omit the interface and go straight into a chain of TB-pedals, I do notice a teeny tiny bit of high loss, but no squeal.

Could you lend me your wisdom on the following, while we're at it ;) ?
In my related thread, I've noticed that using a Visual Sound/Pure Tone buffer gives me back both my highs and takes away the squeal.
However, the VS buffer's input seems to be shorting out.
Instead of fixing it (not too sure where to check it/fix it) I got myself a CMAT buffer.
Only to find out the CMAT's jacks are ok (not shorting out), but it gives me a volume drop...
Aarghhh..
 

stinkfoot

Member
Messages
6,138
So you have an isolation transformer for the tuner out, but no buffer? That might be the problem - the wah circuit output is quite sensitive to the load it is asked to drive, and if the input impedance gets too low, it can react strangely. It's one thing you didn't specify a buffer, but why on earth would anyone offer to build an interface with a tuner out without one? That's not something you as a customer should have to specify - if you ask for a tuner out (that is to constantly be fed from the input), it should be buffered to stop the split from loading down the pickups. That is far more important than transformer isolation (which is more useful on the output, when splitting to two amps). Really odd, if you ask me.

Anyway, what happens when you skip the wah, and go guitar -> interface -> pedals -> interface -> amp? At best, if there is no buffer there, you should get the same amount of treble loss as when you plug straight into the first pedal. If you lose even more top end, the problem is definitely the interface loading down the pickups. In that case, most likely you will need a buffer before the interface (after the wah, when you are using it) if you're going to use the interface as a patching point for the guitar input -> first pedal connection.

Fixing the VS buffer shouldn't be too much trouble, if it's only the jack that needs tweaking. It could even be some component that is touching the inside of the box, in which case a piece of electrical tape to insulate that part of the box would do.
 

stinkfoot

Member
Messages
6,138
And yet... after having written all that, I noticed you said the squeal stopped when you turned one of the pedals on (after the interface). That sort of shoots a hole in my theory about the tuner out - if that transformer was the sole cause of the problem, the wah should squeal no matter what pedals you turn on/off later in the chain. The issue could still be the interface, but maybe not as clear cut. Still, if you can get that VS buffer up and running, that might be the best solution - having a buffer at the start (but after the wah) can be helpful even when there isn't a specific problem it's there to fix :aok
 

nitefly7

Member
Messages
1,056
I've opened up the VS buffer and tried to 'clear' the jacks from touching the enclosure and other stuff.
Otherwise I'll have to whip out the electrical tape for sure.
Any ideas about the CMAT's volume drop? Because I've kinda sold the Visual Sound on an eBay-affiliated channel :p
If the buyer doesn't come through, I'll keep the VS.
But the CMAT should act the same right?

Tack så mycket för att hjälpa :)
 

nitefly7

Member
Messages
1,056
I've contacted the dude that made the interface, and he thinks he might be able to fit a buffer in the current enclosure.
That would stop the squealing in his opinion.

But do you think the squealing will stop when we add the buffer to the interface?
Or should the buffer be further upstream, nearest the wah?

I've tried the buffer almost everywhere between Wah -> interface.
and I think I like it best directly after the Wah.
The CMAT buffer gives me a volume drop no matter where I stick it (...)

signal chain:
Guitar ->
'master looper' in (non-buffered, micro TB-looper for the whole pedalboard)->
Octafuzz -> Phase90(TB modded) -> Vertex wah -> SP Comp -> SD9 -> Green Rhino MkII-> Gain Changer ->
Custom interface in -> modded Boss FV-500L (non-Vertex ;) )
Arion SCH-1 (TB mod) ->
Flashback Triple (I think I have it on the non-TB/buffered bypass)->
HOF Mini ->
'master looper' out ->

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Iso-outs: Octafuzz, Arion, HOF Mini, Custom interface (sharing a 9v-iso with a Pitchblack Portable tuner), Flashback Triple (2 outputs combined), yet-to-buy Line6 M5
Daisy Chain: all drives + phase 90
 

stinkfoot

Member
Messages
6,138
Having the buffer right there in the interface is the best - that's where it needs to be, and while you could add a buffer outside of the box (immediately before the interface) and get the same result, having it built in is definitely the neatest.

If the CMAT buffer is transistor based (as opposed to IC/opamp), it will not get 100% unity gain. So there will always be a small volume drop. However, it should be small enough that you'd normally not notice anything (unless you start stringing together lots of such buffers in line). So if you're getting a clearly noticeable volume drop from inserting it in the chain, something's up with it.
 




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