Lehle P-split3 reamping noise issue

[Humbug]

Greetings. I'm having issues that I can't figure out and I'm hoping you might help me understand what's going on.

I'm using a recently acquired Lehle P-split III as a reamping box. It's connected to a line out of my vintage Focusrite Scarlett 18i20 gen 1via a balanced TRS cable. The ISO connector on the Lehle is then connected to the amp input via unbalanced TS cable. I did a quick reamping of one of my lower gain amps with this setup and the noise floor was pretty good. Not perfect, but manageable. Trying to reamp one of my higher gain circuits with this setup is impossible.

If I remove the P-split and use the opamp buffer I have been using, this noise goes away completely. If I use an unbalanced connection from the interface to the Lehle, the noise is reduced. If I use the "dir" connector on the Lehle into the amp, the noise is reduced. The ground and phase switches on the Lehle have little to no effect. Moving the units away from each other has no effect.

Why does the P-Split seem to amplify white(ish) noise in my setup? Why do all the things that are supposed to be better make it worse??

I have no idea what's going on here. Help?

 

[Eagle]

I have only used the 2 but it sounds exactly like the original signal and prevents additional noise because of ground a phase problems. See if it works properly in other applications.

 

[Humbug]

See if it works properly in other applications.

I was frustrated enough to not think of that Thanks!

 

[Sascha Franck]

According to Eagle that just can't be.

 

[Humbug]

According to Eagle that just can't be.

Ok, that's funny, but I need you to keep the bickering (sp?) out of this thread. I need actual help with this issue

 

[Sascha Franck]

Ok, that's funny, but I need you to keep the bickering (sp?) out of this thread. I need actual help with this issue

Yeah, I know, pretty sorry (honestly!), but it was just too tough so I CNR.

 

[Sascha Franck]

Fwiw, did you try without any extra things in the signal path? Straight from the interface into the amp?
I once got pretty decent results that way (obviously, level checking is crucial), but perhaps that's beyond the point already, you will at least have one more information about where the noise is added.

 

[Eagle]

The passive p split can only deal with phase and ground isolation. If the buffer works better just use it.

 

[laxu]

If I remove the P-split and use the opamp buffer I have been using, this noise goes away completely. If I use an unbalanced connection from the interface to the Lehle, the noise is reduced. If I use the "dir" connector on the Lehle into the amp, the noise is reduced. The ground and phase switches on the Lehle have little to no effect. Moving the units away from each other has no effect.

Why does the P-Split seem to amplify white(ish) noise in my setup? Why do all the things that are supposed to be better make it worse??

I have no idea what's going on here. Help?

These things can sometimes be weird. I sometimes get better results with the P-Split iso out with/without ground lift, sometimes the dir out works better.

I'd just use the solution that gives you the best result. If just a buffer does the job for you, don't look any further. You could also try using the opamp buffer after the iso out and see if that helps.

 

[Eagle]

These things can sometimes be weird. I sometimes get better results with the P-Split iso out with/without ground lift, sometimes the dir out works better.

I'd just use the solution that gives you the best result. If just a buffer does the job for you, don't look any further. You could also try using the opamp buffer after the iso out and see if that helps.

Yes sometimes the particular configuration doesn’t require anything and then a p split is just adding something else that is not needed. Just think ground isolation and phase. If they aren’t an issue don’t use it.

 

[Humbug]

The passive p split can only deal with phase and ground isolation. If the buffer works better just use it.

I was getting some annoying ground noise when using the buffer, so I was hoping a transformer would take care of it. And it did. It just added other stuff too

 

[Eagle]

I was getting some annoying ground noise when using the buffer, so I was hoping a transformer would take care of it. And it did. It just added other stuff too

The p split doesn’t really get rid of existing problems in your core signal it just prevents you inadvertently adding more.

 

[Humbug]

I'm beginning to suspect that I'm just having one of those days. I did some recordings of the noise and response of the amp going straight in vs through the reamp setup and, while the reamped audio is definitely noisier, it doesn't seem that bad when I listen to it now... And it made a perfectly useable NAM profile.

If I can figure out how, I'll upload an audio example so you can hear the difference for yourself and tell me if I'm just being hysterical
...ok, try this link: https://www.dropbox.com/scl/fi/xsmg...ey=vmfx4o4prvpjfiknemhy0hham&st=oey0cd2m&dl=0

Thanks, all, for contributing :)

 

[László]

There are often impedance and level issues going straight into an amp from the output of a converter box; the amplitude of a guitar signal is tiny, and the amp's input impedance is designed to accommodate that. The output of many interfaces is often +4 pro level, and the amp isn't designed for that, or even the IHF -10 prosumer level.

As Eagle says, the P-split (I have one) is simply an electrically isolated splitter box to let you do things like run two amps from one guitar or pedalboard without signal ground noise between the amps, etc, and of course there are other useful things it does.

A box designed for re-amping is the best solution for re-amping.

However, signal levels aside, if you have ground loops, the best cure is to address the ground loops at the source. That can be time-consuming, it's one-thing-at-a-time trial and error. You'll have to do some research, but it's absolutely worth the effort. Your whole rig will be quieter, notes will come out of an inky black background instead of hash, and the sound will be much improved.

You may have already started doing this.