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.

 

[Humbug]

Update, mostly for myself: The Lehle or, perhaps more likely, the Lehle in combination with the rest of my setup was the problem. I splurged on a United Replay Box recently, and it seems to have resolved the issue.

 

[LEHLE]

Hey everyone, I stumbled above this thread via a search result in google, so I thought it would be a good idea to register here.
We're on standby regarding help for LEHLE.

I see this thread is by this day half a year old, but some facts might be interesting.

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.

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.

These answers are quite helpful.
If it works better without any "necessary" tools, then simply don't use them. If a meal tastes well, there's no need to salt or pepper anymore, only because one got used to. (Chilli helps always imho)

The P-SPLIT can be used to let through a signal, but lift the ground, if there are ground issues. This happens quite often in between e.g. an audio interface an amp.
If there's no ground loop, then a ground lift is not necessary. It makes things actually even worse, if you remove proper grounding.
It can also balance or unbalance a signal.

What it not does, is to change the impedance or level.
Also, if you send a high level in, a high level comes out.

So called "reamp boxes" often have a different transformer in combination with a passive potentiometer, to pull down the level.

Btw. the idea of re-amplification comes from the idea to record a copy of the same (!) signal which is sent to an amp.
This signal can then played back to the amp – with the same level.
Only here it can be ensured, the recorded signal is the same as the one sent to an amp. It doesn't see any additional preamps or stuff.
These days signals are often being directly recorded via preamps and HiZ inputs of interfaces to the computer, super "loud", a few dB below clipping so it has the highest dynamics but less noise.
If you playback this signal back to an amp, it is expectable that an amp is not sounding the same, as you would connect a guitar directly to it.
The amplifier has never "seen" this signal after the preamp or HiZ input you were using.

Btw. it's not obligatory necessary to use high impedance signals for your amps only, because every buffer, effects pedals, funny box of your choice is actually a buffer and lowers the impedance.
This means amps can of course work well with low impedance signals.

Customers made very good experiences by using this:
guitar (instrument) -> buffer -> LEHLE P-SPLIT III
DIR to amplifier
ISO to audio interface (balanced line input); this level is pretty low but that's what we want. Don't worry.

Then later playback the recorded signal to the P-SPLIT again in case you need to unbalance and a ground loop occurs.
This works in most cases. Of course you can add overdrives or any device of your choice etc between P-SPIT and amp. Try a few things.
You need to see the DAW as a "looper pedal" in between guitar and amp, you can toggle on and off, resp to the signal path or not. Such as the tape machine years ago.

Remember, there's no "this one way" to do all of this.
If a different way gives better results, do it. Trust your ears.

Best regards
Joki

 

[Humbug]

As this oldie but goldie has been dug up already, I'll add the final update: My neighbour moved out and now both the Lehle and the Replay are dead quiet

 

[laxu]

As this oldie but goldie has been dug up already, I'll add the final update: My neighbour moved out and now both the Lehle and the Replay are dead quiet

"Moved out"