2 HX Effects out of phase when one in the loop of the other.

[z3albw1rr]

I've got 2 HX FX.

 

I just tried to run one in the loop of the other. Let's call Unit A the main unit that has the send/return FX loop block, and the unit that's in the loop, Unit B.

 

Signal is Unit A Send to Unit B In, and Unit B Out to Unit A Return.

 

With the Send, Return, and Mix values at the default, there's a noticeable change in tone when you turn on the FX loop.

 

If I dial the mix down to 50%, it's gone and you can't really tell the loop is being engaged.

 

However, if all the effects blocks are bypassed, or an effect has any dry signal going through, or the unit is bypassed (even in Analog Bypass) it's clearly out of phase (sounds like a chorus, flanger, or phaser with no sweep in the LFO).

 

If I put a Gain Block in, it's out of phase. But if I turn the gain down to 0, it's not.

 

If I put a Delay in, I have to put the mix at 100% - and adjust the level.

 

Now, this last one makes sense to me as it's like using a Send/Return Aux bus on a mixer or in a DAW.

 

That limits you to certain kinds of effects you can use this way though.

 

I thought I'd try to use the Return and Send on Unit B, but that means "wasting" two blocks at the beginning and end just to route signal.

 

 

 

 

[somebodyelse]

That's latency for ya.

[z3albw1rr]

On 12/25/2022 at 2:35 AM, somebodyelse said:

That's latency for ya.

Hmmmm...that does make sense as a potential cause.

[theElevators]

As for the phase invert.... there isn't a direct switch for it, but when using a parallel path the merge block allows you to flip the "b" polarity.I don't know how the LR Baggs implements it... but if it's just a phase reversal on the output (common) you could try this...

• In your chain, drop one effect to the B path
• In the split block, change it from a Y to a Split A/B and route ONLY to the B side
• In the merge block
  • Set your A level to it's lowest setting possible. this is just a precaution to make sure no signal is bypassing the B path
  • Now you can invert your entire signal by changing the "B Polarity" as required. 

source (

)

[somebodyelse]

On 12/26/2022 at 5:45 PM, z3albw1rr said:

Hmmmm...that does make sense as a potential cause.

The longer answer is...

When you use an fx loop in an amp, usually they send the whole signal through the loop, and back in through the return - the path is interrupted between the pre and power amp sections.

With the Helix (I assume, as I haven't tried it), you can send a percentage of the signal out, bring it back in at the return and blend it in over the percentage that wasn't 'sent'. Regardless of what unit you use, it takes time for that signal to travel down the cables and back to the unit, as well as the processing time in the second unit, so the return will be delayed compared to the original signal. As little as 12 ms can be enough to cause audible phasing.

 

You could use a predelay as a work around before the return block in unit one to sync the two together - it'd work for recording purposes, but would probably drive you insane in a gigging scenario.

You'd need to determine the latency - record the send and return at the same time in a DAW, zoom in on a peak on both and measure the time 'distance' - fiddly, but doable - then add a delay block between the send and return on unit one set to the time difference and 100% wet, no feedback.

As I said, I've never used the send/return on the Helix, so I'm assuming it'd be possible to drop a block in, in between the send and return?

 

[CraigGT]

If the FX Loop Mix is set to 100% then latency won't be an issue, it sounds like you've got a parallel path somewhere.

Unplug the output from B and you should lose all signal, if not then it proves the parallel path.

 

 

[codamedia]

@z3albw1rr... it sounds like you have the "send/return" setup as a parallel path yet you appear to want a serial setup. Double check those "send/return" parameters to make sure you are not blending the two signals. 

 

To test this... run the HX Effects unit back to back (not in the loop). If the phasing disappears... the problem is in the loop parameters. 

[z3albw1rr]

On 12/26/2022 at 3:07 PM, theElevators said:

As for the phase invert.... there isn't a direct switch for it, but when using a parallel path the merge block allows you to flip the "b" polarity.I don't know how the LR Baggs implements it... but if it's just a phase reversal on the output (common) you could try this...

• In your chain, drop one effect to the B path
• In the split block, change it from a Y to a Split A/B and route ONLY to the B side
• In the merge block
  • Set your A level to it's lowest setting possible. this is just a precaution to make sure no signal is bypassing the B path
  • Now you can invert your entire signal by changing the "B Polarity" as required

Thanks - I thought I remembered seeing a polarity switch somewhere. I was wondering if putting the loop in the B path and just switching the B path on and off might be a solution. Inelegant, but a solution nonetheless.

[z3albw1rr]

On 12/27/2022 at 7:02 AM, CraigGT said:

If the FX Loop Mix is set to 100% then latency won't be an issue, it sounds like you've got a parallel path somewhere.

Unplug the output from B and you should lose all signal, if not then it proves the parallel path.

 

 

No parallel path - it's when it's set to 50% that the phasing issue is caused.

[z3albw1rr]

On 12/27/2022 at 10:02 AM, codamedia said:

@z3albw1rr... it sounds like you have the "send/return" setup as a parallel path yet you appear to want a serial setup. Double check those "send/return" parameters to make sure you are not blending the two signals. 

 

To test this... run the HX Effects unit back to back (not in the loop). If the phasing disappears... the problem is in the loop parameters. 

It's the single FX Loop block - when set to 50%.

 

That produces half the signal in the A unit going through it, then the other half of that going through the 2nd unit - and any effect that passes dry signal (or the effect itself not set to 100% wet) and I'm sure that's the signal that's causing the phasing.

 

At 100% on the FX loop block it doesn't do it, but there is a tonal change as you engage and disengage the loop.

 

So here's the problem:

 

To avoid the phasing issue, I have to set the FX loop block to 100%. It's just series running through the loop then.

 

But the loop makes a tonal change when being engaged and disengaged.

 

To solve that, I can run it at 50%.

 

But then you get the phasing on any effect not 100% wet (which doesn't work with many effects - unless you want a clean blend on a drive!)

 

_______

 

I get why there's a phase issue with the loop at 50% - you've got dry signal going through both and one's latency is enough to delay the signals relative to each other.

 

But I don't get why there's a tonal change when I put it at 100% and it's serial. Even with no blocks in the path, turning the loop on and off causes a change in volume/tone or a frequency shift that makes some frequencies louder or quieter that equates to a volume difference that can't be corrected with the send/return volumes.

 

But I suspect it's the same reason there's a tonal shift when I just run the two units in series.

 

 

 

 

[CraigGT]

Are you sure there's a tonal change and not just a volume change?

The FX loop should absolutely be set at 100% that's not debatable so there's something else going on.

Do you have the FX loop and B unit in and outs all set to the same Line/Instrument?

 

[codamedia]

On 12/28/2022 at 1:59 AM, z3albw1rr said:

No parallel path - it's when it's set to 50% that the phasing issue is caused.

 

When a loop is set to 50%, that IS creating a parallel path. Set it to 100%, then solve the tonal difference that you are mentioning.

 

@CraigGT provides great advice above. Make sure the LEVEL of the Loop in UNIT A is set the same as the I/O of UNIT B. Both need to be instrument, or both need to be line. 

 

IMO... I wouldn't bother with the loop at all. Why not just run one unit into the other? That would eliminate one unnecessary AD/DA conversation. 

[z3albw1rr]

On 12/28/2022 at 7:17 AM, codamedia said:

 

When a loop is set to 50%, that IS creating a parallel path.

 

OK, yes, sure in that way absolutely.

 

On 12/28/2022 at 7:17 AM, codamedia said:

 

Set it to 100%, then solve the tonal difference that you are mentioning.

 

Well, that is the question. How do I solve that though?

 

On 12/28/2022 at 7:17 AM, codamedia said:

 

@CraigGT provides great advice above. Make sure the LEVEL of the Loop in UNIT A is set the same as the I/O of UNIT B. Both need to be instrument, or both need to be line. 

They are. I tried them the other ways just to be sure, but yes, the problem persists even when they're all set to Instrument.

 

On 12/28/2022 at 7:17 AM, codamedia said:

 

IMO... I wouldn't bother with the loop at all. Why not just run one unit into the other? That would eliminate one unnecessary AD/DA conversation. 

I was just trying it because there's a problem with running them in series as well.

 

There is the advantage of being able to change presets, and so on with the 2nd unit in a disengaged loop, and then bringing it back online.

 

But honestly it's not that big a deal and series works just as well (aside from that issue) because of the Snapshots - and I have two independent sets of 4 which is why I wanted to go the 3 HX Effects route.

 

I'm mainly wondering now if the tonal change is due to the additional conversion, and if it's only slightly less when the units are in series, but still causing my issue with that tonal change.

 

I do have an acceptable solution, but was just hoping the loop might solve it - which it actually does on 50%, but that of course causes the other problem.

 

 

[bassbene]

If your preset does not use a parallel path at all, you might work around it by using one :)
Create a parallel path to the FX-Loop block (100% wet) and add a Simple Delay block into the parallel path. 100% Mix, 0% Feedback. Play around with the delay time - likely something in the 10ms ballpark. This will compensate for the d/a-a/d-d/a-a/d conversion massacre in the loop.

Edit: Mea culpa, a very similar and even more elegant approach was already mentioned by "somebodyelse". (lol)
 

On 12/27/2022 at 9:42 AM, somebodyelse said:

...You'd need to determine the latency - record the send and return at the same time in a DAW, zoom in on a peak on both and measure the time 'distance' ... then add a delay block between the send and return on unit one set to the time difference and 100% wet, no feedback.