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Line 6 - Please confirm Input Signal routing
by Ax3M4n on 2012-02-17 02:42:31

Hi,

this seems to be a recurring issue everytime something doesn't seem to work properly, and unfortunately the solutions contradict each other - they are mutually exclusive.

Does this represent the TRUE signal path in a POD HD (regardless of Input settings):-

Input 1  --> Mono Signal Chain to Mixer Input Left/A --> Mixer Output Channel A @ Left Stereo Pan Setting

Input 2  --> Mono Signal Chain to Mixer Input Right/B --> Mixer Output Channel B @ Right Stereo Pan Setting

So if both Mixer channels are centered you get a stereo output albeit centred in the stereo spread. You only get mono if you put a true mono FX or AMP after the mixer?

So what is the A/B splitter (Y Splitter) box for? It seems that it doesn't actually do anything?

To summarise previous "detailed" enquiries I have been told to:-

1) Set Input 1 - Guitar ;  Input 2 - Mic Trim pot down  - to avoid going in "too hot" to the amps and give me more headroom.

2) Set Input 1 - Guitar ; Input 2 - Variax - to provide a decent output level for USB recrding and provide more amp headroom as above.

3) Set Input 1 - Guitar ; Input 2 - Same - To provide more USB Output volume, more "tonal body" - but this then described as wrong for amp and clipping problems.

4) Set Input 1 - Guitar ; Input 2 - Same - so that there is actually a signal in Channel B. But f channel B is just for ambient FX - then overdriving AMP issue still exists in channel A (as per item 1).

In explaining signal routing, please can you also explain the logic behind it, because my mind still works in Guitar Mono outputs, mono cables and being able to only play one guitar at a time. 

Your help is much appreciated.

Thanks,

Ax3M4n



Re: Line 6 - Please confirm Input Signal routing
by jimsreynolds on 2012-02-17 02:57:59

Whether you hear one input on both channels or both inputs on separate channels is all about how you  setup your patch.

From the HD500 Manual, section 2.6  (for the 1.4x firmware release) ...

2.6 About Source Input Signal Routing:

It is important to note how POD HD500 actually routes Source Inputs 1 and 2 through Amp & FX Blocks that are positioned “Pre” position. The following behaviors apply:

  • In a configuration with no Amp or FX Blocks in Pre, Input 1 is fed only to Path A and Input 2 only to Path B. Therefore, this is the best configuration if you want to retain discrete Input Sources into Paths A & B.

  • Placing an Amp Block or an active mono FX Model in Pre results in a “mix-down” of Input Sources 1 & 2, feeding the same, combined signal into each Path A & B.

  • Placing a Stereo FX Model in Pre results in the left channel FX output being fed to Path A and its right output to Path B.*

  • The Mixer Block’s Volume and Pan options provide independent control for Path A & B outputs before they are fed through any Blocks positioned “Post” the Mixer.

  • By setting Input 2 to “Same,” this effectively routes your Input Source to both stereo Paths A & B (which is how you can feed one guitar input into two Amp Models and/or parallel FX, for example).

* Please also see “Model Types and Mono/Stereo Signal Routing” on page 3•6 for more about how mono and stereo FX affect your signal chain.

3.6 Model Types and Mono/Stereo Signal Routing

It is important to note that some Models (all EQs, Wahs & Volume, and some Modulations, Filters, Pitches and Delays, as well as the FX Loop) preserve a stereo output within the signal chain, while others (all Dynamics, Distortions, all Amps & Preamps, and other various Models) are mono FX and do not. The POD HD500 Inputs 1 & 2 are fed into the signal chain as stereo (see “Page 3, Setup: Input Options” on page 2•4). Therefore, wherever a mono FX or Amp Model is inserted, the Left & Right channels of this stereo signal is “mono-ized” and heard as a two-channel mono signal at the Model’s output. To follow are a few examples:

There are some good illustrated example of this in the advanced manual and I suggest that you download this from this site.  Also check out the diagram posted by Deandinosaur earlier in this thread here  http://line6.com/support/message/328666#328666



Re: Line 6 - Please confirm Input Signal routing
by Ax3M4n on 2012-02-17 03:24:56

Thanks for your answer - I can see one immediate inconsistency in manual , hence my post:-

- Placing an Amp Block or an active mono FX Model in Pre results in a “mix-down” of Input Sources 1 & 2, feeding the same, combined signal into each Path A & B.

So with Iinput 1 Guitar, Input 2 - Mic (trim pot down) - I should get an identical combination of Source 1+2 into both A and B. But I don't - I only get a signal in PATH A.

Input 1 Guitar

Input 2 Mic

--> Q Filter --> A/B Splitter --->

Channel A  - OD - DIST - Dig Delay  - AMP A - Mixer Left/A

Channel B - Pitch Glide - No Amp - Mixer Right/B

Mixer Output --> Reverb ---> USB output



Re: Line 6 - Please confirm Input Signal routing
by jimsreynolds on 2012-02-17 03:40:31

I am a bit confused .... what is this 'A/B Splitter' of which you speak?

I have the HD500 and have been through the full set of effects and cannot see that ... or something that matches this description.  Are you talking about the point where the signal path splits to go through the two chains, as opposed to an effect block?

If so:  the chances are that the Q-Filter is a Stereo effect and will therefore channel Guitar Left and Mic Right through the remainder of the chain.  You could try putting another, Mono, effect directly after the Q-Filter and see what that does for you. 

Make sense?



Re: Line 6 - Please confirm Input Signal routing
by Ax3M4n on 2012-02-17 03:54:33

The AB splitter is the split in the signal path that looks like this:

               I-------

               I

----------O

               I

               I____



Re: Line 6 - Please confirm Input Signal routing
by jimsreynolds on 2012-02-17 04:14:25

OK, yeah, so as I say: the trick is to have a Mono effect in the 'O' position on your diagram.  That will sum/average the two inputs before sending the combined signal into both channels.

               I-------

               I

----------O

               I

               I____

Trying to think of what effect would be suitable though.  The neutral ones all seem to be stereo. 



Re: Line 6 - Please confirm Input Signal routing
by jimsreynolds on 2012-02-17 04:20:41

... and through the magic of search, I got lucky with http://line6.com/support/docs/DOC-2099">http://line6.com/support/docs/DOC-2099">http://line6.com/support/docs/DOC-2099courtesy of Fester2000 - the person that previously brought us DSP usage percentages by effect and amp!

Looking down the list:  all of the distortions and Dynamic effects are mono but I think will effect your tone ... unless you want that.  The EQs are all stereo and therefore out as are reverbs and wahs.   Delays vary but all the (desireable) dry mix versions are stereo. Pitch effects are mono - but very resource greedy.

The best bet may be to select one of the modulation or delay effects with a mix parameter and set it to 100%.  You MAY be able to use a Vol/Pan control centred and not connected to the Expression pedal. 



Re: Line 6 - Please confirm Input Signal routing
by Ax3M4n on 2012-02-17 04:45:18

This....

              I------- 

              I

----------O

              I

              I____

...in every other manual, book, guide, web site or back of fag packet diagram on the PLANET means a split signal path. Mono In - Dual Out. Except with Line 6 it means this:-

Input 1 = Guitar -------------------------------------- Output Left/Channel A

Input 2 = Something Else  ----------------------- Output Right/Channel B

Except when Input 2 = Same  - Then the A/B splitter icon means this:-

Input 1  ---------------------------- Output Left / Channel A (Guitar 1 at double usual volume assuming null input 2)

              \    /

                X

              /    \

Input 2 ------------------------------ Output Right / Channel B (Guitar 1 at double usual volume assuming null Input 2)

Jim, thanks for your answers and thread pointers (I've seen the lengthy discussions and everyone is clearly still confused/unhappy even in the most recent of many posts). Adding another/unwanted FX unit in the A/B split is not feasible because of DSP.  I wouldn't want to do this anyway. The scenario is simple enough and easily enough achieved with logical signal routing and in real life with patch cables.

I'd like to see Line 6 fess up and get to the bottom of this. It's a total mess whichever way you look at it. 99% of guitarist need 1 Input and occasionally an ability to split the signal.  Who needs 2 Live/Active Inputs?  If guitarists want to change guitars without removing cables they have an "A/B Switcher Box". 



Re: Line 6 - Please confirm Input Signal routing
by silverhead on 2012-02-17 06:01:02

I think your conceptual model of an A/B path splitter in the HD device is what's causing the confusion. The A/B paths in the HD device are not 'split' by an FX placement such as your Q-filter. The A/B paths are completely independent from the inputs - both inputs are seperate at the outset, and do not need to be 'split'. In fact, your Q-filter, being a mono FX, acts as a signal merger, not splitter. It takes two independent input signals and merges them into a single mono signal, which is then sent down two different and independent paths.

By not placing any FX before the visual path split you are simply allowing the two independent inputs to be processed sperately, without being merged. You are not splitting them - you are just not merging them. I think the signal flow diagrams would actually be more accurate if they looked like this:

Using mono-FX before Dual-Path processing (note I don't say 'before path split'):

Input 1 ------                   Inputs1+2-----> Path A processing

                    \             /

                   mono-FX (merges inputs)

                    /            \

Input 2-------                  Inputs1+2-----> Path B processing

No FX before Dual-Path processing

Input 1 -------> Path A processing

Input 2--------> Path B processing

The signal flow display on the HD device LCD would, imho, be more accurate if there were no vertical bar at all in the case where there is no FX before the 'split', as in the diagram above.

A final note: if you are not using a dual-amp patch, the signal flow looks like this:

Input1+2 ---> single path processing



Re: Line 6 - Please confirm Input Signal routing
by phil_m on 2012-02-17 06:23:42

To add a little addendum to what's already been said, I think the way to envision the A/B paths is to remember that each one is a stereo path. The A/B splitter, as you're calling it, doesn't separate into left and right, it's really more like a Y-splitter than an A/B box. So you have, potentially, a stereo signal being split into two separate stereo signals. When these stereo signals hit the mixer, they can be combined into one stereo output signal if the pan controls are left centered (or not hard panned), or you can hard pan them and then be left with a stereo signal that gives the left output of Tone A and the right output of Tone B. I won't say it's not complicated. It is, but it also gives you a lot of flexibility and options as to how you route things. It really opens up all sorts of possibilities.

If you want a true A/B split, it can be done if you set up the patch like the attached. But, to your point, there's nothing really like an actual A/B/Y box in the HD500's arsenal of effects.

split tone.JPG



Re: Line 6 - Please confirm Input Signal routing
by silverhead on 2012-02-17 06:27:23

.... and using phil_m's diagram above, I think it would be more accurate if the left side of the signal flow image did not show the portion to the left of and including the vertical line. It should just show the two horizontal lines indicating Input 1 and Input 2 completely seperate from the outset.



Re: Line 6 - Please confirm Input Signal routing
by chimp_spanner on 2012-02-17 06:43:17

Thanks for the diagrams guys. This actually clears up how the routing works, although I can't imagine too many scenarios where I would want to merge the inputs and then process them separately again. Seems the easiest way to avoid confusion is to have it set up like Phil's screenshot from the getgo, and then you know for sure what's going on in your patch.



Re: Line 6 - Please confirm Input Signal routing
by phil_m on 2012-02-17 06:48:20

Yes, that would certainly make more sense.



Re: Line 6 - Please confirm Input Signal routing
by meambobbo on 2012-02-17 07:44:04

I don't think anyone directly answered your question about your patch, but it looks like the Q-Filter must be a stereo effect if you're not getting any signal in path B.  IE

           |-Q-Filter-|   /---- Path A

Input 1 ------------------

Input 2 ------------------

           |__________|   \---- Path B

The Q-Filter is processing each half of the incoming stereo signal individually, where input 1 is the left side and input 2 is the right side. So if Input 2 is a null input, Path B isn't getting any signal.  Compare this to:

           |-Mono FX--|   /---- Path A

Input 1 ----\________/----

Input 2 ----/        \----

           |__________|   \---- Path B

Here the stereo input signal is merged into a mono signal inside the effect, processed as a mono signal and split into two equal signals fed into Path A and Path B.

It would be quite helpful if there was some indication of whether an effect was processing as stereo or mono in Edit or the unit's edit screen.  I guess you just have to experiment, or look at external guides for now.



Re: Line 6 - Please confirm Input Signal routing
by MartinDorr on 2012-02-17 09:52:09

Your comment that each A and B path are (or can be) stereo raised my curiosity before. Honestly, I had my doubts but when I went back to the Advanced Guide I found a few references that support this view:

  • pg 2-4, 2nd bullet:
    By setting Input 2 to “Same,” this effectively routes your Input Source to both stereo Paths A & B (which is how you can feed one guitar input into two Amp Models and/or parallel FX, for example).
  • pg 3-6, last bullet:
    The FX Loop is capable of stereo, just like any stereo-output FX Model, provided that you utilize a stereo cabling configuration from the SEND jack, through your pedals/rack devices, and back into the RETURN jacks.
  • pg 3-7, first bullet:
    The above rules also apply within each of the parallel Paths A and B, since these are each stereo signal paths as well. The Mixer Block offers Pan controls to independently adjust the stereo balance of each of these Paths before they are fed into the first “Post” FX (or Amp Block, if the Amp is placed here), immediately following the Mixer.

The fact that both path A and B can be stereo is probably not often useful for electric guitar applications because at some point you likely go through an amp or a mono effect before recombining the A and B signals with the mixer. But if an A/B path is used to process material from a singer, an accoustic guitar, or a keyboard (something you probably do not want to send through a guitar amp), the stereo capability of the A/B paths could be quite useful.



Re: Line 6 - Please confirm Input Signal routing
by phil_m on 2012-02-17 10:06:59

Yep, it's not a view - it's a fact...

It's easy to prove it to yourself if you want. Just set up a dual tone and put a true stereo effect (stereo delay with a different delay time on either side is a good one to use) after one of the amp blocks. Mute the other path completely in the mixer block. With the pan control in the center position you'll hear the stereo separation from the stereo effect. If you pan hard right or left, you'll only hear the respective side of the delay and not the other.

The thing that is weird is that even though you have the potential of having a pair of stereo signals coming from the mixer block, you are only left with one set of stereo outputs. It would be nice if you could send on tone to the 1/4" outs and the other to the XLR and have them be completely independent of each other. As of now, you can't do that. I don't if it's something that could be changed or not. I suspect it is probably a hardwired limitation, though.



Re: Line 6 - Please confirm Input Signal routing
by Ax3M4n on 2012-02-17 10:40:04

Hi Silverhead,

here is my actual problem (see below). The response to this latest problem is "Make Input 2 = Same".  Input 2 had been set to "Mic - Trim Off", because my problem before was that my Guitar (normal standard USA Strat) was overdriving most amp models (AC30 particularly, no FX, Master @50%-60%, Bias High) with Drive set to only 20% -30%. Line 6 solution was to NOT have "SAME" as input 2 because this doubled guitar signal input power.  Silverhead - I appreciate your assistance, but clearly you are as confused as I am.  Q Filter it seems is a Stereo Output effect, but only if it receives a Stereo Input (Input 1 Guitar, Input 2 Same). So in problem below, with chain as described, the Q filtered Guitar signal is overdriven in the A path, and hopefully just pitch shifted +1 Octave in the B  path (not even pre-amped). But it doesn't get pitch shifted. I hear "quiet, distant, distorted, delayed guitar in my RIGHT headphone", and Strong Distorted Delayed Guitar in my LEFT Headphone. Mixer is Panned HARD Left and Hard Right.

I set Input 2 to SAME - And Channel B does come alive with pitch shifted guitar (clipped Grrrrrr). But now everything is louder and my cleverly adjusted "overdriven" tone in the LEFT Channel is now just MUDDY MUSH.

Now - anyone following this - please go to bottom of thread, for another post on whether or not A and B Channels are independent and Stereo of their own right.

Problem (Copied from other thread)

Chain is this:-

Q Filter (fixed wah) - A/B splitter (or Y Splitter if you want to call it that) ->

Channel A --> Screamer --> Classic Dist ---> Delay w/mod ---> A30TB --> Mixer Left

Channel B --> Pitch Glide ---> No Amp --- Mixer Right

Mixer Output ---> Reverb --> USB Output

Previously Pitch Glide was following Q Filter and before A/B Splitter. On/off is set to EXP Toe switch, Exp 1 controls pitch.

Problem:  When in parallel path there is no effect - the pitch glide does nothing like it isn't there.  Mixer Right is set to 0dB 100% Right. Input 1 = Guitar, Input 2 = Mic, trim pot down.



Re: Line 6 - Please confirm Input Signal routing
by meambobbo on 2012-02-17 10:44:21

Just to add, what Phil is saying below is correct - Paths A and B are also stereo signals, so the diagram should look more like this:

                           ___________     _ Path A Left

                          | Stereo FX |  _/  

Input 1 (pre-split Left)__|___proc____|_/ \_ Path A Right

                          |           |

Input 2 (pre-split Right)_|___proc____|_   _ Path B Left

                          |___________| \_/ 

                                          \_ Path B Right

Pre-split Left (input 1) is processed without mixdown by Stereo FX and feeds into Path A where  it is split into a stereo signal with equal signal in left and right.

Pre-split Right (input 2) is processed without mixdown by Stereo FX and feeds into Path B where it is split into a stereo signal with equal signal in left and right.

                           ___________     _ Path A Left

                          |  Mono FX  |  _/  

Input 1 (pre-split Left)__|           |_/ \_ Path A Right

                          |\__proc___/|

Input 2 (pre-split Right)_|/         \|_   _ Path B Left

                          |___________| \_/ 

                                          \_ Path B Right

Pre-split Left and Right (input 1 and 2) are mixed down to mono and processed by a Mono FX, then split back into a stereo signal with equal left and right signals.  The left signal is fed to Path A, right to Path B, where they are again split into equal left and right signals.



Re: Line 6 - Please confirm Input Signal routing
by meambobbo on 2012-02-17 11:17:39

                           ___________     _ Path A Left
                          |  Mono FX  |  _/             
Input 1 (pre-split Left)__|           |_/ \_ Path A Right
                          |\__proc___/|               
Input 2 (pre-split Right)_|/         \|_   _ Path B Left
                          |___________| \_/            
                                          \_ Path B Right

                           ___________     _ Path A Left
                          | Stereo FX |  _/            
Input 1 (pre-split Left)__|___proc____|_/ \_ Path A Right
                          |           |               
Input 2 (pre-split Right)_|___proc____|_   _ Path B Left
                          |___________| \_/           
                                          \_ Path B Right


          ___________    ___________    _ Path A Left    
         |  Mono FX  |  | Stereo FX | _/            
Input 1 _|           |__|___proc____|/ \_ Path A Right    
         |\__proc___/|  |           |              
Input 2 _|/         \|__|___proc____|   _ Path B Left    
         |___________|  |___________|\_/           
                                       \_ Path B Right

          ___________   ___________     _ Path A Left    
         | Stereo FX | |  Mono FX  |  _/            
Input 1 _|___proc____|_|           |_/ \_ Path A Right    
         |           | |\__proc___/|              
Input 2 _|___proc____|_|/         \|_   _ Path B Left    
         |___________| |___________| \_/           
                                       \_ Path B Right 


                 _________________       
Path A Left  ___|     Mixer       |       
                |\_pan/level______|_Left  
Path A Right ___|/          \  /  |       
                |            \/   |       
Path B Left  ___|            /\   |       
                |\_pan/level/__\__|_Right 
Path B Right ___|/                |       
                |_________________|       

                 _________________       

                |     Mixer       |

Path A Left  ___|_level_panL___   |       

                |              \__|_Left  

Path A Right ___|_level_panR_  /  |       

                |            \/   |       

Path B Left  ___|_level_panL_/\   |       

                |              \__|_Right 

Path B Right ___|_level_panR___/  |       

                |_________________|

   

panL = 100-pan right for channel.   so if the channel is panned 30% right, then panL = 70% of its original volume.



Re: Line 6 - Please confirm Input Signal routing
by daferalo on 2012-02-17 12:06:01

Yeap Ax, the Q filter is a stereo effect. If you do not want to "double" your guitar signal and let your input options as you have, while feeding both paths at the same time, then you need to place a mono effect at the begining of the signal chain, i. e. a noise gate, and just tweak it to taste in order for it to be kind of "transparent" for your tone.

Best Regards,

Daf



Re: Line 6 - Please confirm Input Signal routing
by phil_m on 2012-02-17 12:18:37

I agree with the response right above me. If you put a mono effect in front of you chain, I think it will work the way you're wanting it to. Try the volume pedal. It's probably the lowest DSP solution.



Re: Line 6 - Please confirm Input Signal routing
by Ax3M4n on 2012-02-17 12:21:43

Re: 2 Stereo Paths.  I totally disagree, this is not true.

You have two mono audio channels -  A and B. That's it. I don't call them stereo channels because that implies dual left  vs right panning. But the panning is only applied in the Mixer.

"Stereo" Effects have this arrangement (imagine a real world effects stomp box with 2 input and 2 output jacks). If they only have One Cable connected to mono input (A)  then this is tied internally to Input B and Output B is tied internally to Output A. 

Input A/Mono----------------I*********I---- Output A Mono

                            I  FX     I

Input B/Mono----------------I_________I---- Output B Mono

Mono Effects (including Amps) have this arrangment:-

                           I*********I

Input A+B(Mono)------------I  FX     I-----Output A+B Mono

                           I_________I

With Input 1 = Guitar,  Input 2 = Null

1 AMP Before Split/T/Y

Input A/Mono----------------I*********I---- Output A Mono                                                               A+B Mono in Left Stereo

                            I  FX     I                    A+B mono Input to AMP ----- [AMP] --- A+B MONO OUT--[MIXER}<

Input B/Mono----------------I_________I---- Output B Mono                                                              A+B Mono in Right Stereo

NOTE: Input B is NULL so Stereo FX only Outputs Signal A. So only Signal A is heard in Left and Right Headphones. Example: Stereo Effect is Stereo Delay MIX 100%. LEFT Delay = 300ms 1 repeat. RIGHT Delay = 600ms 1 Repeat.  In your headphones you hear 1 Repeat of 300ms in Left and Right ears.

Example 1.jpg

1 AMP in A Path Only, AFTER Y Split, Before Mixer.

Input A/Mono----------------I*********I---- Output A Mono -- A mono input to AMP ----- [AMP] --- A MONO OUT--[MIXER] A Mono in Left Stereo Out

                            I  FX     I                   

Input B/Mono----------------I_________I---- Output B Mono ---------------------------------------------------[MIXER] B Mono in Right Stereo Out

NOTE: Input B is NULL so Stereo FX only Outputs Signal A. Only Signal A is heard in LEFT Headphone Only.  Example: With above stereo delay setting, you hear 1 Repeat at 300ms in Left Headphone Only.

Example 2.jpg

1 AMP in A Path Only, Stereo FX in A Path Only, Before Mixer.

Input A/Mono----------------I*********I---- Output A Mono -- A mono input to AMP ----- [AMP] --- A MONO OUT-- [MIXER] ---  A Mono in Left Stereo Out

                         \  I  FX     I  /                   

                          \-I__Ch B*__I-/ 

Input B/Mono------------------------------- Output B Mono ----------------------------------------------------[MIXER] --- B Mono in Right Stereo Out

* FX Channel B receives its input from Audio Channel A, and its output is sent to output channel A.

NOTE: Stereo FX is in a MONO Audio Path (Path A), so FX Input B is tied to A , and FX Output B is tied to A. In same example you hear 2 x Delays (300ms  & 600ms) in the LEFT Headphone only.

Example 3.jpg

CONCLUSION:

You can continue with further experiments, with Input 2 set to SAME.  But you will still see that there are only TWO mono channels through the unit - A and B. (TIP: try AMP A Clean and AMP B Dirty with Stereo delay as mentioned above).

- Path A is not a Stereo Audio Channel - it is a Mono Audio Channel.

- Path B is not a Stereo Audio Channel - it is a Mono Audio Channel

Path B is always tied to Input 2 except when Input 2 = Same.

Please can Line 6 make some official amendment to their documentation, preferably including REAL SIGNAL FLOW Diagrams, covering all combinations and correctly worded explanations.



Re: Line 6 - Please confirm Input Signal routing
by daferalo on 2012-02-17 12:24:46

Hi phil_m, I am not very sure and cannot probe by myself at this time, but I think the volume effect is also a stereo one.

Best Regards,

Daf



Re: Line 6 - Please confirm Input Signal routing
by phil_m on 2012-02-17 12:29:23

They are two stereo paths, or to be more accurate, two potentially stereo. It's just that the majority effects aren't stereo (true stereo or even mono in, stereo out). The amp blocks are mono, so if there's a stereo input before them it comes out as summed dual mono.

The pan controls in the mixer should actually be labeled balance, not pan. With a balance control you have to think of it as two volume controls. If you hard pan, you're really reducing the volume of the other channel to zero.

EDIT: I think the one thing I should clarify is that the Input A and B aren't stereo. They are mono inputs, but if you put a mono effect in the path before one that has a stereo output, you can in essence turn them into stereo paths. I think that may be why you're disagreeing with me.



Re: Line 6 - Please confirm Input Signal routing
by phil_m on 2012-02-17 12:36:54

You are be right about that... I always forget that volume is a true stereo effect.



Re: Line 6 - Please confirm Input Signal routing
by phil_m on 2012-02-17 13:00:27

Not to belabor the point, but here's something to try.

Assume Input B is not being used and the Tone B is muted at the mixer.

Without any effects and just and amp block before the in the signal split you'd have:

                                     

Input A -->Split ---> Amp --> Path A Mixer --> Stereo Out

Now, if you put a true stereo effect after the amp in this signal chain, you will have a separated stereo signal coming out of the left and right outputs. You'll hear the separation in your headphones. This wouldn't be possible if this were a mono signal.

                                

                            

Input A -->Split ---> Amp --> Stereo Delay --> Path A Mixer --> Stereo Out

The thing that makes this confusing, and yes, frustrating, is that it's somewhat of a matter of trial and error to determine what effects are true stereo. Most of the ones that are stereo are mono in/stereo out.

Also, note in the scenario I have shown above, the "Split" isn't really doing anything. It's just sending input A to the input of the Amp (or whatever effect you'd have first after the split).

I've attached what I'd make my tone look like if I just wanted a simple mono in to stereo out tone.

split tone 2.JPG



Re: Line 6 - Please confirm Input Signal routing
by silverhead on 2012-02-17 13:04:02

Ax3M4n wrote:

... Silverhead - I appreciate your assistance, but clearly you are as confused as I am.  ..

I think you're right about that! I thought I had understood, but after reading all these posts I'm not sure anymore. You're certainly right about the Q-Filter being a stereo effect, not mono as I had indicated.

As I've said many times - I learn something new here every day. I'm still learning on this topic.



Re: Line 6 - Please confirm Input Signal routing
by daferalo on 2012-02-17 13:14:52

+1 to what Phil_m said above.

Ax, the results of your test are correct, but they do not mean that Path A and B are mono. Be aware that you placed a mono-type effect (the amp) after a stereo one, so it is expected to get those results.

I think Meambobbo's charts are very complete, and as Phil_m said, it can be frustrating to mess around it. However, it is very important to know what happens at "each position" in the signal chain in order to get the best. The only difference between the "path A and B" position and "pre" position in the signal chain, is that in the former you can control what is going to happend to each signal path, independently from the other.

Best Regards,

Daf



Re: Line 6 - Please confirm Input Signal routing
by Ax3M4n on 2012-02-17 13:37:55

Hi Phil,

what I have said stands correct. I will leave it up to readers to prove it to themselves as I have done for the last 4-5 hours. It's up to Line 6 to provide further documentation. I must state I am using a POD HD Desktop, which I am told is identical in processing to the HD500.

To be fair, I tried your last example regarding a Stereo Effect after the mixer block (although this is repeating tests I had tried earlier).

Stereo Effect = Stereo Delay 100% Mix, Left 1 x 300ms Repeat. Right 1 x 600ms Repeat

With Input 2 = Null,  there is 1 x 300ms delay out of the LEFT channel only.

With Input 2 = Null and Right Mixer Channel Muted - There is 1 x 300ms Delay in the Left Channel Only.

With Input 2 = Same - There is 1 x 300ms Delay in Left Channel, followed by 1 x 600ms in the Right Channel

With Input 2 = Same and Right Mixer Channel Muted - There is 1 x 300ms delay in the Left Channel Only.

The above was regardless of AMP being present in Channel A or B or Both.



Re: Line 6 - Please confirm Input Signal routing
by phil_m on 2012-02-17 13:42:02

Where do you have the mixer pan controls set in your experiments?

There isn't really a left and right mixer channel. You have A and B outputs for the mixer, and they each have their separate output level and pan controls. If you have the mixer hard panned, then I would expect to get the results you're hearing.



Re: Line 6 - Please confirm Input Signal routing
by daferalo on 2012-02-17 13:45:48

Hi Ax,

Again, it is the expected behaviour, but it does not mean that path A and B are mono. It is jus the way you are performing the test.

Please, try to do the same test, but placing the stereo delay in the path A only. And then, tweak the pan and level options in the mixer to different values.

Best Regards,

Daf



Re: Line 6 - Please confirm Input Signal routing
by Ax3M4n on 2012-02-17 13:48:49

Yes - without the mixers hard panned you would expect bleed from one channel to the other.

With mixers hard panned there isn't any confusion - nothing coming out of Path/Channel B means there isn't anything coming into Path/Channel B. QED.

If they weren't hard panned what you would hear in Channel B is a copy of Channel A.



Re: Line 6 - Please confirm Input Signal routing
by phil_m on 2012-02-17 13:53:48

Well, the "bleed" as you call it is simply the stereo spread of the signal.

Don't misunderstand me, I'm not saying that A and B are true stereo under every condition, just that they potentially could be. If you repeat you're experiment putting the stereo delay either before or after the mixer - make sure you have a different delay time on each side of the delay - you'll hear stereo separation even while the B path is muted. This simply wouldn't be possible with a true mono signal. You'll hear both sides being processed independently from each other. If you pan hard left or hard right, you'll only hear one of the delay signals.



Re: Line 6 - Please confirm Input Signal routing
by daferalo on 2012-02-17 13:58:50

Phil, I am at "work" right now so I can not probe it, but I am pretty sure that if you perform the test you are proposing by placing the stereo delay before the mixer (I understand in the "pre" position") and then mute path B, you won't hear the right channel of the delay.

Best Regards,

Daf



Re: Line 6 - Please confirm Input Signal routing
by Ax3M4n on 2012-02-17 14:00:59

I appreciate all your involvement and thoughts but I will not be pursuaded otherwise. I have proved to myself that what I say above is correct, and that is different to what is described in the manual. I sympathise with everyone who has ran into difficulties with this confusing subject over the last 6 months, as I have done.   Channel A is MONO and Channel B is MONO.

Please feel free to do your own tests.

LARGE HELPING OF HUMBLE PIE JUST EATEN BY AX3M4N.  Phil - with LEFT Mixer Panned at 0% I hear the Left and Right Delays in the Left and Right Channels.  You have my humble apologies.

Apart from feeling a bit stupid, I am happy that most of the tests were valid, and that the subject has been hammered flat in one afternoon sitting. I still believe that Line 6 documentation is confusing to the extreme and that simple signal flow diagrams should be produced by them.

Thanks to all. I'm going to go play some guitar.

Ax3M4n



Re: Line 6 - Please confirm Input Signal routing
by phil_m on 2012-02-17 14:04:54

I have to double-check as well, but I'm thinking the amp block will give you a dual mono output that will feed both sides of the stereo delay. I'm at work, too, but I will try to check when I get home this evening.



Re: Line 6 - Please confirm Input Signal routing
by daferalo on 2012-02-17 14:29:36

phil_m escribió:

I have to double-check as well, but I'm thinking the amp block will give you a dual mono output that will feed both sides of the stereo delay. I'm at work, too, but I will try to check when I get home this evening.

Phil, I did not read well what you said before and I got confused for a little while, but what you say here is correct!!!!! Apologies for misunderstanding!!

I mean, if you place the stereo delay at "pre" position, it will feed path A with both channels of the delay in the example.

Best Regards,

Daf



Re: Line 6 - Please confirm Input Signal routing
by silverhead on 2012-02-17 16:01:45

Ax3M4n wrote:

...

Apart from feeling a bit stupid,....

Not at all! It's a very complicated issue, which I had also misunderstood. We all had a healthy, respectful exchange of ideas, observations, and opinions. And in the end we all helped each other get to the bottom of it. That's what this forum is for. I think you should feel a bit proud rather than stupid - you were a big part of the learning exercise, for me at least.



Re: Line 6 - Please confirm Input Signal routing
by meambobbo on 2012-02-17 16:26:47

my mixer diagram was wrong - i fixed it.  it's like phil says - you basically have 4 volume controls - channel A left, channel A right controlled by channel A's pan control, and channel B left, channel B right controlled by channel B's pan control



Re: Line 6 - Please confirm Input Signal routing
by Ax3M4n on 2012-02-17 16:58:27

Thanks all for your understanding; my rare afternoon off work spent tearing my hair out,  leaning over my guitar trying to type as I went along.  I'm a dab hand with Power Point - so time permitting I'll try and knock up a few slides with graphics - Picture's paint a thousand words.

When they say "The penny dropped" I think my penny fell from outer space.



Re: Line 6 - Please confirm Input Signal routing
by chimp_spanner on 2012-02-17 17:39:39

Yeah I found this thread really helpful too, if only for the fact that it really forced me to sit down and figure out exactly what the best way is to use the signal routing on the HD. I found a way better method of constructing single tone patches as a result. So, helpful times all around!!



Re: Line 6 - Please confirm Input Signal routing
by phil_m on 2012-02-18 07:10:50

I was thinking about this thread some more, and I wanted to sum up a few things.

I think the way to think about the mono/stereo thing is this. There are essentially three types of effect blocks in the HD500 (and Bean and Pro).

1. Mono in / dual mono out - this is what most things are. Distortions, filters, amp blocks, and some others would fall into this category. And really it's not true to call these true mono in because if you put them after a stereo effect, they will get both sides of the effect as input. It's just that the input is "mono-ized" to quote the advanced guide.

2. Mono in / stereo out - these are similar to the mono effects in that they "mono-ize" the inputs, but the output it a stereo image. The Ping Pong Delay would be a good example of this, as well as the panning effects. I think all reverbs fall into this category as well. If you put them before the split, the left output will go down path A, and the right will go down path B. If you put them after the split, but before the mixer, you will lose one half of the stereo image if you hard pan.

3. True Stereo - these effects maintain a true, separated stereo path through the effect. They will not mono-ize the inputs, so if there's something only on the left side coming into the effect, you won't hear anything coming out of the right side. This is why you using these effects first in the signal chain may not always work the way you want. These include the volume pedal, the panning volume, all the wahs, stereo delay, analog chorus, Q filter, and a few others I'm forgetting now. If you put these before one of the other types of blocks I've described here, the stereo separation will not be maintained. If you put them before the split, the left output will go down path A, and the right will go down path B. If you put them after the split, but before the mixer, you will lose one half of the stereo image if you hard pan.

As I see it, these three groups cover everything. The one sort of odd thing is that none of the effects are "true mono" in the sense that they will only work with one input. All of them will accept a stereo input, it's what they do with it that sets them apart.

I hope this clarifies the issue a bit. If anyone sees anything wrong here, please feel free to offer a correction.



Re: Line 6 - Please confirm Input Signal routing
by Ax3M4n on 2012-02-18 09:15:40

There's definitely some odd (algorithmic) signal paths going on in there because I struggle to imagine how it could be done with hard wires.



Re: Line 6 - Please confirm Input Signal routing
by meambobbo on 2012-02-18 15:08:30

good catch, phil.  does anyone know of a list of what effect is which?  is it worth spending the time to make one?




The information above may not be current, and you should direct questions to the current forum or review the manual.