The Helix is designed for the user to set up a number of signal flow combinations. It allows for unique situations that would normally be extremely difficult to set up in real life. They can now be easily arranged within the unit. For further reading, make you also check out the Helix manual section on Serial vs. Parallel Routing and Moving Split & Merge Blocks.
Having said that, you can also get some un desirable results if you're not careful with how you set up your routing. These can include phasing issues, volume drop, or noise floor increase.
*Notes about Inputs and outputs
Â· 1/4" Returns are unbalanced.
Â· All Helix Â¼â€ outputs (main outs and Sends) are impedance balanced, so you can plug a TRS cable and go to another deviceâ€™s balanced input and profit from some common-mode noise cancellation.
. When the Helix outputs are set to line level, they are +4dBU nominal with approximately 15dB of headroom. When set to instrument level, they -10bBu. Or more simply, they are 20Vpp max input/output.
Noise floor increase due to the introduction of Sends and Returns
â€‹When using the Helixâ€™s sends and returns the noise floor can be increased. This is due to the number of A/D converters now used in the signal chain. Most of the increase is negligible. However, it can become more noticeable if the sends/returns are placed in front of a high gain amp model such as the PV Panama (Peavy 5150) due to its inherent high noise floor. This phenomenon occurs on the Pod HD series as well.
Potential latency issues due to the introduction of Sends and Returns
This is another one that you won't notice in most situations, but could arise given certain circumstances. The tiny amount of latency introduced from another set of A/D converters is impossible to hear on it's own. An issue could occur if you merge that pathway back with another serial pathway that wasn't going through that send/return. The millisecond delay may cause some undesirable phasing. Below I have pictured a signal path that might yield poor results.
If you move the merge block before the Send/Return, then it would eliminate any potential phasing issues.
Using Helix Hardware as an interface to record
When using the Helix as an interface with a DAW, the signal routing can get a little confusing and it might become difficult to balance levels for monitoring. The typical set up would be guitar into Helix, then Helix to computer via USB. You would then monitor from the headphones, 1/4" or XLR outputs.
Given that setup, the guitar and the DAW's playback are sharing the same monitoring. If you have the guitar going into the DAW and then back out, you will hear your guitar twice. You can mute the DAW's return of the guitar track to avoid this.
Also, in this case the volume knob will control the total output making it tougher to balance the sound of the guitar and the DAW's playback. Try setting the volume knob to only control the feed you're monitoring, and it will no longer control the USB feed to your computer. You can also try making the playback volume adjustment from the DAW.
Using Helix Hardware as an interface to record with Helix Native
The above signal flow still applies, but a new level of complexity is added. Since the hardware is no longer processing the guitar, you can't mute your guitar tracks return feed, because you'll want to hear it. What works best is the set up the Helix with a blank preset, and then change the output block to your desired USB output. That way, the only thing you're hearing from the Helix is your DAW's return.
Auto Impedance Switching
With the Helix family, the default setting for the guitar input is auto impedance. The impedance will be determined by the first block in the signal chain. Even if the first block is bypassed, the impedance setting from that effect block will determine the input signal level. This automatic impedance will change the input volume and tone, this is most apparent with guitars that have passive pickups and are directly connected to the guitar in of Helix.
Distortion Pedal Volume Drop
Sometimes when adding a distortion/fuzz pedal, your signal volume drops. Here's a link to a great article written by our sound designer Ben Adrian that can explain in detail what's occurring. Although the article is written to describe what happens in the analogue world, it's affect can be experienced within the Helix and it's digital models.
Distortion Pedal Volume Drop (and how hard diode clipping works)