Controlling Gain, Master Volume and Channel Volume

[amsdenj]

There are a lot of ways to control volume with Helix, and the choices can be a bit confusing. I like to keep each block close to unity gain - meaning that the overall Helix output volume level doesn’t change that much when the block is bypassed. This ensures there’s no volume buildup in the signal path that could lead to digital clipping or volume drop that could lead to increased noise. This general rule doesn’t apply in two special cases. You might be using gain or distortion blocks before the amp to gain stage your distortion. In this case, the level of a block might be set higher or lower than unity gain to control the level into the next block. The second is when you actually need a lead boost. I usually use the output level for this, setting the normal level down a few dB, and having the boost switch simply remove the cut back to 0dB. This again ensures there’s no chance of digital clipping. As a general rule its better to cut what you don’t want/need than to boost what you do want.

 

Using this approach works well for the typical blocks that go before the amp (compressor, Wah, drives, phaser, UniVibe, etc.) and blocks that go after the amp (chorus, flanger, delay, reverb, etc.). But what about the amp block itself?

 

Typical amp blocks will have one or more gain or drive controls that control the preamp levels and distortion voicing, a master volume that controls the input into the power amp, and a channel volume that controls the overall output of the block. These controls are all interactive, so its helpful to have a process for setting them. I start with a reasonably clean preamp (drive controls not too hot), and work on the Master volume to get the power amp distortion I need for the patch. Power amp distortion can be a bit harsh, and abrupt because of symmetric clipping and the effect of negative feedback. So I like to voice this distortion first.

 

Then I adjust the drive controls to get the overall level of distortion I want from the amp. For most of my patches, this is on the edge of breakup where the amp is the most dynamic. I will often use a Drive footswitch to move the drive control from a min to a max value to control the amount of distortion from the amp. Distortion blocks are then used for additional distortion control.

 

For amps that have multiple drive controls, I set Drive 2 for the overall clean tone (because it will often have a bypass cap that adds treble as the control is turned down), and Drive 1 to control the distortion levels.

Preamp distortion can be smooth, but can sometimes limit dynamics, get muddy, or loose too much articulation. I might try moving the Master volume up and down while moving Drive 1 down and up to compare the relative amount of preamp vs. power amp distortion, setting them for the desired distortion voicing.

 

If the master volume and drives are up pretty high, the amp block can add a significant gain boost in the signal chain. I use the Channel Volume to bring the overal output of the block back to close to unity gain. This way I’m pretty sure there’s no chance of digital clipping, and I’m hitting the post amp blocks with a signal level that’s hopefully in their sweet spot, the levels at which they were designed to operate. This also helps to keep levels between patches somewhat normalized and makes sure I’m not sending a really hot signal to my FRFR and/or FOH.

[jbuhajla]

...

Then I adjust the drive controls to get the overall level of distortion I want from the amp. For most of my patches, this is on the edge of breakup where the amp is the most dynamic. I will often use a Drive footswitch to move the drive control from a min to a max value to control the amount of distortion from the amp. Distortion blocks are then used for additional distortion control.

 

...

If the master volume and drives are up pretty high, the amp block can add a significant gain boost in the signal chain. I use the Channel Volume to bring the overal output of the block back to close to unity gain. This way I’m pretty sure there’s no chance of digital clipping, and I’m hitting the post amp blocks with a signal level that’s hopefully in their sweet spot, the levels at which they were designed to operate. This also helps to keep levels between patches somewhat normalized and makes sure I’m not sending a really hot signal to my FRFR and/or FOH.

 

I've noticed on some amps when I control drive and channel volume at the same time with a foot switch, I can get a distinct "POP" when going from high drive to low drive. In that case, I use an expression pedal to smoothly transition instead of instantaneous. 

 

 

It's also good to mention that Channel Volume does not effect tone, it is just overall volume control for the amp block. 

[soundog]

Good info! Copied and pasted parts into my Helix notes...

[svansickle]

I am familiar with all of the ways that block and amp levels can be set and pretty much make use of  all of your techniques.  How can you tell what the final level of the signal is going to the output jack(s)?  Do you know if  the Helix has any kind of output metering capability?  Do you have any techniques for normalizing the levels of your patches?  It seems like there should be an output meter or something like that so you can know what you're sending out.

 

Thanks,

Scott V

[amsdenj]

I just use a meter in my DAW though the USB, or a dB meter on my phone.

[amsdenj]

One more thing to add to this topic. Above I talked about preamp and power amp distortion. There’s some flexibility there for voicing the distortion. For example, the presence control will boost highs when the power amp isn’t clipping, but has almost no effect when it is (because the power amp has no remaining gain to process negative feedback). If there are two gain controls, then often at least one will have a bypass cap that can boost highs when the control is turned down. This can be used to control distortion voicing depending on which gain stage is contributing the distortion - the first or second.

 

But this is pretty limited. Of course you can use EQ after the amp to do most anything. But for simplicity, you can use an on the edge of distortion amp for clean tones, and pedal distortion blocks in front for a lot of flexibility. That’s because most distortion pedals have tone controls that can be used to sculpt the distortion voicing in very specific ways. And turning the pedal off removes them from the signal chain. 

 

Some modern amps with multiple channels and tone voicing switches can also do this. But distortion pedals often have more flexibility. Its also easy to stack them for even more control

[patdixon]

Great  info, thanks! 

On 2/24/2018 at 4:23 PM, amsdenj said:

channel volume that controls the overall output of the block

I hadn't realized this, but it makes sense.