Proper gain staging a Master Volume Amp - 4CM

V

VRokken

Member
I have successfully set up the 4 cable method with my Voodoo V-Rock 100 and my AxeFx III as outlined on page 27 of the manual. I also set the outputs to left only and the boost/pad to +18db as described. All works as expected.

The V-Rock is a Modded JCM 800 style amp with a master volume and a fixed level series effects loop. I am looking to confirm the proper way to gain stage output in this setup.

As there is not an effects send level on the rear of this amp, I assume the amp’s master volume becomes my send level.

If that is correct, I assume I should adjust the master volume level to provide good return signal level on input 4 - in my case about 8 for solid orange lights on input 4‘s front panel meters.

Set up this way, I would then the use the output 4 level control on the front of then Axe FX as the master volume.

In Cooper Carter’s Axe III masterclass he suggested that both outputs 3 and 4 should be at 100% for unity gain In 4CM. That also works but the input signal on input 4 has fairly low input level with my master volume adjusted down at tolerable practice level.

Obvoiusly, I trust Mr. Cater‘s advice but I would also assume I am looking for a decent input 4 level.

As I seem to be able to mix and match the levels between the amp’s master volume and the III’s output 4 with decent results, I am really just looking to confirm the recommended best practice in my situation.
 
VRokken said:
As there is not an effects send level on the rear of this amp, I assume the amp’s master volume becomes my send level.
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we'd need to know this fact exactly to suggest anything. i don't have this amp so i can't tell for certain.

are you sure that the In 4 input level changes with your master volume? typically an effects loop is before the amp master volume. that would mean channel volumes would dictate the amp effects loop send.
 
Thank you for the reply Chris, I hope you are having some improvement with your back.

Yes, if I increase the amplifier’s master volume, the level shown on input 4 meter does increase as does the overall volume.

Honestly, ether of the options seem to work and sound decent.

My question is more about which is better / preferred, a higher level coming into input 4, increasing the input 4 converter level on the Axe to compensate, or unity gain at output 4.

I would guess getting input 4 level back up to the input 1 level would take precedence over unity gain at output level. However this makes the output 4 level control very sensitive. In a quarter turn I am shaking the rafters which is also not ideal.

i was hoping some of the members who work with 4cm on pro rigs could offer some insight.
 
Unity gain on Out 3 is important to maintain the feel of the guitar connected to the amp.

Unity gain in the loop is theoretically nice since it maintains the "transparent" objective, but it's more important if you plan on using a loop bypass switch. Especially if the master volume is before the loop... If not a "flaw" exactly, it's a mediocre design decision that sort of forces your hand.

You have a few choices how to handle this. Thinking "out loud", my thoughts would be:

1) Turn the master volume as high as you would ever imagine using it, configure input 4 such that you are seeing an appropriate input level, set output 4 for unity gain, then use the master volume as normal. You may see low levels in the Axe at lower MV settings, but if it sounds good and noise isn't an issue then don't worry too much. The advantage of this approach is that it makes the Axe most "transparent" in terms of everything being the same if you switched it out of circuit and allows you to use the master volume knob normally.

2) Set the master volume as high as you can without clipping input 4 and use the Axe to control the volume. The advantage here is that you are dumping less signal and SNR should be theoretically better. (If the output 4 knob is too sensitive reduce the level in the output mixer to give you better control over the "useable" range.)

Personally, I think I'd lean towards approach 2, but you should experiment and see what works best for you.

I guess you could also mix... Set the MV as high as you'd use it (rather than as high as in 4 can take) and use out 4 to adjust volume rather than leaving it maxed for unity.
 
VRokken said:
Thank you for the reply Chris, I hope you are having some improvement with your back.

Yes, if I increase the amplifier’s master volume, the level shown on input 4 meter does increase as does the overall volume.

Honestly, ether of the options seem to work and sound decent.

My question is more about which is better / preferred, a higher level coming into input 4, increasing the input 4 converter level on the Axe to compensate, or unity gain at output 4.

I would guess getting input 4 level back up to the input 1 level would take precedence over unity gain at output level. However this makes the output 4 level control very sensitive. In a quarter turn I am shaking the rafters which is also not ideal.

i was hoping some of the members who work with 4cm on pro rigs could offer some insight.
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it's a balancing act. you really want Unity Gain out of the Axe to go back into the amp. sounds like the amp isn't playing along too nicely if the master volume controls these sorts of things.

i wouldn't worry much about Input 4. just get a good master volume on the amp, adjust the Axe input to get the correct input on the front panel VU (not going into red). then adjust from there.

as long as input isn't clipping, you want as much output from the Axe as you can, and generally that's turning the Out 4 knob all the way up.
 
Thank You both for the assistance and advice.

I worked with this for a good bit again today.

Yes, I have alway had output 3 at unity gain - no issue there. The amp sounds exactly the same as it does with a cable straight into he amp.

There is no switching for the loop, if a pair of cables are plugged into the loop, it is active.

I am also using the Humbuster cables from Fractal as suggested in the Manual. I have minimal noise with this setup whichever way I set the master volume and output 4 levels.

I have eliminated increasing levels of input 4 on the Axe setup as an option. I did some reading and learned that was not the proper way to add gain.

In the end I found using my amp’s master volume at settings similar to what I would use without the Axe and using output 4 on the Axe as an overall volume to be the most manageable. Setup this way, I am able to keep output 4 at 50% or greater with good results And use my amp as I normally would.

All of that said, I also have not attempted to increase any block output levels within the grid. All blocks are at their default 0db output level. Should I play around with a level boost somewhere in the grid after input 4 ??

I am sorry if I am being a persistent, there are just so many places I could fix this within the Axe and I want to learn how do do this properly.

Thanks again!
 
VRokken said:
Thank You both for the assistance and advice.

I worked with this for a good bit again today.

Yes, I have alway had output 3 at unity gain - no issue there. The amp sounds exactly the same as it does with a cable straight into he amp.

There is no switching for the loop, if a pair of cables are plugged into the loop, it is active.

I am also using the Humbuster cables from Fractal as suggested in the Manual. I have minimal noise with this setup whichever way I set the master volume and output 4 levels.

I have eliminated increasing levels of input 4 on the Axe setup as an option. I did some reading and learned that was not the proper way to add gain.

In the end I found using my amp’s master volume at settings similar to what I would use without the Axe and using output 4 on the Axe as an overall volume to be the most manageable. Setup this way, I am able to keep output 4 at 50% or greater with good results And use my amp as I normally would.

All of that said, I also have not attempted to increase any block output levels within the grid. All blocks are at their default 0db output level. Should I play around with a level boost somewhere in the grid after input 4 ??

I am sorry if I am being a persistent, there are just so many places I could fix this within the Axe and I want to learn how do do this properly.

Thanks again!
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Watch the VU meter in Layout Zoom (out) to level your presets. You shouldn’t be getting volume to your amp from the preset or blocks necessarily. That’s the output knob’s job.

Why do you need a level boost?
 
I am not sure I do.
This has been my question all along.

Will an input 4 level that is 50% of the input 1 level as it returns from the amp be detrimental to achieving good sound quality (SNR) as it processes through the post loop effects.

If that answer is yes, then I need to boost that level coming from the amp or in the grid itself right after the return and reduce the output 4 level to something tolerable for a practice level.

I have plenty of volume when I set output4 for unity gain. However, my input4 level is then at or below the 50% mark If I want to stay in the room with it.

I guess in the end I have the age old problem with the 100 watt head that most do.
You have to play at 11 to get your sound :).

That is whole reason I went to the Axe fx 10 years ago. I need a solution for practicing at home.

I was just hoping to put my V-Rock to some use. It was a sizable investment as well.

Maybe I need to look at the Fractal load box as another possible solution.

Thank you
 
VRokken said:
I am not sure I do.
This has been my question all along.

Will an input 4 level that is 50% of the input 1 level as it returns from the amp be detrimental to achieving good sound quality (SNR) as it processes through the post loop effects.

If that answer is yes, then I need to boost that level coming from the amp or in the grid itself right after the return and reduce the output 4 level to something tolerable for a practice level.

I have plenty of volume when I set output4 for unity gain. However, my input4 level is then at or below the 50% mark If I want to stay in the room with it.

I guess in the end I have the age old problem with the 100 watt head that most do.
You have to play at 11 to get your sound :).

That is whole reason I went to the Axe fx 10 years ago. I need a solution for practicing at home.

I was just hoping to put my V-Rock to some use. It was a sizable investment as well.

Maybe I need to look at the Fractal load box as another possible solution.

Thank you
Click to expand...
Is the “50%” a number you see or the level on the VU meter?
 
VU meters on the meters page of the main screen of the Axe.

The Input 4 meters show 50-60% of the input 1 levels with the amps master volume at 2 or 3
respectively.

The output 4 levels are also less than output 3 even when I am at unity gain on output 4.

I can improve both of those levels by increasing the amps master volume to 8 or 9, but then I have to drop from unity gain on output 4 or it will be way too loud in the room.

I will have to compromise at one end or the other. I just wanted to garner a little education as to which is the preferred place to do so.

Thank you
 
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