Output 3 Clipping with certain drives

S

Soulfly

Member
Hi, I'm using the FM9 in 4CM with my Mesa Triple Crown and I'm having an issue with the output 3 clipping with certain drives.
I follow the 4CM connections as shown in the FM9 manual, so it is connected as follows:
  • Guitar (Ibanez RG with Seymour Duncan JB) connected to FM9 input using a Shure GLXD16+
  • FM9 output 3 -> Amp input
  • FM9 input 3 -> Amp FX send
  • FM9 output 1 -> Amp FX return
To demonstrate this issue I recorded a video, where I have a simple preset with input 1, drive and output 3. (not using effects loop in here)
I used two scenes where scene 1 is using T808 OD on drive channel A and scene two is using Shimmer drive on channel B.
I only changed the drive and volume in each one, where drive is about 2.5 and volume/level is set to 10 on both.

It also worth noting a couple of global configs:
  • Input 1 A/D Sensitivity is set to 10%
  • Input 1 Gain is set to 1
  • Output 3 Boost/Pad is set to 0 db
Any thoughts on what I could be missing?

Thanks in advance!
 
Last edited:
Is the output only clipping while you are using the shimmer drive, or with the T808 also? The shimmer is a FAS custom model and from my experience it boosts the signal much louder than models based on real boos pedals.

I’ve had the same problem and the only solution is to reduce output 3 pad to 0dB which you’ve already done, and adjust the level on the drive block until it doesn’t clip.
 
It clips with Shimmer and FET Pre, and it does NOT clip with T808.
The FET pre I had with level at 10 and drive at 1.5.
 
Last edited:
From my experience on Ax3, there is limited headroom on output3/4, which restricts the amount of boost level that can be sent from an internal drive block (or any block really), to an external device (ie external amp input). Due to this limitation, I use an analogue external boost pedal in my 4CM setups to do "big" boosts to my external amps' inputs. Despite this, there is still enough room for me to send a fairly healthy boost (about +8 to 10db with boost/pad @ 6 thru loop3 with my strongest guitar) from inside Axfx to external gear.

(as noted above, increasing "boost/pad" on an output, further reduces headroom before clipping on that output - which seems to be the trade off for getting some noise reduction)
 
Last edited:
GlennO said:
You're not missing anything. Many effects change the signal level. That's why blocks have level parameters. If the level is too high, turn it down :).
Click to expand...
I could see that been the case if we were talking about a chorus, phaser, delay, etc. But when talking about a drive that is been used with the intent of boosting the from of an amp, I'm not sure the solution should be to lower the level/volume.
 
sprint said:
From my experience on Ax3, there is limited headroom on output3/4, which restricts the amount of boost level that can be sent from an internal drive block (or any block really), to an external device (ie external amp input). Due to this limitation, I use an analogue external boost pedal in my 4CM setups to do "big" boosts to my external amps' inputs. Despite this, there is still enough room for me to send a fairly healthy boost (about +8 to 10db with boost/pad @ 6 thru loop3 with my strongest guitar) from inside Axfx to external gear.

(as noted above, increasing "boost/pad" on an output, further reduces headroom before clipping on that output - which seems to be the trade off for getting some noise reduction)
Click to expand...
That could explain it.
It's just strange because I believe I saw in other threads saying the level of output (db) it can achieve are pretty high.
(I'll try to find the thread I read it)
 
Soulfly said:
That could explain it.
It's just strange because I believe I saw in other threads saying the level of output (db) it can achieve are pretty high.
(I'll try to find the thread I read it)
Click to expand...
How much headroom you get depends on the guitar used (a standard way to measure it across devices would be with a 0Db signal (ie sine wave) sent to input - comparing digital clipping headroom reports from different players using different guitars won't tell you much).

How much boost headroom are you getting? (you can test this by just having Input1 block fed into Output3 block - see how far you can increase the output3 block's level before getting red on the front panel output3 meter/clip light (set boost/pad@0, Input1Gain@1 for this test).

Edit: Example of how results of this test depends on the guitar used:
  • With my strongest humbucker guitar (Carvin DC127), and pad @ 0 -> 12Db headroom before redlining the FP out3 meter.
  • With my weakest (Vintagy Fender Mexi Strat), and pad @ 0 -> 20Db headroom before redlining the FP out3 meter.
The various drives in Axfx are accurate in their maximum level values afaik - so if the pedal is a strong booster irl (ie MXR Micro Boost), then it's gonna be strong in Axfx also @ level = 10 compared to other drives. It's all usable when operating totally inside a modeller, but in 4CM, some typical real life boosts are too strong to go from inside to out - this applies to any modellers afaik - of the modelling devices I own, Axfx3 seems to yeild the most usable headroom before clipping, so better than other modellers in that way.
 
Last edited:
Soulfly said:
That could explain it.
It's just strange because I believe I saw in other threads saying the level of output (db) it can achieve are pretty high.
(I'll try to find the thread I read it)
Click to expand...
Maybe you are talking about this thread…

From user FractalAudio: “Fractal Audio products can output up to 20dBu which is about four times what a typical drive pedal can output.”
 
jbeattie246 said:
Maybe you are talking about this thread…

From user FractalAudio: “Fractal Audio products can output up to 20dBu which is about four times what a typical drive pedal can output.”
Click to expand...
That might be it, I also found this same information in the wiki.
But honestly, 20db, all though could be more than enough, there are many pedals with more than this, like the TC Spark with 26db, as an example.
And maybe that's where the problem lies, if there is a limit, I just have to be mindful that with some drives, I might not be able to do the usual drive all the way down and level all the way up that I tend to use. (I pretty much only use drive to boost my amp)
 
sprint said:
How much headroom you get depends on the guitar.

How much boost headroom are you getting? (you can test this by just having Input1 block fed into Output3 block - see how far you can increase the output3 block's level before getting red on the front panel output3 meter/clip light (set boost/pad@0, Input1Gain@1 for this test).

Edit: Example of how results of this test depends on the guitar used:
  • With my strongest humbucker guitar (Carvin DC127) - 12Db headroom before redlining the FP meter.
  • With my weakest (Vintagy Fender Mexi Strat) - 20Db headroom before redlining the FP meter.

The various drives in Axfx are accurate in their maximum level values as far as I know - so if the pedal is a strong booster irl (ie MXR Micro Boost), then it's gonna be strong in Axfx also. It's all usable when operating totally inside a modeller, but in 4CM, some typical real life boosts are too strong to go from inside to out - this applies to any modeller afaik.
Click to expand...
Thanks for the tip on checking input levels, I was wondering how I could check if it's too hot.
When I ran the test I could go up to 9db. After that it clips easily.
(I tend to strum pretty hard, and that doesn't help here neither)

I thought it could be a bit on the higher side, but didn't think it could be too high.

Any suggestion what I could do to lower the level without affecting dynamics and how it interacts with my amp?
I also would like to increase the pad in output 3 to at least 12db if I can.

I can also lower the db output of my Shure wireless system as well, if that could be a good way to do this.
 
Last edited:
Soulfly said:
Thanks for the tip on checking input levels, I was wondering how I could check if it's too hot.
When I ran the test I could go up to 9db. After that it clips easily.
(I tend to strum pretty hard, and that probably doesn't help here neither)

I thought it could be a bit on the higher side, but didn't think it could be too high.

Any suggestion what I could do to lower the level without affecting dynamics and how it interacts with my amp?
I also would like to increase the pad in output 3 to at least 12db if I can.

I can also lower the db output of my Shure wireless system as well, if that could be a good way to do this.
Click to expand...
Not many options here since the limit is the limit with the Axfx physical output3 knob at max. Increasing the pad will further reduce your headroom, and reducing guitar input level in any way will give you more headroom out, but your signal to the amp will be weaker so the amp won't respond the same.

Here's something to think about though: If you are currently clipping the loop output, then I'm not sure you're getting more than that +9Db out of the drive block to the external amp's input anyway, so try backing off the Drive block level untill you no longer clip the loop output and you may find that you're not really losing anything in terms of how the amp is responding.

If you need more boost to the external amp than the amount of loop out headroom available given your input signal, then as I mention above, the only option I see is to put another gain stage outside of Axfx (ie add an analogue boost pedal just before external amp input - can be painful for switching I know). To me, this is one of the main disadvantages of 4CM vs all digital or all analogue - there are some constraints to consider when going back and forth between digital and analogue which 4CM does (latency, noise floor, dig clipping headroom).
 
Last edited:
sprint said:
Not many options here since the limit is the limit with the Axfx physical output3 knob at max. Increasing the pad will further reduce your headroom, and reducing guitar input level in any way will give you more headroom out, but your signal to the amp will be weaker so the amp won't respond the same.

Here's something to think about though: If you are currently clipping the loop output, then I'm not sure you're getting more than that +9Db out of the drive block to the external amp's input anyway, so try backing off the Drive block level untill you no longer clip the loop output and you may find that you're not really losing anything in terms of how the amp is responding.

If you need more boost to the external amp than the amount of loop out headroom available given your input signal, as I mention above, the only option I see is to put another gain stage outside of Axfx (ie add an analogue boost pedal just before external amp input - can be painful for switching I know). To me, this is one of the main disadvantages of 4CM vs all digital or all analogue - there are some constraints to consider when going back and forth between digital and analogue which 4CM does (latency, noise floor, dig clipping headroom).
Click to expand...
That sums it up well.
My initial concern was if I was doing something that could be degrading the signal in some way, which except for the high levels, doesn't seem to be the case.
Now that I understand what's going on, I can play with it and adjust levels accordingly.

I'll be honest, the best ways I could drive my amp was either with an FX8 or an AXE FX II/III.
The amount of flexibility these units offer on the drive block allows me to shape the tone in ways I can't with a normal pedal.
As an example, I can't lower bass or adjust mid frequency on a TS808 pedal.

Thanks again for your help.
(and others that helped as well)
 
Soulfly said:
But honestly, 20db, all though could be more than enough, there are many pedals with more than this, like the TC Spark with 26db, as an example.
Click to expand...

I thought I should clarify something here: dB are different from dBu, @FractalAudio explained the difference in this thread:

Secondly, dB is a ratio of powers so 25dB is not a voltage level. 25dBV or 25dBu would be voltage levels.

However, a drive pedal can't get anywhere near 25dBV or 25dBu. Most drive pedals operate off of 9V which means their output is necessarily limited to less than 9V peak-to-peak. Usually quite a bit less. A typical drive pedal using, say, TL072 op amps (or NE5532 or etc.) can only output about 6Vp-p (3V peak). A pedal using 18V can output about 15Vp-p (7.5V peak).

For a sine wave this is only 2.12Vrms which is only 8.7dBu.

Fractal Audio products can output up to 20dBu which is about four times what a typical drive pedal can output.
Click to expand...

From my understanding of this, output 3 is going to output a louder signal that what is possible with pretty much any analog pedal.
 
Outputs 3 has the same headroom as 1&2 if Boost/Pad is at 0dB.
 
Last edited:
You must log in or register to reply here.
Back
Top Bottom