Calibrating Input Level for Plugins

[Orvillain]

And FWIW, I get the same measurement from the multimeter for a C note across 8 octaves of pitch, at the same output level.

 

[Orvillain]

My mate has some signal generators and oscilloscopes. Might see if I can borrow a pair - completely take all of the digital shit out of the equation!

 

[SillyOctpuss]

SSL2 Spec for Instrument Inputs:

View attachment 3711

+15dBu is 4.356 RMS.
20*log(0.500/4.356) = -18.8 dBFS
Our target with 0.500v is -15.3 dBFS.

Going by manufacturer specs alone you had to boost +3.5dB, if you did everything correctly it demonstrates that specs can be FAR off.

I just did this on my new ssl2 and if I followed it properly I had to boost by 3.8db

 

[James Freeman]

@laxu
We need another tech savvy axefx3 owner that can put a 500mV sine tone through it to confirm.
Will you help us?

 

[laxu]

@laxu
We need another tech savvy axefx3 owner that can put a 500mV sine tone through it to confirm.
Will you help us?

Can't be bothered to read the whole thread. Can you give some step by step instructions?

 

[SillyOctpuss]

Can't be bothered to read the whole thread. Can you give some step by step instructions?

The instructions are in the original post.

 

[James Freeman]

Can't be bothered to read the whole thread. Can you give some step by step instructions?

Generate a pure sine tone at 400Hz with a synth block in the AxeFx and rout it to one of the Outputs.
Adjust the output volume until you read exactly 500mV AC RMS with a DVM on the 1/4" plug of a guitar cable connected to that output.
Loop the 1/4" back into Instrument Input 1 on the AxeFx front and read the dBFS value of Input 1 in your DAW when used as a USB interface.
Make sure input 1 is not routed to the same output of course.

Basically, I need a dBFS reading of Input 1 with a 500mV sine tone on it.

 

[MirrorProfiles]

Can someone with a Quad Cortex also test this please?
I just got a response from Neural's customer support via their devs.

If you are using QC as an audio interface, the USB output has to be boosted by 2.26 dB (2.2 or 2.3 dB works) to match an interface such as an UA Apollo, for example.

This can be done either on Quad Cortex by adding a GAIN block in The Grid or in the plugin itself by boosting the INPUT knob by 2.2dB.

I didn't mention Apollo or anything, I just mentioned about using the QC as an interface for using Neural plugins. So now I'm presuming that Neural plugins are set up for 12dBu. The only thing that doesn't add up is the QC specs - they haven''t posted the DI's maximum input level. The reamp send's output a 9.5dBu signal, so I assumed this is what the input uses too.

The information from NDSP here suggests that the QC DI is actually giving a 14.26dBu signal. So either there is some internal levelling going on to make the capturing matched, OR they just mixed up boost and cut (which would get closer to that 9.5dBu range).

Either way, the above quote makes me think NDSP have set their plugins up for 12dBu inputs - the most sensible choice given how common it is on most consumer level interfaces.

 

[laxu]

Generate a pure sine tone at 400Hz with a synth block in the AxeFx and rout it to one of the Outputs.
Adjust the output volume until you read exactly 500mV AC RMS with a DVM on the 1/4" plug of a guitar cable connected to that output.
Loop the 1/4" back into Instrument Input 1 on the AxeFx front and read the dBFS value of Input 1 in your DAW when used as a USB interface.
Make sure input 1 is not routed to the same output of course.

Basically, I need a dBFS reading of Input 1 with a 500mV sine tone on it.

-15.6 dB is the reading I got.

Synth @ 400 Hz -> Out 3 -> In1. Synth set to +20 dB volume as that is what my ancient DT830B multimeter would measure as 500 mV.

In Reaper I monitor In1, Axe-Fx 3 as audio interface.

Input 1 sensitivity on the Axe-Fx is set at 50%.

Input 3 boost/pad is set to 18 dB because that seems to minimize noise if I want to hook up my pedalboard. My current apartment, despite being built in 2009, seems to have plenty of EMI issues as single coils hum a lot more than they did in my previous one. The boost/pad setting does not seem to have any effect on the measurement though, which means it's working as expected.

 

[James Freeman]

Thank you Laxu!

Ah, you got the same POS yellow DVM like Orvillain.
You got a -15.6 dBFS, and Orvillian got -16.5dBFS, that's the same reading as far as I'm concerned.

Either these cheapo DVMs can't read 500mV accurately or the AxeFx3 actually does have 12dBu input instead of 17.5dBu like the FM series.

 

[laxu]

Thank you Laxu!

Ah, you got the same POS yellow DVM like Orvillain.
You got a -15.6 dBFS, and Orvillian got -16.5dBFS, that's the same reading as far as I'm concerned.

Either these cheapo DVMs can't read 500mV accurately or the AxeFx3 actually does have 12dBu input instead of 17.5dBu like the FM series.

Yeah the DVM doesn't really show much for the AC scale. It has worked totally fine for everything else tho.

 

[SwirlyMaple]

If somebody wants to donate their AxeFX3T to me, I’ll measure it with a high quality recently calibrated DVM that actually works… for the greater good

 

[JiveTurkey]

If somebody wants to donate their AxeFX3T to me, I’ll measure it with a high quality recently calibrated DVM that actually works… for the greater good

 

[MirrorProfiles]

Anybody up for trying to crack the IK input levels once and for all?

I spent some time today with SJ50 and compared to my 5150 Block Letter, as well as a few other emulations that I know the internal operating headroom of. I found on the real amps, having the red channel's gain at 6 is where it noticeably flubs out and gets overly squishy and pretty useless.

Boosting the AT5 input to around 1V=0dBFS seemed to get this behaviour (sometimes it feels like it may be lower than this though). I could try and use my Mark III to determine gain levels, and some Marshalls. Maybe some others here have some real amps they can reference that are part of AT5? Such as Fender, Orange, VH4, TC100, JVM Satriani JMP-1. The manual barely even mentions input level besides saying "just make it clip and then back off a little". Following their advice, I have my headroom at about 4.6dBu - playing as hard as I can clips the AT input LED but generally its hovering near the top. This at least seems to match the behaviour of the 5150 quite close. Some other models it seems closer to 12dBu, and some closer to 0dBu. Having to guess, and have doubts is a workflow killer that doesn't exist when using real amps.

@IK Multimedia - Pete you'd win a ton of respect from me if you can give us some concrete numbers from the devs? Or maybe there is the opportunity to invite someone to discuss it here?

Come back Peter! @IK Multimedia there are plenty of passionate and heavily invested customers with questions about the software. Someone at IK will know these values - it would go a long way towards encouraging me to spend more money on other IK products

 

[StratsoundFan]

I spent half the night playing through at least 50 random captures, while tweaking the input knob for each capture separately. It's unbelievable how much this affects the character of an amp, in a good way. A lot of captures sound and feel completely lifeless, when the input gain is at default value, but if it's raised until you reach a sweet spot, the amp suddenly comes to life. Like some Fenders for example, they get that flubby low end, so typical for crancked Fenders which is simply missing, when the input gain is at zero, where it acts just like a clean amp, even though the author him/herself has marked it as an overdriven/hi gain capture. There was this Vox amp from Amalgamaudio, which totally sucked at first. until I rasied the input to around 8, only then did it sound like a proper overdriven Vox amp. Beautiful sounding Vox amp. I have to admit though, it's such a pain in the ass, having to do all the guesswork for every single capture. It kills the fun.

 

[MirrorProfiles]

Come back Peter! @IK Multimedia there are plenty of passionate and heavily invested customers with questions about the software. Someone at IK will know these values - it would go a long way towards encouraging me to spend more money on other IK products

View attachment 7829

bump.

Good to see you back Peter. New Oil Can Delay sounds great. Would love to know if you managed to find any more information about this stuff for us?

 

[StratsoundFan]

I don't think you will be hearing from him anytime soon. At least that's my impression.

 

[MirrorProfiles]

I don't think you will be hearing from him anytime soon. At least that's my impression.

I’m going to be optimistic about it - I’m genuinely happy to have the posts announcing new products and sales etc, but I also hope he values and respects the passionate and invested existing customers enough to look after us here.

Communicating this kind of information about their products is precisely what his job entails, and he’ll score a lot of points from people if he does it.

The improved poweramp to speaker interactions, and updated “optimised internal gain structure” features were genuinely big factors in me upgrading to v5.

I know people have been asking for years and have been met with radio silence, but I’m still going to be optimistic/give him the benefit of the doubt to get this one resolved finally.

 

[Rocco Crocco]

Just want to add that it would be nice if these plugins would allow you to lock the input control to whatever level is optimal for your interface. Scrolling through presets or building a new one, sometimes I forget to adjust it.

 

[Bob Zaod]

I tried to read through this thread....