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Amp sim noise

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Re: Amp sim noise

Postby jthzp9 » Wed Oct 28, 2020 10:38 pm

https://soundcloud.com/user-500797446/a ... e-no-input

This is also what makes me believe this is the noise of my interface.
There is no cable connected to 2nd preamp of my interface. Hi-z is selected.

Clip 1: interface hi-z input
Clip 2: interface hi-z input with sgear applied as plugin.

There is nothing connected, so this is just the noise being generated by the interface itself. This is the sound that I'm trying to get rid of.

This is also the same exact noise I'm hearing when I have my guitar plugged in and volume off. It is present throughout the guitar track when recording which I don't like.

Again, comparing to a real guitar amp, when the guitar volume is off, it's quiet, even with enough gain on tap to be in crunch/rock territory.
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Re: Amp sim noise

Postby blinddrew » Wed Oct 28, 2020 10:45 pm

Apologies if you've covered this already, but if you take your current set up and record so that your peak signals are at a healthy -10dB and the average is burbling along around -18, what level is this background noise showing on the meters?
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Re: Amp sim noise

Postby James Perrett » Wed Oct 28, 2020 10:58 pm

Recording your Soundcloud link into Reaper gives me an RMS noise level of around -93dBFS with no effects and -83dBFS with the amp sim enabled. I wouldn't call these levels excessive.

If I'm wrong it might help if you could provide a downloadable link so that we can see the real numbers.
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Re: Amp sim noise

Postby merlyn » Thu Oct 29, 2020 4:03 pm

jthzp9 wrote:Again, comparing to a real guitar amp, when the guitar volume is off, it's quiet, even with enough gain on tap to be in crunch/rock territory.

Something to bear in mind is that the speaker in a guitar amp doesn't reproduce much above 5k. To do a like for like test you could take the output of your interface into the guitar amp with a clean setting or straight into the power amp if that's possible and you know how.

It's the high frequency noise that is particularly noticeable/annoying so you could look at a cabinet emulator with a 5k rolloff or tweak the HF and presence settings on the virtual power amp.
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Re: Amp sim noise

Postby jthzp9 » Sun Dec 06, 2020 4:12 am

So I had a chance to do some additional tests tonight and just wanted a bit more feedback from folks.

I have come to the conclusion that the noise I'm hearing is either the preamp noise or the converter noise of my audio interface. Perhaps it is just me, but I find this noise extremely annoying.

I did a quick test between my Hi-z input on my scarlett interface vs using the fx send from my tube amp into the line input of the interface and the noise ratio is far more acceptable to me. Furthermore, the noise is acceptably dropped by turning down my guitar volume. Where as when using the DI, the audio interface noise is at an unacceptable level.

I'm just curious if there is a reason for this? I guess I'm just not meant to jive with amp sims which is too bad because I like the idea of them, but I just can't handle listening to the underlying noise floor.

Here is a short example of what I'm talking about. In the first portion I'm using my amp into the audio interface. When the guitar volume is down, no noise is barely perceivable. Then you can hear some 60 cycle hum from the single coil pickups when not in hum cancelling positions. To me this is just a natural sound of a guitar and it doesn't bother me. The 2nd clip is the same guitar, through my audio interface and the noise floor is just unacceptably loud to me. In the beginning the guitar volume is all the way down and yet the noise is annoying and loud in my opinion. And when I go to turn down the guitar volume to clean up the signal like I do with the real amp, the tone is gone and the noise is again too loud to be useable.

https://soundcloud.com/user-500797446/amp-vs-amp-sim
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Re: Amp sim noise

Postby ef37a » Sun Dec 06, 2020 5:21 pm

I felt that the noise to riff ratio in the first clip very acceptable. The hum would bother me more.

I have looked up the noise spec of a 5watt valve guitar amplifier*.

With ALL controls at maximum and a shorting jack in the input the noise at the 8 Ohms speaker jack for a clean setting is -46dBV or better. For the overdrive setting it gets much worse at -15dBV (n.b. guitar amp tech s do not use an outdated measuring system based of over a hundred years old telephone technology!)

It is likely therefore that any amp sim' is simply going to boost system noise quite a very lot.

*And that is one of THE quietest guitar amps you will find.

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Re: Amp sim noise

Postby Wonks » Sun Dec 06, 2020 8:59 pm

On almost all guitar amps, the input is taken to ground with no jack inserted. On an audio interface or DI this is not the case, so with nothing inserted, the wiring is able to pick up electrical noise that is then amplified through the system and any software that adds gain.

If you want to find out what your true audio interface background noise level is (and it should be very low if it's not faulty), they you really need to insert as jack plug into the AI (in Hi-Z mode) with the tip and sleeve connected together with a 470k resistor (which will simulate the DC resistance of an 8k humbucker and 500k volume pot in parallel). You could also just short to ground (which is what a guitar volume pot set to 0 would do) but the resistor is a bit more real world 'ideal guitar plugged-in but not playing' scenario. Any noise you then hear on that channel will be the result of the noise picked up or generated within the audio interface itself with no contributions from the

Turn down the gain on any unused inputs and make sure that the AIs' and DAW's own audio routing setups aren't mixing in any signals from unconnected inputs to that channel.

Set the input channel gain to a value you'd use with a guitar plugged in. Record the noise onto a plain audio track with no plugs and no gain applied to the channel input in software. That will be the audio interface noise level you are recording and which is then getting amplified.

Then simply remove the shorting plug, plug in the guitar with the volume knob up full, position yourself for minimum hum with your hands on the strings so you are grounded and record the noise level again. You should notice a substantial increase in level. You'll need to tell us how much, it increases by, but I'd suggest that it will be a considerable increase. And it's that noise which is then being amplified by your amp sim plugs.

Which doesn't really help you in a practical sense, but it might help you understand where the noise is coming from, which is very unlikely to be the audio interface itself.

My HF hearing is completely shot, and I simply can't hear any real noise in the clips, though I can see the waveform on the screen, but it does also indicate that the noise is almost all at frequencies that a normal guitar speaker would filter out. So are the cab sims working properly?

An amp sim isn't a valve amp, it hasn't got the same input circuitry, so it won't react like a valve amp when you turn your guitar's volume down. It's got a high input impedance so that it won't load a passive the guitar pickup and roll off a lot of the treble, but that's as far as it goes. The rest is down to the amp software and how well it simulates the amps it's modelling. And that model will be based on getting an input signal that's equivalent to the signal level going into a real amp. Presumably the amp sim manual tells you at what level that should be, so try and get that level feeding into the amp sim. You may need to add a simple gain plug in to set that level if your DAW doesn't have an input gain control on the channel input. If it's supposed to be at a maximum of say -20dBFS, then try and get the signal peaking at that. If the input signal is too low or too high, then you'll get a different feel to a real amp. I've messed about with amp sims on previously recorded guitar tracks, but never tried to use them live. By which time I've normally gone and edited the guitar tracks to cut out noise between sections.

But I do have quite a few amps (Two Rock Studio Pro22, Fender 68 Custom Deluxe Reverb, handwired Fender 5E5A tweed Super style combo, Sound City 50 Plus head with the Hiwatt passive EQ mods, Laney Ironheart IRT30 combo, Orange Tiny Terror, Fender Vibro Champ and a Blackstar HT5) and none of them are particularly quiet, especially with the gain/volume turned up. In my real world, I get a lot more hum and hiss from them than you are getting with the Scuffham software. But if recording, the moment they get slotted into a track, the noise magically gets hidden by the bass and drums and vocals. Or at least it sounds like that to me.
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Re: Amp sim noise

Postby CS70 » Mon Dec 07, 2020 1:25 am

Wonks wrote: But if recording, the moment they get slotted into a track, the noise magically gets hidden by the bass and drums and vocals. Or at least it sounds like that to me.

+1
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