Level vs. Master Vol.

The input trim changes the input. It doesn't change the model. The model remains the same. I was just trying to say that it only effects the amplitude of the signal and doesn't actually change the model. The model will react to higher or lower input but the input trim does not effect the way the model reacts or functions. The input amplitude itself changes and the model reacts but the trim doesn't change the way the model reacts. When you change MV and Gain you are changing the way the model reacts or is operating; adding more or less power tube distortion, changing the EQ of the input to the preamp and so it follows the kind of distortion it produces while reacting to the differing input.
 
If you limit the definition of "changing the model" to "changing the model's EQ," the no, it doesn't change that. But I think changing the gain of the amp fits the definition of changing the way the model behaves. :)
 
It doesn't change the way the amp responds to input signal. It does change the input signal.
The rest goes to more than just the EQ AFAIK. Doesn't matter really.
Maybe it's mislabeled. I just choose to look at it as an input trim.
 
Last edited:
blearyeyes said:
It doesn't change the way the amp responds to input signal. It does change the input signal.
The rest goes to more than just the EQ AFAIK. Doesn't matter really.
Maybe it's mislabeled. I just choose to look at it as an input trim.
Click to expand...

The "Input Trim-Parameter" is programmed (modeled) as a part of the real hardware in a real amp!
So its value affects the behaviour of the first gain stage of an amp.
Even it is a part of the (software)modeling process.
It doesn't only change the input amplitude, like the "(Block)Level-Parameter" only changes the output amplitude of the amp-block without changing the signals structure.

BTW, in the last version of "JMA Amp_&_Cab_Quick_Reference Q9.00_AE 3.14.3_24.10.2017" you can read the whole story.
Here's a dump of the file:

Input Trim
The Input Trim control adjusts the input attenuation without changing the frequency response. If you turn down the Input Drive and the model has a bright cap the amp will get brighter. Now you may like the brighter tone but wish there were more gain. Input Trim allows you to increase the gain without changing the tone. Conversely you may like the darker tone with Input Drive set high but wish there were less gain. In this case you can lower Input Trim.
Most real amps do not possess an Input Trim control. Instead they usually have a switch or two input jacks that select between a high-gain and low-gain input. Almost invariably the di erence between these two jacks is 6 dB. All the Axe-Fx amps are modeled using the high-gain input or switch position (if any). To simulate the low-gain input set the Input Trim to 0.5 which is 6 dB less.

Regards
Mike
 
There seems to be some confusion with the use of the terms gain and trim. They are concise audio terms that describe different things. If you want less gain in a circuit you have to reduce the amount of gain the circuit is producing. Saying that you can trim the input signal to reduce the GAIN is not correct usage of the terms. Similar to the use of the term "Tremolo Arm" on a guitar. It is a actually a vibrato arm. Just because it is called a Tremolo doesn't mean it acts like the tremolo circuit in your amp. It modulates the frequency and not the amplitude of your guitar. I come from an audio engineering background. Trims do not control the amount of gain in a circuit. They only reduce the input signals amplitude. The gain that the following circuit adds to the signal remains the same.

If the input trim adjusts the gain of the amplifier then it isn't a trim at all.

You don't trim a piece of paper to make it bigger.
 
Last edited:
blearyeyes said:
There seems to be some confusion with the use of the terms gain and trim. They are concise audio terms that describe different things. If you want less gain in a circuit you have to reduce the amount of gain the circuit is producing. Saying that you can trim the input signal to reduce the GAIN is not correct usage of the terms.
Click to expand...
Gain is amplification — nothing more. If an amplifier gives you twice as much power as you put into it, that's a gain of +3 dB. If a trim circuit cuts the signal's power in half, that trim circuit has a gain of -3 dB.

Input Trim is part of the Amp block. If you adjust Input Trim, you're changing the overall gain of the Amp block.


blearyeyes said:
...the use of the term "Tremolo Arm" on a guitar. It is a actually a vibrato arm. Just because it is called a Tremolo doesn't mean it acts like the tremolo circuit in your amp. It modulates the frequency and not the amplitude of your guitar.
Click to expand...
True story.


blearyeyes said:
Trims do not control the amount of gain in a circuit. They only reduce the input signals amplitude.
Click to expand...
A change in amplitude is a change in gain.


On the subject of misused terminology, guitarists often use the words "gain" and "distortion" as if they were the same thing. They're not. You can add distortion to a signal by increasing gain, but it's possible to increase gain without causing distortion. It's also possible to increase distortion without adding gain (that's what the saturation circuit in a guitar amp does).
 
Gain is what is added to the amplitude of the signal by an amplifying circuit. It is the amplitude that is gained during the process. Like I said just because we guitar players use a word for something doesn't change the base meaning of the word. The input trim does not change the amount of gain added to the signal by a circuit. It changes the amplitude of the incoming signal. The amount of gain that is added to the signals amplitude, by the circuit, remains the same.

Are we having fun yet?

How is losing 3db of signal a gain?
So if you turn down your guitar by 3db then that is considered gain?
 
Last edited:
blearyeyes said:
How is losing 3db of signal a gain?
So if you turn down your guitar by 3db then that is considered gain?
Click to expand...
If your guitar is turned down by 3 dB, you've introduced -3 dB of gain into the circuit. That's how the math works. You can have negative gain just like you can have negative pressure.


Gain is as I described in my previous post. That's what it means in the two engineering disciplines I've studied (electrical and audio). If you don't accept that, I'm cool. But I'll leave you with this question:

What happens when you turn up Input Trim past noon — above 1.0? Would you still say that Input Trim isn't gain? Would you still use the trimming-a-piece-of-paper analogy?
 
Rex said:
If your guitar is turned down by 3 dB, you've introduced -3 dB of gain into the circuit. That's how the math works. You can have negative gain just like you can have negative pressure.


Gain is as I described in my previous post. That's what it means in the two engineering disciplines I've studied (electrical and audio). If you don't accept that, I'm cool. But I'll leave you with this question:

What happens when you turn up Input Trim past noon — above 1.0? Would you still say that Input Trim isn't gain? Would you still use the trimming-a-piece-of-paper analogy?
Click to expand...

If it is able to add gain then it isn't a trim control. It is an input gain control.
 
blearyeyes said:
If it is able to add gain then it isn't a trim control. It is an input gain control.
Click to expand...
It's a trim control. It works just like trimming out an airplane. You add positive or negative bias to the controls, as the situation demands.
 
blearyeyes said:
If it is able to add gain then it isn't a trim control. It is an input gain control.
Click to expand...
Very close but not exactly that; check the manual on page 40 about INPUT TRIM
Post scriptum ; as far as I understand Input Trim is available only for amps that don't have an overdrive knob on their original version. It's a kind of clean boost or cut down before the preamp section that can help to easily adapt to different guitars; example SC guitar instead of Humbucker. Of course when putting up your clean boost before the preamp section, the amp will breakup earlier which is fine and appreciable for Fender amps for example.
 
Last edited:
It sets the level plus or minus going into the amp. Good enough. Terminology is changing as the years go by and trim is used on input gain controls on mixers now. When I started out things were not digital and I taught audio through the transition. Lot's of things changed then and lots since. It suffices to know that you can change the level regardless of the label on the knob. I've never noticed an amp model that didn't have the trim control. So I don't know what that's all about.
 
chris said:
It allows the Input Gain control to add more or less gain. It can’t be called an Input Gain Gain.

Perhaps this isn’t a big deal?
Click to expand...

Clarity is helpful.
Input Gain and Amp Gain/ Trim and Gain. Whatever...
GUI / Interface design and clarity is a personal preference of mine and it is somewhat important to the user friendliness of any given device. Whether or not user friendliness is a important is really up to the designers. I would have tried to make the device easier to operate but I don't build em so I'll keep my peace. :)
 
Last edited:
You must log in or register to reply here.
Back
Top Bottom