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SoftAmp PSA

AXP's picture

SoftAmp PSA

Latest Version: 
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SoftAmp PSA is a virtual-analog guitar pre-amp supplemented with noise gate and compressor, all modeled after famous guitar gear that needs no introduction.

At its core there are 5 distortion stages. First three are based on op-amps with zener diodes in the feedback chain, while the last two are just op-amps being overdriven into saturation. They are followed by tonestack, speaker simulator and an output level control. Each overdrive stage has a distinct frequency shaping quality according to their names. See the EQ plot in the bottom right corner for details.

All stages are modeled as nonlinear filters with their outputs depending on both the frequency and the amplitude of the input signal. It gives the most accurate digital representation, compared to cascaded filter/static waveshaper approach.

In addition to the basic controls, there are two more knobs that control the speaker simulator parameters - Shape and Rolloff. With both knobs at 0, the speaker simulator is completely bypassed (for example, to be used with external impulse loader).

Giving even finer control over the gain structure, there are two more buttons - Asymmetric and Soft-Clip. The former applies to the zener diode stages and replaces the default 4.7v/4.7v zener pair with intentionally unbalanced 3.3v/4.7v pair to saturate the signal with even harmonics. The more the first three stages are overdriven, the more pronounced is the effect. See the clipping LED indicators to have a feel of which stage gets the most saturation from the signal. The Soft-Clip function applies to the two overdriven op-amps and changes their open-loop gain from 1 million to just 200. This effectively makes the transition from linear to saturated region much more softer, making the distortion less harsh and also helping the fading notes sound smoother.

The PSI Denoiser is noise gate with adaptive release time. It has a handy "Learn" function. Don't play anything on your guitar and hit the Learn button. As soon as the LED goes off, the gate threshold will be automatically set to match your noise level. The noise gate is applied directly to the input signal.

The Squeezo Range compressor is applied to the signal right before entering the PSA pre-amp. It's a very nonlinear, but musical sounding device. It acts as both upward and downward compressor depending on the gain and bias setting. In the original device those controls were not available for user adjustment.

This plugin was made for KVRAudio Develope Challenge 2016. If you like it, and happen to have a KVRAudio account, please consider voting for it before December, 18th!

Version History: 

1.0.00 - 01.12.2016
- Initial Release

1.0.01 - 06.12.2016
- Double click now properly resets the knob position
- Drive knob now has a correct range (extended towards lower gain)
- Version update availability text is now properly colored
- Default preset now initializes all the controls
- Fixed a bug that could affect the compressor/gate gain plot when multiple instances are launched

1.0.02 - 16.12.2016
- Fixed a bug that affected channel balance of Squeezo Range in stereo mode


AXP's picture

I know. I'm slowly doing some rework of my software in the backgroud to make it easier to port and support. I'm not familiar with OSX though, so it will take a good while before I can produce anything useable.

Anonymous (not verified):

Non-Reaper user here...I'm on Cubase, since presets don't work on my DAW, I'd love it if someone could post the SVT settings here. Even better if someone made a YouTube video going through each preset. That way at least we could view the settings there and copy the.. Aside from that, this is a wonderful plugin. Cheers

Tim (not verified):

Man, awesome job. I love this plugin.
You can throw it on almost any source and it Sounds
Thank you.

AXP's picture

Thanks, you are very welcome!

joaocalbino (not verified):

Hi. This works whit Mac also?

AXP's picture

Unfortunately, no. I don't own a Mac, so it's quite painful for me to develop for one...

Anonymous (not verified):

Man, I'm a studied Sound Engineer working for Germanys biggest Broadcast and doing Music Productions for over 12 Years by now. Tried to find a software Sansamp just to play around with, because sometimes I just can't reamp through my B7K hardware. First I was disappointed, but just until I found out that you have to push the "Enable" knob at first!
I'm really blown away by this, especially on how the Squeezo reacts with the Ampsim.
Really, really great work!!!

AXP's picture

Thanks a lot for your feedback! I wish I had time back then to further fine-tune the Squeezo.

The PSA has inherently tightly coupled tone/harmonics/dynamics and sometimes having a compressor in front to take care of dynamics alone allows more freedom in setting up the PSA. I'm glad it works well for you.

Mara (not verified):

I notice those earlier posted sansamp presets go to 255 and in software it only goes to 100 so is 100 equal to 255? annoying hehe. thanks for the amp it rocks

AXP's picture

Yes, 100 = 255. That's an overlook from my side. I though 100 was more intuitive for normal (i.e. non-engineer) people, before I learned about the existing tables of presets that otherwise could have been easily imported.

Rodrigo Soto Medina:

Se ve perf4cto