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SoftAmp PSA

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SoftAmp PSA

AXP SoftAmp PSA download
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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

Now comes with a user manual! 

Anonymous (not verified):

Ya bugger! Almost got me with that "leave blank" in the regisration page! Off to make samsapy noises with the new toy. Good luck in the challenge!

AXP's picture

Haha, you woldn't want to know how much spam I have to fight with!
And thanks!

Declan White (not verified):

This is incredible. thank you!

AXP's picture

You are welcome! Thanks!

DiegoC (not verified):

You did such a great job in this plugin that I was sincerely expecting people to put you in the top five list of the developers challenge this year (if not in the top 3 or even as winner).... And not that simple "volume checker" as winner...weird world.. However..all my respect and, thanks for this and for releasing it as freeware.
Best Regards

elizza (not verified):

so ttrue

AXP's picture

Thank you! Audio tools and generic effects are apparently used by wider audience than guitar amps. 
I'm not disappointed though, I got a lot of positive responses from guitar players. Also I think the guys who won have put in as much work as I did and their results are well deserved.

I'll continue to do what I'm doing regardless of the contest results :)

SadamJR (not verified):

Are there any presets?

urival (not verified):

Congratulations for this great amp simulator. I rated it with the highest score at KVR Developer Challenge.
I use it to play guitar live in the studio with Cantabile Lite (2 and 3) host. It souds gorgeously.
But every time I start the host with Softamp PSA inside, it makes a annoying loud noise click. This only happens with this plugin. How can I avoid this?
Thanks for sharing your wonderful creation.

AXP's picture

Thank you!

At the startup all the capacitors are charged up to their DC voltage, so there might be a click. 
Ideally, the algorithm should precompute the bias values and initialize the caps, that would alleviate any startup transients (the click you hear).

I'll add that to my bug list and fix it in one of the updates.

urival (not verified):

Thanks!!!! :-)

Flo (not verified):

This really nice!! thanks so much!! its about the sound..... but look really pretty also, just awesome.

AXP's picture

Thank you!

Chelo (not verified):

Hello, this plugin is really good, I was able to try it on a windows system, but I work mostly on Logic and PT on a mac, in PT i have the PSA-1, but I would love to use this in Logic where I do most of my mixing, will you ever make this an Audio Unit? please????

AXP's picture

Thanks! I'd like to, but I don't have time for this at the moment. It's not as straightforward as I'd like it to be, since I would need to get a Mac and learn to write code for it first.

Pat Autrey (not verified):

Norton 360 immediately uninstalls the app after install - Im not saying there is anything infectious, but Norton is certainly uncomfortable. Perhaps it's a false positive detection. Would you please ask them to update their virus definitions, so me and others in similar circumstances can use yo0ur product

AXP's picture

Hi, thanks for letting me know. What do you mean by installation? Unzipping the DLL?

As far as I remember Norton marks as suspicious everything that is not installed on many PC's, and my plugins apparently fall into that category. And from Norton's perspective I'm just one of shady developers who might put any malicious code into their applications. So I think the only way is to manually override your antivirus warnings. I'll see what I can do on my side.