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SoftAmp 3OD

Vacuum Tube Model Plugin by AXP
SoftAmp 3OD
SoftAmp 3OD
SoftAmp 3OD by AXP is a Virtual Effect Audio Plugin for Windows. It functions as a VST Plugin.
SSE2-capable CPU (at least Pentium4 or Athlon64)
32-bit display color depth
Windows XP SP3 or later
Copy Protection
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AXP SoftAmp 3OD
Vacuum Triode Stage simulator.

A single triode stage circuit typical for guitar preamps is captured in this plugin. The model engine is based on a system of non-linear ODEs. Some smart calculation techniques are used to reduce the computational load.

This effect could be used to apply mild tube overdrive to add some presence to your tracks, or you could chain a couple of instances together for a full-blown high-gain overdrive. You may want to throw in some EQ as well to better shape the signal and use a poweramp/speaker simulator afterwards.

The plugin UI has a real-time transfer characteristic plot display. It provides an overview of the things going on inside the tube. It also has a peak-detecting algorithm that will flash a line when the level exceeds 0dB. You can monitor stereo channels separately or at once by clicking the corresponding buttons under the plot display.

16x switchable oversampling is also implemented to reduce the aliasing effects. Please note that for the most time the aliasing is low enough to switch off the oversampling. When oversampling is enabled, the plot display will not be of much use, because of the phase smearing introduced by the oversampling filters. Still good enough for monitoring the in/out levels.

The model has 3 core controls to configure the circuit:

  • 3 different triode models: 12AX7, 12AU7, 12AT7.
  • 3 different plate voltages: 150v, 250v, 350v.
  • 3 different cathode capacitors: 0.47uF, 1uF, 22uF.

The gain/level controls are combined into a single knob that is operated with left and right mouse buttons.

The "Normalize Output" control enables the normalization of peak-to-peak output voltage swing across all triode configurations, particularly different plate voltages. By default it's turned off to reflect the natural triode stage behavior, which could be regarded as a normalized small-signal gain.

Please note that output signal is not clipped at 0dB to let you overdrive chained stages using more that one plugin instance connected in series. Make sure to watch the output level or use a hard limiter somewhere in your signal chain.

Clicking on the SoftAmp logo in the plugin will bring up the "About" window with a version number and contact details.

Thanks to everyone who has voted for SoftAmp 3OD in the Developer Challenge and used it in their work.

Change history:

1.0.6 (15-Sep-2013):

  • 64-bit version.
  • Fixed memory leak on UI close.
  • Size optimization.
  • Different stability improvements.
  • Added more presets.

1.0.5 (20-Dec-2012):

  • Fixed a bug with UI not opening if another instance of the plugin is closed.

1.0.4 (10-Dec-2012):

  • Significantly reduced the amount of "clicks" during the parameter change. More user feedback is appreciated.
  • Reworked GUI code to fix some drawing problems. The plugin scanning/loading should be come much smoother across different hosts. Thanks to Martin LeFever for reporting this one and helping to narrow-down the issue.

1.0.3 (5-Dec-2012):

  • "Normalize" feature wasn't working as intended. Fixed, added description.

1.0.2 (16-Nov-2012):

  • Prevented possible floating-point underflow.

1.0.1 (10-Nov-2012):

  • Fixed dependency on MS CRT library.
  • Changed signal phase to allow external dry/wet mixing.
  • Fixed UI buttons half-lit at startup.
  • Optimized CPU load (should no longer cause audio dropouts during parameter change) and model accuracy.
  • Slightly reduced audible clicks during triode mode/plate voltage change.

1.0.0 (20-Oct-2012):

  • Initial release for DC-12.


Unzip the archive and put the "AXP SoftAmp 3OD.dll" or "AXP SoftAmp 3OD x64.dll" to
your VST folder. Make sure to select the one appropriate for your system (Win32 or x64).


  • This plug-in requires the Windows Imaging Component library. It's included in all Windows versions starting with Windows XP SP3. If you are using Windows XP SP2, you can get it as a stand-alone library here: http://www.microsoft.com/en-us/download/details.aspx?id=32
  • It is my hobby to develop the VST audio effect models. I'm not getting paid for it and I use my own limited spare time to do this work. If you like my projects and would want to encourage the future work please consider doing anything from the following list:
    - Tell your friends about my site and my plug-ins
    - Send me audio samples you've made with my plug-ins
    - Drop me a line or two with any comments and suggestions
    - Make a small donation through my web site.

This software is licensed for an unlimited usage by everyone, including personal,
commercial and scientific applications. You are NOT allowed to modify it (including both the binary code and the copyright information) or sell it, in either stand-alone or
bundled form. The plug-in is provided "as is" without a warranty of any kind. In no event I shall be liable for any damage associated with the usage of this software. I encourage further distribution by sharing a link to the effect web page.

Please send your questions and suggestions to my e-mail or post them on the site.

VST is a registered trademark of Steinberg, GmbH.

AXP SoftAmp 3OD (c) 2012-2013 Alexander Petrov-Savchenko.

Latest User Reviews

Average user rating of 5.00 from 1 review
SoftAmp 3OD

Reviewed By Mark Wilkins [all]
January 5th, 2022
Version reviewed: 1.0 on Windows

the only thing that I can really say about this is that I would love to see it updated to 64-bits. It sounds great and is incredibly useful in 32 but I still can hope.

Read Review

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Comments & Discussion for AXP SoftAmp 3OD

Discussion: Active
9 November 2012 at 1:05pm

very good tones but sometimes cubase (the 5 in my case) doesn't recognise it

9 November 2012 at 10:02pm

Alb, thank you for feedback.

I will try to reproduce it. Could you please provide more details? It doesn't find it when it scans the VST plugin folder?

10 November 2012 at 8:39am

yes it sometimes appears and ad sometimes it doesn't appears.

it's annoyng because this plugin is great on vocals and now I want in in every session

10 November 2012 at 1:25pm

I still can't reproduce it in Cubase (5.1.0)

Can you provide a more detailed description? Does it happen when Cubase scans the VST plugins on start, or when you do it manually from the Devices->Plugin Information menu? What do you do to make it reappear?

10 November 2012 at 3:26pm

when cubase scans nothing happens, when I go to devices->plugin iformation it doesn't appears

I restart windows and when I'm lucky the plugin appears.

Maybe I need a format and a fresh SO install, but some other VST had this issue and the developer fixed it but I don't know how

18 May 2019 at 9:22pm

good 4 mastering too.

9 November 2012 at 6:26pm

Really sexy sound, the only downside is the delay because I have to route a signal through two channels if I want to mix the dry signal into the wet signal because adjusting the dry/wet knob in the mixer in my DAW just gives me phasing from the delay.

I still route it through two channels though it's totally worth it on my drums to make the kick into this earthquake fart sound.

9 November 2012 at 10:08pm

Hi Ligidium,

thanks for feedback.

That's a really interesting one. There are two places where the delay could be introduced. One is the cathode capacitor, but that's inherent to the modeled circuit and shouldn't cause any problems (try the 22uF setting just in case). The other one is the oversampling. It will introduce 8 sample delay. You can try to turn off oversampling and see if it helps (button in the upper part of the UI). Unless you drive the tube very hard you can get away without oversampling.

I will check if there are no other glitches with delays and get back to you shortly.

Now it comes to my mind that a delay-compensated dry/wet mix know could be handy.

10 November 2012 at 12:01am

Ok, I think I've got something. The nastiest phase interaction comes from the fact that it's an _inverting_ triode stage. I've kept it as is in the model but nothing is keeping me from changing it to non-inverting.

Cathode cap indeed introduces some phase shifting and will attenuate some frequencies when output is mixed with dry signal.

Oversampling severely affects the phase, so dry/wet mixing is not possible with oversampling in the current implementation. After DC-12 is finished I will add mix control in the future version that will be phase-corrected. As a positive side effect it will make the transfer function plot in oversampled mode a bit more meaningful as well.

I'm going to fix the invertion and release an updated version soon.

10 November 2012 at 9:07pm

Please try out the new version (1.0.1) and see if it helps.

12 November 2012 at 8:05am

Alb, could you please check if the new version works for you? If it doesn't then could you please give me the name of the other VST plugin that gave you similar issues?

Renan L.B
Renan L.B
2 December 2012 at 4:44pm


Are there plans to release a x64 windows version of SoftAmp 3OD?

2 December 2012 at 7:44pm

Hi Renan,

Yes, it's on a list. Though I still have to set up my environment, so it won't be ready before the end of DC-12.

20 December 2012 at 3:03am

thanks for the review

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