A professional-grade, open-source equalizer built directly into the Windows audio pipeline. Unlimited filters, near-zero latency, and full VST plugin support — completely free.
Equalizer APO is an open-source parametric and graphic equalizer for Microsoft Windows, built by Jonas Thedering and offered completely free of charge. What sets it apart from the typical equalizer for PC is its architecture — it installs as an Audio Processing Object directly inside the Windows audio service, which means every sound your computer produces passes through it before reaching your headphones or speakers. No per-application setup, no compatibility exceptions, no fuss.
People reach for the apo equalizer for all kinds of reasons. Some are headphone enthusiasts who want to apply a correction curve they measured with Room EQ Wizard. Others are streamers trying to shape a microphone signal before it hits OBS. Gamers use it to dial in clearer footsteps and sharper spatial cues. Home theater fans use it to compensate for uneven room acoustics. Whatever the goal, the equalizer handles it without breaking a sweat — and since the resource footprint is genuinely tiny, there's no reason not to leave it running around the clock.
The equalizerapo project has been steadily improved since its initial public release. The current version, 1.4.2, landed in March 2025 and brought native ARM64 support, a fix for Bluetooth audio on Windows 11, and a repair for a crash that affected CPUs without the AVX instruction set. If you haven't updated in a while, now is a good time. The process takes under five minutes and preserves your existing configuration files.
From unlimited filter stacking to near-zero CPU overhead, the equalizer for PC packs everything a serious listener needs — and it's all free from day one.
Stack as many peaking, shelving, notch, all-pass, or custom filters as you need. Equalizer APO imposes no cap — it handles everything the configuration file can throw at it.
Because the apo equalizer runs inside the Windows audio service, it adds almost no measurable delay. Games, live streaming, and voice chat all behave completely naturally.
The processing engine uses hardware-accelerated SIMD math. You won't see it in Task Manager even with dozens of active filters running simultaneously.
Stereo, 5.1, 7.1 — the equalizer handles any number of channels individually or as a group. Perfect for home theater setups and professional monitoring environments.
Load any 32-bit or 64-bit VST 2.x effect right into the signal chain. Third-party compressors, reverbs, and dynamic processors all work alongside the built-in filters.
The graphical editor lets you build filter chains visually. Changes apply in real time without restarting audio or rebooting — hear every adjustment the moment you save.
Draw frequency curves freehand or dial in precise center frequency, bandwidth, and gain values. Both modes are fully supported and can be mixed in the same chain.
Every setting lives in a simple text file you can edit, share, or back up. No proprietary format, no locked-in database — just readable lines of text.
Released under GNU GPL v2. Inspect the code, contribute fixes, or build your own version. No subscriptions, no nag screens, no hidden costs — ever.
One feature that consistently surprises new users is convolution filter support. By supplying the equalizer with a room impulse response file — measured with a tool like Room EQ Wizard — you can apply precise room correction that turns a plain pair of headphones into a system that mimics world-class loudspeaker measurements. This capability normally costs hundreds of dollars in dedicated software. The equalizerapo approach makes it entirely free. On top of that, the Include and Device filter commands let you maintain separate configuration files for different headphones, speakers, and microphones, switching between them in an instant without touching the main config. It's a workflow that becomes second nature quickly, and it's why so many power users never look at paid alternatives. The equalizer apo peace combination, covered in its own section of this site, takes convenience even further with a polished graphical layer on top of everything described here.
In this Equalizer APO installation guide we show you exactly how to set up the equalizer on your Windows machine. The whole process takes under ten minutes from download to a fully working setup.
Head to the download page and grab the version that matches your Windows installation — x64 for almost everyone on a modern PC, ARM64 for Surface Pro X and Snapdragon-powered laptops, x86 only for 32-bit Windows. Once you have the file, double-click it. Windows may ask for administrator permission; click Yes to let the installer proceed. The setup wizard is brief and the defaults are sensible for most users.
Midway through the installation, the Configurator window appears listing every audio device Windows recognises. Check the boxes next to the devices you want the apo equalizer to process — typically your main speakers or headphones for playback, and your microphone if you want input processing too. Avoid ticking "Select all" indiscriminately; virtual devices like VoiceMeeter can behave unexpectedly when selected alongside physical hardware. You can always reopen the Configurator later from the Start Menu to adjust device selection.
After installation completes, you'll be prompted to restart. This step is mandatory — Windows loads Audio Processing Objects only when the audio service initialises at boot. Until you restart, the equalizer files are on disk but not yet active in the audio chain. Go ahead and reboot; the process takes under a minute and nothing else on your system is affected.
After rebooting, find "Equalizer APO Configuration Editor" in your Start Menu or navigate to C:\Program Files\EqualizerAPO and open Editor.exe. You'll notice a slight change in overall volume immediately — that's the default example configuration applying a preamplification value and mild low-frequency boost. That change confirms the equalizer is active and processing your audio. Everything from here is personal fine-tuning.
A common question at this stage is whether a sound card driver needs to support APOs. Virtually every onboard audio driver shipped since Windows Vista does, as do most USB DACs and PCI-e sound cards. The main exception is ASIO drivers, which bypass the Windows effect infrastructure intentionally. If you use an audio interface in ASIO mode for low-latency recording, the equalizer won't process that stream — and that's by design. Switch to WASAPI shared mode if you need system-wide equalization to apply to that device. Planning to add the Peace graphical interface on top? Install the apo equalizer first, confirm it's active, then visit the Peace Equalizer page for next steps.
Once you install Equalizer APO and reboot the computer, you can launch it from Program Files or the taskbar. Here's how to find your way around the interface.
When you open the Configuration Editor for the first time, it can look a bit daunting. The left panel holds your filter chain — a list of processing modules that execute from top to bottom. The central area shows the controls for whichever module is currently selected. The bottom panel draws a real-time frequency response graph that updates the moment you change any value. That graph is your best friend: it shows exactly what you're doing to the sound before you even listen. Spend a few minutes clicking around, resizing panels, and getting the layout comfortable. Once the three-panel logic clicks, the whole tool becomes surprisingly intuitive.
Behind the graphical editor, everything lives in plain text files at C:\Program Files\EqualizerAPO\config\. The main entry point is config.txt. Lines starting with # are comments. Preamp lines set overall gain. Filter lines define individual EQ bands. Include lines pull in other text files, letting you organise separate profiles for different devices without duplicating your base settings. You can open any of these files in Notepad, edit them directly, and the equalizer picks up changes automatically — no restart required.
Click the green plus button at the top-left of the editor and choose "Basic Filters." You'll see Peak, Low Shelf, High Shelf, Low Pass, High Pass, Band Pass, and Preamplification. A Peak filter is the most versatile starting point. Set a center frequency, a gain in decibels (positive to boost, negative to cut), and a Q value controlling how broad or narrow the adjustment is. Lower Q values affect a wide range of frequencies; higher values create surgical corrections. Move the sliders while music plays — the real-time graph and your ears will tell you everything you need to know.
Press Ctrl+S or go to File → Save at any point. Changes apply instantly because the equalizer watches the configuration file and reloads it on the fly. The power button icon at the top of the editor toggles the entire filter chain on and off — great for A/B comparisons. Save early, save often, and keep manual backups by copying config.txt to a folder with a descriptive name before experimenting with anything drastic.
So now, what I'll demonstrate is how to amplify your mic or speaker volume using Equalizer APO. Follow these steps to build a clean amplification chain from scratch.
On the main screen you'll see three configuration tabs already there. Remove them all — select each module in the filter chain and delete it using the red minus button. Once the chain is empty, the frequency graph shows a perfectly flat line. No boost, no cut, no coloration. This is your starting canvas, and it avoids any confusion between your new settings and whatever the example config was doing.
Click the small green plus mark and go to Control → Include. This creates a new module that loads a separate configuration file. It says "No file is selected" because we still haven't created the actual file yet. Click the folder icon, navigate to C:\Program Files\EqualizerAPO\config\, type a filename — for demonstration purposes I'm going to name it Tutorial — and click Save. The editor creates an empty text file and links it. Click the arrow icon to navigate into that file's own editor tab.
Once we're back on screen again and inside the new Include tab, click the plus icon once more and go to Control → Device. A dropdown lists all audio endpoints registered in Windows. Untick the "Select all" checkbox and pick only the device you want to amplify — your speakers, headphones, or microphone input. Limiting the filter to one device prevents unintended side effects on other outputs.
Click the plus icon again and go to Basic Filters → Preamplification. A simple gain slider appears. Now, you can use this to amplify your output sound for the selected device. Drag it right to increase volume — the value is in decibels. A boost of 6 dB roughly doubles perceived loudness; don't exceed +12 dB without checking for distortion. For microphone boosting, +6 to +10 dB is usually the sweet spot. Play audio while adjusting so you hear the effect in real time.
At the bottom of the screen you can see the Analysis Panel confirming the boost is active. All you have to do is go to File and Save. Close the current tab and you'll see the main screen again. On there, click the power button icon to turn on the filter and now you're good to go. Play some music to confirm it works. If it doesn't work, delete every filter and follow the steps again — the most common mistake is forgetting to link the Include file or selecting the wrong device.
Even though using the APO Equalizer is very easy, sometimes things get a bit difficult. Work through these known solutions before assuming something is fundamentally broken.
The most common cause is forgetting to reboot after installation. The APO only becomes active after the Windows audio service restarts. Also verify in the Configurator that the correct device has a checkmark next to it.
Updates can reset audio driver configurations. The fix: open the Configurator from the Start Menu, uncheck then re-check your audio device, click OK, and restart. This re-registers the APO with the current driver stack.
This typically affects CPUs without AVX support on versions before 1.4.2. Upgrade to version 1.4.2 from the download page — your configuration files are preserved through a reinstall.
GraphicEQ and Convolution commands could fail silently on Bluetooth devices running Windows 11. Version 1.4.2 addresses this specifically — upgrade if you're on an older build.
Applications using ASIO drivers or WASAPI exclusive mode route audio around the Windows effect chain. The equalizer apo cannot process these streams. Switch to WASAPI shared mode in the application's audio settings to bring it back into the pipeline.
VST plugins run inside the Windows audio service, which has strict file permissions. Ensure the DLL and its supporting files are in a folder the audio service account can read. The equalizer will warn you if a permission problem is detected and suggest how to fix it.
Our sincerest thanks to Jonas Thedering and the other contributors who helped develop Equalizer APO. Jonas built the original architecture and has continued refining it through every release. Community members have added translations, fixed platform-specific bugs, and improved compatibility with newer hardware. The project lives on SourceForge and the source code is open to anyone who wants to contribute.
Download Equalizer APO now and start hearing your music, games, and calls the way they were meant to sound.
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