Getting glitch-free performance from any interface
This guide assumes your audio interface is already configured. If not, see: Audio Interface Setup in REAPER.
Clicks, pops, delays, or sluggish guitar sims — buffer size is usually the villain behind the crime scene. In REAPER, your buffer (or “block size”) determines how quickly your interface handles audio. Set it too low, and your CPU throws a tantrum. Set it too high, and your performance feels like it’s travelling by Australia Post.
The good news? REAPER makes it easy to balance latency, stability, and CPU load. In this guide, we’ll break down what the buffer actually does, how to test settings effectively, and how to pick the right value whether you’re tracking, mixing, or somewhere in-between.
1. Buffer Size vs Latency (What’s Really Going On?)
Your buffer size determines how much audio REAPER processes at once. Smaller buffers give you lower latency — great for tracking — but they demand more CPU power. Larger buffers do the opposite.
What Larger Buffers Do
- Reduce CPU workload
- Prevent crackles and pops
- Make large mixes smooth
- Increase latency
The REAPER User Guide specifically notes that if you hear dropouts, you should “consider increasing buffer size,” even up to 1280 samples, because the project may be running “at a latency too low for your system.”
👉 Source:
https://www.reaper.fm/userguide.php (Audio Device Settings section)
What Smaller Buffers Do
- Improve responsiveness while recording
- Reduce round-trip latency
- Increase risk of audio artifacts if the CPU can’t keep up
Adam Steel (Hop Pole Studios) explains this trade-off clearly: a smaller buffer lowers latency “at the cost of processing power”, while larger buffers ease CPU load during mixing.
👉 Source:
https://promixacademy.com/blog/reaper-tutorials
Real-world tests show:
- 128-sample buffer ≈ ~5.5 ms latency on common interfaces
- 64 samples on the same system caused audible crackles
👉 Source:
https://nolabelnoproducernolimits.com
Typical Useful Ranges
| Buffer Size | Use Case | Notes |
|---|---|---|
| 64 samples | Demanding real-time tracking | Great for amp sims/virtual drums if your CPU can handle it |
| 128 samples | Most live recording | Stable for vocals/instruments |
| 256 samples | Hybrid tracking + light mixing | Adam Steel recommends 256 as a “good place to start” |
| 512–1024+ samples | Mixing/mastering | Stability over responsiveness |
2. Testing and Adjusting Buffer Size in REAPER
Step 1 — Open Audio Preferences
Options → Preferences → Audio → Device
Here you’ll see:
- Driver selection (ASIO/Core Audio)
- Sample rate
- Block size
- Measured input/output latency
REAPER links:
https://www.reaper.fm/videos.php (Device Setup Tutorials)
Step 2 — Start with a Medium Buffer
Begin at 128 or 256 samples — both widely stable.
Step 3 — Play a “Real” Session
Open a typical project and check:
- CPU % (overall processing)
- RT CPU % (real-time processing — the important one)
If RT CPU climbs toward 100%, glitches are coming.
Step 4 — Adjust for Tracking
Reducing buffer → reduces latency → increases CPU strain.
Try: 128 → 64 → 32, and back off if crackles appear.
Supporting reference:
https://promixacademy.com/blog/reaper-buffer-settings
https://nolabelnoproducernolimits.com
Disable heavy plug-ins and use REAPER’s Freeze feature when needed.
Jon from The REAPER Blog regularly recommends freezing tracks or bypassing mix-bus FX during tracking to reduce CPU load:
https://reaper.blog
Step 5 — Adjust for Mixing
Increase to 256 → 512 → 1024 to:
- Enable oversampling
- Run linear-phase EQs
- Add mastering chain plugins
- Prevent real-time dropouts
Official documentation also reinforces this:
https://www.reaper.fm/userguide.php
Step 6 — The RT CPU Rule of Thumb
If RT CPU > 70–80%, you’re flirting with glitches.
Raise the buffer or freeze CPU-heavy tracks.
3. When to Prioritise Stability vs Responsiveness
Tracking (Responsiveness First)
You want the lowest buffer your system can handle without artifacts.
Typical guidelines:
- 64 samples → drums, amp sims, MIDI-heavy parts
- 128 samples → vocals & most instruments
Freeze unnecessary tracks and bypass heavy mix FX (master bus limiters, convolution reverbs).
👉 Recommended by The REAPER Blog: https://reaper.blog
Mixing (Stability First)
When you’re not performing in real time:
- Increase buffer to 512–1024+
- Enable oversampling
- Use CPU-heavy linear-phase tools, mastering limiters, convolution reverbs
This mirrors guidance from:
https://promixacademy.com
https://nolabelnoproducernolimits.com
Hybrid Tracking + Mixing Sessions
If you must record while mixing-heavy plugins are running:
- Freeze non-record tracks
- Disable master FX temporarily
- Use zero-latency alternatives
- Or monitor via hardware (amp modeller, vocal chain)
This allows low-latency monitoring while running a more comfortable buffer for the CPU.
4. Advanced Tips for Smooth REAPER Performance
Use the Right Driver
- Windows: Use your interface’s native ASIO driver
- macOS: Core Audio is already low-latency
- Avoid ASIO4ALL unless your interface has no proper driver
(ASIO4ALL often introduces higher latency or instability.)
Beware Plug-In Latency
Some effects add significant delay:
- Linear-phase EQ
- Lookahead compressors
- Convolution reverb
- Oversampled distortion
REAPER compensates automatically, but your system still has to crunch the numbers in time.
Keep the System Clean
Disable/pause:
- Cloud sync (OneDrive iCloud Dropbox etc.)
- Antivirus scans
- Wi-Fi/Bluetooth drivers during critical sessions
- USB hubs causing under-powering
Quick Glitch-Fix Checklist
If you hear crackles:
- Increase buffer size
- Disable Wi-Fi/Bluetooth
- Switch USB ports (or cables)
- Stop background sync
- Restart REAPER
These address most intermittent glitches that aren’t caused by REAPER settings.
My Final Thoughts
Reliable audio performance doesn’t come from chasing the lowest buffer — it comes from choosing the right buffer for the moment. Recording needs responsiveness. Mixing needs stability. Once you feel the rhythm of switching between these two priorities, REAPER becomes smoother, faster, and far less glitch-prone.
You’ve just unlocked one of the most important system-level skills in modern recording. Your future mixes — and your future self — will absolutely thank you.
I’d Love to Hear Your Thoughts…
- What buffer size gives you the best balance when tracking or mixing?
- Which plug-ins push your system hardest?