Cubase 15 – External Summing Return Turns Into White Noise (Works Fine in 14 & 13)

Cubase
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1

Hi everyone,

I’m running into a major issue in Cubase 15 when printing my external analog chain. Everything works perfectly in Cubase 14 and 13, but Cubase 15 produces distorted audio and eventually full white noise.

My Setup / Hardware Chain

  • Audio Interface: UAD Apollo

  • Outputs: 16 channels out from Apollo →

    • SPL MixDream (summing mixer)

    • SSL Fusion

      • SSL Bus+ (inserted inside the Fusion’s insert point)

  • Return: Stereo return (2 channels) from Fusion/Bus+ back into Apollo 16 inputs

  • DAW: Stereo print/record track in Cubase

This chain has been stable for years.

The Issue (Cubase 15 Only)

When printing the analog return in Cubase 15, the audio becomes:

  • Fuzzy / degraded,

  • Drops out,

  • Then shifts into white noise.

Monitoring directly through Apollo Console is clean.
Opening the exact same projects in Cubase 14 or 13 = clean, stable, no issues.

This strongly points to a Cubase 15 audio engine or external routing bug.

Steps to Reproduce

  1. Route 16 outputs from Apollo → MixDream → SSL Fusion (with SSL Bus+ on Fusion insert).

  2. Return the processed stereo signal back into Apollo.

  3. Create a stereo track in Cubase to record/print the return.

  4. Hit record → within seconds the signal degrades or becomes white noise.

Always reproducible.

Already Tested

  • Updated to the latest Cubase 15 hotfix

  • Re-measured external FX latency

  • Reset Audio Connections

  • Tried multiple buffer sizes

  • Verified the full analog chain and Apollo hardware (no issues)

  • Confirmed Cubase 14 and 13 behave normally with the same routing

Request

Can anyone else confirm issues with external summing or analog returns in Cubase 15?

And @Steinberg — this looks like an audio engine or external FX routing regression in Cubase 15. Any guidance or investigation would be appreciated.

Good times.

Thanks!