A pre out is a line-level output that sends an amplifier’s preamp signal to an external power amp, active speaker, or subwoofer, bypassing the internal power stage.
If you’ve ever stared at the back of an AV receiver and wondered what is pre out on amplifier, the honest answer is simple: it’s the audio signal before the power amplification stage. That port lets you use your receiver or integrated amp as a controller while an external amplifier does the heavy lifting of driving your speakers. It’s the difference between a one-box system and a modular, upgradable one.
What a Pre Out Does
A pre out carries a line-level signal that has already passed through the preamp section — meaning volume control, tone controls, and input selection have all been applied. The signal is ready for power amplification but is not strong enough to drive passive speakers on its own.
In an AV receiver, the pre out taps the signal after source decoding and processing but before the internal power amp stage. Connect it to the Main In, Power Amp In, or Pre In on another amplifier, and that external amp handles the speaker driving instead.
Yamaha’s own FAQ confirms this design: pre-out/main-in connections route the preamp output to an external power amp, bypassing the internal amplifier. It’s a standard architecture across integrated amplifiers, AV receivers, and standalone preamplifiers, and it’s exactly what makes systems modular.
Why You’d Use One
The most common reason to use a pre out is upgrading your power stage. Your AV receiver might have excellent decoding and room correction, but its internal amps may struggle with demanding speakers. A pre out lets you add a dedicated external power amplifier for cleaner, louder, more controlled sound.
Pre outs also enable bi-amping, subwoofer integration via a specialized Sub Out, and clean multi-box setups where the receiver acts purely as the preamp/controller. If you want to know which AV receivers with pre outs are worth buying, that roundup covers tested models with the connections you need.
Some devices expose multiple pre outs — front left/right for the main amplifier, plus a sub out for the subwoofer. That’s how a modern home theater splits the job between different components.
What Pre Out Isn’t
The most common mistake is confusing pre out with line out. A line out is typically a fixed-level source output — a tape loop, for example — while a pre out is usually volume-controlled by the device’s preamp section. Plugging passive speakers straight into a pre out is the other classic error; it won’t work because the signal is line-level, not speaker-level.
Also, not every amp has a pre out. Feature availability is model-specific, and implementations vary — some pre outs are fixed, others variable, and some use RCA while others use XLR. To use one safely, match it to an amplifier input designed for line-level or preamp input, never to speaker terminals.
| Output Type | Signal Level | Best Used For |
|---|---|---|
| Pre Out | Line-level, often volume-controlled | Feeding an external power amp or active speakers |
| Line Out | Fixed line-level | Recording, tape loops, or feeding a second device |
| Speaker Out | Amplified, speaker-level | Driving passive speakers directly |
| Sub Out | Line-level, specialized | Sending bass signal to a powered subwoofer |
| Main In | Line-level input | Receiving an external preamp’s signal, bypassing internal preamp |
| Pre In | Line-level input | Same function as Main In on integrated amps |
| XLR Pre Out | Balanced line-level | Long cable runs and pro audio gear |
Should You Care About Pre Outs?
If you’re building a system you plan to upgrade, yes. A receiver or integrated amp with pre outs gives you a clear path to add external amplification, swap power stages, or integrate a subwoofer without replacing the whole unit. If you’re a casual listener running bookshelf speakers at moderate volume, the internal amp is plenty — pre outs matter most when speaker demands exceed what the built-in amp can deliver.
One honest trade-off: pre outs add cost and complexity. You’re paying for output stages and connections you may never use. But for anyone who wants separates-style flexibility in a single box, it’s the feature that makes it possible.
References & Sources
- Yamaha. “Pre-Out/Main-In Connections.” Official Yamaha USA FAQ explaining pre-out/main-in routing to external power amplifiers.